The production of high-current and intense spin polarized electron beams is of great importance in electron-based facilities. Tests are planned to produce such beams in 2023 using GaAs-based photocathodes installed in the Brookhaven National Lab RHIC Coherent electron Cooling superconducting radiofrequency (SRF) photogun [1]. A fast and efficient electron polarimeter operating in the MeV energy range is required to measure the beam spin polarization.
While Mott polarimeters provide larger measured asymmetries, a Compton Transmission polarimeter is well suited in the few MeV energy range. In this work, we report on a relatively compact and cost-effective Compton transmission polarimeter which has been built and calibrated at Jefferson Lab (JLab). First, we present the design of the polarimeter radiator, polarized target analyzing magnet, BGO detector assembly and data acquisition system. Next, results of a two-week commissioning study performed at the JLab Upgraded Injector Test Facility will be described. Here, a well-known polarized electron beam produced from a bulk GaAs photocathode in a dc high-voltage photogun was first measured in a 180 keV Mott scattering polarimeter, then used to characterize and calibrate the Compton transmission polarimeter as a function of the polarized target magnetization and beam properties. Finally, we report an effective analyzing power of the Compton polarimeter and compare experimental results with those produced via Geant4 simulations.
Dielectric gratings are used in Dielectric Laser Acceleration due to their high damage thresholds in high acceleration gradients. When an electron bunch passes close to these gratings, it emits radiation, and the features of this radiation will be dependent on the beam position relative to the grating, the bunch charge, and the bunch length. A compact high-resolution diagnostic device will be developed that consists of multiple dielectric gratings with different periodicities; these types of devices are required for the accurate operation of future compact accelerators which are currently undergoing development and testing.
The ARES linac at DESY is able to provide sub-fs electron bunches and has a range of high-resolution diagnostic devices installed, such as the PolariX Transverse Deflecting Structure, which will allow for performance verification of a new diagnostic. The electron bunches can be altered, allowing for the measurement and analysis of the emitted radiation for different bunch lengths and charges. This work will present the current progress in this area, including the presentation and discussion of simulations, and a discussion of the planned experiments at ARES.
Grid-controlled electron gun usually uses specially designed power supplies to supply power, the performance of the power supplies can directly affect the beam performance of the accelerator. In this paper, a nanosecond power supply for a grid-controlled electron gun is designed. It uses avalanche transistors and superimposes Marx generators to improve the power. Finally, its rise edge is less than 1 ns. The power supply can be used in the thermal cathode grid-controlled electron gun, the electronic source scheme of Hefei Advanced Light Facility (HALF), which is practical and feasible.
Beam monitoring for Ultra High Dose Rate (UHDR) radiation therapy using pulsed beams, i.e. Very High Energy Electrons (VHEE), is a major challenge. The lower pulse repetition of VHEE beams means a larger dose-per-pulse is necessary to achieve the mean dose rates required for UHDR therapy (so-called FLASH). The currently used transmission ion chambers suffer drastic recombination effects under these conditions. A proposed detector consisting of a 2D array of silica optical fibres connected to a photodetector which measures the Cherenkov radiation emitted by the VHEE beam as it passes through the fibres could be a promising alternative due to its high spatial and temporal resolution and its low material budget. First measurements with such a detector, consisting of silica optical fibres with a diameter of 200 μm, have been conducted at the CLEAR facility at CERN using 200 MeV electrons up to the UHDR required for FLASH. Measurements on the dynamic range of the fibre detector showed that it had a linear response at mean dose rates of over 300 Gy/s. Such results show that this fibre-optic based beam monitor is able to provide fast direct real-time measurements of the VHEE beam dose and profile up to the UHDR. This makes them an excellent candidate for online dosimetry and beam diagnostics in future clinical FLASH machines with VHEE and other beam types.
A design study is currently underway at the University of Melbourne for a large energy acceptance beamline to enable future hadron therapy modalities. As part of the TURBO project, a beam delivery system demonstrator is being developed for a DC Pelletron accelerator, which will provide 3 MeV H+ beams. Fixed Field Accelerator optics will be used to maximise momentum acceptance, with dispersion minimised at both ends of the transport line. This project aims to be the first `closed dispersion arc' with fixed fields ever constructed. As part of the design process, the input beam phase space from the Pelletron has been characterised. Our results show that the Pelletron beam can be injected into the novel transport line successfully, and Zgoubi simulations show that near-zero dispersion at each end will be achievable. This is supplemented by error studies and magnet investigations, demonstrating that beam transport can be achieved under realistic circumstances. This initial study establishes the feasibility of this beamline design and work is continuing toward further optimisation for implementation.
Space charge forces represent main induced effects in an RF-injector that degrade the beam quality. In this scenario the laser distribution sent on the photocathode acquires an
important role in the emittance compensation process, as the slice analysis shows. A novel model of space charge forces is proposed for bunch with arbitrary charge distribution to derive expressions of self-induced forces. As the performance of the fields near the cathode is under present analysis, we can investigate use of this model in low charge regime. Further, the model has been benchmarked with the behavior of the distributions present in the literature and studied for new ones. It has also been applied for the study of the optimization of a C-band hybrid photoinjector now being commissioned, thus explaining the factor two reduction of the emittance observed at the exit of the gun by changing the initial distribution at the cathode.
Developments in current and future experiments in the SPS North Area (NA) and PS East Area (EA) fixed target beam lines at CERN, including the “Physics Beyond Colliders” (PBC) program, require accurate determination of the number of protons on target (POT). The re-calibration of Beam Secondary Emission Intensity monitors (BSI), recently completed in one of the NA branches, reduced the estimated uncertainty on the absolute POT to a few percent. The calibration is based on an activation technique, applied to metal foils (Al, Cu), installed in front of the BSI and irradiated with the nominal proton intensity for a short period. The number of protons is determined from offline gamma spectrometry analysis of the foils and compared to the total integrated signal of the BSI. A description of the method, data analysis and results, will be presented and followed by considerations intended to standardise the procedure for future regular use in all SPS NA beamlines.
The development of high-power, attosecond methods at free-electron lasers has led to new possibilities in the probing and control of valence electron dynamics. Beyond simple observation of ultrafast processes, one of the longstanding goals of atomic physics is control of the electronic wavefunction on attosecond timescales. We present a scheme to generate sub-femtosecond pulse pairs from x-ray free-electron lasers with fs-scale separation, few eV energy separation, and a coherent phase relationship. This shaping method can be employed to coherently control ultrafast electronic wavepackets in quantum systems. We study in detail the Auger-Meitner decay process initiated by such a pulse pair and demonstrate that quantum beats of the decaying electronic wavepacket can be shaped by controlling the separation in energy and time of the pulse pair.
Boron Neutron Capture Therapy(BNCT) is useful for cancer therapy. To generate safe and efficient neutron beams, we accelerate 2.5 MeV protons and irradiate a lithium target. This is an endothermic reaction that avoids activation of the accelerator and produces neutrons of relatively low energy. We are designing a beamline to deliver such protons to a lithium target. Tokyo Institute of Technology has been developing a high duty factor RFQ in collaboration with Time Co. A 5% demonstrator is already in practical use. This paper describes a lossless beam transport system from the RFQ to the lithium target. The beamline consists of a quadrupole magnet, a bending magnet and a multipole magnet. The bending magnets prevent the backflow of neutrons into the RFQ. The expected beam current is 20 mA. The results of the design study of this beamline will be presented at the conference.
The Large Hadron Electron Collider (LHeC) is a study
at CERN to construct an energy recovery linear accelerator
(ERL) tangentially to the High Luminosity Large Hadron
Collider (HL-LHC). This would enable deep inelastic scat-
tering collisions between electrons and protons in the ALICE
interaction region (IR2). In this design, one of the two pro-
ton beams of the HL-LHC collides with the electron beam in
IR2, while the second proton beam avoids this collision. This
way, the e-p collisions can take place concurrently with p-p
collisions in ATLAS, CMS and LHCb. The LHeC/ALICE
interaction region is laid out for alternate e-p and p-p data,
using a common detector, suitable for this novel way of in-
teraction. It therefore requires a highly precise beam optics
and orbit for the three beams: the two proton beams of the
HL-LHC, as well as the electron beam from the ERL. The
highly asymmetric optics and orbits of the two proton beams,
allowing concurrent operation of the HL-LHC experiments
and e-p collisions, have been investigated with MAD-X. The
impact of an optimized electron mini-beta insertion, focus-
ing and bending the electrons, on the proton beam dynamics
has been considered.
At EuPRAXIA@SPARC_LAB an X-ray FEL user facility is driven by a plasma accelerator in the particle-driven configuration where an ultra-relativistic beam, the driver, through a plasma generates a wake of charge density useful for accelerate a witness beam. The electron bunches are generated through the so-called comb technique in an RF injector that consist of a 1.6 cell S-band gun followed by four S-band TW accelerating structures. The main working point foresees a 30pC witness and a 200pC driver longitudinally compressed in the first accelerating structure operated in the velocity-bunching regime, that allows to accelerate and manipulate the beam to reach proper transverse and longitudinal parameters. The optimization of the witness emittance is performed with additional magnetic field around the gun and the S-band structures and by shaping the laser pulse at the cathode. The paper reports on beam dynamics studies performed also for beams with higher charges to maximize the transformer ratio in the plasma and the beam brightness. In addition, the insertion of an X-band RF cavity after the gun is proposed aiming to shape the beam current distribution as needed and stabilize it with respect to RF jitters.
Accelerating technology is evolving towards compactness and high intensity. In such a scenario, beam loading effects result in significant energy losses for long trains of bunches. To address these effects, we generalised the Beam Loading module of the tracking code RF-Track to allow the study of beam loading independently of the particle type and velocity or the accelerating cavity design. This paper describes the implementation of this effect in standing wave (SW) structures. Particular attention has been devoted to guns for photoinjectors, where causality plays an important role, and one must address the non-ultrarelativistic behaviour of the emitted particles. Finally, we will discuss the simulation of these effects in the CLEAR facility at CERN.
In recent work, it has been shown that reinforcement learning (RL) is capable of outperforming existing methods on accelerator tuning tasks. However, RL algorithms are difficult and time-consuming to train and currently need to be retrained for every single task. This makes fast deployment in operation difficult and hinders collaborative efforts in this research area. At the same time, modern accelerators often reuse certain structures within or across facilities such as transport lines consisting of several magnets, leading to similar tuning tasks. In this contribution, we use different methods, such as domain randomization, to allow an agent trained in simulation to easily be deployed for a group of similar tasks. Preliminary results show that this training method is transferable and allows the RL agent to control the beam trajectory at similar lattice sections of two different real linear accelerators. We expect that future work in this direction will enable faster deployment of learning-based tuning routines, and lead towards the ultimate goal of autonomous operation of accelerator systems and transfer of RL methods to most accelerators.
The understanding of beam-beam effects, which influence the choice of the FCC-ee design parameters for several aspects, require sophisticated and high-performance numerical simulations. The self-consistent study of the interplay of nonlinear dynamical phenomena resulting from collisions in the machine is key to accurately assess its potential performance. Although current simulation frameworks can address specific aspects of the dynamics separately, they are difficult to interface with each other for more complex studies. To address this challenge, Xsuite, a new general purpose software framework for beam dynamics simulations, is currently under development. We discuss the implementation of the beam-beam interaction in this new toolkit and the evaluation of its performance on multiple platforms.
Laser-wake field accelerators (LWFAs) are potential candidates to produce intense relativistic electron beams to drive compact free electron lasers (FELs) in VUV and X-ray regions. In High-Field Physics and Ultrafast Technology Laboratory at National Central University (NCU), an LWFA is being developed to produce a 250 MeV high-brightness electron beam by their 100-TW laser system. An FEL seeded by a 266-nm UV laser is under design to generate extreme ultraviolet (EUV) radiation. The initial phase of the project is to develop a beam energy modulator through the interaction of the LFWA-produced electron beam with the 266-nm seed laser in a 10-period planar undulator of 35-mm period length. An electron beamline has been designed based on linear optics to deliver the intense electron pulse from LWFA to the undulator and focus properly. However, due to the large energy spread of the beam, chromatic effects on beam transportation may be severe. In this work, we perform a detailed simulation of the LWFA FEL from experimental data of the NCU LWFA electron source. A 6D phase space analysis of multi-particle dynamics using IMPACT code [1] is to determine how significant the effects of beam energy spread on beam properties along the beamline are. The electron beam is then transferred to GENESIS [2] and Puffin [3] to see the laser beam interaction in the undulator. Further study of the HGHG scheme is evaluated using both FEL codes to see the influence of ultra-short electron bunch.
A set of twelve Polycrystalline Chemical Vapour Deposition (pCVD) diamond detectors are installed in the beam injection, extraction and betatron collimation areas of the Large Hadron Collider (LHC) as fast beam loss monitoring detectors. Their high-radiation tolerance and time resolution in the order of a few ns makes them an ideal candidate to monitor bunch-by-bunch losses in the LHC beams, which have a nominal bunch separation of 25 ns. Considering their location in some of the most critical areas for beam loss studies, a signal-to-lost-particle calibration of these detectors provides a useful insight of the various LHC bunch-by-bunch beam loss mechanisms.
This contribution shows the principle of the calibration of the LHC diamond Beam Loss Monitors (dBLMs) as well as a description of the machine tests run to study and perform this calibration.
Novel particle accelerators based on plasma technology allow a drastic reduction in size, due to the high accelerating field established inside plasmas, which are created and confined by specific devices. Plasma Wakefield Acceleration experiments are performed at the SPARC_LAB test facility (Laboratori Nazionali di Frascati - INFN) by using gas-filled capillaries, in which the plasma formation is achieved by ionizing hydrogen gas through high voltage pulses.
In this work, the characterization of gas-filled plasma-discharge capillaries is presented. Several geometrical configurations are tested, including capillaries with different channel shapes and arrangement of inlets positions for the gas injection. Such configurations are designed in order to enhance the uniformity of the plasma density distribution along the plasma channel, which is necessary to improve particle beam acceleration. Plasma sources are characterized by means of the spectroscopic technique based on the Stark broadening method, which allows to measure the evolution of the plasma density profile along the channel. In addition, the CFD software OpenFoam is used to simulate the dynamics of the neutral gas during the filling of the capillary.
The Compact Linear Collider (CLIC) is a proposed linear accelerator designed to collide electrons and positrons at energies up to 3 TeV. In order to explore new physics and to be more competitive with other collider projects, CLIC is exploring the increase of the center-of-mass energy to 7 TeV. The CLIC Beam Delivery System (BDS) transports the lepton beams from the exit of the Main Linac to the Interaction Point (IP). This paper reports on the studies and the challenges of the new BDS design, such as minimizing the extent of trajectory bending for collimation and chromaticity correction to reduce the effects from synchrotron radiation, ensuring a good transverse aberration control at the IP.
In the frame of ongoing initiatives for the design of a new generation of synchrotron-based accelerators for cancer therapy with ion beams, an analysis of linac designs has been started, to address a critical element with strong impact on performance and cost of the accelerator. The goal is to identify alternatives at lower cost and similar or possibly smaller footprint than the standard 217 MHz injector presently used in all carbon therapy facilities in Europe. As an additional feature, a new linac design can be tailored to produce radioisotopes for treatment and diagnostics in parallel with operation as synchrotron injector.
In this paper is analysed the attractive option of moving to 352 MHz frequency, to profit of reliable mechanical designs already developed for protons and of the cost savings that can be obtained using as RF power sources klystrons with a much lower cost per Watt than tubes or solid-state units.
The paper will present a Quasi-Alvarez Drift Tube Linac (DTL) version of an injector linac for carbon ions at q/m=1/3 and compare it with recently developed DTL and IH designs. The option of a separated-IH type linac will be also discussed, together with a standard IH design at 352 MHz. Finally, a DTL design at 352 MHz for injection of fully stripped helium ions into the synchrotron will be presented.
Laser wakefield acceleration (LWFA) using metal targets has been developed for high-vacuum and high-repetition rate operations compare to the gas targets[1-2]. However, the ionization effect due to high intensity fs laser should be considered as propagating through the plasma and the difference of LWFA mechanisms between aluminum plasma and helium plasma has been investigated with the simulation. The partially ionized aluminum ions are ionized to higher charge state up to Al11+ as the main laser is propagating through the metallic plasma. As comparing to helium plasma case, a lot of electrons are injected into the wake cavity even at lower laser power and the energy of accelerated electrons are decreased. By increasing the plasma density, the charge and the oscillating amplitude of injected electrons can be optimized for betatron radiation.
We proposed a structured metal target using a thin Ti or Cu wire in aluminum to improve the beam quality. The aluminum plasma with a thin Ti or Cu plasma zone can be produced by laser ablation. When changing the focal position of fs laser pulse with respect to the position of the thin-layered zone, the injection timing of electrons depleted from Ti or Cu ions can be adjusted. We present and discuss the simulation results depending on the thickness and the position of the thin layer.
The damage mechanisms and limits of superconducting accelerator magnets caused by the impact of high-intensity particle beams have been the subject of extensive studies at CERN in the recent years. Recently, an experiment with dedicated racetrack coils made of Nb-Ti and Nb3Sn strands was performed in CERN’s HiRadMat facility. In this paper, the design and construction of the sample coils as well as the results of their qualification before the beam impact are described. Furthermore, the experimental setup is discussed. Finally, the measurements during the beam experiment such as the beam-based alignment, the observations during the impact of 440 GeV protons on the sample coils and the obtained hotspots and temperature gradients are presented.
Dielectric wakefield acceleration (DWA) is a promising approach to particle acceleration, offering high gradients and compact sizes. However, beam instabilities can limit its effectiveness. In this work, we present the result of a DWA design that uses alternating gradients to counteract quadrupole-mode induced instabilities in the drive beam. Through simulation and experimental results, we show that this approach is effective at suppressing beam breakup, allowing for longer accelerating structures.
We have designed and fabricated a new apparatus for positioning the DWA components in our setup. This allows us to precisely and independently control the gap in both transverse dimensions and consequently the strength of the destabilizing fields.
Our results show that the use of alternating gradient structures in DWA can significantly improve its performance, offering a promising path forward for high-gradient particle acceleration.
LEAF (Low Energy heavy ion Accelerator Facility) is a low-energy high-intensity heavy-ion LINAC complex for multidiscipline research. At present, the beam repetition rate is the same as the LINAC frequency of 81.25 MHz. A lower frequency would be desirable for many types of experiments employing time of flight data acquisitions. A method of increasing the bunch spacing to 98 ns by combining a 10.156 MHz pre-buncher before the RFQ and an RF chopper after the RFQ has been proposed. This paper reports the design studies of such a low-frequency pre-buncher. A resonator-based buncher is the best choice since lumped circuit-based buncher cannot provide the high voltage we expect for the efficient bunching of ion beams with an A/q of 7. According to the simulation result, the bunching efficiency of a 3-harmonic buncher will merely increase by 1% compared to a 2-harmonic buncher. We decide to design a two-harmonic buncher based on the little improvement in bunching efficiency. We optimize the length of electrodes so that the utilization of the parasitic field is maximized. The beam dynamics analysis indicates that the voltage amplitude and the RF power can be lowered by 1.3 times and 2.2 times by optimizing the electrode length.
The Lanzhou Light Ion Cancer Therapy Facility (LLICTF) is a compact medical accelerator currently under construction. It is designed to treat cancer using a 230MeV, 30mA H+ beam and a 85MeV/u, 1mA 3He2+ beam. The facility comprises two ion sources, a low-energy beam-transport (LEBT), a Radio Frequency Quadrupole (RFQ), a medium-energy beam-transport (MEBT), and the main ring accelerating structure. Due to the presence of two ion sources, it is necessary to introduce a dipole magnet which is symmetrically focused as much as possible to meet the symmetrical focusing requirements of the LEBT beam. Therefore, a gradient dipole magnet has been designed to achieve this symmetrical focusing. This paper discusses the theoretical and simulated symmetric focusing of the gradient dipole magnet. It also analyzes the effect of fringe fields and space charge. Additionally, the paper presents the results of the model design with CST and the multi-particle simulation results with TraceWin.
In modern accelerator facilities, femtosecond synchronisation between an optical master oscillator (OMO) that provides facility-wide timing pulses and an external experiment laser is needed to achieve the few-fs resolution required for experiments such as pump-probe spectroscopy. This can be achieved with a balanced optical cross-correlator (BOXC), which determines the timing delay between two laser pulses via the generation of sum-frequency radiation in a nonlinear crystal.
In this paper, a design for a two-colour fibre-coupled BOXC using waveguided periodically-poled lithium niobate (PPLN) crystals is presented. An all-fibre two-colour BOXC is highly desirable as it would be more robust against environment fluctuations, easier to implement, and can achieve greater synchronisation performance compared to free-space coupled BOXCs that are currently used in accelerator facilities. This proposed design can theoretically achieve 5 - 10 times greater sensitivity to relative timing changes between laser pulses than current free-space two-colour BOXCs, which can make sub-fs synchronisation between an OMO and an external experiment laser of different wavelength achievable.
Spin is one of the intrinsic properties of particles. However, there are many incomprehensible problems about it. High energy polarized electron-ion collisions will provide unprecedented conditions for the study of spin physics and lead us to the study on the inner structure of matter and fundamental laws of interactions, and other forefronts of natural science. As the Phase II of the HIAF (High Intensity heavy ion Accelerator Facility) project, Electron-Ion Collider in China (EicC)* is under conceptual design phase. The production, acceleration and collision of polarized ions and electrons are essential for EicC accelerator facility. Therefore, R&D work such as key technologies prototyping has already been initiated. A spin polarized ion source for the production of intense proton and deuterium ion beams with high polarization is under development at the Institute of Modern Physics (IMP). Polarization is one of the key characteristics for polarized ion beams. To make the polarization measurement more precise, faster and more convenient, a polarimeter based on nuclear spin filter (SFP for short) is under design, which measures the polarization directly behind the ion source. Scheme of the SFP will be presented, the measurement process, simulations for crucial physical questions and design of the SFP will be discussed.
Tokyo Institute of Technology is planning a linac facility to produce 211 astatine, an isotope for αemitter cancer therapy. To produce astatine, we aim to bombard a bismuth target with helium ion beam of sufficient intensity at 28 MeV. Unlike a cyclotron, this facility will be able to accelerate a milliampere class high intensity helium ion beam. In addition, the subsequent accelerator system can be made compact by providing fully stripped helium ions. For this purpose, the ECR ion source is best suited. The multiply charged ions are generated by resonant absorption of microwaves by electrons orbiting in a magnetic field and are capable of supplying high-intensity beams. The ECR ion source will use an RF frequency of 10 GHz, and a suitable magnetic field distribution will be designed to confine the plasma by a composite magnetic field consisting of a mirror field using two solenoid coils and a magnetic field generated by a sextupole magnet to increase the charge states of the ions in the chamber. The final goal is to extract He2+ at 15 mA. In this presentation, the design and magnetic field distribution are reported.
A Low Energy Branch is being built at Micro Analytical Centre * that will allow us to produce a variety of high current (up to 50 $\mu A$) ion beams, ranging from light (i.e. H, He, C, B, $^{15}N$), mid-mass (i.e. Si) to heavy (Ag, W, Pb, Bi) ion beams in the energy range of 100 eV up to 30 keV. Ions will be produced with the use of ion sources that are currently available at the facility.
The branch will provide beams: a) for implantation of gases into solid targets, b) for the creation of Nitrogen-Vacancy centres in diamond ** needed for quantum computing research, c) for simulation of the effects of solar wind on the lunar surface, d) for studies of ion-gas reactions at low energies and e) for commissioning of ion optics and testing of machine learning algorithms for automatic beam control.
The branch will employ electrostatic steerers for beam position control, Einzel lenses for minimising beam size, a magnetic dipole to purify the ion beam and a Wien filter to produce ion beams with the highest possible monochromaticity.
The poster will present the progress and development of the ion optics, experimental stations and beam profile monitors designed for the above branch.
Polarized beam is an effective tool in basic research. An Electron-ion collider in China (EicC)*, as a future high energy nuclear physics project, has been proposed. Eicc can provide good research conditions for precision measurements of the partonic structure of nucleon or nuclei and the study on the interactions between nucleons and so on. High quality polarized beam is helpful to the accurate measurement of the relevant experiment date. Polarized proton and deuterium (H&D) beam source is one of the key technologies for EicC. Based on the atomic beam polarized ion source (ABPIS) scheme, a polarized H&D ion source with polarization more than 0.8 and beam current more than 1mA is under construction at the Institute of Modern Physics (IMP), providing theoretical and technical support for the design and construction of Eicc polarized source. In the ABPIS, the separating magnet ensures the electron polarization and the effective transmission of the atomic beam; the radiofrequency transition(RFT) unit ensures that the electronic polarization is converted into deserved nuclear polarization. In order to generate high intensity and high polarization H&D atomic beam, these assemblies need to be precisely designed and optimized. In the paper, key issues such as electron polarization, nuclear polarization and atom transmission is studied.
The muon-dedicated linear accelerator is being developed for the muon g-2/EDM experiment at J-PARC. To suppress the decay loss during acceleration, the alternative phase focusing (APF) method inter-digital H-mode drift tube linac (IH-DTL) is adopted in the low-velocity region following a radio-frequency quadrupole linac (RFQ). We are planning to accelerate muons in 2024 using the RFQ and the IH-DTL which will accelerate muons from 8% to 30% of the speed of light with an operating frequency of 324 MHz. After the IH-DTL, a diagnostic beamline will be placed to measure the beam energy and quality after acceleration, and its design, which consists of magnets and bunchers, is underway. In this poster, we will report on the development status of the diagnostic beamline.
Standard methods of measuring the transverse beam profile are not adaptable for sufficiently high-intensity beams. Therefore, the development of non-invasive techniques for extracting beam parameters is necessary. Here we present experimental progress on developing a transverse profile diagnostic that reconstructs beam parameters based on images of an ion distribution generated by beam-induced ionization. Laser-based ionization is used as an initial step to validate the electrostatic column focusing characteristics, and different modalities, including velocity map imaging. This paper focuses on measurements of the ion imaging performance, as well as the dependence of Ion intensity on gas density and incident beam current for low-energy electron beams (<10 MeV).
For the purpose of indirect search of dark matter, we designed laterally driven Dielectric Laser Acceleration (DLA) structure that achieves 1.2 MeV energy gain in 6 mm length together with 6D confinement. The design originated from a relativistic DLA structure and was supplemented with non-homogeneous shapes following the APF segments and optimized using a genetic algorithm together with the DLAtrack6D tracker. The achieved throughput could be increased to 98%.
Solid-state plasma wakefield acceleration might be an alternative to accelerate particles with ultra-high accelerating gradients, in the order of TV/m.
In addition, due to their thermodynamic properties, 2D carbon-based materials, such as graphene layers and/or carbon nanotubes (CNT) are good candidates to be used as the media to sustain such ultra-high gradients. In particular, due to their cylindrical symmetry, multi-nm-aperture targets, made of CNT bundles or arrays may facilitate particle channelling through the crystalline structure.
In this work, a two-bunch, driver-and-witness configuration is proposed to demonstrate the potential to achieve particle acceleration as the bunches propagate along a CNT-array structure.
Particle-in-cell simulations have been performed using the VSIM code in a 2D Cartesian geometry to study the acceleration of the second (witness) bunch caused by the wakefield driven by the first (driver) bunch.
The effective plasma-density approach was adopted to estimate the wakefield wavelength, which was used to identify the ideal separation between the two bunches, aiming to optimize the witness-bunch acceleration and focusing.
Simulation results show the high acceleration gradient obtained, and the energy transfer from the driver to the witness bunch.
The CLEAR facility at CERN allows users to receive an electron beam with energy up to 200 MeV, allowing flexibility in intensity, beam size and bunch structures. Separate from the main CERN accelerator complex, it is capable of hosting numerous experiments with rapid installations at two test stands.
It would be highly desirable for many applications, but particularly those of a medical nature, to be able to provide a ‘flat’ beam at CLEAR, with a uniform intensity distribution over a significant component of its transverse dimensions.
Over the winter shutdown 2022-2023, a dual-scattering system has been installed in the CLEAR beamline to generate such a beam distribution. It was placed several metres upstream of the beamline end to reduce X-ray contamination in the flattened beam and increase total transmission of the beam. Studies on the flattened beam composition in terms of structure and dose were carried out, utilising a dipole directly upstream of the in-air test stand to separate the electron and X-ray components for analysis.
Vertical orbit excursion Fixed Field Accelerators (vFFAs) feature highly non-linear magnetic fields and strong transverse motion coupling. The detailed study of their Dynamic Aperture (DA) requires computation codes allowing long-term tracking and advanced analysis tools to take the transverse motion linear and non-linear coupling into account. This coupling completely transforms the beam dynamics compared to a linear uncoupled motion, and an explicit definition of the DA is needed to characterize the performance and limitations of these lattices. A complete study of the DA in the 4D phase space in highly non-linear and strongly coupled machines must give a measure of the stability domain but also means to assess the operating performance in the physical coupled space. This work presents a complete set of methods to perform such detailed analysis. These methods were explored and compared to compute and characterize the DA of an example vFFA lattice. The whole procedure can be further applied to evaluate DA using realistic models of the magnetic fields, including fringe fields and errors.
High temperature superconductor REBCO has the property of maintain a high critical current density under strong external magnetic field, which makes a promising material for electromagnets in cyclotron and ECR ion source. Therefore, an ECR ion source using iron-less REBCO coils as electromagnet is under development in Research Center for Nuclear Physics (RCNP), Osaka University. A coil system with 3 circular solenoid coils and 6 racetrack sextupole coils was fabricated, and low-temperature performance tests in 77 K were carried out. The test results upon the stability and capability of magnet field inducing will be presented in this work. The design of the ion source will also be discussed. Results yielded in this research will also be made the best use of the development of a skeleton cyclotron, a compact air-core cyclotron being developed in RCNP, which is also planned to use REBCO coils as electromagnets.
Optical Stochastic Cooling (OSC) is a feedback beam cooling technique that uses radiation produced by a beam to correct particles' own momentum deviation. This system is made up of two undulator magnets, the pickup and kicker, separated by a bypass chicane that introduces a momentum-dependent path length. The beam produces radiation in the pickup and arrives in the kicker with a delay relative to its momentum, where it is coupled with the undulator radiation, receiving a corrective kick. The undulator radiation can be amplified to increase the strength of the corrective kick; this is done using an optical amplifier. The optical amplifier is driven by a pump laser which can be used to selectively amplify temporal slices of the undulator radiation. In this paper, we propose a method to use the amplified-OSC mechanism to create micro-bunches within the beam and study the performance of this multi-bunch-formation mechanism by considering diffusive effects and gain of the amplifier.
Ultrafast electron probing techniques offer unique experimental tools for investigating the structural dynamics of ultrafast photo-induced processes in molecular and condensed phase systems. In this work, we propose using the SEALAB Photoinjector's exceptional and versatile electron beam parameters to develop a state-of-the-art facility for ultrafast electron diffraction and imaging (UED and UEI) experiments with high sensitivity in space, energy, and time. We first address the design of an electron lens based on quadrupoles that enables easy switching between diffraction and direct imaging modes with minimal system changes. We compare the performance of the quadrupole-based lens with a simpler solenoid-based lens with similar functionality by calculating their respective aberration coefficients. Furthermore, we introduce the necessary beam-line modifications for enabling dark field imaging in the SEALAB Photoinjector. This development is crucial to achieve high-resolution imaging and enable the study of a wide range of material systems.
Polarization levels in the Electron Storage Ring (ESR) of the Electron-Ion Collider (EIC) must be maintained for a sufficient time before depolarized bunches are replaced. The depolarizing effects of synchrotron radiation can be minimized with spin matching, however the optics requirements for the ring must still be satisfied. Furthermore, the robustness of the polarization in the presence of misalignments, beam-beam effects, and the eventual insertion of a vertical emittance creator – necessary to match the electron and ion beam sizes at the interaction point – must be ensured. In this work, the results of various polarization analyses of the ESR lattices are presented, and their implications discussed; the necessity for a longitudinal spin match in the 18 GeV case is investigated, and vertical emittance creation schemes with minimal effects on polarization are analyzed.
Limited dynamic aperture which is in the consequence of strong nonlinearities in a low emittance storage ring, is a challenging issue from beam dynamics point of view. In the present study, we have applied three families of focusing and defocusing octupoles to the storage ring lattice with the aim of increasing dynamic aperture and beam lifetime . We have discussed different methods to optimize of the position and strength of octupoles so that each octupole family fights a specific resonance driving term.
The beam screen for the Future Circular hadron-hadron Collider (FCC-hh) has a baseline design based on a copper (Cu) coating. Calculations have indicated that the resistive wall impedance will be the major contributor to the beam impedance for the FCC-hh at both injection and collision and that Cu might be on the limit to ensure beam stability. To increase the safety margin, it is desirable to reduce the resistive wall impedance. In this contribution, we present an approach to reduce the beam impedance based on the reduction of the surface resistance of the beam screen coating by using High-Temperature Superconductors based on REBaCu3O7-x coated conductors (REBCO-CCs). These HTS-CCs have transition temperatures around 90K, and critical current densities which are high enough even in the presence of strong magnetic field, being therefore good candidates to substitute Cu in the FCC-hh beam screen which will be operating at around 50K and under a magnetic field of 16T. Using experimental data generated on the surface impedance of REBCO-CCs, CST simulations have been performed and the beam impedance has been estimated for an elliptical beam screen with the same vertical dimensions as that of a pure Cu beam screen. A position and REBCO-CCs contribution dependence study to determine the optimum beam screen configuration will be shown. Resistive wall impedance studies using an ellipse is a step forward towards determining the performance of the REBCO-CCs on the FCC-hh beam screen.
The ongoing Plasma-driven Attosecond X-ray source experiment (PAX) at FACET-II aims to produce coherent soft X-ray pulses of attosecond duration using a Plasma Wakefield Accelerator [1]. These kinds of X-ray pulses can be used to study chemical processes where attosecond-scale electron motion is important. For this first stage of the experiment, PAX plans to demonstrate that <100 nm bunch length electron beams can be generated using the 10 GeV beam accelerated in the FACET-II linac and using the plasma cell to give it a percent-per-micron chirp. The strongly chirped beam is then compressed in a weak chicane to sub-100nm length, producing CSR in the final chicane magnet at wavelengths as low as 10s of nm. In this contribution we describe the results expected from this initial setup, as well as future iterations of the experiment in which we plan to use short undulators to drive coherent harmonic generation to produce attosecond, terawatt X-ray pulses down to 1-2 nm.
In addition to PAX, a similar ongoing experiment at the XLEAP beamline at LCLS-II plans to demonstrate GW-scale attosecond pulses at UV wavelengths. We discuss tapering strategies which enable precise tuning of the XUV bandwidth and the generation of few-cycle micron wavelength pulses in this experiment which can be used for time-synchronized attosecond pump-probe experiments.
[1] C. Emma, X.Xu et al APL Photonics 6, 076107 (2021)
The Hefei Advanced Light Facility (HALF) is a diffraction limited storage ring (DLSR) being constructed. As the main component of the storage ring vacuum system, the vacuum chamber transports the beam and withstands the thermal effect of synchrotron radiation simultaneously. The thermal and mechanical condition of the vacuum chamber of HALF were quantitatively analysed by means of ANSYS WORKBENCH in this work. Combining the Computational Fluid Mechanics (CFD) and Finite Elements Analysis (FEA), the temperature and thermal stress maps of the vacuum chamber were calculated. The CFD calculation displays that the heat transfer coefficient between the water and the chamber is 7966-13093 W/(m2·℃). The thermal-mechanical simulation shows that the maximum temperature and thermal stress are 53.5 °C and 42.1 MPa, respectively. The static structural analysis was performed on vacuum chamber under the ultra-high vacuum condition, with the maximum stress of 1.7 MPa and the maximum deformation of 0.0003 mm. These results show that the vacuum chamber meets the design requirements and provide a critical theoretical basis for the design of the vacuum system of HALF.
Within the framework of FLASH2020+, substantial parts of the injector of the FEL user facility FLASH have been upgraded during a nine-month shutdown in 2022 to improve the electron bunch properties in preparation for FEL operation with external seeding starting in 2025. As part of the injector upgrade, a laser heater has been installed upstream of the first bunch compression chicane to control the microbunching instability in the linear accelerator by a defined increase of the uncorrelated energy spread in the electron bunches. In this paper, we present first results of beam heating studies at FLASH. Measurements of the induced energy spread are compared to results obtained by particle tracking simulations.
For the first time, photoemission of spin-polarized electron beams from gallium nitride (GaN) photocathodes are observed and characterized. The spin polarizations of the emitted electrons from epitaxially grown hexagonal and cubic GaN photocathodes activated to Negative Electron Affinity (NEA) via cesium deposition are measured in a retarding-field Mott polarimeter.
Chromaticity up to the third order in the LHC has been well observed in the LHC’s first and second operational runs, with regular beam-based measurements performed during commissioning and machine development. In previous runs however, no higher-order chromaticity could be observed. In 2022, dedicated collimators setups meant optics measurements could benefit from an improved range of momentum-offset for the chromaticity studies. This allowed the observation of fourth and fifth order chromaticity in the LHC at 450GeV for the first time. Measurements were performed for several machine configurations. In this paper, results of the higher order non-linear chromaticity are presented and compared to predictions of the LHC magnetic model.
Upcoming projects requiring ~650 MHz medium-to-high-beta elliptical cavities such as Michigan State University’s Facility for Rare Isotope Beams’ energy upgrade and Fermilab’s Proton Improvement Project-II drive a need to understand magnetic RF loss mechanisms in greater detail. It remains to be seen whether flux trapping mitigation techniques used in 1.3 GHz cavities are as effective at ~650 MHz, given differences in cavity geometry, material of manufacture vendor, and frequency-dependent superconducting RF dynamics. We explore the fast-cooldown method, and high-temperature annealing (900°C), which promote flux-expulsion efficiency, but are more difficult to implement in ~650 MHz cavities. In high-power RF testing, we measure the cool-down temperature gradient vs flux expulsion efficiency, the cavity’s residual resistance sensitivity to trapped flux as a function of cavity treatment. We further used the Physical Property Measurement System available at Fermilab to directly measure the flux pinning force in bulk niobium samples, and correlate changes in the flux pinning force with different niobium vendors, heat treatments, and cavity flux expulsion performance.
Energy recovery linacs (ERLs) possess bright prospect of the fully coherent x-ray generation. Recently, we designed a 600 MeV energy recovery linac capable of producing high power fully coherent radiation pulses at 13.5 nm with a relatively low-intensity 256.5 nm seed laser profited from the employment of angular-dispersion-induced microbunching (ADM) technology. We also designed a matched multiplexed system that can deflect each radiator by 8 mrad with a carefully choreographed multi-bend achromat (MBA) scheme. As a result of downstream MBA’s dispersion compensation, bunching factors will be enhanced both at fundamental wavelength and high harmonics. The bunching factor of the 19th harmonic increased from 10% to 26%, and that of the 57th harmonic became 7.8%, which is sufficient to generate fully coherent radiation in the soft X-ray range.
A periodic system of spirally arranged magnetized annular sectors creates near the axis a helical field, which is close in structure and magnitude to the field in the set of helical magnets. Such a system of relatively few available magnets can be easier to manufacture and assemble than a system containing magnetized helices made from a single piece. In this paper, we theoretically study the dependence of the helical field on the number of sectors per undulator period. Short prototypes consisting of longitudinally and radially magnetized sectors, as well as a hybrid system assembled from longitudinally magnetized NdFeB sectors and preliminarily non-magnetized steel helices, was experimentally studied. The maximum measured value of the field on the axis of an undulator with a period of 2 cm and a relatively large inner diameter of 8 mm is 0.7 T. Such undulators can provide a large oscillatory electron velocity and seem promising for increasing the efficiency of FELs and IFELs in various frequency ranges.
Charged particles moving through a carbon nanotube may be used to excite electromagnetic modes in the electron gas produced in the cylindrical graphene shell that makes up a nanotube wall. This effect has recently been proposed as a potential novel method of short-wavelength-high-gradient particle acceleration. In this contribution, the existing theory based on a linearised hydrodynamic model for a localised point-charge propagating in a single wall nanotube (SWNT) is reviewed. In this model, the electron gas is treated as a plasma with additional contributions to the fluid momentum equation from specific solid-state properties of the gas. The governing set of differential equations is formed by the continuity and momentum equations for the involved species. These equations are then coupled by Maxwell’s equations. The differential equation system is solved applying a modified Fourier-Bessel transform. An analysis has been realised to determine the plasma modes able to excite a longitudinal electrical wakefield component in the SWNT to accelerate test charges. Numerical results are obtained showing the influence of the damping factor, the velocity of the driver, the nanotube radius, and the particle position on the excited wakefields. A discussion is presented on the suitability and possible limitations of using this method for modelling CNT-based particle acceleration.
Magnetic field errors pose a limitation in the performance of circular accelerators, as they excite non-systematic resonances, reduce dynamic aperture and may result in beam loss. Their effect can be compensated assuming knowledge of their location and strength. Procedures based on orbit response matrices or resonance driving terms build a field error model sequentially for different accelerator sections, whereas a method detecting field errors in parallel yields the potential to save valuable beamtime. We introduce deep Lie map networks, which enable construction of an accelerator model including multipole components for the magnetic field errors by linking charged particle dynamics with machine learning methodology in a data-driven approach. Based on simulated beam-position- monitor readings for the example case of SIS18 at GSI, we demonstrate inference of location and strengths of quadrupole and sextupole errors for all accelerator sections in parallel. The obtained refined accelerator model may support set up of corrector magnets in operations to allow precise control over tunes, chromaticities and resonance compensation.
The LHC particle-physics program requires that the delivered luminosity be measured to an absolute accuracy in the 1% range. To this effect, the absolute luminosity scale at each interaction point (IP) is calibrated by scanning the beams across each other according to the van der Meer method. During such scans, the orbit and the shape of the colliding bunches are significantly distorted by their mutual electromagnetic interaction; the resulting biases, if left uncorrected, would absorb a major fraction of the systematic-uncertainty budget on the luminosity calibration. The present report summarizes recent studies of such biases in the single-IP configuration, and generalizes it to the more typical case where bunches collide not only at the scanning IP, but also experience additional head-on encounters at up to 3 locations around the ring. Simulations carried out with the COherent-Multibunch Beam-beam Interaction multiparticle code (COMBI) are used to characterize the dependence of beam--beam-induced luminosity-calibration biases on the phase advance between IPs, and to derive scaling laws that relate the multi-IP case to the simpler and better understood single-IP configuration.
Impedance-induced tune shifts and instability growth rates in the CERN Proton Synchrotron are studied thanks to the recently updated impedance model of the machine. Calculation of these beam observables are obtained using both Vlasov solvers and macroparticle tracking simulations, and are compared with those observed during dedicated measurement campaigns. Thanks to improvements in the measurement procedure, including the careful monitoring of losses, bunch length, linear coupling and chromaticity, uncertainties on the tune shifts were noticeably reduced compared to previous years. Finally, the effect of linear chromaticity on tune shift slopes and growth rates has been examined, allowing for a detailed comparison with both past measurements and simulations.
Free-electron lasers (FEL) producing ultra-short X-ray pulses with high brightness and continuously tunable wavelength have been playing an indispensable role in the field of materials, energy catalysis, biomedicine, and atomic physics. A core challenge is to maintain and improve the transverse overlap of the electron and laser beams. This requires high-dimensional, high-frequency, closed-loop control with magnetic elements, further complicated by the diverse requirements across a wide range of wavelength configurations. In this work, we introduce a proximal policy optimization architecture for FEL commissioning that autonomously learns to control the set of magnetic elements. We experimentally demonstrated the feasibility of this technique on the alignment of electron beams and laser beams automatically in Shanghai Soft X-Ray Free Electron Laser User Facility, by adjusting groups of corrector magnets to maximize the FEL output power.
The IBA ProteusOne (P1) system is suitable to treat ocular tumors and achieves efficient dose conformality using state-of-the-art pencil beam scanning. Nevertheless, with the limited cyclotron current of the P1 system, clinically relevant (> 15 Gy/min) dose rates can barely be achieved in eye tumors treatment cases with the baseline configuration of the system due to the significantly high energy degradation required (from 230 to 70 MeV). One way to improve this dose rate is to modify the degrader to use a material causing a smaller emittance increase. In this work, we compare the performances of the P1 system in the context of eye tumors treatment when using Beryllium degrader on the one hand and Diamond degrader on the other. For the latter case, the optics is modified to reduce the losses along the beamline and ultimately increase the dose rate of the system while maintaining a symmetrical spot at the isocenter. Using Beam Delivery SIMulation, the dosimetric properties of the system are assessed and compared for the two configurations, and the differences in dose rate are quantified and discussed in detail.
The future AMBER experiment aims to measure the inner structure and the excitation spectra of kaons with a high intensity kaon beam at the CERN secondary beam line M2. One way to identify the small fraction of kaons in the available beam is tagging with the help of differential Cherenkov detectors (CEDARs), whose detection efficiency depends critically on the beam parallelism. In the framework of the Conventional Beams Working Group of the Physics Beyond Colliders Initiative at CERN, several possible improvements of the conventional beam optics have been studied, trying to achieve a better parallelism, investigating especially the reduction of multiple scattering. Additionally, with the aim of increasing the Kaon purity of the beam, a Radio-Frequency separation technique has been also studied. This method exploits the differences in velocity due to the particle mass in the beam, kicking out unwanted particles with the help of two RF cavities. The limitations posed by the beam line for intensity and purity will be presented along with preliminary results of the potential purity and intensity reach of the RF-separated beam. Finally, the RF-separated beam is compared with the conventional hadron beam in terms of potential physics reach.
Diffraction-limited light sources have garnered significant interest -- yet the smaller equilibrium size of their electron bunches also reduces the beam-lifetime. One remedy is to vertically excite the electron beam, for instance using a Multi Bunch Feedback (MBF) system. Previous work has demonstrated that this approach can safely increase the vertical emittance, thus beam-lifetime. However, not all operational vertical emittances are created equal. Driving the beam at frequencies near resonances can generate large coherent beam-centroid motion that results in an enlarged apparent photon-source. In this work, we present a methodology, justified with theoretical reasoning and simulation, that finds the optimal combination of frequency and kick strength that satisfies both the operational requirements and the beamline interests. The methodology is then demonstrated for the Diamond-II lattice, including short-range wake effects.
Landau damping plays a crucial role in preserving single-bunch stability. In view of delivering the beam to the High-luminosity LHC (HL-LHC), the Super Proton Synchrotron (SPS) must double the intensity per bunch. In this intensity range, the loss of Landau damping (LLD) in the longitudinal plane can pose an important performance limitation. Observation of the beam response to a rigid-bunch dipole perturbation is a common technique to study the LLD. This contribution presents measurements for a single bunch at 200 GeV in a double-harmonic RF system with a higher harmonic voltage at four times the fundamental RF frequency are presented, showing the impact on Landau damping. Beyond the analytical estimates, the observations are moreover compared to the results from novel stability criteria implemented in the semi-analytical code MELODY, as well as with macroparticle simulation in BLonD.
The photon flux resulting from a high energy electron beam's interaction with a target, such as in the upcoming FACET-II experiments at SLAC National Accelerator Laboratory, should yield, through its spectral and angular characteristics, information about the electron beam's underlying dynamics at the interaction point.
This project utilizes data from simulated plasma wakefield acceleration-derived betatron radiation experiments and high-field laser-electron-based radiation production to determine which methods could most reliably reconstruct these key properties. The data from these two cases provide a large range of photon energies; this variation of photon characteristics increases confidence in each analysis method. This work aims to compare several reconstruction methods and determine which best predicts original energy distributions based on simulated spectra.
PERLE (Powerful Energy Recovery LINAC for Experiment) is a high-power Energy Recovery LINAC (ERL) facility with 20 mA beam current and beam energy from 250 MeV to 500 MeV featuring three passes through two cryomodules. It is a hub for validation of the ERL technology development towards future energy and intensity frontier machines. Design challenges of PERLE and its beam parameters make it a testbed to validate multi-turn high current ERL operation for the LHeC. It will be the first ERL for some pioneering experiment of the eN interaction with radioactive nuclei.
In this work, design and optimization of the commutational magnet (B-com) used to spread/combine the three beams and one series of the quadrupole magnet is discussed. It gives the design parameters including: yoke geometry, pole profile, and material, and calculation of the excitation current needed to drive the magnet, the coil parameters and the number of turns.
The B-com magnet is optimized for a 30° bending angle with magnetic field of 0.88 T along the magnet length and a harmonic content of 0.036%. The quadrupole magnet is designed for a gradient field of 34.15 T/m and experiences saturation above this value. Further studies to avoid saturation and achieve the maximum gradient of 44.1 T/m required by the beam dynamics is undergoing.
An 800 MHz, Radio Frequency Quadru-pole (RFQ) was designed to accelerate the proton beam to 2 MeV energy at a distance shorter than one meter in KAHVE-Lab, Turkey. A half-length test module was previously produced to investigate the local manufacturability of this RFQ cavity. The manufactured test module was subjected to mechanical, vacuum and electromagnetic tests to adjust the pressure, EM field and frequency parameters to the desired operational settings. Results from these tests were used to improve the final manufacturing process for the two modules of the RFQ which ended successfully in Q4 2022. The finished RFQ, after being fully assembled for the first time, will initially be subjected to vacuum tests followed by low-level RF and power tests. The KAHVE-Lab proton beamline is planned to be fully integrated and commissioned by the end of 2023. This study introduces a general framework about the current status of the 800 MHz RFQ, and discusses the ongoing commissioning studies.
Nb3Sn superconducting radiofrequency (SRF) cavities have been an ongoing research topic for many years motivated by the potential for higher accelerating gradients and quality factors compared to niobium SRF cavities. The highest performing Nb3Sn cavities are manufactured using tin vapor-diffusion coating, which creates a Nb3Sn film with a surface roughness of around 100-200 nm. This is thought to be one of the limiting factors for the accelerating gradient of Nb3Sn cavities due to enhancement of magnetic field near sharp surface features. To smooth Nb3Sn SRF cavities, we have developed a mechanical polishing procedure which uses centrifugal barrel polishing to smooth the surface followed by a secondary tin coating step to repair the surface. We show that the accelerating field of a Nb3Sn SRF cavity is improved by applying this procedure. We also investigate the quench mechanism of the polished cavity by utilizing temperature mapping to measure which regions of the cavity experience heating during RF operation. We then cut samples from these regions and analyze the film microstructure and chemical composition in 3D using EDS and EBSD measurements together with a focused ion-beam (FIB) tomography technique.
One of the most fundamental measurements since the Higgs boson discovery, is its Yukawa couplings. Such a measurement is only feasible, if the centre-of-mass (CM) energy spread of the e+e- collisions can be reduced from ~50 MeV to a level comparable to the Higgs boson’s natural width of ~4 MeV. To reach such desired collision energy spread and improve the CM energy resolution in colliding-beam experiments, the concept of a monochromatic colliding mode has been proposed as a new mode of operation in FCC-ee. This monochromatization mode could be achieved by generating a nonzero dispersion function of opposite signs for the two beams, at the Interaction Point (IP). Several methods to implement a monochromatization colliding scheme are possible, in this paper we report the implementation of such a scheme by means of dipoles. More in detail a new Interaction Region (IR) optics design for FCC-ee at 125 GeV (direct Higgs s-channel production) has been designed and the first beam dynamics simulations are in progress.
IFMIF-DONES* is a key device in the EUROfusion roadmap for studying and licensing materials for future fusion reactors. It will be a unique neutron fusion-like irradiation facility equipped with a linear particle accelerator impinging an intense deuteron beam (125 mA, 40 MeV) onto a liquid lithium target. In terms of safety analysis of the facility, relevant accidental scenarios are related to the technical impossibility of having a separation window between the liquid lithium target chamber and the accelerator vacuum chambers. In case of Loss of Vacuum Accident (LOVA), such as a sudden air/water inrush or leakage in the accelerator or target vacuum chambers, the beam duct could serve as a transport line and lead to air/water contact with liquid lithium, with the risk of exothermic reaction. The use of Fast Isolation Valves (70-100 ms closing time) is envisaged as mitigation mechanism for these events. The MuVacAS Prototype is an experimental setup to study in detail these scenarios and validate the Safety Credited mitigation requirements. For this purpose, it recreates the last 30 meters of the accelerator and target vacuum chambers and, it is equipped with dedicated instrumentation and modules for simulating LOVAs. This contribution presents an overview of the experimental setup together with preliminary numerical simulation of these accidental events.
Optical Transition Radiation (OTR) is commonly used in imaging systems of highly relativistic charged particle beams as the light yield and collection efficiency would increase with beam energy. For low beam energies, scintillating screens are typically preferred but would saturate or even get damaged when using high beam current. For such a beam, OTR screens can, therefore, still be an attractive diagnostic tool when using thermally resistant materials such as Glassy Carbon. This work presents the OTR based beam imaging measurements of a high-intensity low energy (7keV) hollow electron beam at the Electron Beam Test Stand at CERN. The mechanical design of the monitor as well as the expected OTR angular distribution are presented. Beam images performed with an aluminium oxide scintillating screen are also shown and compared to the OTR results.
This paper proposes a new coupling slots design for the Pi-Mode structure high-frequency cavity in the China Spallation Neutron Source (CSNS) Phase II. Through simulation calculations and experimental verification, it was found that the new coupling slots design significantly improves the Q value and transmission efficiency of the high-frequency cavity. This study is of great significance for improving the performance of the high-frequency cavity in CSNS II, and thus improving the accuracy and efficiency of neutron scattering experiments.
One of the Grand Challenges in beam physics relates to the use of virtual particle accelerators for beam prediction and optimization. Useful virtual accelerators rely on efficient and effective methodologies grounded in theory, simulation, and experiment. This work extends the application of the Sparse Identification of Nonlinear Dynamical systems (SINDy) algorithm, which we have previously presented at the North American Particle Accelerator Conference. The SINDy methodology promises to simplify the optimization of accelerator design and commissioning by discovery of underlying dynamics. We extend how SINDy can be used to discover and identify underlying differential systems governing the beam’s sigma matrix evolution and corresponding invariants. We compare discovered differential systems to theoretical predictions and numerical results. We then integrate the discovered differential system forward in time to evaluate model fidelity. We analyze the uncovered dynamical system and identify terms that could contribute to the growth(decay) of (un)desired beam parameters. Finally, we propose extending our methodology to the broader community's virtual and real experiments.
Electropolishing (EP) and buffered chemical polishing (BCP) are conventional surface preparation techniques for superconducting radiofrequency (SRF) cavities that remove damaged material from the cavity surface. One main issue with EP and BCP treated SRF cavities is high field Q-slope (HFQS), a drop in quality factor at high gradients that limits quench field. High gradient performance in EP cavities can be improved by applying a low temperature bake (LTB), but LTB does not consistently remove HFQS in BCP cavities. There is no consensus as to the why LTB is not effective on BCP prepared cavities, and the cause of HFQS in BCP cavities is not well understood. We examine the origins of quench in EP, BCP, EP+LTB, and BCP+LTB treated SRF cavities. We also show the effect of these treatments on the onset of HFQS, heating within the cavity up to quench, concentration of free hydrogen, and surface roughness.
The cryocooled DC electron gun at Arizona State University (ASU) is the first electron gun built to implement single-crystal, ordered surface and epitaxially grown photocathodes to produce cold and dense electron beams at the source. These high brightness electron sources are extremely desirable for ultrafast electron applications such as Xray Free Electron Lasers (XFELs), Ultrafast Electron Diffraction/Microscopy (UED/UEM), and electron-ion colliders. Electron beams are produced from a cryogenically cooled photocathode using a tunable wavelength LASER to emit electrons close to the photoemission threshold. The full four-dimensional transverse phase space of the electron beam can be measured by a single pinhole scan technique, allowing us to directly calculate the transverse emittance in both dimensions. In this contribution we report and discuss the beamline setup and first measurement results.
Integrating the advances made in photonics with efficient electron emitters can result in the development of next generation photocathodes for various accelerator applications.
In such photonics-integrated photocathodes, light can be directed using waveguides and other photonic components on the substrate underneath a thin (<100 nm) photoemissive film to generate electron emission from specific locations at sub-micron scales and at specific times at 100 femtosecond scales along with triggering novel photoemission mechanisms resulting in brighter electron beams and enabling unprecedented spatio-temporal shaping of the emitted electrons. In this work we have demonstrated photoemission confined in the transverse direction using a nanofabricated Si3N4 waveguide under a ∼20 nm thick cesium antimonide (Cs3Sb) photoemissive film. This work demonstrates a proof of principle feasibility of such photonics-integrated photocathodes and paves the way to integrate the advances in the field of photonics and nanofabrication with photocathodes to develop next-generation high-brightness electron sources for various accelerator applications.
We present the latest updates to the PLACET3 tracking package which focus on the impact of both transverse and longitudinal wakefields on a beam travelling through accelerating and decelerating structures. The main focus of this update was the first implementation of 6D tracking through Power Extraction and Transfer Structures (PETS) for the Compact Linear Collider (CLIC) which is described through short and long-range longitudinal wakefields. Additionally, we present the impact of different numerical schemes on the computation of wakefields in accelerating structures.
In this paper we will show the injection philosophy and the design of timing and filling scheme for high luminosity CEPC scheme under different energy modes. It is found that the RF frequency choice in CDR cannot meet the injection requirements for the bunch number at Z pole. A modified scheme was proposed to support the design luminosity,which basically meets our current design requirements and retains more flexibility for future high luminosity upgrade.
Recent studies showed significant improvement in quantum efficiency (QE) by negative electron affinity (NEA) GaAs nanopillar array (NPA) photocathodes over their flat surface peers, particularly at 500 ─ 800 nm waveband. However, the underlying physics is yet to be well understood for further improvement in its performance. In this report, NEA GaAs NPA photocathodes with different dimensions were studied. The diameter of the nanopillars varied from 200 ─ 360 nm, the height varied from 230 ─ 1000 nm and the periodicity varied from 470 ─ 630 nm. The QE and photocathode lifetime were measured. Mie-resonance enhancement was observed at tunable resonance wavelengths. Simulations was also performed to understand the mechanism of photo-absorption and possible ways to further improve the photocathode performance to meet the stringent requirement of the electron sources in large scale electron accelerators.
Acknowledgement
Authored by Jefferson Science Associates, LLC under U.S. DOE contract no. DE-AC05-06OR23177. The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for U.S. Government purposes.
*mrahm008@odu.edu
The Large Hadron Collider at CERN is equipped with instruments that exploit collisions between beam particles and gas targets, one of them being the Beam Gas Vertex monitor. By design, its operation generates secondary particle showers used to measure beam properties, that also result in radiation levels in the tunnel proportional to the beam intensity and gas pressure. In this work, the radiation showers are characterised using measured data from LHC Run 2 operation and Monte Carlo simulations with the FLUKA code, and predictions are made for the operation of these devices in the HL-LHC era.
As a scientific system with many subsystems, particle accelerator system is getting more complex， due to rising demands on accelerator performance. Meanwhile, it is increasingly difficult to study such complex systems using traditional research methods based on physical models. At present, machine learning (ML) is mature enough to be applied in accelerator science such as beam diagnostics and equipment control. Compared with traditional research methods, machine learning has strong generality and high computational efficiency. However, problems such as incomplete database or insufficient test time often hinder the application of ML in accelerator operation control and optimization.
To further explore the application of ML in accelerator science, in this paper, we demonstrate the feasibility of reinforcement learning in accelerator control using: 1) replacement model of linear accelerator components based on neural network; and 2) reinforcement control and fast matching of the LEBT and RFQ of the linear accelerator, which is based on reinforcement learning. These methods will be experimentally verified on a linear accelerator.
As the precise sensor system for monitoring the rela-tive altitude changes among multiple points, the capacity hydrostatic leveling system (HLS) is widely used in particle accelerators. To expand its application in provid-ing the elevation constraint for the control network ad-justment, the research on the issue of the HLS for alti-tude difference measurement between multiple points is carried out. Based on the working principle of the HLS sensor, a comparison system composed of dual-frequency laser interferometer, high-precision Z stage, HLS sensors and others is designed and manufactured. The system is used to control multiple sensors to observe the same liquid level in the same coordinate system. The zero-position difference among sensors can be obtained by comparison. Then the altitude difference measure-ment can be realized, and it is verified that the measure-ment accuracy is better than 5 μm. In addition, a simula-tion experiment for 3D control network measurement is run, in which the HLS system provides the elevation constraint for the adjustment processing. The results show that for the 100m linear tunnel, the errors accumu-lation in the elevation direction is significantly improved compared to the classics adjustment.
The CERN Super Proton Synchrotron (SPS) aims at providing stable proton spills of several seconds to the North Area (NA) fixed target experiments via third-integer resonant slow extraction. However, low-frequency power converter ripple (primarily at 50 and 100 Hz) and high-frequency structures (mainly at harmonics of the revolution frequency) modulate the extracted intensity, which can compromise the performance of the data acquisition systems of the NA experiments. In this contribution, the implementation of Radio Frequency (RF) techniques for spill quality improvement is explored, with particular focus on empty bucket channelling. It is shown that both the main RF systems (at 200 and 800 MHz) can be successfully exploited to improve the SPS slow extraction.
Externally seeded high-gain free electron lasers (FELs) are capable of providing fully coherent radiation with high shot-to-shot stability at wavelengths down to the soft X-ray range.
However, present seed laser sources are not suitable for the generation of short wavelength FEL radiation at high repetition rates. As a result, such setups have been unable to make use of the full repetition rate of superconducting machines.
Cavity-based FELs have been proposed as one possible way to overcome these limitations, allowing to combine short wavelengths and high repetition rates, while preserving the full coherence.
We present simulation studies for such a high-gain FEL oscillator planned for FLASH, which is aimed at the generation of fully coherent radiation at 13.5 nm and the repetition rate of 3 MHz. Achieving bunching on that wavelength would make it possible to generate fully coherent radiation at much shorter wavelengths with the use of harmonic conversion schemes.
In the KIT storage ring KARA (Karlsruhe Research Accelerator), two parallel plates with periodic rectangular corrugations are planned to be installed. These plates will be used for impedance manipulation to study and eventually control the electron beam dynamics and the emitted coherent synchrotron radiation (CSR). In this contribution, we present simulation results showing the influence of different corrugated structures on the longitudinal beam dynamics and how this influence depends on the machine settings in the low momentum compaction regime, which are related to the bunch length changes.
The effect of radiation reaction is often negligible in inverse Compton scattering. However, in the nonlinear Compton regime, at high laser fields and high electron beam energies where electron recoil must be properly accounted for, there is experimental data which demonstrates the onset of radiation reaction * . We model the radiation reaction as a series of emissions from individual electrons with decreasing energy. This allows us to use the code we previously developed for simulating single-emission inverse Compton scattering events ** . We use the new code to simulate the experiment reported in Cole et al. 2018, and to compare it to other models of radiation reaction.
Fixed Field Accelerators are a candidate for future hadron cancer therapy facilities as their high repetition rate and large energy acceptance enables novel treatment modalities such as high dose rate FLASH. However, conventional dose delivery mechanisms are still necessary, requiring continuous beam delivery over 1--30s. This work is the first study of slow extraction from a scaling Fixed Field Accelerator, using the LhARA facility for baseline parameters. At a horizontal tune of 10/3, the intrinsic sextupole strength of the nonlinear FFA magnetic field is sufficient to excite the resonance, although extraction is better controlled using an additional excitation sextupole at a tune close to 8/3, with radiofrequency knock-out extraction. Including considerations of issues due to nonlinear fields and limitations required to keep the tune energy-independent, slow extraction from Fixed Field Accelerators is successfully demonstrated.
The high precision measurement of the centre-of-mass energy in the Future Circular Collider e+e- (FCC-ee) at Z and W energies can be realized through resonant spin depolarization utilizing transversely polarized beams. This requires a guaranteed sufficiently-high spin polarization in the presence of lattice imperfections. Investigations of the impact of misalignments on the equilibrium polarization are conducted using analytical and Monte-Carlo spin simulations with Bmad. Potential optimization schemes to ensure high polarization using orbit bumps have been explored.
With the high beam current in storage ring, it is necessary to consider the instability problem caused by the heavy beam loading effect. It has been demonstrated that direct RF feedback (DRFB), autolevel control loop (ALC) and phase-lock loop (PLL) in the main cavity can lessen the impact of the beam effect. This paper regarded the beam, main cavity, harmonic cavity and feedback loops as double harmonic cavity system, and extended the transfer functions in the Pedersen model to this system. Some quantitative evaluations of simulation results have been got and conclusions have been drawn. In the case of a passive harmonic cavity, the optimization strategy of the controller parameters in the pre-detuning , ALC and PLL, as well as the gain and phase shift of DRFB were discussed. Meanwhile, it also involved the impact of the harmonic cavity feedback loop on the system stability at the optimum stretching condition when an active harmonic cavity was present. The research results can be used as guidelines for beam operation with beam current increasing in the future.
In recent years, high-gradient, symmetric focusing with active plasma lenses has regained significant interest due to its potential advantages in compactness and beam dynamics compared to conventional focusing elements. A promising application could be optical matching of highly divergent positrons from the undulator-based ILC positron source into the downstream accelerating structures to increase the positron yield.
In a collaboration between University Hamburg and DESY Hamburg a downscaled prototype for this application has been developed and constructed. Here, we present the current status of the prototype development.
Superconducting dipoles with a strong curvature (radius smaller than 2 meters, for an aperture of about 100 mm and a length of 1-3 meters) are required for applications where compactness is key, such as the synchrotron and gantry for Carbon-ion therapy developed within the European program HITRIplus.
Such magnets challenge several assumptions in the field description and put to the test the range of validity of beam optics codes. In particular, the equivalence that holds for the straight magnets between the transverse multipoles description obtained from the Fourier analysis (used for magnet design and measurements) and the Taylor expansion of the vertical field component along the horizontal axis (used in beam optics) is not valid any longer. A proper fringe field modelling also becomes important, due to the curved geometry and the aperture being large compared to the magnetic length.
We explore the feasibility and the limits of modeling such magnets with optics elements (such as sector bends and multipoles), which allows parametric optics studies for optimization, field quality definition and fast long-term multi-pass tracking.
Modelling electron cloud driven instabilities using a Vlasov approach enables studying the beam stability on time scales not accessible to conventional Particle In Cell simulation methods. A linear description of electron cloud forces, including the betatron tune modulation along the bunch, is used in the Vlasov approach. This method is benchmarked against macroparticle simulations based on the same linear description of electron cloud forces. Applying high chromaticity settings is the main mitigation strategy for these instabilities. The effect of chromaticity can be taken into account using the Vlasov method. The Vlasov approach agrees with macroparticle simulations for strong electron clouds, and a stabilizing effect from positive chromaticity can be seen in both approaches. For positive chromaticity, the Vlasov approach shows the existence of weak instabilities which are not observed in the macroparticle simulations. This feature suggests the existence of damping mechanisms that are not captured by the linearized Vlasov equation.
The development of compact accelerator facilities providing high-brightness beams is one of the most challenging tasks in the field of next-generation compact and cost affordable particle accelerators. Recent results obtained at SPARC_LAB show evidence of the FEL laser by a compact (3 cm) particle beam plasma accelerator. This work is carried out in the framework of the SPARC_LAB activities concerning the R&D on particle-driven plasma wakefield accelerators for the realization of new compact plasma based facilities i.e EuPRAXIA@SPARC_LAB. The work here presented is a theoretical study demonstrating a possible scheme concerning the implementation of an innovative array of discharge capillaries, operating as active-plasma lenses, and one collimator to build an unconventional transport line for bunches outgoing from plasma accelerating module. Taking advantage of the symmetric and linear focusing provided by an active-plasma lens, the witness is captured and transported along the array without affecting its quality at the exit of the plasma module. At the same time the driver, being over-focused in the same array, can be removed by means of a collimator.
Slowly extracted beams from a synchrotron have temporal fluctuations, the so-called spill micro structure. The reason is related to power supply ripples that act on the quadrupole magnets, leading to unintended tune fluctuations during extraction. Related simulations regarding the dependency of spill quality on the power supply ripples are executed with varying excitation levels of the sinusoidal ripples and bandwidth-limited white noise. In addition, transit time spread is simulated, a few simulation approaches are proposed, and related data analysis procedures and preliminary results are described.
Surface annealing using intense nanosecond laser pulses is an emerging technique for SRF cavities. This technique can effectively reduce the cavities’ surface defects and improve their RF performance. However, previous studies in this field limited themselves on solid state lasers or gas lasers, which have very low average power and are not practical for processing actual SRF cavities with ~m2 inner surface area. IMP innovatively built a practical whole-cavity processing system with a kW-level nanosecond fiber laser, which is designed to process an SRF cavity within a working day. In this work, the system design and feasibility analysis will be given, together with the comparison between pristine Nb thin film samples on copper substrates and their fiber laser processed counterparts. The results show that our fiber laser system can deliver comparable surface treatment as that from the solid-state laser system, but with higher efficiency. The authors believe such results could boost the application of laser surface annealing technique in the particle accelerator community.
The performance of operating particle accelerators has been seriously affected by the electron cloud (e-cloud) effect. The secondary electron emission (SEE) and the e-cloud can be effectively suppressed through laser-etching the inner surface of the vacuum chamber. Oxygen-free copper (OFC) has become the first choice for the vacuum chambers of modern accelerators due to its high electric and thermal conductivity and effective radiation shield-ing property. It is necessary to study the vacuum proper-ties of the laser-etched OFC for the application in the particle accelerators. In this paper, the photon stimulated desorption (PSD) yield and the outgassing rate of the laser-etched OFC were measured. The results show that the laser-etched OFC presents lower PSD yield compared to the untreated OFC, while the outgassing rates of the laser-etched and unetched samples are similar.
Radiation resistance of materials is an important area of research, relevant to nuclear reactor technology. Various challenges are associated with this research; one of which is the selection of radiation resistant material for the plasma facing wall of the reactor due to its harsh operating environment. Recent studies reveal that WC has the potential to be developed as radiation resistant material.* To explore this possibility, WC thin films synthesized using RF Magnetron sputtering at a substrate temperature of 700 K have been irradiated with 100 MeV Ag8+ ions from 15 MV Pelletron accelerator at three different fluence. Glancing angle X-ray diffraction (GAXRD), Atomic Force Microscopy (AFM), Field Emission Scanning Electron Microscopy (FE-SEM) and Raman spectroscopy of the films have been performed to determine structural and morphological changes due to ion irradiation. GAXRD of the pristine and irradiated thin films reveal the reduction in grain size and loss of crystallinity with ion irradiation. FESEM images of the thin films showed no significant change in surface morphology and the thin film continuity is maintained even after ion irradiation of higher fluence. Raman spectroscopy of the WC thin films shows the decrease in intensity of peaks corresponding to Raman shift resulting in the decrease in polycrystalline nature of WC upon ion irradiation. Further, thermal spike calculations are also done to estimate the evolution of lattice temperature with ion irradiation.
The superconducting radio-frequency (SRF) community has shown that introducing certain impurities into high-purity niobium can improve quality factors and accelerating gradients. We question why some impurities improve RF performance while others hinder it. The purpose of this study is to characterize the impurity profile of niobium with a low residual resistance ratio (RRR) and correlate these impurities with the RF performance of low RRR cavities so that the mechanism of impurity-based improvements can be better understood and improved upon. The combination of RF testing and material analysis reveals a microscopic picture of why low RRR cavities experience low temperature-dependent BCS resistance behavior more prominently than their high RRR counterparts. We performed surface treatments, low temperature baking and nitrogen-doping, on low RRR cavities to evaluate how the intentional addition of oxygen and nitrogen to the RF layer further improves performance through changes in the mean free path and impurity profile. The results of this study have the potential to unlock a new understanding on SRF materials and enable the next generation of SRF surface treatments.
Particle Accelerators demand high particle transmission and reduced longitudinal emittance; hence, effective bunching systems are requested. The concept based on an efficient, compact design called “Double Drift Harmonic Buncher - DDHB” fulfills these two requirements for a c.w. or pulsed beam injection into an RFQ, a DTL, or a cyclotron. The proposal is associated with two buncher cavities separated by a drift space and an additional drift at the end of the system for a longitudinal beam focus at the entrance of the next accelerator unit, whose candidates can be one of those mentioned above. The investigations are focused on exploring accurate acceptance rates. To obtain successful and understandable outputs from the DDHB concept, a new multi-particle tracking beam dynamics code called “Bunch Creation from a DC beam - BCDC” has been developed for detailed investigations of space charge effects. It allows to calculate the transformation of intense dc beams into particle bunches in detail with a selectable degree of space charge compensation at every location. This paper presents the results from various investigations with and without space charge effects.
A uniform distribution of nucleation tin sites is essential to the growth of high quality Nb3Sn thin film by vapor diffusion method. The less-nuclear zones were commonly observed in previous nucleation experiments. However, a fully understanding of the occurrence of less-nuclear zones has not yet been achieved. Here, the adsorption energy of nuclear agent SnCl2 on different crystal planes of niobium (Nb) including Nb (110), Nb (100), Nb (211) are studied through density functional theory (DFT) calculations and several types of adsorption configurations are optimized. The large differences of calculated adsorption energy of SnCl2 on three different crystal planes reveal strong crystal direction selectivity during nucleation stage. In addition, the phenomenon of nucleation experiment on large grain samples further consolidates the accuracy of the calculation results. The calculation results explain the presence of less-nuclear zones during nucleation process and provide guidance for the subsequent suppression of these regions.
Real-time dosimetry for ultra-high dose-rates (UHDR) and Very High Energy Electrons (VHEE) is a challenge which is currently being studied using the electron beam at CERN Linear Accelerator for Research (CLEAR). These studies are motivated by the demand for reliable dosimetry for FLASH radiotherapy. This mode of irradiation relies on UHDR, a dose rate regime where conventional dosimetry monitors such as ionization chambers saturate. One potential approach is the use of a calibrated beam-based dosimetry method. The existing beam instrumentation provides real-time information on charge and both transverse and longitudinal profiles of the pulses, as well as making possible a measurement of the beam Twiss parameters. In the context of achieving a real-time prediction of the dose deposition, this paper presents experimental studies of the correlation of these parameters with the read-out of passive and dose-rate independent methods such as radiochromic films, and compares them with simulation results.
A new electron cooling experiment is being planned at the Integrable Optics Test Accelerator (IOTA) at Fermilab for cooling ~2.5 MeV protons in the presence of intense space-charge. Electron cooling is integral to the study of beam dynamics and has valuable applications for producing high-intensity hadron beams in particle accelerators. For such goals, an electron lens to be placed in the IOTA ring will be used for electron cooling, space-charge compensation, and non-linear dynamics. Here we present the simulations and designs of two thermionic electron sources for the cooling at IOTA. One cooler is a basic electron source and will be used for cooling the proton beam and as a tool for other experiments at IOTA. The other cooler is a strong electron source, which will be used for studying effects of electron cooling in ion beams with intense space-charge. We particularly discuss parameters of the thermionic sources’ electrodes, as well as the simulation results. We also present a new electron source test-stand at the University of Chicago, which will be used to test the thermionic electron sources. We also discuss the results from analyzing the test stand operations with a currently existing electron source. Furthermore, we present future steps for production and commissioning of these thermionic sources at IOTA.
LhARA, the Laser-hybrid Accelerator for Radiobiological Applications, is a proposed facility for the study of proton and ion radiation biology. The accelerator is designed to deliver a variety of ion species over a wide range of spatial and temporal profiles at ultra-high dose rates. The facility requires that the deposited dose distribution be measured in real-time. For this purpose, an ion-acoustic dose mapping system has been developed that, exploits the ultrasound waves generated by the ion beam*. The feasibility of this approach is being evaluated using a two-stage simulation.
A water phantom modelled in Geant4 with beam energies up to 250 MeV is used to calculate the energy deposited by the beam as a function of position and time. The time-dependent 3D energy distribution is then used as the source in k-Wave to simulate the ion energy generation of acoustic (pressure) waves and their propagation in the three-dimensional space. A hemispherical acoustic sensor array is also simulated and its ability to reconstruct the generated pressure distribution is evaluated.
The results show that the 3D deposited-energy distribution can be reconstructed with sub-millimetre accuracy and suggest, that further development of the system can lead to real-time, non-invasive Bragg peak localization and dose deposition profile measurement during ion-beam therapy.
The quest of laser plasma accelerators is of great interest for various applications such as light sources or high energy physics colliders. This research has led to numerous performance improvements, particularly in terms of beam energy versus compactness [1] and ultra-short bunch length [2]. However, these performances are often reached without the achievement of sufficient beam quality, stability and reproducibility. These are the objectives of PALLAS, a test facility at IJCLab, that aims to advance laser-plasma from acceleration to accelerators.
To this end, one of the main lines of research is the electron beam control and transport.
The primary goal is to have a lattice design that allows for a fine characterization of the output beam as a function of the laser-plasma wakefield acceleration target cell and laser parameters, while paying a particular attention to preserving the quality of the beam during its transport.
I will present the detailed strategy, considered for PALLAS, on the problematic of chromaticity and divergence for the transport of laser-plasma accelerated electron beams.
Inverse Compton Scattering (ICS) is an ideal source of tunable monochromatic gamma rays. These gammas have uses for Nuclear Resonance Fluorescence, and production of novel medical radioisotopes. The gamma energy can be tuned by changing the electron energy. An ICS source can be made quasi-monochromatic by using low energy spread electron and laser beams, and using a collimator.
Currently ICS gammas are only available from large synchrotron driven electron sources. These sources suffer from a smaller flux in the desired bandwidth than ERLs or linacs. A new planned gamma source is under consideration as part of the proposed UK-XFEL project, this would involve part of the XFEL linac being enabled for an energy recovery mode.
A demonstrator experiment to support the UK-XFEL project is being discussed for the upgraded CLARA facility at Daresbury Laboratory. The experiment will scatter Ti:Sapphire laser pulses at 800 nm off 250 MeV electrons. The gammas will be collimated. This experiment will characterise the source to determine the bandwidth and flux of the source. The maximum energy of the gamma photons in this experiment is 1.48 MeV and the bandwidth of the collimated source is 3.2%.
In this work I will present simulations of the planned experiment, showing the scattered gamma energy, bandwidth and tunability of the source.
In this proceeding, we demonstrate the synthesis of epitaxial Cs$_3$Sb films with a high degree of crystallinity on silicon carbide substrates. Films less than 10 nm thin are grown in vacuum and exhibit percent level quantum efficiencies at 532 nm. We find a positive correlation between quantum efficiency and improved crystallinity of the photocathode film, particularly in the longer wavelengths of the visible spectrum. We present a model describing the optical interference effects observed in the SiC - Si substrate multilayer that enhance quantum efficiency of the thin film photocathodes by almost a factor of two at particular wavelengths. Additionally, we characterize the surface and bulk crystallinity of epitaxial Cs$_3$Sb films using both X-ray diffraction (XRD) and reflection high energy electron diffraction (RHEED) in an endeavor to identify relationships between crystalline phases and photocathode performance.
https://www.youtube.com/watch?v=7CTj7PM7r3w
https://www.youtube.com/watch?v=7CTj7PM7r3w
The upgrade project for the LHC injectors is described in detail, highlighting the major improvements implemented in the injector chain. Lessons in technical progress, project management and planning are presented. The performance of the upgraded systems in intensity, average particle flux and beam brightness is described and compared to the upgrade goals and LHC`s original design parameters. The LHC performance with the upgraded injection chain and the luminosity achieved are presented. A future outlook to future developments is given.
An overview of the project status of the future Italian 2.4 GeV 4th generation light source Elettra 2.0 that will replace the existing 3rd generation light source Elettra is presented, including challenges and perspectives in the design and construction of such light sources. Elettra 2.0 will be the ultra-low emittance light source that will provide ultra-high brilliance and coherence and at the same time also aims to provide very short pulses for time resolved experiments. The discussion includes the technical challenges requiring specific R&D studies, for example on injection schemes, high performance magnets, vacuum, diagnostics for stability, feed-backs, harmonic cavities, etc. The upgrade also addresses on the request from the established user community to minimize the duration of beam-time interruption, imposing the need of a careful organization and planning of all the phases of the project, from the removal of the old machine to the installation and successful commissioning of the new one.
LCLS-2 should be completed in 2022, producing first light from its new SC linac. The status of beam commissioning and the performance of the new SC CW linac should be shown in detail. Performance should be compared with the design values and an outlook to further steps should be shown.
The Linear IFMIF Prototype Accelerator (LIPAc) has been constructed in Rokkasho, Japan to demonstrate the validity of the low energy section of an IFMIF deuteron accelerator up to 9 MeV with a beam current of 125 mA in continuous wave (CW) under the joint collaboration between EU and Japan. The short-pulse 125-mA deuteron beam acceleration to 5 MeV was successfully demonstrated in 2019. Now LIPAc is under commissioning toward the CW beam acceleration. The effort to realize the high-current CW beam, e.g. the commissioning of the ion source at high-current, CW and the conditioning of the RFQ cavity at CW, and the result of the beam commissioning campaign will be presented.
Superconducting RF thin film (SRF-TF) technology for RF cavities has only recently began to achieve accelerator field gradients and Q-factors close to that of bulk niobium SRF cavities. These thin films (such as Nb3Sn, NbTiN, Mg2B and multilayer structures) offer the ability to operate at higher temperatures (4.2 K instead of 1.9 K) thereby increasing the operating efficiency of the RF system and also the potential for achieving higher operating gradients (>50 MV/m) thereby reducing the practical accelerator footprint, both of which aiming to help maximise future sustainability. Much more development however is needed to optimise and master the thin film deposition process on RF cavities, as well as to understand the fundamental RF performance of these enhanced films. In order to develop SRF-TF capabilities beyond current limits, there are a number of international collaborations ongoing which will be described, in Europe it is being conducted under the umbrella of the H2020 ARIES and IFAST programmes.
Laser-plasma acceleration is a technique for producing ultra-relativistic electrons that takes advantage of the ability of plasma to carry arbitrarily intense fields. In practice, fields of several hundred GV/m can be produced simply by focusing an ultra-intense laser pulse in a sub-critical plasma [1]. These fields, which are 3 orders of magnitude larger than those produced in conventional plasma accelerators, are nevertheless useless if the field is not maintained over a significant distance or if the accelerated electron beam does not remain trapped in it.
In practice, three phenomena limit the acceleration length in a laser-plasma accelerator: pump depletion, diffraction, and dephasing. Pump depletion, i.e. the laser energy transfer to the plasma wave, and laser diffraction tend to decrease the laser intensity during its propagation down to a level from which it can no more drive a steady plasma wave.
Dephasing originates from the difference in velocity between the electron bunch and the laser, which results in a progressive shift of the electron beam towards a decelerating phase of the electric field.
Here we discuss several approaches for tackling this limitations and increasing the beam energy: the rephasing technique, which extends the effective dephasing length [2], the acceleration in a laser-plasma waveguide, which prevents diffraction [3], and finally a dephasing-less, diffraction-free acceleration scheme that solves all three issues at once [4]. We will also present the first demonstration of the controlled injection of electron beams in a plasma waveguide which has allowed the production of quasi-monoenergetic electron beams at the GeV level. These results remove a major bottleneck to development of high energy plasma accelerators and pave the way to the stable production of high-quality, multi GeV beams [5].
[1] Esarey, E., Schroeder C. B. and Leemans, W. Review Modern Physics 81, 1229–1285, (2009).
[2] Guillaume, E. et al. Physical Review Letter 115, 155002 (2015).
[3] Smartsev, S. et al.Optics Letter 44, 3414–3417 (2019).
[4] Caizergues, C., Smartsev, S., Malka, V., and Thaury C. Nature Photonics 14, 475–479 (2020)
[5] Oubrerie, K. et al. arXiv:2108.03000 (2021)
The European Eupraxia project has recently been included in the ESFRI roadmap. EuPRAXIA is a world-wide first, new kind of compact facility and will be constructed at two European sites. One of the two sites for Eupraxia will be the INFN LNF at Frascati. The facility will be integrated with the already planned 1GeV linear accelerator.
This talk will cover the status of the technical design of the accelerator, general infrastructure plans and future pilot applications in the user community.
Delivering and tailoring high brightness electron beams for a wide range of novel applications is a challenging task in single pass accelerator test facilities. This paper will review beam dynamics challenges at single pass accelerator test facilities in Europe to generate, transport and tailor low- to medium-energy high brightness electron beams for a range of novel applications.
Next generation storage ring light sources will dramatically increase the electron beam brightness, thereby significantly increasing the X-ray brightness for science. Such intense electron beams exhibit numerous collective effects that potentially drive instabilities. Advanced numerical simulation methods are compared with theory and experimental measurements at different machines. One important issue is longitudinal collective beam dynamics with very low synchrotron frequency when higher-harmonic rf systems are used to lengthen the bunch and beam lifetime. Ion effects are also discussed in these very low emittance machines. This paper gives an overview of these and other collective physics, and discusses efforts to predict and mitigate any potentially deleterious effects.
The Fermilab Linac delivers 400 MeV H- beam to the rest of the accelerator chain. We are exploring several machine learning (ML) techniques for automated RF tuning, with an emphasis on time-evolving modeling that can account for parameter drift. Providing stable intensity, energy, and emittance is key since it directly affects downstream machines. To operate high current beam, accelerators must minimize uncontrolled particle loss; this ca be accomplished by minimizing beam longitudinal emittance via RF parameter optimization. However, RF tuning is required daily since the resonance frequency of the accelerating cavities is affected by ambient temperature and humidity variations and thus drifts with time. In addition, the energy and phase space distribution of particles emerging from the ion source are subject to fluctuations. Such drift is not unique to Fermilab, but rather affects most laboratories. Our methods include several variations of RF system modeling based on diagnostics data from beam position monitors (transverse positions and longitudinal phase). We will present the status of each approach and future plans.
In the commissioning and operational stage of X-ray free-electron lasers (XFELs), it is a challenging problem to efficiently tune the large-scale scientific machines which consist of hundreds and thousands of components. Here we tried to introduce several tuning algorithms to achieve automatic tuning in XFELs and compared the performance. This also paves the way for further development of intelligent online optimization schemes.
Although beam emittance is critical for the performance of high-brightness accelerators, optimization is often time limited as emittance calculations, commonly done via quadrupole scans, are typically slow. Such calculations are a type of multi-point queries, i.e. each query requires multiple secondary measurements. Traditional black-box optimizers such as Bayesian optimization are slow and inefficient when dealing with such objectives as they must acquire the full series of measurements, but return only the emittance, with each query. We propose using Bayesian Algorithm Execution (BAX) to instead query and model individual beam-size measurements. BAX avoids the slow multi-point query on the accelerator by acquiring points through a virtual objective, i.e. calculating the emittance objective from a fast learned model rather than directly from the accelerator. Here, we use BAX to minimize emittance at the Linac Coherent Light Source (LCLS) and the Facility for Advanced Accelerator Experimental Tests II (FACET-II). In simulation, BAX is 20x faster and more robust to noise compared to existing methods. In live LCLS and FACET-II tests, BAX performed the first automated emittance tuning, matching the hand-tuned emittance at FACET-II and achieving a 24% lower emittance at LCLS. Our method represents a conceptual shift for optimizing multi-point queries, and we anticipate that it can be readily adapted to other similar problems commonly found in particle accelerators and beyond.
The Eupraxia@SPARC_LAB project, foreseen a 1GeV Linac based on a X-band booster composed by 16 accelerating structures working at the nominal gradient of 60MV/m. In this framework, an intense activity has started in the last years in order to prove the reliability and functionality of the X-band technology at very high peak power. The main step of this activity has been the implementation of a X-band test station TEX, based on an RF power source capable to deliver 50MW RF pulses that are used for accelerating structures and RF components conditioning and testing. This test facility has been successfully commissioned and entered into operation at the end of 2022. Together with the source commissioning different RF components in X-band, necessary for the Eupraxia Linac, have been developed and will be tested soon at the nominal peak power in the TEX facility. In this article the status and operation of the TEX facility is reported together with a report on the main activities on the X-band technology performed at INFN-LNF.
A systematic study of microbunching instability is being carried out in the FERMI free-electron laser linac driver. This talk will report about modelling and experiments related to the instability, including the development of an infrared (IR) spectrometer for the diagnostic of microbunching-induced coherent emission in the IR spectral range.
Particle accelerators, relevant to LANL’s mission spaces will rely on the use of copper based rf structure for charged particle acceleration. Additively manufactured (AM) copper structures offer the usual well-known advantages in terms of relaxation of physical design (shape) constraints, and thus hold the promise of making complex shaped rf structures. To rapidly demonstrate the potential to additively manufacture accelerator structures with existing technology, a bound metal deposition (BMD) metal 3D printer will be used to build a scaled design and the results of this effort will be presented.
An important part of the new accelerator MESA (Mainz Energy-recovering Superconducting Accelerator) is the beamline connecting the pre-accelerator with the main accelerator. The setup includes a vertical parallel beam offset realized with two dipoles. These are designed in a way, that they can serve as steerer for the main accelerator and will be discussed in this contribution. Furthermore, the beamline contains a horizontal 180°-beam deflection realized with four dipoles. It is also possible to extract the beam to a Mott-polarimeter* and to a separate diagnostic beamline. The layout and the lattice- and particle simulations leading to this will be discussed concerning beam dynamics especially with regard to the high beam currents of 1 mA in cw-mode.
This study is motivated by the search for the electric dipole moment (EDM) of elementary particles. The most promising idea in that regard is the “Frozen Spin” concept first proposed by the BNL. This concept, however, requires the building of a brand-new facility devoted to the EDM-search. NICA is not such a facility, hence the need for a modification compatible with the existing optics; one that wouldn’t disrupt the ring’s capability for parallel experiments. Such a modification is the “Quasi-Frozen Spin” idea, realized by adding transport channels, bypassing the ring’s straight sections. Wien-filters are placed in these channels in order to compensate spin-rotations caused by the ring’s arc dipoles, thus making its net spin-transfer matrix unitary. Even though, during its movement along the beam line, the beam’s polarization vector deviates from alignment with the momentum vector, this motion is regular and fits within one beam revolution, allowing for the buildup of the EDM-signal. The present study shows that the “Quasi-Frozen Spin”-specific optics is consistent with the existing NICA lattice and that the modified structure is capable of maintaining a requisite spin-coherence time.
Many applications of synchrotron light sources such as imaging, lithography and angle-resolved photoemission spectroscopy can benefit from high photon flux, which, unlike the brightness, is almost independent of electron beam transverse emittance. To realize high photon flux, it is desired to increase the stored current or number of periods of insertion devices. To this end, a low energy (500\,MeV) and high current (1000\,mA) storage ring with long straight sections is under design in Chongqing University of China. This paper presents the physical design, highlighting both the feasibility and challenges.
Hefei Advanced Light Facility (HALF) was designed as fourth generation light source based on the diffraction-limited storage ring (DLSR). The pre-research has been completely done, due to the smaller beam dynamic aperture, about 10mm, beam inject could not completed by the traditional bump magnet. We purposed and designed a novel dual-channel kicker, with other two traditional kicker, they were combined the new injection system. The paper presented the principle and layout and the detail of the novel dual-channel.
The High Energy Photon Source (HEPS) is a fourth generation photon source, including a storage ring, a booster ring and a Linac. Due to the small dynamic aperture of the storage ring， a novel on-axis swap-out injection scheme was chosen. Here, the 6GeV booster acts as an accumulating ring during that injection process. To extract 6 GeV beam from the booster before injection into the storage ring, four slow bumper magnets are applied to assist the extraction kicker to accomplish. The bumper pulse magnetic field waveform is a half-sine wave with 1ms pulse bottom width. Depending on the simulation and test， a classic LC resonance circuit topology with IGBT switching in series with fast recovery diodes is adopted . In addition, an energy recycle circuit and capacitor charging circuit are designed, to decrease power loss and reduce the influence on the output pulse current waveform during the capacitor re-charge process. A pulsed power supply prototype has been completed， and the testing results show that the bumper pulser can fully meet the all requirements of HEPS booster high energy extraction system.
Nowadays, Energy Recovery Linacs (ERLs) became really appealing thanks to their low environmental impact and high sustainability.
ERLs require a special low energy injector, usually named merger. The energy at merger exit is clearly the energy that can’t be recycled in the ERL machine and is the amount dumped at the end. The lower the injection energy is the more efficient is the energy recovery process.
A physiological issue of low energy ERL injection is the presence of space charge in the dispersive section that introduces to dispersion leaks.
Worldwide ad hoc solutions for mergers beamlines design have been studied to address this problem.
Here we present a different approach that allowed us to exploit a standard dogleg to design a very low energy merger for an ERL. This has been made possible thanks to the application of the GIOTTO AI code that optimizes of the optics setting finding a proper achromatic configuration.
Diamond Light Source has been operating in top-up mode for users since late 2008. To date, Diamond’s electron gun has operated in single-bunch mode for multiple-shot top-up of user beam, and multibunch mode for storage ring fill. The uneven bunch-to-bunch charge of the multibunch train is visible in the storage ring and so the fast multibunch fill must be followed by a slower single bunch correction before beam can be given to users. A new pulser has been developed that will generate a flat, fast-rising 500 MHz train of electron bunches from the gun that will enable a uniform fill of the storage ring without single bunch correction. Arbitrary bunch-by-bunch shaping of the train can be used for multibunch fill and top-up of any required fill pattern, thus exploiting the greater charge available in multibunch mode to reduce the number of top-up shots and consequent disturbance to users. Pulser development and results are presented, together with a report of progress towards multibunch top-up.
The nominal Diamond-II storage ring optics have been designed to produce a pseudo twenty-four-fold symmetry by maintaining equal phase advance across the long and standard straights [1]. In this paper, the impact of introducing a high beta section in the injection straight and reducing the ring symmetry to one have been extensively investigated. This solution does not require any additional hardware and so can be switched on or off as required. In this paper we present the optics solution and study the expected performance.
[1] Diamond-II Technical Design Report, (2022).
The accelerator high-power system provides electromagnetic energy to the acceleration structure to establish a high-power acceleration field. In pace with the current intensity development of accelerator beam, heigtening RF system performance is put on a new agenda. Temperature is a momentous parameter of accelerator RF system, which will directly affect the mechanical, electromagnetic and signal stability of high frequency system. Therefore, an optimized water cooling scheme for solid-state power source is designed to obtain the most reliable and convenient cooling system with the least cost. Firstly, the diverter of the overall water cooling system is designed to ensure that each power amplifier module can achieve the same heat dissipation effect when output the same power. Next, the runner of a single power amplifier module is optimized to ensure that the pressure at the plug connector is appropriate. Finally, the power module is designed in the form of water and electricity separation, that is, the way of contact cooling is adopted to increase the maintainability.
The High Luminosity Large Hadron Collider (HL-LHC) project foresees the upgrade of a large fraction of primary and secondary collimators of the betatron cleaning system to reduce the collimation impedance. The new collimator design also includes the installation of in-jaw beam position monitors (BPMs) to align the collimators faster and to continuously monitor the beam orbit, ensuring an optimum collimation hierarchy. This upgrade is being done in two stages: 12 of the 22 new collimators were already installed during the Long Shutdown 2 (2018-2021), four primary collimators and eight secondary collimators. They have been used in normal operation since the recommissioning in 2022. This paper discusses the experience gained with collimator BPMs during the recommissioning of the LHC, in particular orbit stability throughout a complete cycle, comparison of the alignment with BPMs and the traditional method based on beam loss monitors, as well as interlock strategies.
A lattice of a storage ring for the future plan of UVSOR synchrotron facility, UVSOR-IV, is designed at 1 GeV electron energy. The lattice of 12 compact double achromat cells conducts to an emittance of 4.2 nm at 1 GeV electron energy and 2.3 nm at 750 MeV electron energy in achromat condition, 82.5 m circumference, and six straight sections of 4 m long and six of 1.5 m long. The lattice has the flexibility of beta function and dispersion function at the straight sections which can produce lower emittance in the non-achromatic condition and short bunch length in isochronous condition. The lattice requires strong sextupole magnets to compensate the natural chromaticity. To help deal with the challenge of dynamic aperture associated with strong nonlinearities, we examined optimizing the dynamic aperture with the sextupole arrangement based on the Bayesian method. In the conference, the latest results from the design study will be reported.
After the successful conclusion of Run1 in 2018, the AWAKE experiment is presently undergoing its second phase (Run2), which aims to demonstrate the possibility of producing high quality electron beams for high energy physics applications.
Over the last year, a significant time-investment was made to study proton beam centroid modulation effects in plasma induced by a seeding electron bunch (i.e. hosing). The high beam pointing accuracy needed for the study translated in tighter constraints for the 18 MeV electrons injection line. To address the new requirements, a measurements campaign was dedicated to the characterization and optimization of the beam line. In the first part of this paper, we present the results of the measurements and simulations carried out for the line characterization. The second part focuses on the description of the operational tools developed to address the new beam requirements and performance.
Heavy-ion single event effect (SEE) test facilities are critical in the development of microelectronic components that will be exposed to the ionizing particles present in the hostile environment of space. CHARM High-energy Ions for Micro Electronics Reliability Assurance (CHIMERA) and HEARTS have developed a high-energy ion beam capable of scanning a wide range of Linear Energy Transfer (LET) at low intensities to study ionization effects on space-bound technology using CERN's Proton Synchrotron (PS). This contribution describes the extraction and transport of low-intensity lead ions at multiple energies to the CHARM facility at the East Area of CERN. Furthermore, it discusses the implementation of a Radio Frequency Knockout (RFKO) technique that streamlines beam extraction and enhances particle flux control and reproducibility across different energies, thereby improving performance and reliability in SEE testing.
The Large Hadron Electron Collider (LHeC) is a study at CERN to construct an energy recovery linear accelerator (ERL) tangentially to the High Luminosity Large Hadron Collider (HL-LHC). This would enable deep inelastic scattering collisions between electrons and protons in the ALICE interaction region (IR2). In this design, one of the two proton beams of the HL-LHC collides with the electron beam in IR2, while the second proton beam avoids this collision. This way, the e-p collisions can take place concurrently with p-p collisions in ATLAS, CMS and LHCb. The LHeC/ALICE interaction region is laid out for alternate e-p and p-p data, using a common detector, suitable for this novel way of interaction. It therefore requires a highly precise beam optics and orbit for the three beams: the two proton beams of the HL-LHC, as well as the electron beam from the ERL. The highly asymmetric optics and orbits of the two proton beams, allowing concurrent operation of the HL-LHC experiments and e-p collisions, have been investigated with MAD-X. The impact of an optimized electron mini-beta insertion, focusing and bending the electrons, on the proton beam dynamics has been considered.
The electron-positron Future Circular Collider (FCC-ee) foresees stored beam energies up to 20.7 MJ, a value almost two orders of magnitude higher than any previous lepton collider. Considering the intrinsic damage potential of the FCC-ee beams, a halo collimation system is under study to protect the most sensitive equipment from unavoidable losses. Beam dynamics and tracking studies are key aspects to evaluate the cleaning performance of the collimation system, as they help in an iterative process to converge on an optimum performance. The first results of such studies, exploring various configurations of materials and collimator lengths, are presented, including also estimated beam loss distributions around the ring. In addition, an impact parameter scan on the primary collimators is studied to identify the most critical case for the protection of sensitive equipment.
The Insertion Region 2 (IR2) will accommodate a Pre-Cooler at injection energy ($24~\mathrm{GeV}$) and a Strong Hadron Cooling
(SHC) facility at top energy ($100~\mathrm{GeV}$ and $275~\mathrm{GeV}$) in the Hadron Storage Ring (HSR) of the Electron-Ion Collider
(EIC). This paper summarizes the lattice update in HSR-IR2 to meet the requirements from the Pre-cooling and the SHC. The layout has been
changed to provide a longer cooling section.
It also describes how to enable vertical cooling for the SHC in IR2.
The proposed REDTOP experiment is a $\eta$/$\eta'$ factory aiming to explore dark matter and physics beyond the Standard Model. The $\eta$ and $\eta'$ mesons are almost unique in the particle universe because of their quantum numbers and the dynamics of their decay are strongly constrained. This effect increases the branching ratio of rare decays which can be studied to probe physics BSM. The integrated eta meson samples collected in earlier experiments have been about ~$10^9$ events, dominated by the WASA at Cosy experiment, limiting considerably the search for such rare decays. A new experiment, REDTOP, is being proposed, aiming at collecting more than $10^{14}$ eta/yr ($10^{12}$ eta'/yr) for studying of rare $\eta$ decays.
Such statistics are sufficient for investigating several symmetry violations, and for searches of new particles beyond the Standard Model.
Recent physics and detector studies indicate that REDTOP has excellent sensitivity to probe all four portals connecting the dark sector with the Standard Model. Furthermore, conservation laws and violation of discrete symmetries can be probed in several ways.
Several production mechanisms are available for a super $\eta$/$\eta'$-factory. They require different beam species and properties, available at different HEP or nuclear laboratories around the World.
The beam options, the corresponding physics program, and the detector for REDTOP will be discussed during the presentation.
The “Pre-Conceptual Design Report” (preCDR) of the BESSY III facility (https://doi.org/10.5442/r0004) has been finalized at the end of August 2022 and reviewed by a Project Advisory Committee beginning of September 2022. In this paper, we give a status report of the BESSY III facility project and will discuss aspects of lattice design, technical specifications, initial developments and a first estimate of power consumption compared to BESSY II.
The Southern Advanced Photon Source is a diffraction-limited storage ring at middle energy. The popular injector which includes a low energy Linac and a full energy booster is proposal. The concept design of the booster is presented in the paper. The booster is a high intensity synchrotron accelerator. The impedance model is obtained and the instability threshold is predicted.
NICA is mainly designed for experiments with heavy ions and polarized proton and deuteron beams at an energy of the former about 13 GeV. For these purposes, appropriate SPD and MPD detectors, as well as other necessary implements, are installed in the straight sections. EDM experiment supposes use deuterons at an energy of about 240 MeV. To ensure the «Quasi-Frozen Spin» mode, E+B elements (namely, Wien Filters) are required as well. Such elements can be placed in straight sections to compensate the arc spin rotations. For EDM measurement experiments, it is necessary to operate NICA in the storage ring, and not the collider mode. To do this, it is proposed to install ByPass channels. Thus, it is possible to create a completely new regular structure in a straight section. Creating ByPass channels will make possible to engage NICA in various experiments at once.
The Electron-Ion Collider (EIC) uses the local crab crossing scheme to compensate the geometric luminosity loss of the $25 ~\mathrm{mrad}$
crossing angle in the interaction point. Due to space limitations and other optics constraints, the beam optics at the crab cavities in
the Hadron Storage Ring (HSR) is not perfectly matched to fully compensate the crab dispersion.
This paper discusses the possibility of closing the
crab dispersion by a dispersive RF cavity. The formula is derived and the required momentum dispersion at the RF cavity is calculated.
The weak-strong simulation is performed to demonstrate this idea
The High Luminosity upgrade of the CERN Large Hadron Collider (HL-LHC) aims to achieve stored beam energies of 680 MJ. One possible limit to the achievable intensity is the quench limit of the superconducting magnets downstream of the betatron collimation insertion. At HL-LHC beam intensities, even a tiny amount of particles leaking out of the collimation system may be sufficient to quench them. The quench limit of these magnets, when exposed to proton loss, depends crucially on a variety of parameters. It can only be accurately estimated through dedicated beam tests that determine it under realistic operating conditions. In this paper, we present the design and execution of a quench experiment carried out at the LHC in 2022 with proton beams at 6.8 TeV. We describe the experimental approach, the result, and the analysis of the test that aims to probe the collimation cleaning performance while deliberately inducing beam losses of up to 1000 kW. The result of these tests is crucial input for the need of future collimation upgrades.
For the Future Circular Collider (FCC) Conceptual Design Report (CDR), the FCC-hh collimation system was studied and optimized for proton and heavy-ion operation with up to 8.3 GJ stored beam energy. There are currently studies ongoing for an updated design baseline, including a new ring layout, compatible with the FCC-ee, and optics, where the collimation insertions have undergone major changes. A first iteration on the adapted collimation system layout and settings for the new baseline is presented. The beam loss cleaning performance for proton beams is studied in multi-turn tracking simulations.
Storage ring commissioning-like simulations are necessary to assess the feasibility of proposed future lattice designs. This paper proposes a python package for commissioning-like simulations based on python accelerator toolbox (pyAT). The software includes: 1) errors definition, 2) correction routines from open trajectory to optics and coupling correction and 3) the evaluation of the relevant parameters, such as dynamic aperture, injection efficiency and Touschek lifetime. The software is fully exploiting parallel resources (local or on a computing cluster) and is thought to be easily configured for any machine (examples are given for EBS DBA and HMBA, for PETRA IV and for FCC-ee). Whenever possible analytic formulas are made available to the user. Several examples are detailed in this paper and included in the code as demonstrations of use.
Modern synchrotron light sources are competing intensively to increase X-ray brightness and, eventually, approach the diffraction limit, which sets the final goal of lattice emittance. Recently, we propose a new optics solution aimed at reaching low emittance, using a lattice element “Complex Bend”. The Complex Bend is a sequence of dipole poles interleaved with strong alternate focusing so as to maintain the beta-function and dispersion oscillating at low values. By integrating this element in NSLS-IIU upgrade, the designed lattice emittance is around 30 pm-rad. To prove the feasibility of this new design, we have planned the key element prototype test, in the beam line with 200 MeV beam energy. We designed and fabricated the prototype complex bend, with gradient at 140 T/m. It is installed and commissioned at NSLS-II linac beamline. In this paper, we’ll report the test beamline design and beam commissioning progress
The SHADOWS experiment is a proposed beam dump experiment in the CERN North Area, aiming to search for feebly interacting particles (FIPs) created in 400 GeV/c proton interactions. Due to its intended off-axis location alongside the K12 beam line, the SHADOWS detector can be placed potentially very close to the dump, enabling it to look for FIPs in non-covered parts of the parameter space. To guarantee a good quality of a potential signal, it is crucial to reduce any backgrounds of Standard Model particles as much as possible. The dominant background downstream the beam dump is caused by muons. This gives rise to introducing a dedicated muon sweeping system consisting of magnetised iron blocks (MIBs) to actively mitigate this background component. We present the conceptional design studies in the framework of the Conventional Beams Working Group of the Physics Beyond Colliders Initiative at CERN.
Commissioning a test beamline in KEK Photon Factory Advanced Ring (PF-AR, 6.5GeV and 5.0GeV) is proceeded under cooperation with the KEK Institute for Particle and Nuclear Studies (IPNS) to use electron beams in the GeV-range for the development of detectors in particle physics experiments. The inauguration of the project which was mainly directed by the IPNS was launched back in 2014, but the project progressed after the budgeting in FY2020, and the construction was completed in the summer of 2021. The electron for beam test can be obtained from gamma-rays emitted by collisions between the halo of a stored beam, which is the synchrotron radiation source in PF-AR, and a wire target using a copper converter to electron-positron pair creation. A yielded monochromatic electron beam is guided to the test area by quadrupole magnets and a bending magnet on the test beamline; the first interaction test between the wire target and the stored beam was successfully performed in the fall of 2021 and the trial of long user operation with top-up injection was completed in the fall of 2022. In this presentation, we will report on the overview of the construction and the beam commissioning of the test beam line.
Coordinate conversion is used in many aspects, such as laser tracker transfer problem, the conversion between WGS84 coordinate system and local coordinate system and so on. The high precision of coordinate conversion model is beneficial to improve the accuracy index of the network. The dual quaternion can integrate rotation and translation, which effectively simplifies the complexity of the trig function calculation of rotation matrix, and the overall least square adjustment considers the error problem of common points, and improves the accuracy of the model from two aspects.
The Future Circular Collider project is built around two main pillars: the construction of 100 km lepton collider running at increasing energies from the Z-pole to the t-tbar threshold (FCC-ee) followed by a hadron collider in the same tunnel (FCC-hh) to explore unprecedented energy frontier.
The realization of FCC-ee relies on a very challenging injector complex that should provide the highest ever realized source of positrons, which will serve the first phase of the collider operations (Z-pole). In this contribution the relevant aspects related to the damping of the high-emittance beam coming from the positron source and the transport of the damped beam within the different LINAC of the injector complex are presented and discussed.
An MeV ultrafast electron diffraction (MUED) instrument system, such as is located at the Accelerator Test Facility (ATF) of Brookhaven National Laboratory, is a structural characterization technique suited to investigate dynamics in the ultrashort range in a variety of materials via a laser pump method. It is a unique characterization technique especially suitable for highly correlated materials. This technology can be advanced further into a turnkey instrument by using data science and artificial intelligence (AI) mechanisms in conjunction with high-performance computing. This can facilitate automated operation, data acquisition, and real-time or near-real-time processing. The AI-based system controls can provide real-time feedback on the electron beam or provide virtual diagnostics of the beam. Deep learning can be applied to the MUED diffraction patterns to recover valuable information on subtle lattice variations that can lead to a greater understanding of a wide range of material systems. A data-science-enabled MUED facility will also facilitate the application of this technique, expand its user base, and provide a fully automated state-of-the-art instrument. Another beamline enhancement planned is the extension of the beamline sample area to include additional instrumentation for simultaneous measurement of a standard baseline sample. EM modeling of the beamline components facilitates this. Updates on research and development for the MUED instrument are presented.
Within the Standard Model the electric dipole moment (EDM) of the muon is heavily suppressed. Observation of a non-zero EDM value would be an additional source of CP violation that would aid in answering the many open questions about the universe and the Standard Model. As part of an investigation into the feasibility of measuring the muon EDM at the g-2 storage ring at Fermilab, a study on the delivery of low momentum muons to the g-2 ring using the existing accelerator infrastructure is presented.
The main SPS users are the experiments installed in North
experimental Area (NA) which are served with a continuous 4.8 s long
spill of protons and heavy ions. A third-integer resonant slow extraction is used to provide a uniform, long spill. Such a technique
comes at the cost of particles directly hitting the electrostatic septum
wires and activating the surrounding of the extraction
channel. In recent years, silicon bent crystals have been exploited to shadow
the wires of the septum blade and reduce the beam induced activation.
It was then demonstrated the experimental success of local shadowing in
the SPS and a way to further reduce losses with a non-local
installation of the crystal. After the last yearly stop, a new Si bent
crystal was installed in LSS4 of the SPS. In this paper, the first
results from measurements with beam are reported together with
limitations and possible upgrades of the present installation.
In the J-PARC Muon g-2/EDM experiment, to measure muon g-2 and EDM, it is necessary to accumulate 300 MeV/c muon beams with a 66 cm diameter region with a 3 T solenoid-type magnetic field. A new three-dimensional spiral injection scheme has been invented to achieve this target. Since this is the first instance to employ this injection scheme, a scale-down experiment with an electron beam of 297 keV/c and storage beam diameter of 24 cm is established at KEK. A simplified storage beam monitor using scintillating fiber has been designed and fabricated to measure the stored beam. The 100 nanosecond width pulsed beam is injected and observed a few microsecond signals by stored beam monitor. According to this result, the beam storage is confirmed. And the recent result shows that the stored beam deviated from the design orbit and caused betatron oscillations. To measure the beam deviation quantitatively and tune the beam, the storage monitor has been updated. The data from this stored beam monitor are the primary data for considering the conceptual design of the beam monitor for the Muon g-2/EDM experiment. This talk will discuss the measurement of beam storage by three-dimensional spiral injection and beam tuning using a scintillating fiber monitor.
CNAO is one the six hadrontherapy centers all around the world that produce
both proton and carbon
ions beams.
It is based on a synchrotron in which the beams are extracted by a slow extraction mechanism that uses a betatron core.
In the last years an electrostatic exciter has been installed along the ring in order to allow
beam extraction using the RF-KO method.
The system has been commissioned and allows extraction according to the clinical beam parameters.
The paper illustrates how the RF-KO method has been implemented in CNAO under the hardware and software
point of view. The characteristics of the proton and carbon beams will be also presented.
The baseline scheme for hadron beam cooling in the Electron Ion Collider (EIC) calls for Coherent electron Cooling (CeC) of the hadrons with non-magnetized electrons at high energy (150 MeV electrons), and additional cooling via conventional bunched beam cooling using a precooler system. The electron beam parameters for these concepts are at or beyond the current state of the art, with electron bunch charges of the order of 1 nC and average currents on the order of 100 mA and require an Energy Recovery Linac (ERL) to produce such beams. Using specifications provided by BNL and Jefferson Lab, physicists and engineers at Xelera Research are working on a complete design of an ERL system capable of satisfying such a cooler.
this paper briefly introduces the layout theory and analysis basis of the first-level control network, calculates the accuracy index of the first-level control network of Hefei Advanced Light Source, designs the basic scheme of the first-level control network, and analyzes the absolute precision and relative precision of the control network in detail through the simulated adjustment data.According to the design of the basic scheme of the first level control network, the author carries on the simulation calculation of the datum, adjustment scheme, factors affecting the accuracy and measures to improve the accuracy of the control network, and determines the optimal scheme.
The Southern Advanced Photon Source (SAPS) is a 4th generation storage ring based light source under design started several years ago, which is planned to be constructed
at Guangdong province at China. The equilibrium emittance of the storage ring will be below 100 pm.rad and the beam energy is determined to be 3.5 GeV. During the past two years, the nominal current of the storage ring was increased from 200 to 500 mA, so the injector system has to provide more bunch charge. Besides, the injection beam energy for the booster was increased from 150 to 250 MeV, which means two more accelerating cavities have to been added. In this paper, the update of the linac injector is presented, which consists of a thermionic electron gun, a bunching system, a 200 MeV linac. The beam transfer line from linac to booster is also presented
The Super Proton Synchrotron (SPS) injection system plays a fundamental role to preserve the quality of injected high-brightness beams for the Large Hadron Collider (LHC) physics program and to maintain the maximum storable intensity. The present system is the result of years of upgrades and patches of a system not conceived for such intensities and beam qualities. In this study, we propose the design of a completely new injection system for the SPS using multi-level numerical optimisation, including realistic hardware assumptions. We also present how this hierarchical optimisation framework can be adapted to other situations for optimal accelerator system design.
As compared to traditional magnets, permanent magnets can effectively reduce energy consumption and eliminate the impact of current ripple and the wa-ter cooling system on beam current. The use of perma-nent magnets in accelerators has become a new trend as permanent magnet technology has advanced. In HALF, we have designed a permanent magnet based on the quadrupole magnet, and the central magnetic field strength of the permanent magnet can be adjusted, indicating that single or multiple permanent magnets can be developed to replace different sizes of quadru-pole magnets in accelerators, greatly improving sys-tematization. The magnet’s mechanical design has been finalized, and the prototype of the permanent magnet will be manufactured and tested soon.
The Advanced Wakefield Experiment (AWAKE) has demonstrated during its first run (Run1, concluded in 2018) the capability of accelerating electrons up to the energy of 2 GeV using proton driven plasma wakefield acceleration.
AWAKE Run 2 has started and during the third phase of the program, Run 2c, which aims to demonstrate stable accelerating gradients of 0.5-1 GV/m and emittance preservation of the electron bunches during acceleration, the layout of the experiment will be modified to accommodate a second plasma cell. Among the many changes, the position of the primary 18 MeV electron beam line will be shifted. The beam line layout and optics will need, therefore, to be redesigned to fit the new footprint constraints and match the new beam requirements.
This paper presents the proposed layout of the new 18 MeV line, detailing the constraints and specifications, describing the design procedure and showing the main results.
The High Energy Photon Source is a 6 GeV synchrotron radiation light source being built in Beijing, China. The electron beam inside the storage ring is designed to run with ultra-low emittance. To ensure high beam quality, the coupled bunch instabilities must be carefully investigated and controlled, therefore an effective feedback system is essential. Stripline kickers are designed for transverse feedback in the HEPS storage ring. The basic structure and main simulation results of these kickers are introduced, including the reflection parameter, transverse shunt impedance, and wake effects.
A new fourth-generation synchrotron radiation source(4GSR) will be built in Ochang, South Korea by 2027. A technical design review for the Korea 4GSR is currently in progress and is expected to be completed in mid-2023.
The storage ring has a circumference of 800 m. It has been designed for a maximum current of 400 mA at 4 GeV electron beam energy. A target emittance is 58 pm-rad, 100 times less than PLS-II that is 3rd generation light source in Korea.
The RF system for the Korea 4GSR consists of 10 or more normal conducting cavities, a low-level RF(LLRF) system, a high-power RF(HPRF) system and so on. In order for the beam stability highly-HOM damped cavities will be indispensible. Subsidary the feedback system such as a longitudinal feedback system(LFS) and transverse feedback system(TFS) will be installed in the storage ring. Additionally we are planning to install harmonic cavities for Landau damping, on the other hand for improving of beam life time and less wake field. In case of the LLRF, we would try to apply new digital feedback control scheme. And the HPRF is taking account of solid state RF power amplifier.
This presentation shows the current status and plans of the RF system for the Korea 4GSR.
The Electron-Ion Collider is gearing up for "Critical Decision 2", the
project baseline with defined scope, cost and schedule.
Lattice designs are being
finalized, and preliminary component design is being carried out. Beam dynamics
studies such as dynamic aperture optimization, instability and polarization
studies, and beam-beam simulations are continuing in parallel. We report on
the latest developments and the overall status of the project, and present
the plans for future activities.
MYRRHA will be a research infrastructure focussed on the construction of a first prototype of an accelerator driven sub-critical nuclear reactor (ADS). The driver ac-celerator will deliver a 600 MeV, 4 mA Proton beam to the reactor core. The first phase called MINERVA aims for the construction of a 100 MeV, 4 mA proton linear accel-erator with a focus on reliability. Attached to this 100 MeV linear accelerator are a Proton Target Facility (PTF), which is essentially a high power Isotope Separation On-Line (ISOL) Facility, and a Full Power Facility (FPF) for fusion material research. This paper presents the status of the beam optic studies and overall layout of the Protons Target line towards the PTF, the Full Power line towards the FPF and the beam line towards an energy tuning beam dump.
Manipulating high energy beams with bent crystals has applications ranging from beam collimation to slow or direct beam extraction. These systems are now integrated parts of accelerators and studied for future experimental set-ups.
With growing achievements and expectations of crystal beam manipulation, requirements for the devices that operate the crystals become more stringent. They must retain the extreme angular precision required by the tight acceptance of crystal channeling. But they also must sustain longer operation, with higher beam energy, and provide additional functions.
In this paper are presented crystal channeling devices in operation or development at CERN. Target Extraction Crystal devices, operated in SPS ring, reduce beam power losses during slow extraction. Target Crystal Primary Collimators are now part of LHC collimation system for ions runs. Finally, two devices are currently developed for dipole moments measurement of short-lived baryons in the LHC.
This paper focuses on the relations between requirements, environment, and design of the different devices. It emphasizes how the specificity of items that share the same principle leads to unique design solutions.
Beam-based alignment (BBA) is a standard tool at accelerators for aligning particle beams to the centre of quadrupole magnets. Traditional BBA measurements have been slow, potentially taking many hours for a whole machine. We have developed a tool, based on results previously reported at the ALBA synchrotron, that uses fast excitation of magnets to greatly speed up measurements. We show results of different measurement and analysis techniques, and comparison with the currently used slow method.
Southern Advanced Photon Source (SAPS) is a 3.5GeV fourth-generation storage ring light source, considered to construction in Guangdong province of china, adjacent to the China Spallation Neutron Source(CSNS). Its natural emittance of the beam is close to the diffraction limit. Since the dynamic aperture of SAPS is far smaller than the physical aperture in the low emittance storage ring, on-axis swap-out injection scheme was adapted. Several couple sets of superfast kickers and nanosecond pulsers are needed. Due to the RF-frequency in the ring is 166.7 MHz, the gap of adjacent bunches is 6ns. In order to realize bunch-by-bunch control, the pulsers’ duration needs to be shorter than twice the minimum bunch spacing, which is a big challenge for SAPS. A prototype of fast nanosecond pulser based on semiconductor opening switch (SOS) was developed. A two-stage magnetic pulse compression system was used to pumping the SOS, which can provide with forward and reverse current of several hundreds of amperes. In this condition, the cutoff time of SOS can be reach several nanoseconds, which could meet the requirements of SAPS. The performance of the prototype can produce a pulse at 50Ω, with FWHM （50%-50%）of 5.6ns，bottom width(10%-10%) <12ns，an amplitude of 18kV. In this paper, the design, simulation and test results are presented.
MINERVA (MYRRHA phase 1) aims at demonstrating the requirements related to the reliability and the fault tolerances of the MYRRHA accelerator-driven system (ADS) by the realization of a superconducting linac for 100 MeV/4 mA proton beams. The design and the performance of the Medium Energy Beam Transfer section (referred to as MEBT-3) of the accelerator are critical for reaching the goals of MINERVA.
The purpose of the MEBT-3 is to fast-switch between a 17 MeV beam coming from one injector to another to ensure a continuous injection of 17 MeV proton beam in the main superconducting linac, in case one of the injectors would fail. The design goals of the MEBT-3 are to reach maximal beam transmission, accurate beam definition for matching the linac and a double achromaticity after the last switching dipole. For the protection of the main linac, a dedicated collimation system consisting of multiple slits was designed and incorporated into the MEBT-3 section.
The expected performance of the MEBT-3 has been studied extensively by beam dynamics simulations in order to reach the desired specifications. The non-accelerating MEBT-3 section includes multiple transverse and longitudinal beam focusing elements, such as magnetic quadrupoles and room temperature re-bunchers. The latest beam dynamics studies for achieving the MEBT-3 design goals will be presented.
The Electron-Ion Collider (EIC) presently under construction at Brookhaven National Laboratory will collide polarized high energy electron beams with hadron beams with luminosities up to 10^34cm^{-2}s^{-1} in the center mass energy range of 20-140 GeV. Besides high luminosity and high polarization, it is also recommended for the EIC design to incorporate a possible second interaction region (IR). In this article, we evaluate the dynamic aperture of the Hadron Storage Ring (HSR) design lattice with two IRs. The large nonlinear chromaticities from the two IRs will be compensated with multiple arc sextupole families. The tolerances of IR magnetic field errors are to be determined.
The Electron-Ion Collider (EIC) will be constructed at Brookhaven National Laboratory with the goal of providing high luminosity, high average beam polarization, and a wide range of colliding beam energies. One critical requirement is a large dynamic aperture (DA) of the collider rings, in both transverse and momentum dimensions. The ring lattices have been continually optimized to improve the geometric and optics conditions. This paper presents results of the DA studies for the recent lattices of the Electron Storage Ring at different energies, including non-linear chromaticity correction, effects of errors, magnet field quality, and orbit correction options.
We frequently experience earthquakes in Japan. Even though countermeasures against earthquake is deeply considered and well carried out, sometime troubles are occurred on facilities or experimental devices. When we focus on the relative displacement due to an earthquake, it is possible to cause damage of a beam pipe bellows or interference by disappearing tolerance between the sub-detectors. And magnet quenches have been triggered due to relative displacement of magnetic fields between three superconducting solenoids, i.e., the detector solenoid and two compensating solenoids in each final focus magnets, when earthquake occurred. So, we set acceleration sensors, the relative displacements had been measured. And also, laser distance sensors and gap sensors mounting on the final focus magnets were referred for this study. From these measurement data, characteristics of earthquakes were analyzed. Measurement acceleration data was also applied for response spectrum analysis. In this presentation, we will present the measurements and analysis results, and comparison between the measurements and the FEM calculations are shown.
Proton bunches will collide with electron bunches in the Electron-Ion Collider (EIC) to produce a luminosity of up to $10^{34}~\mathrm{cm}^{-2}\mathrm{s}^{-1}$. Various sources can lead to electron orbit ripple at the interaction point (IP). This ripple will cause emittance growth of the proton beam via beam-beam interaction. This paper presents weak-strong simulations for the case where a strong electron beam experiences orbit ripple. The frequency of the ripple is scanned to obtain the maximum tolerable amplitude. At the low frequency, different proton parameters are tested to reduce the emittance growth. These results will inform the engineering design of the Electron Storage Ring (ESR) in the EIC.
Polarization levels in the Electron Storage Ring (ESR) of the Electron-Ion Collider (EIC) must be maintained for a sufficient time before depolarized bunches are replaced. The depolarizing effects of synchrotron radiation can be minimized with spin matching, however the optics requirements for the ring must still be satisfied. Furthermore, the robustness of the polarization in the presence of misalignments, beam-beam effects, and the eventual insertion of a vertical emittance creator – necessary to match the electron and ion beam sizes at the interaction point – must be ensured. In this work, the results of various polarization analyses of the ESR lattices are presented, and their implications discussed; the necessity for a longitudinal spin match in the 18 GeV case is investigated, and vertical emittance creation schemes with minimal effects on polarization are analyzed.
The EIC electron beam parameters will feature 320 kJ stored kinetic energy and beam sizes leading to the melting of most metals in case of normal impact of a single bunch. In order to protect the aperture, focusing magnets and experimental detectors from beam losses and backgrounds a dedicated collimation system will be included in IR2 and IR4. Additionally, to protect against accidental losses from failures and continuous losses from swapping bunches, kickers and absorbers will be added to IR12 and IR2. This paper describes the current design for these two systems including material choices and specifications.
Dust particles interacting with the proton beams have caused many thousand beam-loss events at CERN's Large Hadron Collider (LHC), some of which led to premature beam dumps and even magnet quenches. It has been hypothesized that dust particles on the vacuum chamber wall of the LHC are negatively charged due to electron clouds and can detach from the chamber wall by the electric field of the beam. To test this hypothesis, we performed experiments to study the electrostatic lofting of dust particles from a conducting surface. A monolayer of SiO2 particles with a diameter of <44 um is deposited on such a surface and exposed to an electron beam of 80-140 eV. An external electric field of up to 3 kV/cm is then applied. The properties of dust charging and levitation are characterized from recorded high-speed videos. We observed that dust particles are lofted both during electron beam charging and during the application of the external electric field. Our results provide experimental evidence that dust particles can be detached from a conducting surface and help to understand the mechanism of how dust particles can enter the LHC beam.
Elettra 2.0 is the name of the upgrade project of the existing Elettra Storage Ring (SR) and its ancillary systems. The project comprises also new beamlines (BLs) and the re-allocation of some of the currently operational ones.
Consequently, the “Experimental Hall” (EH) of Elettra, i.e. where the beamlines are installed, is another working area with activities that have started well before the scheduled “Dark Period” (DP) when we will dismantle Elettra and install Elettra 2.0.
The installation of the beamlines implies, among many more activities, the partial reconfiguration of the shielding wall of the SR tunnel. Some of these local re-arrangements can be performed before the DP, during maintenance shutdowns of Elettra, in those portion of the EH not currently occupied by working beamlines.
The reconfiguration of the shielding wall requires a design that merges SR and BLs specifications, as well as careful planning of on-site activities, spanning from survey and tracing of the new positions of the blocks, to plants re-arrangement, to handling and transportation of concrete blocks up to 6 tons.
This paper illustrates the status of the reconfiguration activities of the Experimental Hall.
The LHC beam dump system has the task of safely and reliably disposing of the extracted beams from 450 GeV to 7 TeV. The present dump assembly consists of a multi-segment graphite core, which is contained in a duplex stainless steel vessel with titanium windows. To reduce the energy deposition density in the core and windows, the extracted beams are swept across the dump front face with dedicated dilution kickers. In the High Luminosity-LHC (HL-LHC) era, the dump must withstand beams with a significantly higher stored energy (about 700 MJ) than has been achieved so far (380 MJ). The high temperatures and vibrations generated in the core and vessel require a redesign of the dump assembly to ensure safe operation with HL-LHC beams. This work presents energy deposition studies for the different dump components in case of regular dumps and possible dilution kicker failure scenarios during HL-LHC operation. The impact of different design choices, such as the dump core segmentation, on the energy deposition and the leakage of particles from the dump is discussed.
We discuss the beam power loss related to the heating of the beam pipe walls of the FCC-ee interaction region. We analyse the excitation of trapped modes, which can accumulate electromagnetic energy and determine the locations of these modes. We study the unavoidable resistive-wall wake field, which is responsible for the direct beam pipe walls heating. We show the distribution of the heat load along the central part of the interaction region. We also present the cooling system design and results for temperature distribution in interaction region in the operational mode.
The BEPCII has already realized the collision luminosity target of $1.0\times10^{33}cm^{-2}s^{-1}$ in April 2016. However, in the past six years of practical operation, the collision luminosity usually remains between $6.0\times10^{32}cm^{-2}s^{-1}$ and $8.5\times10^{32}cm^{-2}s^{-1}$. In the operation with high beam current, the BEPCⅡ displayed serious beam instabilities, which greatly limits the increase of collision luminosity. A series of machine studies and analyses were conducted. According to the bunch lengthening experiments, the longitudinal effective impedance is $0.162\Omega$ for electron storage ring and $0.195\Omega$ for positron storage ring. According to the tune shift measurements, the transverse effective impedances are $0.02840\Omega/m$ horizontally and $0.05253\Omega/m$ vertically for electron storage ring, and $0.04223\Omega/m$ horizontally and $0.06714\Omega/m$ vertically for positron storage ring. The oscillation mode distribution was obtained from experiments, showing that the transverse beam coupling instability has become an important factor for limiting the increase of beam current and luminosity. Finally, some possible origins of transverse narrow-band impedance, such as the resistive wall and vertical masks, were checked. The calculated results match with the experiment results quite well. The results in this study give important references for establishing feedback systems and increasing the collision luminosity in the future research.
Steady-state microbunching (SSMB) is envisioned to enable the generation of high-power coherent synchrotron radiation at an electron storage ring for wavelengths up to the extreme ultraviolet. The underlying mechanism has been shown to be viable in a proof-of-principle (PoP) experiment at the Metrology Light Source (MLS) in Berlin*.
An enhanced detection scheme allows systematic studies of the conditions needed for the creation of microbunches within the continuing PoP experiment**. It was found that the generation of coherent radiation from microbunches is favored in specific nonlinear longitudinal phase space structures, known as “alpha buckets”, which arise when the momentum compaction function becomes dominated by higher order terms.
We present the most recent experimental results and their interpretation as well as accompanying simulation results.
A new collaboration between ESRF and DESY within the EURIZON project is aiming at building tools and concepts that can be used for the next generation light sources. The developed tools will be applied to the ESRF-EBS and the PETRA IV lattice models to validate concepts to improve the injection efficiency or the lifetime of storage rings.
In this project framework, the bounded Extremum Seeking (ES) algorithm is being studied as a Touschek lifetime optimization procedure. This contribution presents the tests performed on the ESRF-EBS electron beam where several sextupole and skew quadrupole knobs were tuned at the same time for vertical emittance minimization first and subsequently lifetime maximizsation.
To improve the performance of beam orbit correction, it is necessary to perform beam-based alignment in modern storage ring light sources. For the High Energy Photon Source (HEPS), a 4th generation storage ring light source being built in China, because of the large number of BPMs in storage ring, it may take dozens of hours to complete the alignment with a conventional BBA algorithm. To reduce the time cost, it has been proposed to use ac excitation for fast beam-based alignment. We tested the feasibility of applying this method to the HEPS storage ring through numerical simulations. In the following, we will introduce the simulation settings and the corresponding results.
The Fermilab Muon Campus, repurposed Tevatron-era Antiproton Source facilities, is currently the home to the g-2 and Mu2e muon experiments. Collecting data since 2017, the g-2 experiment is wrapping up a final run before the Muon Campus transitions to Mu2e operation. Currently in the commissioning process, the Mu2e experiment is expected to begin calibration and data collection in fiscal year 2024. A majority of the Muon Campus is shared between the two experiments, however the modes of operation for each are significantly different. An 8 GeV primary proton beam strikes a target to produce a 3.1 GeV/c secondary muon beam for g-2, while the Mu2e experiment uses the Delivery Ring, formerly the Antiproton Accumulator Ring, for a pulsed, resonantly extracted, 8 kW, 8 GeV proton beam incident on a target in the experiment's target hall to produce a muon beam for the experiment. The design and current state of the Muon Campus and the current and future plans of the g-2 and Mu2e experiments, including the transition between operating modes, will be presented.
The SuperKEKB accelerator, a collider consisting of 7 GeV electron and 4 GeV positron rings, is ongoing in order to supply a great number of interaction events of electrons and positrons to the Belle II detector which explores the new physics beyond the standard model.
The important milestone is to obtain integrated luminosity of 15 /ab in the next decade,
so that the luminosity should exceed 2 x 10^35 /cm^2/s in several years.
One of the essential issues is the injection performances for both rings to be capable of storing beams of a few amperes due to overcoming their short lifetimes.
The key component of the injection system is the septum magnets.
It has been found that a transverse fringe field near the septum plate has sizable multipole components.
A tracking simulation shows such fringe fields induce a vertical non-Gaussian tail,
which could cause a beam background as well as a bad injection efficiency.
Adjustment of Q-magnets for cancellation does not work perfectly for non-linear components.
To reduce the multipole region contributes to the injection amplitude to be smaller, and so, that derives improvements of injection performances.
This paper reports about the field quality improvement of the septum magnet for the SuperKEKB HER injection system.
The PERLE (Powerful Energy Recovery Linac for Experiments) project relies on superconducting RF (SRF) cavities to reach its goals. The installation of coaxial couplers on the cutoff tubes of SRF cavities is foreseen for damping cavity’s Higher Order Modes (HOMs). The prototyping and fabrication of 3D-printed HOM couplers for the PERLE cavity have recently started in collaboration with JLab and CERN. This paper provides an overview of the design of the fabricated HOM couplers and the first RF measurements of the cavity’s HOMs performed at warm on an 801.58 MHz 2-cell copper cavity to validate coupler design performances. Measured cavity data is also compared to eigenmode simulations to confirm simulated results and see to what extent any reduction in damping can be predicted.
The Mu2e Experiment has stringent beam structure requirements; namely, its proton bunches with a time structure of 1.7µs in the Fermilab Delivery Ring. This beam structure will be delivered using the Fermilab 8-GeV Booster, the 8-GeV Recycler Ring, and the Delivery Ring. The 1.7-µs period of the Delivery Ring will generate the required beam structure by means of a third order resonant extraction system operating on a single circulating bunch.
The electrostatic septum (ESS) for this system is particularly challenging, requiring mechanical precision in a ultra high vacuum of 1E-8Torr to generate 100kV across 15mm. This paper describes a graphical user interface that has been developed to automate the conditioning and commissioning process for the electrostatic septa. It is based on an interface to the Fermilab ACNET system using the ACSys Python Data Pool Manager (DPM) Client produced and maintained by Fermilab Accelerator Controls.
Network interfacing between data pool managers made by the application and ACNET devices introduce an inherent (approximately 1s) latency in throughput of the readouts. This delay is utilized to process and graph incoming data events of devices crucial to conditioning of a electrostatic septum (ESS). Ramping' andMonitoring' modes adjust settings of the power supply based on internal logic to efficaciously increase and maintain the high voltage (HV) in the ESS, easing the voltage setting on incidence of sparking or other possibly damaging events. A timestamped log file is produced as the application runs.
The longitudinal distribution of the electron beam in the electron storage ring of the Electron-Ion Collider will be modified by the machine impedance. The modified distribution, combined with crab cavities may have an impact on the quality of the hadron beam during the collision. In this paper, we will explore the possible impact on the hadron beam quality with strong-strong and weak-strong beam-beam simulations.
Energy Recovery linear accelerator (ERL) light source facilities based on superconducting radiofrequency (SRF) are deemed of the most resplendent techniques in the future of accelerator physics. Running in a continuous waves mode with a high repetition rate for a long timescale, we discuss High order modes (HOMs) analysis in a two-pass two-way ERL scheme where acceleration and deceleration of electron bunches are supported by a standing wave structure of the RF cavity. The analysis reported in this paper is based on differential equations that describe the beam dynamics (BD) to overcome the limitations imposed by high currents and insure energy recuperation over millions of interactions.
The new EBS machine was commissioned in 2020 with a targeted nominal beam emittance of 139pm.rad in the horizontal plane. The radiated energy in the 70 insertion devices present from the restart was expected to change the equilibrium emittance. This paper presents the prevision and the measurements performed as a function of the total radiated power in the machine. The comparison shows that the non zero dispersion present in the insertion devices has a visible impact on the emittance reduction.
The concept of steady-state microbunching (SSMB) as a new scheme for the production of high power synchrotron radiation has been demonstrated at the Metrology Light Source in Berlin-Adlershof (MLS) [1].
At the MLS the same undulator section is used for the generation of the micro-structures onto the electron bunch as well as for the detection of the resulting coherent radiation from the micro-bunches one turn later. Due to the enormous difference in the pulse energy of the micro-bucket generating laser and the coherent undulator pulses showing up 160 ns later, the detection is not straightforward. We show in detail the detection scheme, mostly based on fast optical shutters, and the triggering scheme of the experiment. Ideas for further improvements are discussed.
[1] X. Deng et al., Nature, Volume 590, Issue 7847
The 7-GeV low-emittance electron beam is essential to be delivered to the SuperKEKB double-ring collider. One of the issues at the complicated beam transport between the linear accelerator and the High-Energy Ring (HER) is significant transverse emittance growth. In general, both incoherent and coherent synchrotron radiation effects play crucial roles in beam behavior. In this paper, we present the measured emittance results of the nominal optics with the help of particle tracking simulations.
CNAO is one the six centers all around the world able to treat patients affected from cancer by proton and carbon
ions beams. Beams are produced by a synchrotron equipped with two sources. A third source has been recently
installed in order to produce new species that will be interesting both for clinical and R&D purposes.
A new low energy line has been designed, installed and commissioned to transport beams from the new source
to the accelerator. In this paper the new line, called LEBTO3, is presented.
The Electron-Ion Collider, to be constructed at Brookhaven National Laboratory, requires a large dynamic aperture (DA) of the electron storage ring (ESR) for stable operation of 10 beam sigma for the transverse aperture and 10 times the RMS momentum spread in the longitudinal plane. In particular for operations at the top energy of 18 GeV this has not been easy to achieve, and the DA has proven sensitive to small changes. Nevertheless, a chromaticity-correction scheme has been developed for the bare lattice. There are several important effects in the interaction region that are potentially damaging to the ESR’s DA, including the beam-beam interaction, crab cavity kicks, the detector solenoid field, and skew quadrupoles for coupling compensation. In this contribution, these effects are modelled to evaluate their impact on the dynamic aperture of the ESR at 18GeV.
Initiated through the Physics Beyond Colliders (PBC) Study Group there is a strong interest from the scientific community to exploit the full intensity potential of the Super Proton Synchrotron (SPS) at CERN for Fixed Target physics experiments before the end of this decade. With the ECN3 cavern in the North Area (NA) identified as a suitable candidate location for a future high-intensity experimental facility compatible with a large variety of experiments, the new PBC ECN3 Beam Delivery Task Force was mandated to assess the feasibility of delivering a slow extracted beam of up to 4x10^19 protons per year at 400 GeV. This contribution summarises the conclusions of the multifaceted beam physics and engineering studies that have been carried out recently to understand the present intensity limitations and to find technical solutions to meet the request for higher intensity in the NA transfer lines towards ECN3. The necessary modifications to the beam lines, the primary target area, beam instrumentation and intercepting devices, as well as the relevant infrastructure and services are outlined, along with a timeline compatible with the NA consolidation project that is already underway.
The Southern Advanced Photon Source (SAPS) is a 3.5 GeV, kilometer-scale, ultra-low emittance storage ring to be built next to the CSNS(China Spallation Neutron Source) in Guangdong Dongguan, China. A preliminary lattice design for SAPS storage ring with an emittance of 32 pm.rad has been proposed before. Now, the SAPS lattice is continuously under extensive design and optimization. In this paper, the latest design of lattice is introduced, and the linear and nonlinear optimization is presented.
Among the possible future lepton colliders under study, circular muon colliders have the largest potential of reaching center-of-mass energies of 10+ TeV. Being more massive than electrons and positrons, muons are much less affected by synchrotron radiation emission, but they suffer from the drawback of having a limited lifetime. As a consequence of their decay, intense secondary radiation fields are generated in the collider, which can considerably disrupt the detector performance, both as physics background and as a cause of long-term material degradation. The machine-detector interface in a muon collider therefore requires a careful design, integrating massive shielding elements between the detector and final focus magnets. In this paper, we devise an interaction region design for a 10 TeV muon collider with a final focus triplet. We quantify the flux of secondary particles entering the detector by means of shower simulations and provide a first optimization of the shielding configuration. We also present first estimates of the power deposition and radiation damage in final focus magnets.
The Metrology Light Source (MLS) is a 630 MeV electron storage ring as a synchrotron radiation source for the terahertz (THz) to the extreme UV spectral range. Its upgrade project MLS II is defined as a compact 0.8 GeV storage ring with multiple operation modes, which pursues lower emittance (<50 nm) in standard user mode and preserves
the strong capability of MLS to manipulate the momentum compaction and its higher-order terms for short-bunch mode. This paper presents the lattice options based on double-bend achromat (DBA) and quadruple-bend achromat (QBA). The linear optics and nonlinear beam dynamics of both lattices were investigated.
The Electron-Ion Collider (EIC) at Brookhaven National Laboratory will feature an electron storage ring that will circulate polarized beams with energies up to 18 GeV. Recently a study has been undertaken to extend the minimum energy from 6 GeV to 5 GeV. As the solenoid-based spin rotators around the interaction point require specific bending angles that depend on the energy range, this change results in major changes to the geometry. Moreover, avoiding interference of the electron beamline with the other beamlines in the tunnel, as well as with the tunnel walls, is a formidable challenge, especially at the location of the large-diameter superconducting solenoids. In this contribution, the details of the modified spin rotators, geometrical layout, and optics of the revised lattice are presented.
UVSOR, a low energy synchrotron light source, has been operational for about 40 years. It has been providing high brightness VUV radiation to users but also providing a research environment for light source technology developments. In this paper, first, we briefly review the history of the light source developments at UVSOR. Then, we describe a beamline BL1U, which is currently used for developments and applications of novel light source technologies. The beamline is equipped with two variable polarized undulators with a phase-shifter magnet and with a femto-second laser system which is synchronized with the RF acceleration. We have been developing resonator free electron laser, coherent harmonic generation, coherent synchrotron radiation, inverse Compton scattering, spatiotemporal-structured light and have been exploring their applications, in collaboration with researchers from universities and research institutes. We present the present status of BL1U and some recent results.
The proposed strong hadron cooler for the Electron-Ion Collider contains regions that transport beams with different energies. In this paper we present a possible magnet design for a broad range of beam energies.
PERLE (Powerful Energy Recovery LINAC for Experiment) is a high-power Energy Recovery LINAC (ERL) facility with 20 mA beam current and beam energy from 250 MeV to 500 MeV featuring three passes through two cryomodules. It is a hub for validation of the ERL technology development towards future energy and intensity frontier machines. Design challenges of PERLE and its beam parameters make it a testbed to validate multi-turn high current ERL operation for the LHeC. It will be the first ERL for some pioneering experiment of the eN interaction with radioactive nuclei.
In this work, design and optimization of the commutational magnet (B-com) used to spread/combine the three beams and one series of the quadrupole magnet is discussed. It gives the design parameters including: yoke geometry, pole profile, and material, and calculation of the excitation current needed to drive the magnet, the coil parameters and the number of turns.
The B-com magnet is optimized for a 30° bending angle with magnetic field of 0.88 T along the magnet length and a harmonic content of 0.036%. The quadrupole magnet is designed for a gradient field of 34.15 T/m and experiences saturation above this value. Further studies to avoid saturation and achieve the maximum gradient of 44.1 T/m required by the beam dynamics is undergoing.
The diffraction-limited storage ring (DLSR) of the Southern Advanced Photon Source (SAPS) use a large number of ultra-high gradient quadrupoles and sextupoles, which leads to the tight tolerance of beam parameters to magnetic errors. We showed the results of the magnetic error effects in previous published article. On this foundation, the magnetic error corrections are finished, including the closed orbit correction, beam optics correction and vertical dispersion correction.
Modernization of the NESTOR hard X-ray generator storage ring for switching to the operating frequency of the accelerator of 2.856 GHz requires corresponding changes in the design of the high-frequency system, and this, in turn, leads to the need to modernize the laser-optical system. The necessary calculations were carried out to determine the new characteristics of the pulsed laser, the Fabry-Perot cavity, and the lens optical system matching the beam geometry. The obtained results confirm the possibility to use an already existing laser-optical system at a new operating frequency of the accelerator with some changes in the design.
To satisfy up-to-date technical requirements NSC KIPT hard X-ray source on the base of Compton scattering NESTOR should be modified. Essential modernization should be done in accelerator-injector, lattice of the storage ring, RF and optical systems.
In the paper the technical proposals of the facility modernizations and results of beam dynamic simulations in the modified facility are presented and described.
KEK has two light sources: Photon Factory (PF, 2.5 GeV) and Photon Factory Advanced Ring (PF-AR, 6.5 GeV). In 2017, the use of a new beam transport line (BT) of PF-AR was started, and the simultaneous top-up injection for both PF and PF-AR was realized. These days, there have been strong demands for the reduction of the operating cost of accelerators, and its importance is greater in PF-AR with higher ring-energy. In 2019, the 5 GeV operation was started in PF-AR. However, the new BT of PF-AR (ARBT) was designed for the energy of 6.5 GeV, then the simultaneous top-up injection is no longer available under the condition of 5 GeV operation of PF-AR and 2.5 GeV operation of PF. In order to mitigate this impact, the pseudo-top-top injection has been employed by fine-tuning the current of a common DC bending magnet placed at the intersection of ARBT and the BT of PF (PFBT) within a given time frame. However, this scheme limits the operation schedules, and will not be able to respond adequately to low emittance optics of PF-AR that may bring the shorter beam lifetime. In order to realize true-top-up injection, a modification of BTs’ optics design was carried out. This time, details of modified design of BTs’ optics and its extended plan will be presented.
The system in place for remote alignment of the girders, which carry the storage ring elements of the PETRA III light source in the Max von Laue experimental hall, were never used to perform re-alignments after the initial installation of the storage ring in 2009. Since the planned upgrade, PETRA IV, can benefit from the fine control of the girder position to achieve the design beam performance, a movement test of one of the PETRA III girders was performed in December 2022. The ability to safely and precisely remote control the equipment was demonstrated and the accuracy of the optics model that describes the effect of the girder movement on the orbit could be evaluated. The findings of this experiment are summarized in this paper.
Transverse multibunch instabilities are of significant interest in accelerators with strong wakes and large bunch trains. In such cases, wakes that do not damp sufficiently from bunch to bunch can drive instability along the entire bunch train. Simulations are useful for understanding such instabilities, but the multiscale nature of the system and numerical noise can make results uncertain. A linearized multibunch model will be applied to study multibunch instabilities, and potential applications for the future electron ion collider project will be explored.
A method to reconstruct the momentum distribution of the injected muon beam in the Muon g-2 Storage Ring at Fermilab has been developed, which is based on beam profile measurements from the Muon g-2 straw tracking detectors as input. Extending a spectrometric perspective to the muons injected into the Muon g-2 storage ring, a direct transformation of the beam radial coordinates when the distribution recreates the initial beam conditions and when the muons are separated proportionally to their magnetic rigidities provides a precise method to measure the energy distribution of the stored beam. The obtained energy distribution can be used to quantify the dominant beam-dynamics corrections to the final measurement of the muon g-2 experiment.
The 18 GeV Electron Storage Ring (ESR) lattice of the Electron-Ion Collider (EIC) showed various undesirable effects in nonlinear Monte Carlo tracking, including a vertical core emittance exceeding radiation-integral predictions and a low asymptotic polarization. These problems were resolved in a newer lattice where dispersion in the solenoidal spin rotators was set to zero. Here we identify the cause of the effects as a 2nd order synchro-beta resonance which is driven by vertical dispersion in the quadrupoles of the rotators. The 5 and 10 GeV ESR lattices have small but nonzero dispersion in the rotators, and misalignments in the 18 GeV case will inevitably create some dispersion, so care must be taken that this 2nd order resonance is not excited. Zero dispersion in the spin rotators may therefore not be the best solution, and a new working point is sought that is not close to this resonance. The implications of this result on the design of the ESR – including achieving a longitudinal spin match – are explored.
The booster ring of High Energy Photon Source is responsible for ramping the beam energy from 500 MeV to 6 GeV. Six 5-cell copper cavities of PETRA-type were chosen to provide a total accelerating voltage of 8 MV. To fulfill the specific requirements of the HEPS booster, several modifications were made on the original design from Research Instruments (RI). Six cavities manufactured by RI have been delivered to HEPS and high-power tested successively from April to December 2022. Cavities were tested up to a maximum rf power of CW 120 kW, which is the reliable capability of the power coupler specified by RI. Power-keeping at the maximum rf power was conducted subsequently, with an average time of 100 hours. Finally, in order to verify the performance during real operation, the ramped run was conducted according to the pre-defined curve required by the physics design at a repetition rate of 1 Hz, with all control loops closed (cavity frequency loop, cavity field amplitude/phase loop, amplifier amplitude/phase loop). Details on the design modifications, the low-power test, the high-power conditioning and the ramped commissioning are presented in this paper.
Taiwan Photon Source (TPS) had delivered the first synchrotron light on the last day of 2014. Installation of 16 beamlines of the first and second phases of TPS beamline project was completed. The third phase project also had been launched in 2021. To confront the situation that the experimental hall is more compact, we per-formed Computational Fluid Dynamic (CFD) simulation to analyse the effects of the air conditioning system and various heat sources to the temperature and flow fields in the experimental hall.
The ESRF-EBS is the first 4th generation source making use of the Hybrid Multi-Bend Achromat (HMBA) lattice cell, reaching an equilibrium horizontal emittance of 140 pm.rad in user mode (insertion devices (ID) gaps open). An off-energy operation was proposed to further reduce the equilibrium emittance by about 20 pm.rad. A first proposal rematched the HMBA optics at an energy deviation of -1\% and evaluated its dynamic aperture in the machine. Further experiments were dedicated to this study at the ESRF-EBS, including injection efficiency and lifetime optimisation.
The European Synchrotron Radiation Facility - Ex-tremely Brilliant Source (ESRF-EBS) is a facility upgrade allowing its scientific users to take advantage of the first high-energy 4th generation storage ring light source. In December 2018, after 30 years of operation, the beam stopped for a 12-month shutdown to dismantle the old storage ring and to install the new X-ray source. On 25th August 2020, the user programme restarted with beam parameters very close to nominal values. Since then beam is back for the users at full operation performance and with an excellent reliability. This paper reports on the present operation performance of the source, highlighting the ongoing and planned developments.
In this paper, we present the possible use of laser Compton back scattering (CBS) to adjust and tune the bunch intensity. In the future circular electron-positron collider “FCC-ee”, the intensity of the colliding bunches should be tightly controlled, with a maximum charge imbalance between collision partner bunches of less than 3–5%. The control of such tolerance is necessary due to the strong effect of beamstrahlung on the bunch length and “flip-flop” instability. We show a realistic beam optical line and simulation results of CBS in the "FCC-ee", including the distribution of scattered positrons.
The Electron-Ion Collider (EIC) presently under construction at Brookhaven National Laboratory will collide polarized high energy electron beams with hadron beams with luminosities up to 10^34cm^{-2}s^{-1} in the center mass energy range of 20-140 GeV. Preliminary beam-beam simulations resulted in an optimum working point of (.08, .06) in the Electron Storage Ring (ESR). However, during the ESR polarization simulation study this working point was found to be less than optimal for electron polarization. In this article, we present beam-beam simulation results in a wide range tune scan to search for optimal ESR design tunes that are acceptable for both beam-beam and polarization performances.
The observation of the Higgs boson by the LHC (2012), and the direct observation of gravitational waves (GW) from a collapsing binary systems by LIGO (2016) marked the successful end of long-standing efforts, and hopefully the dawn of a new era where both fields, Particle Accelerators (PA) and GW Physics, may benefit from knowledge/technologies developed by the other party. CERN recently hosted a meeting (SRGW2021) where such synergies were discussed, including the possibility of operating storage-rings/colliders as GW sources/detectors. Earth-bound interferometric GW detectors may explore only a tiny subset of the GW spectrum. Spaceborne detectors (LISA) and pulsar-timing observatories will open a window in the LF to ELF range, and different HF to SHF detectors have been proposed (SISSA2019). Observations at these frequencies would bring rich astrophysical/cosmological information. On the other hand, PA advances in superconducting magnets, and extremely high-Q RF cavities, and the (still controversial) possibility that superconductors may act as GW reflectors, suggest to reconsider the feasibility of a GW “Hertz experiment” based on Gertsenshteyn effect; while progress in (big) data analysis, control systems and optical materials from GW experiments may be useful for next gen PA. We review these ideas from a dual perspective, and highlight possible directions for common work.
NSLS-II is a 3 GeV third generation synchrotron light source at BNL. The storage ring was commissioned in 2014 and began its routine operations in the December of the same year. Since then, we have progressed steadily upwards in beam current and reached 500 mA in five years while increasing new insertion devices. Along this path, we report various challenges and the improvements to reach high current.
The community studying facilities to measure a possible Electric Dipole Moment of a charged particle (cpEDM) in a storage ring agreed that a Prototype Storage-Ring (PSR) is required as intermediate step to address critical questions, gain experience and rule out showstoppers. In what follows, a new lattice proposal of the PSR with a periodicity five is described and spin tracking simulations are shown. The main feature of this new lattice proposal is to use weak focusing quadrupolar components to achieve vertical stability while the horizontal optics properties are dominated by the focusing from the bending elements with a little impact from the quadrupoles.
The Synchrotron Light Source PETRA III is one of the core facilities at DESY offering each year more than 2000 users unique opportunities for experiments with hard X-rays of a very high brilliance. The light source is operated mainly in two operation modes with 480 and 40 bunches at a beam energy of 6 GeV. The availability and failure statistics is reviewed for the year 2022 in comparison with previous years. Studies at PETRA III are supporting the technical design phase for the planned upgrade PETRA IV. Several diagnostic devices have been tested and the installation of a cavity has been prepared. Furthermore, the operation of PETRA III at 5 GeV has been studied with the goal to reduce the electric power consumption of the accelerator. But a 5 GeV test run for all beam lines at PETRA III showed that this operation mode is impairing the experimental opportunities due to the lower brilliance and photon flux for hard X-rays.
To explore the beyond standard model of elementary physics, we proceed a new fundamental physics experiment, J-PARC muon g-2/EDM experiment. To realize very precise measurement of the muon spin precession frequency in the level of sub-ppm, a relativistic energy of muon beam is injected into a precisely adjusted storage magnet of sub-ppm uniformity by applying medical MRI magnet technologies.
Three-dimensional spiral beam injection scheme is intended to storage in 0.66 m diameter compact ring, we have carefully studied of a spatial distribution of a radial magnetic field of the storage magnet and required beam phase space, especially for a strong X-Y coupling. In this presentation, we will discuss about a strategy to precise control of the X-Y coupling at the beam transport line: how to detect X-Y coupling from a beam phase space, how to control X-Y coupling with eight independent rotatable quadrupole magnets. We also discuss about how to apply fine-tuning of the beam trajectory without disturbing the magnetic field in the beam storage volume, by use of active shield multipole coils.
Finally, we will report detailed studies of X-Y control at a demonstration beam line in KEK which proves the three-dimensional injection scheme is realistic one, as well as further challenges towards the original beam line at J-PARC.
The Korea 4th Generation Storage Ring(Korea-4GSR) project has been launched in 2022. The Korea 4GSR aims to generate the ultra-low emittance beam with the beam current of 400 mA and the beam energy of 4 GeV. In order to accelerate and store the beam to desired parameter, the Storage Ring RF(SRRF) is composed of 10 or more RF Stations and each RF Station includes LLRF(Low Level RF), HPRF(High Power RF), NCC(Normal Conducting Cavity) system.
For stable operation and machine safety, sub systems are operated by the Control System for the SRRF. In this paper, we describe the design of the Control System. It will include control network, operating interface, emergency interlock, data archiving and so on.
In the FCC-ee study, it is proposed that electron and positron beams circulate at high current and high energy in a 92-km circumference ring. The present operational scenario foresees a first running step at an energy of 45.6 GeV and around 1.4 A current, which would generate copious amounts of synchrotron radiation (SR) power and flux. To guarantee a quick decrease of the photon desorption yields and so a fast vacuum conditioning, it has been proposed to use localized SR absorbers along the vacuum chamber, spaced about 6 m apart. This would also help contain the high-energy Compton-scattered secondaries once the beam energy is increased up to 182.5 GeV, later in the experimental program.
In the preliminary design of FCC-ee vacuum chamber absorbers presented in this work, the SR thermal power is intercepted along around 100 mm of slanted surface. The temperature distribution in the adsorbers is estimated by Finite Element Analysis (FEA) and needs to be assessed to avoid any liquid-gas phase change within the water-cooling circuit. The cooling channels contain a twisted tape that increases the turbulence of water. This results in the desired heat transfer coefficient. The mechanical deformations due to the non-uniform temperature map are presented and analyzed as well.
Rapid cycling synchrotron (p-RCS) is the first synchrotron of the accelerator chain in the proposed Super Proton-Proton collider (SPPC) project. It will provide high-energy and high-power beams for the injection to the downstream accelerators for SPPC collision with the required beam characteristics such as bunch spacing, bunch population and emittance, but also serve independent application program with less restricted beam characteristics and a higher beam power of 3.4 MW. With a designed energy range of 1.2-10 GeV and a repetition rate of 25 Hz, the lattice design plays a mandatory role in beam dynamics. In this paper, three types of linear lattice for the p-RCS, which are based on the basic FODO module, triplet module and negative momentum compaction (NMC) factor module, respectively, are compared. Taking into consideration the longitudinal beam dynamics which requires as a large absolute of slippage factor as possible at the extraction energy, the NMC lattice is considered a preferable solution.
In this paper we will show the injection philosophy and the design of timing and filling scheme for high luminosity CEPC scheme under different energy modes. It is found that the RF frequency choice in CDR cannot meet the injection requirements for the bunch number at Z pole. A modified scheme was proposed to support the design luminosity,which basically meets our current design requirements and retains more flexibility for future high luminosity upgrade.
Since the upgrade and renovation of the East Experimental Area at CERN during Long Shutdown 2 (LS2: 2019 - 2021), demand has increased for slowly extracted beam from the CERN Proton Synchrotron (PS). The East Area is a multi-user facility carrying out a diverse experimental physics programme. It requires a wide range of slowly extracted beams to be delivered by the PS. This contribution summarises the gained understanding, progress and improvements made since LS2 in the slow extraction of both proton and ion beams. Furthermore, it describes the production of low intensity, variable energy, heavy-ion beams for a collaboration between CERN and the European Space Agency, striving to establish a novel and flexible high-energy heavy-ion radiation test facility.
We report on progress developing the Energy and RF ramp for the EIC’s Rapid Cycling Synchrotron (RCS). The development of the RF voltage and phase ramp from injection energy at 400 MeV to 5, 10 and 18 GeV extraction energy requires control of the bunch’s longitudinal aspect ratio to avoid both collective instabilities, RF bucket height and width as well as lattice dynamic aperture limits. Further the ramp profile must meet the technical limits for the current super conducting cavity design.
A new ISOL rare isotope beam production facility, ARIEL, is being commissioned to triple the availability of radioactive ion beams for the ISAC experimental facilities at TRIUMF. Part of ARIEL is the new CANREB charge breeding facility that includes RFQ cooler, EBIS and Nier separator, and a high-resolution mass separator system (HRS). The HRS is designed to achieve a resolving power of 20,000 for a transmitted emittance of 3 µm with an energy spread of less than 0.5 eV for a beam energy up to 60 keV. The beam commissioning with stable ion beams was staged, using optical tunes developed for different mass resolving power: 5000, 10,000 and 20,000. Presently we are in the final development stage where we seek to reach the highest resolving power as per design, which requires correcting the high-order aberrations using our innovative and unique electrostatic multipole featuring an unconventional rectangular design. In this paper we are going to discuss issues encountered during the commissioning runs, and present recent results.
The LHC beam dump system was developed to safely and reliably dispose of the LHC beams at the end of physics fills or in case of emergency aborts. The beams are extracted by means of kicker magnets, deflecting the beams horizontally, and septa, which provide a vertical kick. The system must be able to cope with rare failure scenarios, such as an asynchronous beam dump, where the rise time of the extraction kickers is not synchronized with the 3 $\mu s$ long particle-free abort gap. This type of event would lead to bunches impacting on downstream accelerator equipment if not properly absorbed by a system of beam-intercepting devices. In the High Luminosity-LHC (HL-LHC) era, the protection absorbers have to withstand significantly higher bunch intensities of up to $2.3\cdot10^{11}$ protons. In this paper, we study the robustness and protection efficiency of the septum protection absorbers for HL-LHC operation. In particular, we present energy deposition simulations for the absorber blocks and downstream equipment and define the required absorber upgrades for HL-LHC.
The user service mode of ESRF started in August 2020 after the installation of the new EBS machine, replacing the original ESRF DBA storage ring. All the insertion devices (IDs) were stored and re-installed to be available from day-1 of the accelerator commissioning. A major concern was, and still is, to preserve them as much as possible from demagnetization, both low gap in-vacuum devices and in-air undulators. This paper presents the strategy put in place for the commissioning, and in a longer term over the first years of operation, to reduce the risk of radiation damage of the IDs.
The design of Southern Advanced Photon Source (SAPS), which is a 3.5 GeV storage ring based light source, has been actively updated in the past two years. In addition, many relevant research activities such as the development of an electron source, high gradient accelerating structures, RF cavities and power supplies for fast injection kickers have already been started. The updated overall design for SAPS will be introduced in this work, along with a brief overview of the on-going activities related to the project.
The High Energy Photon Source (HEPS) is a 6 GeV diffraction-limited storage ring light source being built in China. Basic accelerator physical design and vacuum design have been completed. Interactions between the accelerated particles and the residual-gas molecules will lead to a reduction in the beam lifetime. The residual gas lifetime includes contributions from elastic gas scattering and gas bremsstrahlung. To simulate the residual gas lifetime in the HEPS storage ring, the position-dependent gas pressure for various gas species is first evaluated according to the layout of the vacuum elements. And then simulations of the elastic gas scattering and gas bremsstrahlung at multiple locations are performed with gas pressure profiles using ELEGANT. This paper will present the residual gas lifetime and the particle loss distribution obtained by the multi-particle tracking method.
10Hz horizontal orbit oscillation due to helium flow was observed in the routine operation of the Relativistic Heavy Ion Collider (RHIC). Without compensation by 10Hz orbit feedback, this will cause sizeable luminosity variation and reduce the beam lifetime during physics stores. In this article, we revisit the effects of this beam oscillation with weak-strong beam-beam simulation and dynamic aperture calculation. The goal is to determine the tolerable 10 Hz orbit oscillation amplitude at the interaction region and we will use this tolerance determine the power supply ripple requirements in the Electron-Ion Collider (EIC).
The CERN Super Proton Synchrotron (SPS) aims at providing stable proton spills of several seconds to the North Area (NA) fixed target experiments via third-integer resonant slow extraction. However, low-frequency power converter ripple (primarily at 50 and 100 Hz) and high-frequency structures (mainly at harmonics of the revolution frequency) modulate the extracted intensity, which can compromise the performance of the data acquisition systems of the NA experiments. In this contribution, the implementation of Radio Frequency (RF) techniques for spill quality improvement is explored, with particular focus on empty bucket channelling. It is shown that both the main RF systems (at 200 and 800 MHz) can be successfully exploited to improve the SPS slow extraction.
The hybrid multi bend (HMBA) lattice has been introduced to the accelerator community with the ESRF-EBS storage ring. Scaling an HMBA storage ring (SR) to different number of cells or cell length may lead to loss of performances, in terms of dynamic aperture (DA), momentum acceptance (MA) and natural horizontal emittance of the resulting SR. In this article we present several (non-exhaustive) scaling rules that guarantee minimal performance loss. A comparison of lattice cells with varying number of dipoles shows that the H6BA cell* outperforms other layouts in both, DA and MA, while a larger number of dipoles per cell is required to produce the lowest emittance.
China Spallation Neutron Source (CSNS) is a high density complex with a high repetion rate of 25Hz. The Rapid Cycling Synchrotron is the key part of the CSNS. By adopting the sextupoles with pulsed beam power system, CSNS has been operating steadily at 140kW. The CSNSII is aim to deliever above 500kW with the upgrations of many aspects of the accelerator. The sextupoles upgration is very important for CSNSII. By optimization the location of the sextupoles with MOGA algorithm, the dynamic aperture of RCS is increased impressively. In this paper, we will review the operation status of the sextupoles and give some proposals about sextupole upgration plans.
The Proton Storage Ring (PSR) of LANSCE compresses the pulse of a linac-produced beam by a factor of more than 2000 into an ultra-short high intensity beam, making the Lujan Center a leading facilities in the delivery of instantaneous beam power. This short-pulse feature allows a variety of experiments from neutron science to fundamental nuclear physics. Further shortening the beam pulse by another factor of 2 is necessary to achieve high-resolution nuclear data the search for Beyond Standard Model particles. We will report on our current status in our research to simultaneously stack two shorter pulses into the PSR by repurposing existing components in a system that, unlike synchrotrons, has limited flexibility.
We propose a computationally efficient algorithm to calculate a single statistical realization of partially coherent synchrotron radiation fields at a given frequency. The proposed algorithm relies on a method for simulating Gaussian random fields. We cross-checked the algorithm’s consistency with other well-established approaches, and, in addition, we show its advantage in terms of computational efficiency. The algorithm exploits the assumption of quasi-homogeneity of the source. However, we show that it is applicable with reasonable accuracy outside of this assumption. This algorithm can be extended to other types of sources that follow Gaussian statistics beyond the assumption of the quasi-homogeneity. Finally, the demonstration of the algorithm is well-suited for educational purposes.
The High Energy Photon Source (HEPS), is an ultra-low emittance storage ring (USR) light source beingto be built in Beijing, China. Due to the characteristics of the compact 7BA structure with strong focusing, beam accumulation in an USR is expected to be very challenging. Our simulations confirmed the difficulty in the HEPS storage ring. This paper introduces the preparations made for the first-turns commissioning of the HEPS storage ring from the first injection to beam storage. The commissioning methods and simulation results for several key steps are discussed, including first-turns trajectory correction, RF parameters’ optimization, as well as tune measurement and adjustment in the first turns.
The High Energy Photon Source (HEPS) is a 6 GeV, 1.3 km storage ring light source being built in Beijing, China. To get an ultralow emittance, high-gradient quadrupoles, combined-function magnets and longitudinal gradient dipoles (BLG) are adopted in the design of the storage ring. The impact of fringe field effects is of interest. To this end, several methods based on one-dimensional and three-dimensional magnetic fields are used to model dif-ferent kinds of magnets of the HEPS storage ring. In this paper, we will introduce detailed modeling methods and the impact of fringe field effects on the HEPS storage ring.
The Electron-Ion Collider (EIC) presently under construction at Brookhaven National Laboratory will collide polarized high energy electron beams with hadron beams with luminosities up to 10^34cm^{-2}s^{-1} in the center mass energy range of 20-140 GeV. To compensate the geometric luminosity loss due to a large crossing angle in the EIC, crab cavities are to be installed on both sides of interaction point (IP) to construct a local closed crabbing bump. However, for the current design lattice of the Hadron Storage Ring, the crab dispersion bump is not closed because the ideal 180 degree horizontal phase advance between the crab cavities on both sides of IP cannot be achieved. We carried out numerical simulations to evaluate the negative impacts with this imperfectly closed crab dispersion bump. We also simulated various schemes to close the crab dispersion.
The High Energy Photon Source (HEPS) is a 6 GeV diffraction-limited storage ring light source, which started construction in 2019. The sextupole and octupole magnets in the storage ring of HEPS are divided into several groups, and each group of magnets shares one power supply. In the lattice design, magnets in the same group are identical, but the real magnets have errors, which violate the symmetry of the lattice. To optimize the performance of HEPS, it is necessary to carry out sorting of these magnets. By doing simulations with elegant, we studied the effect of sorting on the performance of the nonlinear beam dynamics. The details are presented in this paper.
The possibility of spin control for dEDM experiment can be done by setting Wien Filters in straight section, which ensure that the particles spin retains mean direction in accordance with «Quasi-Frozen Spin» mode. However, the spin of different particles, due to their different motion in 3D space, in any case rotates with slightly different frequencies around the invariant axis, which one violates spin coherence. To ensure spin coherence, nonlinear elements, sextupoles, with a special placement on arcs must be used. Since sextupoles simultaneously affects the betatron chromaticity, we consider this complicated case.
Building new experimental facilities to house experiments is an expensive and time-consuming activity. Although usually less expensive, repurposing old experimental facilities to accommodate new ones has its own set of challenges with regard to obsolete equipment, adequacy of electrical power, radioactive shielding and cooling capacity. At Los Alamos National Laboratory (LANL), one such facility was previously used to provide a platform for Free Electron Laser (FEL) experiments that were completed 20 years ago. This paper explores the techniques and process to repurpose an existing experimental facility to accommodate the CARIE compact accelerator and the choices made to select and size equipment for success. Radio Frequency (RF) energy waveguide layout with vacuum calculation methods will be included as well as electrical power and radiation shielding requirements.
The International Linear Collider is a proposed electron-positron linear collider, where the positron beam is generated by undulator radiation hitting a target. The resulting, highly divergent positron beam requires immediate optical matching to improve the luminosity and ensure the success of the intended collision experiments. Here, optical matching refers to the process of capturing particles and making them available for downstream beamline elements like accelerators. In the past, this has been done with sophisticated coils, but more recently the usage of a current-carrying plasma, a so-called plasma lens, has been proposed as an alternative.
For the International Linear Collider, idealised particle tracking simulations have already been done in the past with the purpose of finding the optimal plasma lens design with respect to the captured positron yield. The proposed design is conical in shape to accommodate for the large beam divergence [1]. Now further research and development of this design is required, including both experiments with a downscaled prototype set-up as well as corresponding simulations modelling the hydrodynamics of the current-carrying plasma. The accuracy of the latter will benefit greatly from the former. In this work, first preliminary hydrodynamic simulations instil confidence into further endeavours.
In recent years, high-gradient, symmetric focusing with active plasma lenses has regained significant interest due to its potential advantages in compactness and beam dynamics compared to conventional focusing elements. A promising application could be optical matching of highly divergent positrons from the undulator-based ILC positron source into the downstream accelerating structures to increase the positron yield.
In a collaboration between University Hamburg and DESY Hamburg a downscaled prototype for this application has been developed and constructed. Here, we present the current status of the prototype development.
Provisions are being made in the Electron Ion Collider (EIC) design for future installation of a second Interaction Region (IR), in addition to the day-one primary IR [1]. The envisioned location for the second IR is the existing experi- mental hall at RHIC IP8. It is designed to work with the same beam energy combinations as the first IR, covering a full range of the center-of-mass energy of ∼20 GeV to ∼140 GeV. The goal of the second IR is to complement the first IR, and to improve the detection of scattered particles with magnetic rigidities similar to those of the ion beam. To achieve this, the second IR hadron beamline features a secondary focus in the forward ion direction. The design of the second IR is still evolving. This paper reports the current status of its parameters, magnet layout, and beam dynamics and discusses the ongoing improvements being made to ensure its optimal performance
The collimation system of the electron-positron Future Circular Collider (FCC-ee) will have two main tasks: protect equipment from the multi-MJ beams and mitigate detector backgrounds. An integrated collimation system layout is presented, including beam halo collimation system in one insertion and synchrotron radiation collimation around the experimental interaction points. The Z-production operating mode is considered, which has a beam energy of 45.6 GeV and a stored beam energy of 20.7 MJ, making it the most critical one for machine protection. The collimation insertion optics, aperture model, and collimation configuration for this mode are presented. The beam loss cleaning performance of the collimation system is studied for selected beam loss scenarios using a set of novel tools that enable multi-turn tracking simulations.
Optimization and realistic estimates of the sensitivity of the measurement of charged particle Electric Dipole Moment (EDM) in storage rings require a good understanding of systematic errors that can contribute to a vertical spin build-up mimicking the EDM signal to be detected. A specific case of systematic effect due to offsets of electrostatic bendings and longitudinal magnetic fields is studied. Spin tracking simulations to investigate whether this special case generates spin rotations, which cannot be disentangled from the ones due a finite EDM by combining observations made with both counter-rotating beams as predicted by analytical derivations, will be presented.
In this paper,we combines the problems in the determination of the adjustment weight of the current control network and the increasingly updated information processing model, taking the typical level network and making rational use of the function of MATLAB to systematically study the determination of the weight in the adjustment of control network.A variety of objective weighting methods are applied in the leveling network, the sub-method models are introduced in turn and the prior weighting methods such as entropy weighting method, coefficient of variation method, CRITIC weight method are applied in the leveling network combined by programming with actual engineering case to improve reliability. The determination of the adjustment weights of commonly used leveling control networks from the perspective of a priori confirmation of weights was studied by us, lays a foundation for the research on the reasonable weighting and data fusion of multiple types of observation data when using various measuring instruments such as DNA03,AT960 to establish leveling control networks in the construction of Hefei Advanced Light Facility.
The Superconducting Electron Accelerator Lab (SEALab)* is the SRF-accelerator physics research facility at HZB created in 2021 following official completion of the bERLinPro project. It provides opportunities for SRF-accelerator related research beyond the ERL program, yet ERL-related research continues in this facility (“bERLinPro@SEALab”).
The first stage of commissioning and operation will focus on the SRF injector, in 2022 mainly the SRF photo-injector. It is planned to study a wide range
of beam parameters from shortest pulses low charge regime applicable to e.g. ultrafast electron diffraction (“UED@SEALab”) to high charge and medium current
beam studies for ERLs, whether this may be for a light source or high-energy physics collider machine.
Here, we will mainly present the current status of the commissioning of the SRF photo-injector cryo module, the state of the Booster cryo module and plans towards a Linac allowing for a more sustainable and effective implementation of an ERL, including studies of fast reactive tuner implementation at 1.3 GHz for microphonics compensation and a potential test site for 4K operation of new SRF coating materials finally with beam.
SIS100 is a new superconducting heavy ion synchrotron optimized for the acceleration of high intensity heavy ion beams. Most crucial intensity limitation for heavy ion beams in SIS100 is the dynamic vacuum and corresponding beam loss by projectile ionization. Ionization loss and ion induced desorption drive the residual gas pressure into an instability, generating an intensity barrier at much lower intensity levels than any space charge limit. Technologies for stabilizing the dynamic vacuum, such as extensive charge separator lattice, pumping by cryogenic magnet chambers, cryo-adsorption pumps and cryo-ion catchers had to be implemented. SIS100 will also be the first user synchrotron comprising a laser cooling system for cooling at relativistic beam energies. Combined with a strong bunch compression system, laser cooling will support the generation of short ion bunches. Meanwhile, a large amount of the SIS100 components have been delivered and preparations for installation are launched. The shell construction of SIS100 underground tunnel is completed. Installation of the technical building infrastructure and the cryogenic distribution system are ongoing.
In the Advanced Photon Source Upgrade storage ring, the horizontal collimators protect the rest of the machine from whole beam aborts; however, as shown in previous experiments, the collimators themselves must also be protected from the full intensity of the lost store. The suitability of a vertically-deflecting fan-out kicker was evaluated experimentally. Aborted beam strikes the surface of the collimator with the expectation that the absorbed energy density or dose is reduced sufficiently to maintain the integrity of the device. We discuss the results from recent measurements where a fan-out kicker was employed to test this concept. 6 GeV, 200 mA (737-nC) APS stored beam was used to irradiate both aluminum and copper collimator test pieces.
The ultimate goal of studying spin-radial motion in a ring with "Quasi-Frozen Spin" is to develop a procedure for measuring the deuteron electric dipole moment. For a ring with a "Frozen Spin", the authors developed the Frequency Domain Method. A distinctive feature of a ring with a "Quasi-Frozen Spin" is spin oscillation with a small amplitude around the direction of motion. In this work, we study the influence of these oscillations on the final sensitivity of deuteron EDM search.
High Energy Photon Source is a 6 GeV diffraction-limited synchrotron light source currently under construction in Beijing. To provide the required 6 MV of RF voltage and 850 kW of beam power, five 166.6 MHz superconducting quarter-wave beta=1 cavities have been chosen for the fundamental RF system of the storage ring. Each cavity will be equipped with one fundamental power coupler (FPC) capable of delivering over 200 kW continuous-wave (CW) RF power. Based on the test performances of the two prototype couplers, formal couplers have been optimized, fabricated and high-power tested up to CW 250 kW in the traveling-wave mode and CW 100 kW in the standing-wave mode covering 16 phase points. Subsequently, one FPC was mounted on the first 166.6 MHz SRF cavity and participated in the horizontal high-power tests of the first cryomodule. The high-power test performances of the formal FPCs on the test bench and with the dressed cavity are presented in this paper, focusing on the effectiveness of the various design modifications compared with previous prototypes.
The Beijing Electron-Positron Collider II (BEPC-II) is a 1.89 GeV two-ring e+/e- collider. It consists of two superconducting (SC) cavities in the ring and the design of the cavity is the same as the ones used in HEPS (High Energy Photo source) storage ring. During operation of the SC cavities of BEPC-II, sideband close to 46 Hz and 100 Hz were found, which decreased the controlling accuracy of the cavity frequency. To trace the vibration sources, PCB sensors were fixed on the rack which is connected directly with the cavity pipe. The whole starting up process of the BEPC-II after long shutting down were monitored for determining the vibration sources. To investigate the sensitivity of the cavity under different vibrations, 500 mV bias input voltage were added on the cavity using pizeo to produce longitudinal motions with frequencies from 10 Hz up to 150 Hz. With the same amplitude of bias voltage, the cavity has different response to vibrations with different frequencies. The preliminary results of the investigation will be presented in this paper.
The Elettra 2.0 upgrade project requires the realization of a new storage ring that will replace the existing one of Elettra. The Elettra 2.0 optic, developed on the basis of the magnet feasibility studies, include a total of 552 iron-dominated electro magnets, with all sextupoles and octupoles equipped with additional coils to achieve the combined fields of corrector and skew quadrupoles. This paper reports all the latest magnetic and pre-engineered designs and the comparison with the main magnet prototype performances.
A new linear induction accelerator named Scorpius is being designed for multi-pulse flash radiography. The solid-state pulsed power system offers a technological breakthrough by delivering multiple independent pulses to accommodate a wide variety of pulse formats. The design provides pulse modulation capabilities which will mitigate reflected waves and reduce voltage variations across a temporal window twice as large as existing multi-pulse radiography accelerators. Successful coupling of the solid-state pulsed power with prototype induction cells has demonstrated these capabilities, and the project will assemble the Scorpius injector with a number of accelerating cells for integrated testing.
We present the latest development for the FCC-ee interaction region. It represents a major challenge for the FCC-ee collider, which has to achieve extremely high luminosity over a wide range of centre-of-mass energies. The FCC-ee will host two or four high-precision experiments. The machine parameters have to be well controlled and the design of the machine-detector-interface has to be carefully optimized. In particular, the complex final focus hosted in the detector region has to be carefully designed, and the impact of beam losses and of any type of radiation generated in the interaction region, including beamstrahlung, have to be simulated in detail. We discuss mitigation measures and the expected impact of beam losses and radiation on the detector background. We also report the progress of the mechanical model of the interaction region layout, including the engineering design of the central beampipe, and other MDI components.
Matched first order transition crossing in the Relativistic Heavy Ion Collider (RHIC) is performed by using two families of jump quadrupoles when ramping species through transition to storage energy. The jump quadrupole families control $\gamma$ transition and the working point of the accelerator by compensating for the tune shift from the jump and minimizing optical distortions. After transition, amplitude and phase of the RF cavities need to be rematched to maintain constant acceleration. This configuration has proven to be effective in maintaining beam quality and reducing beam loss. The Hadron Storage Ring (HSR) retains the arcs and most of the insertion regions of RHIC. This paper discusses the gamma transition crossing of the HSR by the implementation of a matched first order transition jump.
We investigate the upgrade of Elettra 2.0 to radio-frequency transverse deflecting cavities generating a steady-state vertical deflection of selected electron bunches. The study demonstrates the feasibility of 1 to few ps-long x-ray pulses at MHz repetition rate provided simultaneously to several beamlines, and transparent to the standard multi-bunch operation. The short pulse exhibits total flux at 1-10% level of the standard single bunch emission, and transverse coherence preserved in both transverse planes up to approximately 0.5 keV.
We report on experimental investigations of a single electron, circulating in the Fermilab IOTA storage ring, focusing on two-photon undulator emissions. We employ a Mach-Zehnder (MZ) interferometer for the undulator radiation to determine the photon coherence length as well as to measure its statistical properties. In this experiment, the pulse of radiation in one arm of the interferometer is delayed by a certain optical delay. The optical delay can be adjusted with a step as small as 25 nm. We show that when the optical delay is varied, we observe oscillations of photon count rates in the two outputs of the interferometer. This interference pattern contains information about the temporal shape of the undulator radiation pulse, also known as the radiation coherence length. It may also contain information on non-classical two-photon statistics. In this paper, we present and discuss our measurements of this coherence length and statistical properties in both multi-electron and single-electron regimes.
The High Luminosity Large Hadron Collider (HL-LHC) is an ongoing project to upgrade the LHC, to increase the instantaneous luminosity by a factor of five compared to the nominal LHC and reach an integrated luminosity of 3000~fb$^{-1}$ in the first ten years. One of the driving factors to achieve this goal is an increase of the bunch population from $1.15\cdot10^{11}$ to $2.2\cdot10^{11}$ protons. This places unprecedented demands on the performance of the collimation system, which needs to be upgraded to fulfil the HL-LHC performance goals. In this paper, the planned upgrades of the collimation system and the performance of the system with proton beams is reviewed, taking into account recent baseline changes. Tracking simulations in SixTrack coupled to FLUKA are used for the studies. The beam loss scenarios considered are betatron cleaning and asynchronous beam dumps.
The Diamond-II storage ring lattice has continued to be developed after publication of the Diamond-II’s technical design report. This study provides the updated information needed for the commissioning simulation. Firstly, changes to the reference lattice and phase-one insertion devices are briefly described. Then the error specifications are amended to be consistent with the magnet measurement and girder installation strategy. The commissioning strategy is revised accordingly with the associated errors. Finally, the commissioning simulations of multiple random machines are performed. Some of the statistical results are shown to justify the engineering feasibility of off-axis injection and beam accumulation with high injection efficiency.
Located between the Delivery Ring and the Mu2e experiment in the Muon campus, the M4 beamline serves as the transport line for a resonantly extracted, 8kW, 8GeV pulsed proton beam to the Mu2e production target. In addition to challenges posed by elevation and directional changes, the M4 line is tasked with removing beam halo from resonant extraction and ensuring adequate inter-pulse beam extinction. A brief overview of the M4 line will be presented alongside on-going work to optimize halo collimation and minimize the radiological effects while maintaining adequate beam extinction downstream. An additional topic of the transport of the beam halo to the production target as a low-intensity beam for Mu2e calibration is also presented.
The future Electron-Ion Collider (EIC) adopts a horizontal crab crossing scheme to compensate for the geometric luminosity loss from a 25 mrad crossing angle. The crab cavity noise-induced emittance growth in the deflecting plane (horizontal for EIC) has been well studied and a feedback system is effective to suppress the growth. However, simulations also showed emittance growth in the vertical plane when the beam profile is flat at IP. In this article, we will validate this observation and propose countermeasures to this emittance growth.
The SuperKEKB accelerator, a 7 GeV electron and a 4 GeV positron double-ring collider, is in progress in order to explore the new physics beyond the standard model.
The next milestone is to obtain integrated luminosity of 15 /ab data in the next decade,
so that the luminosity should exceed 2 x 10^35 /cm^2/s in several years.
One of the essential issues is the injection performances for both rings to be capable of storing beams of a few amperes due to overcoming their short lifetimes.
To preserve the emittance of the injection beam passing through the transport line is very important for the injection performances.
However, the large emittance growths have been observed in the both of electron and positron beam transport lines.
After many efforts on the research this issue from both sides of the simulations and measurements,
finally the coherent synchrotron radiation (CSR) wakefields has gotten to be suspected as the cause of the emittance growths.
According to the parallel conducting plates model, CSR wakefields are reduced when the beam passes through the offset position from the median plane surface of the plates.
In this study, it will be reported that the measured emittance variation of the injection beam with the bump orbit at the arc section of
transport line for the SuperKEKB 7 GeV electron ring.
The material for this paper/poster has been merged with WEPL037:
Robust design of modern Chasman-Green lattices – a geometric control theory approach
The Large Hadron Collider (LHC) arcs have been designed for a FODO optics with roughly 90° betatron phase advance per arc cell, but not necessarily with exactly the same optics in the eight sectors of the ring. Measuring an optics with a significantly different arc cell phase advance, e.g. 60° which is at the limit for aperture at LHC injection, offers the possibility of understanding the LHC in an unprecedented depth. Furthermore, this optics would allow focusing higher energy beams, since the required quadrupole settings are lower than for the standard 90° optics for the same beam energy. Such an optics has therefore been designed, respecting all constraints for one low intensity pilot bunch per beam, and tested during commissioning of LHC Run 3 in 2022. First measurements, performed only for one beam at injection, are presented and compared to results obtained for the nominal 90° optics.
750 MHz IH-DTL with the capability to accelerate protons from 3 to 10 MeV was proposed for the compact therpy linac that now under development in IMP. Four drift tube sections were housed in a single vacuum chamber and coupled with three large drift tubes which housing focusing triplet lens inside. In each drift tube section, there were 9 to 10 drift tubes, supported by the separated ridges. This cavity will be powered by a 1 MW klystron at 0.1% duty cycle, the kp factor is about 1.7 at the operation power level. The tank is now under construction and expected to be ready for beam commissioning in the middle of 2023. The overall cavity design and the status of the power cavity are presented in this paper.
Acceleration of polarized electron and positron beams to ultra-high beam energies is of interests for polarized beam applications in future 100km-scale e+e- circular colliders. However, it was widely envisaged that crossing hundreds of spin depolarization resonances would lead to severe depolarization during the energy ramp in the booster synchrotron. In this work, we have studied the spin resonance structure of a booster lattice for the Circular Electron Positron Collider (CEPC). The 100 km-scale booster lattice has a periodicity of 8 and each arc region contains hundreds of FODO cells. We show that the first super strong depolarization resonances only occur beyond 120 GeV, and other resonances are much weaker, due to the effectively very high periodicity of the lattice structure in terms of spin resonances. This finding is similar to the concept of ``Spin resonance free injector’’ for the Electron Ion Collider [V. Ranjbar, Phys. Rev. Accel. Beams, 20, 111003, 2018]. Spin tracking simulations verify that beam polarization can be mostly maintained in the fast ramping to 45.6 GeV and 80 GeV beam energies, without using special hardware like Siberian snakes. We also discuss possible measures to maintain beam polarization up to 120 GeV. This study opens the way for injection of highly polarized beams generated from the source into the collider rings, to enable resonant depolarization measurements as well as longitudinally polarized colliding beam experiments.
After the PIP-II linac is commissioned as a new start of the Fermilab Acclerator Complex, the Booster will become a bottleneck for future high intensity particle physics research at Fermilab. An SRF linac is proposed as a replacement for the booster to enable future higher power proton beams in the Fermilab complex - this would include neutrino-based and muon-based studies, dark matter searches, and a platform for R&D for a muon collider. In this contribution, we overview the early conceptual accelerator design under development and discuss potential configuration options.
Production of super heavy elements of which atomic number is larger than 118 can provide new prospects in the field of nuclear physics. Extremely low production rate of these elements makes the experiments time consuming. This difficulty can be solved by using the energy recovery internal target, so-called ERIT, because the number of interactions can be increased as a circulating beam hits the target located in the ERIT ring. Here, we present a conceptual design of the FFA ring for super heavy element production adopting the ERIT mechanism.
To reach the desired energy for a muon collider, muons should be accelerated to 5 TeV. This acceleration must be rapid to avoid muon decays, while simultaneously having a high average bending field to minimize the the required RF voltage. One concern with high energy muons is radiation from neutrinos, produced from muon decay, interacting with matter far from the accelerator. While this is less of a concern for acceration than for the collider ring, maximizing the number of straight sections in the acceleration ring would minimize this radiation. Doing so requires minimizing the length of the arcs while maintaining zero dispersion through the RF cavities. The most compact cell that would accomplish this would be a double bend achromat (DBA). I present a double-bend achromat lattice cell for muon acceleration in a hybrid pulsed synchrotron. "Hybrid" refers to the use of a mixture of superconducting fixed field magnets and bipolar pulsed warm dipoles to maintain a high average bending field. The design considers the required magnet aperture for the beam size and an estimate for shielding. I will discuss the longitudinal dynamics for this design.
I describe a fixed field alternating gradient (FFA) lattice design to accelerate muons final energy for a muon collider. Ideally the muons would be accelerated to 5 TeV to reach the desired energy for physics studies*. An FFA allows the acceleration of muons over a large energy range without changing magnetic fields. It is an alternative to a pulsed synchrotron in which magnet fields must be varied very rapidly to minimize muon decays. I present a design for a linear non-scaling FFA which is optimized to minimize the required magnet fields. That optimization target is chosen since magnet fields are limited by magnet technology, and those technological limits will therefore limit the energy reach or bound the minimum size of the accelerator. I consider a design that would fit on the Fermilab site as well as a design with an unconstrained but minimized size. I compare the FFA design to a pulsed synchrotron design with similar technology limitations. I discuss longitudinal dynamics for acceleration, benefits of adding nonlinearity to the magnets, and the challenges of extraction from the FFA ring.
Betatron coupling resonance has been considered by many low emittance upgrade light sources as a candidate to produce round beams. Due to the limited literature on the topic, last year an experimental campaign was undertaken on the ALBA storage ring to establish limits and requirements to operate a light source in full coupling. The work highlighted how coupling can indeed produce a round beam with certain easiness but not free from shortcomings: the fractional betatron tunes must be set equal, resulting in a substantial constraint to the optics and requiring a sophisticated control of the optics itself in order to keep the resonance condition despite the movement of insertion devices and drifts.
To work around these limitations, this year a different approach, based on the excitation of the coupling resonance with an A.C. skew quadrupole was tested. A first experiment was attempted by converting the existing tune excitation stripline into a skew quadrupole, but the limited available power allowed to produce only a barely perceptible coupling. The stripline was then turned into an electric deflector by removing the resistive terminations and allowing to drive the electrodes to higher voltage. Here the newly obtained results with the A.C excitation are presented.
New R\&D concepts for particle acceleration, generation, and focusing at ultra high acceleration gradients (GeV/m and beyond) have the potential to enable future e+e- and $\gamma - \gamma$ colliders to and beyond 15 TeV energies. In addition to proven high gradient and ultra-bright beam generation, these systems have the potential to increase luminosity per unit beam power via short beams, for practical energy recovery to extend the reach of high energy physics, and for fast cooling. They hence have potential to reduce the dimensions, CO$_2$ footprint, and costs of future colliders, with added potential to reduce power consumption. The last decade has seen tremendous experimental progress in performance, together with development of concepts to address potential collider issues. Conceptual parameter sets for colliders have been developed for e+e- and $\gamma \gamma$ colliders at a range of energies, which present potentially competitive options with prospects for future cost reduction. In addition to a strengthened ongoing R$\&$D program, continuing to develop these collider concepts in interaction with the collider and high energy physics communities, starting with an integrated set of parameters, is important; as is development of technologies through nearer-term applications. Progress in these concepts, next steps, and results of Snowmass Accelerator Frontier topical group # 6, Advanced Accelerator Concepts (https://doi.org/10.48550/arXiv.2208.13279) will be discussed.
The performance of the Low Energy Ion Ring (LEIR) at CERN is mainly determined by the number of charges extracted from the machine and transferred to the downstream chain of accelerators. While the required target of 9e10 charges has now been surpassed, a series of studies have been undertaken to further push the intensity reach of LEIR. In this work, we quantify the effect of the stray fields generated by the adjoining Proton Synchrotron (PS), which were recently partially shielded, and the effect of the stripper foil in the Linac supplying LEIR with its ions, Linac 3. The impact of the stray field was measured by observing the variation in injection trajectory, while that of the stripper foil was determined from the evolution of the Schottky energy profile in LEIR. Models have been developed to extrapolate the impact of these effects to the injection efficiency of LEIR, and consequently to the extracted beam intensity.
Electron beam central-axis percentage depth dose (PDD) curves in water phantom are routinely employed to evaluate the electron beam energy at the phantom surface, in particular the mean and most probable energies from the values of R50 (half-value range) and Rp (practical range). However, these two quantities are not enough to evaluate important details of the energy distribution, such as the FWHM (Full Width Half Maximum) and the possible presence of a low-energy tail. This paper presents a numerical method that allows estimating the shape of the energy spectrum from a PDD curve. The algorithm uses a database consisting of a set of depth dose curves for monochromatic beams computed by FLUKA in the range 0.1-6.0 MeV by steps of 0.1 MeV and, using an adaptive iterative Monte Carlo process, reconstructs the incident energy spectrum by minimizing the distance between the measured PDD and the computed one. Applications of a MATLAB code based on this algorithm to simulated and real measurements of electron beams done at APAM lab (ENEA Frascati) are presented. This approach represents a strong simplification with respect to energy analysis based on the use of a magnetic spectrometer.
While large circular colliders rely upon analysis of turn-by-turn beam trajectory data to infer and correct magnetic lattice imperfection and beam optics parameters, historically storage-ring based light sources have been exploiting orbit distortion, via the orbit response matrix. However, even large collider usually benefit of the orbit analysis during the design phase, in order to evaluate and define tolerances, correction layouts and expected performances. The proposed FCC-ee is no different, though its length (about 100 km) and amount of magnets (about ???) make the standard closed-orbit analysis time consuming. We applied new analytic tools to cope with this issue, showing a significant gain in computational time with practically no loss of accuracy. Examples of applications to the ESRF EBS storage ring and to the CERN FCC-ee are reported with an outlook to an additional challenge provided by the FCC-ee.
Iterative learning control(ILC) is a effictive algorithm for transient beam loading compensation. However, considering the algorithm complexity and the hardware cost, the ILC algorithm is usually implemented outside FPGA. This practice would decrease the real-time ability of the control system. In this paper, a real-time ILC algrithm will be introduced. And the result is summarized.
All high-energy beam dump events at the Large Hadron Collider (LHC) are analysed to verify correct functioning of the Machine Protection System and to allow early identification of potential issues. This includes the evaluation of particle losses before and during the beam dump event.
The paper describes a newly developed tool for the automated evaluation of beam losses during high energy proton dumps. It presents the approach to derive individual thresholds for more than 3600 Beam Loss Monitors based on historic data from Run 2 of the LHC (2015–2018) and reviews the performance of the tool.
RF-Conditioning of a room temperature cavity is a long and resource intensive process. The need for constant supervision by experienced personal to avoid damage to the cavity and used equipment makes it a very expansive endeavor. To reduce the workload of the experimentalist, it was decided to develop a program utilizing machine learning, which, once finished, should have the probabilities to greatly reduce the need for constant supervision by human personal or even to conduct a full RF-conditioning on its own. After a training with existing data of already conducted conditioning of room temperature cavities and a virtual cavity, it is planned to improve and expand the program during the RF-conditioning of 15 CH-cavities, designated for the MYRRHA project, with similar properties. In this paper, the outline of the program, as well as the existing and planned goals shall be given.
We fabricated corrugated wakefield structures and did cold test of them. Since the wakefield frequency of our structure is about 0.2 THz, there are several technical issues in the bead-pull.
We present issues concerning to bead size and the wire. And issues concerning to mode converter are described as well. We manufacture a customized mode converter which change electromagnetic mode from rectangular TE10 to circular TM01. The biggest issue was not only the TM01 but also the TE11 excited. So we suggest a method of extracting only the results by TM01. And the operating frequency of the wakefield structure was calculated with this method. The operating frequency by cold test matched well with the simulation.
The baseline beam parameters of the FCC-ee contemplate different operation modes, with beam energies ranging between 45.6 GeV and 182.5 GeV. The highest expected beam stored energy reaches 20 MJ for the so-called Z operation mode (45.6 GeV), i.e. two orders of magnitude above that found in previous and operating lepton colliders.
In order to protect sensitive equipment and to limit background to the experiments, a two-stage collimator system is planned to be implemented.
Considering that collimator materials need to have a relatively low density in order to minimise the energy density deposited by the beam, the active length of the jaws would be relatively high (30-40 cm); hence, producing a significant impact on the impedance of the machine.
For this reason, materials with high electrical conductivity are to be considered. Another important property is thermal conductivity (to be able to dissipate the heat deposited by the beam).
A preliminary study of energy deposition and thermal stresses in different candidate materials for primary collimators is presented here.
The Beijing Electron Positron Collider II will upgrade to achieve a higher beam energy and higher luminosity which need a higher beam current and smaller beam size. The consequent high beam background should be controlled within in a safety range. The beam related background at BEPCII is mainly from the Touschek effect and the beam gas effect. This paper presents the beam background study at BEPCII, which includes the recent results of experiment and simulation.
The machine-detector interface (MDI) issues are one of the most complicated and challenging topics at the Circular Electron Positron Collider(CEPC). Comprehensive understandings of the MDI issues are decisive for achieving the optimal overall performance of the accelerator and detector. The CEPC machine will operate at different beam energies, from 45.5 GeV up to 180 GeV.
A flexible interaction region design will be plausible to allow for the large beam energy range. However, the design has to provide high luminosity that is desirable for physics studies but keep the radiation backgrounds tolerable to the detectors. In this paper, the latest design of the CEPC MDI based on the TDR draft will be presented, covering the following topics:
The design of the beam pipe, which would foresee several constraints: In the central region (z = ±12 cm), it should be placed as close as possible to the interaction point and with a minimal material budget. But it should still stay far away enough not to interfere with the beam backgrounds.
The estimation of beam-induced backgrounds. A detailed simulation covering the main contributions from synchrotron radiation, pair production, and off-momentum beam particles has been performed.
The suppering/mitigating schemes. A preliminary design of the collimation scheme has been studied, including the position, material, shape of the collimators, and also the effectiveness of them.
A high-charge, low-emittance injection beam is essential for SuperKEKB. For its both rings, HER and LER, the injection efficiencies and detector backgrounds have not been good enough up to the recent run. There are many reasons for the issues. For example, serious emittance growths are observed through the beam transport lines between the injector linac and both rings. It is considered that some parts of them are due to coherent synchrotron radiation as the observed horizontal emittance blowups depend on the bunch charge. Especially for the HER injection, physical aperture around the injection point and ring dynamic aperture also contribute, as both are narrower than the design.
In this paper, we discuss the injection issues up to 2022 operation and outlook for the future to maximum collision currents.
In the electron-driven ILC positron source, the positron is generated a multi-bunch format with gaps, because it corresponds to a part of the damping ring fill pattern. The beam loading is compensated by amplitude modulation on the input RF (*). In this article, we derive the exact solution for the compensation with gaps. In addition, we evaluate the effect of the time constant (delay) of the input RF modulation due to klystron Q-value.
In the future 100 km-scale Circular Electron Positron Collider (CEPC), beam polarization is an important design aspect. Transverse beam polarization for resonant depolarization is essential for precision measurements of the beam energies at Z-pol and WW threshold. Longitudinally polarized colliding beams are also beneficial for expanding the capability of the physics program. This paper reports the progress in the design studies of polarized beams for the CEPC. We focus on the approach of injection of polarized beams generated from the source into the collider rings for both applications. Our investigation into key issues in this approach is summarized, including polarized positron beam generation, beam polarization maintenance in the booster, and spin rotator design in the collider rings. Implications to resonant depolarization measurements are also discussed.
The understanding of beam-beam effects, which influence the choice of the FCC-ee design parameters for several aspects, require sophisticated and high-performance numerical simulations. The self-consistent study of the interplay of nonlinear dynamical phenomena resulting from collisions in the machine is key to accurately assess its potential performance. Although current simulation frameworks can address specific aspects of the dynamics separately, they are difficult to interface with each other for more complex studies. To address this challenge, Xsuite, a new general purpose software framework for beam dynamics simulations, is currently under development. We discuss the implementation of the beam-beam interaction in this new toolkit and the evaluation of its performance on multiple platforms.
For the Future Circular Collider (FCC-ee), particular attention is drowned to the crucial role of the positron source. Two positron production schemes are considered for the FCC-ee: conventional and crystal-based (hybrid), implying the use of channeling radiation in the oriented crystals. To design and optimize the positron production and capture by considering the positron injector parameters, including the electron drive beam and the final system acceptance, a start-to-end simulation toolkit should be developed.
This paper will present the first results of benchmarking the FCC-ee positron source simulation tools using the SuperKEKB positron source currently in operation. The model starts with the production of positrons and target studies in Geant4. Then, a new tracking code RF-Track is used for capturing and tracking the generated positrons through the capture section composed of the matching device and several accelerating structures embedded in the solenoid field to accelerate the positrons until ~120 MeV. Afterward, the positrons are further accelerated to the energy of the Damping Ring (1.1 GeV).
The measurement of Bhabha scattered leptons enables a direct estimate of luminosity in lepton colliders. Currently existing Monte Carlo event generators for this process are optimized for high precision detector background simulations. From a beam dynamics point of view, emitted photons will modify the bunch distribution and lead to beam losses
due to the limited momentum acceptance of the machine. Hence the interest in building an event generator which is optimized for beam dynamics studies requiring efficient multi-turn tracking simulations. We discuss the implementation of such a model in the newly developed Xsuite simulation framework as well as its benchmarking and performance.
We carried out the study of the beam lifetime at SuperKEKB to investigate beam instabilities. We analyzed the injection interval for individual bunches to evaluate their beam lifetime ratio. SuperKEKB performed the top-up operation with the equalized bunches currents. This particular condition enables us to evaluate the lifetime ratio among all operation bunches. This report introduces the analysis results for the 2020 and 2021 data. We observed the beam lifetime has dependent on the bunch spacing and the relative position in the bunch train. Besides, in the December 2021 data, we determined the magnitude of the forward/backward asymmetry of the lifetime in the bunch train depends on the bunch current. They become good hints to understand the beam instabilities such as the electron cloud, the ion cloud, the beam-beam
effect in the collision, and so on.
I describe the method used for calibration the amplitudes and phases of the cavities in the Main Linac Cryomodule (MLC) for the CBETA energy recovery linac at Cornell University. The cavities are powered one at a time, and the phase of each cavity is set to a uniformly spaced set of values over a full 360 degree range, with cavity voltages set to one or more values. For each cavity, voltage, and phase, arrival time measurements are taken at BPMs upstream and downstream of the linac. No magnets lie between the linac and the BPMs. These measurements are used to obtain a least-squares fit the parameters of a model. The model is based on integrating through a fieldmap that was generated from a finite element computation. The parameters to be fit are the scaling factors between the programmed and actual cavity voltages, the offset between the programmed and actual cavity phases, and the the energy of the beam coming into the linac. The fitting process is accelerated by constructing a good initial guess for the parameters, and by computing the arrival time and its derivatives to the parameters so that Newton's method can be used to solve for the fitting parameters.
Extending the energy reach of CEBAF by increasing the number of recirculations, while using the existing linacs is explored. This energy upgrade is based on the multi-pass acceleration of electrons in a single non-scaling Fixed Field Alternating Gradient (FFA) beam line, using Halbach-style permanent magnets. Encouraged by the recent successful demonstration of CBETA, a proposal was formulated to nearly double the energy of CEBAF from 12 to 22~GeV by replacing the highest energy arcs with FFA transport. The new FFA arcs would support simultaneous transport of an additional 6 passes spanning roughly a factor of two in energy. One of the challenges of the multi-pass (11) linac optics is to assure uniform focusing over a wide range of energies. Here, we propose a triplet lattice that provides a stable periodic solution covering an energy ratio of 1:33. The current CEBAF injection at 123 MeV, makes optical matching in the first linac impossible due to the extremely high energy ratio (1:175). Replacement of the current injector with a 650 MeV recirculating injector will alleviate this issue. Orbital and optical matching from the FFA arcs to the linacs is implemented as a compact non-adiabatic insert. The design presented here is anticipated to deliver a 22 GeV beam with normalized emittance of 76 mm·mrad and a relative energy spread of 1×10^{-3}. Further recirculation beyond 22 GeV is limited by the large (974 MeV per electron) energy loss due to synchrotron radiation.
The CEPC is a proposed high luminosity Higgs/Z factory, with the potential to be upgraded to top factory at center-of-mass energy of 360GeV. We perform an optimization study on the circumference of CEPC. We calculate the instant luminosity, the construction and operation cost for different circumferences. With respect to the total cost and average cost per particle, we conclude that the optimal circumference for the CEPC Higgs operation is 80 km. Taking into account of the Z pole operation, the potential high-energy upgrade of CEPC (top factory), the optimal circumference increased to 100 km. The long future proton-proton upgrade of CEPC (SPPC) also favors a larger circumference, and we conclude that 100 km is the global optimized circumference for this facility.
A damping ring system which includes a small 1.1 GeV ring and two transport lines is introduced in CEPC linac in order to reduce the transverse emittance of positron beam at the end of linac and hence reduce the beam loss in the booster. The repetition rate of Linac is 100 Hz and one-bunch-per-pulse is considered. The double-bunch scheme of Linac is only considered for the high luminosity mode at Z pole. The positron beam is generated by 4 GeV electron beam hitting tungsten target and then is captured by an AMD flux concentrator. Each positron bunch is injected into damping ring every 10 ms and two bunches are stored in the ring so that the storage time for each bunch is 20 ms. The bunch number in the damping ring can be increased to 4 with an upgrade and hence the storage time for each bunch can be increased to 40 ms. The reversed bending magnet scheme is adopted for TDR in order to reduce the emittance significantly. The normalized emittance of positron beam is expected to be reduced from 2500 mm.mrad to 166 mm.mrad (or 97 mm.mrad) in the damping ring.
The future upgrade to the High-Luminosity Large Hadron Collider (HL-LHC) will impose tight tolerances on IP optics measurements. k-modulation is currently the preferred method in the LHC for IP optics measurements and will play a critical role in the HL-LHC. As such, Run 3 of the LHC provides an ideal test-bench for addressing challenges in k-modulation. In the first commissioning year of Run 3, this method was used to measure and validate optics with beta ranging from 30cm to 24m. However unsatisfactory reproducibility was observed for low beta measurements. This paper presents the k-modulation results for the start of Run 3 with in depth analyses and it highlights the sensitivity of this method in view of the challenging HL-LHC runs.
I describe a method for finding a set of cavity voltages and phases for the CBETA multi-pass energy recovery linac. The beam in CBETA makes up to 8 passes through its 6 cavity linac. The voltage and phase for each cavity can be set individually, and the path length for each arc energy can be set as well. I show that solutions can be found where each cavity has energy gains and losses balanced and all of the arc energies are precisely their design values. There are multiple families of solutions characterized by where the beam is with respect to the linac crest on each pass. I will choose the solution family that reduces the amount of energy spread generated by the beam going through cavities off-crest. I will plot solution parameters as a function of the effective linac phase (which I will define) for the first pass, and show that a given solution family can be found only for a certain range of that first pass phase.
Magnetic fields in the 12-16 T range are needed to bend the beams in future hadron colliders, such as the CERN FCC-hh. For these magnets, made with Nb3Sn superconducting cable, a small reduction of the field brings a non-negligible reduction of cost and complexity. Increasing the dipole filling factor is hence a priority to provide higher energies for the same magnetic fields - or the same energies for lower magnetic fields. To this aim, the use of combined-function magnets is proposed to design the ring lattice in place of the standard separate-function solution. The properties of the combined-function solution and of the magnets that would be needed for the FCC-hh are presented and discussed in detail in this paper.
Hollow electron lenses (HELs) could be used in the HL-LHC to selectively remove halo particles from the circulating beams. While the ideal design should leave particles in the beam core unaffected, in reality, the core particles will be exposed to a small residual kick that could induce transverse emittance blowup if not properly compensated while the HEL is operated in pulsed mode. One possible solution would be to couple the HEL pulse with the adjacent HL-LHC transverse damper (ADT). The principle consists of exerting an oppositely directed kick with the ADT at each turn the HEL is switched on, thus compensating the HEL residual kick on the beam core. In this contribution, we simulate the performance of this compensation scheme and possible commissioning scenarios, aiming at reliably setting up the compensation scheme when the direction and amplitude of the residual kick are, a priori, unknown.
The interaction of particle beams with materials is important for muon colliders, as it causes particle scattering, energy loss and energy-straggling processes. Such interactions are also relevant in high-precision applications such as radiation oncology treatment planning, where the beam travels through air before reaching the patient, and are also the crucial mechanism for ionization cooling processes, such as those required for generating high-brightness beams for muon colliders. Few particle tracking codes integrate such effects in an environment suitable for lattice design. This work presents the simulation of these effects in the beam tracking program RF-Track (v2.1), compares the beam-matter interactions with the tracking programs ICOOL (v331.1) and G4Beamline (v3.08) and discusses the results.
The Configuration Management of the LHC and its injectors ensures a clear and coherent representation of the CERN accelerators at a given point in time. It has been evolving steadily. The methodology has been continuously improved, incorporating best practices and was also extended to the injectors to face the Long Shutdown 2 (LS2) with a set of rigorous and homogenised processes for the entire accelerator complex. Lessons learnt from the LS2 provide a strong basis to further improve the effectiveness of the change management process.
This paper describes the action plan, concerning the processes and engineering tools, to further improve configuration management efficiency to face the numerous changes foreseen during the Long Shutdown 3 (LS3), with principally the equipment installation foreseen by the HL-LHC project. In addition, it reports on the smooth transition between the LHC and HL-LHC configuration teams to ensure the long-term operation and maintenance of the LHC.
The current injector complex design of the FCC-e+e− project consists of e+/e− linacs, which accelerate the beams up to 6 GeV, a damping ring at 1.54 GeV, a pre-booster ring, accelerating the beam up to 16 GeV and a booster synchrotron ring integrated in the collider tunnel accelerating the beams up to the collision energies. The purpose of the damping ring is to accept the 1.54 GeV beam coming from the linac-1, damp the positron/electron beams and provide the required beam characteristics for the injection into the linac-2. The purpose of this paper is to provide a new layout of the damping ring. In this study, the beam parameters are established, including the optics design, layout and consideration for non-linear dynamics optimization.
In this paper we present the first results of full 6D multi-bunch tracking through the new Drive-Beam decelerator lattice for the first-stage of the Compact Linear Collider (CLIC). Using the new PLACET3 tracking code, we evaluate the coupling between transverse and longitudinal dynamics in the lattice finding an indirect impact of the Drive-Beam's transverse emittance in the Main-Beam performance.
Crystal collimation is studied to improve the collimation efficiency with ion beams at the High-Luminosity Large Hadron Collider (HL-LHC). Bent crystals are used instead of conventional primary collimators to deflect high-energy halo particles at angles orders of magnitude larger than what can be achieved with scattering by conventional materials. Following the promising results obtained during Run 2 (2015-2018) and the first year of Run 3 (2022), this collimation technique is planned to be used operationally already for LHC Run 3 heavy-ion operation, starting in 2023, to mitigate the risk of magnet quenches from beams of higher energy and intensity. Tests with low-intensity proton beams are extremely important to characterize the crystal collimator hardware, assess the performance and investigate other operational aspects in preparation for the ion run. This paper presents the results of tests carried out in 2022 with proton beams at the record energy of 6.8 TeV.
DAFNE, the Frascati electron-positron collider, based on the Crab-Waist collision scheme, has successfully completed the preliminary phase with the SIDDHARTA-2 detector aimed at testing and optimizing the performances of the machine and the experimental apparatus.
In this configuration the collider has delivered to the experiment, using gaseous 4He targets, a data sample suitable to perform studies about the kaonic helium transitions with an accuracy which is the status of the art in the field.
As a next step DAFNE is planning a new run finalized to deliver data to the detector in order to study the more elusive kaonic deuterium transition.
In this context the setup and the performances of collider the are presented with special attention to the strategy adopted to reduce the background shower on the experimental apparatus.
We discuss the beam requirements for indirect searches of dark matter and feebly coupled particles using advanced accelerator concepts. A parameter comparison reveals dielectric laser acceleration as a promising candidate for delivering the needed single-electron beams in the 5-100 GeV energy range or beyond. We suggest a parameter set for a baseline DLA-based dark sector accelerator. Enhancements through combining dielectric laser deflectors with a segmented detector or by making the dielectric structure be part of the laser oscillator could offer a performance significantly exceeding the ``Extended LDMX'' proposal based on LCLS-II.
After the discovery of the Higgs boson at the LHC, particle physics community is exploring and proposing next accelerators, to address the remaining open questions on the underlying mechanisms and constituents of the present universe. One of the studied possibilities is FCC (Future Circular Collider), a 100-km-long collider at CERN. The feasibility study of this future proposed accelerator implies the definition of tolerances on magnets imperfections and of the strategies of correction in order to guarantee the target performances of the High Energy Booster ring. The efficiency of the correction scheme, used to control the orbit, directly bounds the corrector needs and magnet tolerances. Analytic formulae give a first estimation of the average rms value of the required linear correctors’ strengths and of the allowed magnets misalignments and field quality along the entire ring. The distribution of the correctors along the ring is simulated in order to verify the quality of the residual orbit after the proposed correction strategy and compared with the analytical predictions. First specifications of the orbit correctors strength and tolerances for the alignment of the main elements of the ring are presented. The limits of the studied correction scheme and method are also discussed.
Nb3Sn, NbTiN and NbN are superconductors with a critical temperatures of 18.3, 12.6-17, 11.6-17.5 K, respectively, that are higher than that of Nb (9.3 K). Hence, at 4 K they have an RF resistance of an order of magni-tude lower than that of Nb, which leads to quality factors above those of Nb. In recent years, there has been an extensive effort converting Nb cavities into Nb3Sn by alloying the top inner layer of the cavity using Sn diffusion at a high temperature with some degree of success, however, the reproducibility remains a major hindering and limiting factor.
In this study, we report on PVD deposition of NbTiN and NbN inside 6 GHz cavity in an external magnetic coil configu-ration. The deposition is done at elevated temperature of about 650 C using Nb53Ti47 target and Nb rod.
We report on the superconducting properties, film structure and its stoichiometry and surface chemical state. The films have been characterised with SEM, XRD, XPS, EDS, SIMS, SQUID magnetometer and direct RF measurement of the cavity.
The Spallation Neutron Source (SNS) employs six cavities in the Drift Tube Linac (DTL) section to accelerate the H- ion beam to 87MeV. Each cavity is energized by a 2.5MW peak power klystron at 402.5MHz using rapid tapered waveguide iris couplers. All six original iris couplers have been in operation without replacement for over two decades. The increased RF power demands of the Proton Power Upgrade (PPU) project and operational problems, including arcing, temperature excursions, and vacuum bursts, have prompted the development of new iris coupler spares. The original iris couplers were made of GlidCop material, which is known to be mechanically strong and thermally stable, but is porous, expensive, and difficult to use in fabrication. To overcome these problems, the new spare couplers use Oxygen-Free Copper (OFC) and stainless steel (SS). This paper will discuss the mechanical, thermal and RF design, as well as challenges in the final coupler fabrication.
The Future Circular electron-positron Collider (FCC-ee) is planned to operate with beam energies from 45.6 to 182.5 GeV and beam currents from 5 to 1400 mA. This will enable precision physics at the four operational points, Z, W and Higgs boson and the top and anti-top quarks. This work will focus on the RF structure design for the ttbar operation point to reach a beam energy and current of 182.5 GeV and 5 mA, respectively. A 5-cell elliptical SRF cavity operating at 801.58 MHz is designed and optimized with a strong focus on minimizing higher-order modes impedances.
In the Electron Ion Collider (EIC), to be built at Brookhaven National Lab, the beams collide with a crossing angle of 25 mrad and an aspect ratio of 12 to 1. The orbit control in the interaction region is critical to achieve and to maintain the design luminosity and polarization, and to control synchrotron radiation induced detector background. In his report, the authors will introduce the IR orbit control system, including a slow orbit feedback and a fast local IR orbit feedback, and the associated simulation studies.
High brightness beams are desired for application to Inverse Compton Scattering (ICS) systems for generation of high-quality x- and γ-rays. It opens new opportunities for nuclear physics research in fields such as nuclear photonics, nuclear astrophysics, photo-fission, production of exotic nuclei, applications in medicine, industry and space science. In ICS mechanism high energy electron is interacting with photon. It results in scattered photon with high energy.
Results from computer simulations are presented. Different configurations of S-band injector were analysed. Photocathode RF electron source with diverse arrangement of magnetic devices for beam confinement, and standing wave cavity for initial particle acceleration were implemented. Electron beam parameters have been investigated with use of computer program for tracking particle beam through defined external electric and magnetic fields. Because cross-section of collision between electron and photon beam is very low, high brightness electron beam is crucial specification for gamma beam systems. Electron beam parameters of interest are emittance, beam spot size, average energy, energy spread, electron bunch length, Twiss parameters. Beam density, number of particles in bunch must find good compromise between optimum necessary for creation of high-performance gamma rays and limit in available technology.
LEAF (Low Energy heavy ion Accelerator Facility) is a low-energy high-intensity heavy-ion LINAC complex for multidiscipline research. At present, the beam repetition rate is the same as the LINAC frequency of 81.25 MHz. A lower frequency would be desirable for many types of experiments employing time of flight data acquisitions. A method of increasing the bunch spacing to 98 ns by combining a 10.156 MHz pre-buncher before the RFQ and an RF chopper after the RFQ has been proposed. This paper reports the design studies of such a low-frequency pre-buncher. A resonator-based buncher is the best choice since lumped circuit-based buncher cannot provide the high voltage we expect for the efficient bunching of ion beams with an A/q of 7. According to the simulation result, the bunching efficiency of a 3-harmonic buncher will merely increase by 1% compared to a 2-harmonic buncher. We decide to design a two-harmonic buncher based on the little improvement in bunching efficiency. We optimize the length of electrodes so that the utilization of the parasitic field is maximized. The beam dynamics analysis indicates that the voltage amplitude and the RF power can be lowered by 1.3 times and 2.2 times by optimizing the electrode length.
We propose to develop a compact superconducting cyclotron to accelerate H2+ ions for isotope production since using H2+ allows the use of a stripper foil after extraction from the cyclotron to remove the binding electron, thereby doubling the electrical beam current. An RFQ, partially embedded in the cyclotron yoke, will be used to bunch and axially inject the H2+ beam into the cyclotron’s central region because RFQ has excellent bunching capability. In this paper we are presenting the design of the RFQ, including beam dynamics, electromagnetic structure and geometrical cavity.
Super Tau Charm Facility (STCF) proposed in China, is a future electron-positron collider project with symmetric double ring. It’s designed to be operated in the center of mass energy (CME) range between 2 GeV and 7 GeV. The goal luminosity is beyond $0.5\times 10^{35} cm^{-2} s^{-1}$. Hybrid multi-bend-achromat (HMBA) concept, proposed to develop low emittance lattices with large dynamic aperture, has been adopted in some diffraction-limited storage ring (DLSR) designs. In this paper, we will show a lattice with hybrid 7BA arc for STCF. On the basis of last published lattice version, we optimize the interaction region, arc as well as technique region, add the damping wigglers and construct the geometry of double-ring.
A S band high power klystron for BEPCII operating at frequency of 2856 MHz has been designed and simulated at Institute of High Energy Physics, Chinese Academy of Sciences. A thermionic electron gun have been designed. A beam current of 379 A is obtained at operating voltage of 325 kV with cathode current density of 6.6 A/cm2. Then, the full 3-dimensional particle-in-cell simulation of the whole klystron in CST verified that the klystron efficiency was achieved about 40% with output power of 50 MW. In additon, the RF design of cavities for interaction region is described. So far, the mechanical design of this klystron has been completed and the fabrication is in progress.
The Compact Linear Collider (CLIC) is a proposed linear accelerator designed to collide electrons and positrons at energies up to 3 TeV. In order to explore new physics and to be more competitive with other collider projects, CLIC is exploring the increase of the center-of-mass energy to 7 TeV. The CLIC Beam Delivery System (BDS) transports the lepton beams from the exit of the Main Linac to the Interaction Point (IP). This paper reports on the studies and the challenges of the new BDS design, such as minimizing the extent of trajectory bending for collimation and chromaticity correction to reduce the effects from synchrotron radiation, ensuring a good transverse aberration control at the IP.
Presented in this paper is the beam optics design of the final focus system (FFS) for the Super tau charm facility (STCF) in China, which is an electron positron circular collider with center-mass-energy (CME) from 2 GeV to 7 GeV. To achieve a luminosity of more than $ 5 \times 10^{34} cm^{-1}s^{-1}$, FFS with Large Piwinsky angle and crab waist scheme.
A Boron Neutron Capture Therapy facility requires a high flux of neutrons (approx. 10^9 thermal or epithermal n/s*cm^2) with low contamination content (gamma and off energy neutrons). The core of such a facility is a low energy high intensity proton linac, coupled with a high power beryllium neutron production target, followed by a proper Beam Shaping System. In this paper we shall discuss various aspects of the optimization of this system, on the bases of the R&D results available in view of the construction of a high performance BNCT facility in Italy.
Based on the key scientific questions in the frontier of particle physics field, the current status and future development trend globally and domestically of accelerator-based particle physics experiments, a Super Tau-Charm Facility (STCF) is proposed by taking into account the advantages in the relevant fields in China. The STCF is a new-generation electron-positron collider facility that has a center-of-mass energy of covering 2 to 7 GeV and a peak luminosity of 5×10^34cm^-2s^-1 at a center-of-mass energy of 4 GeV. It consists of an accelerator, including double storage rings of circumference approximately 800 meters and a linear injector of length approximately 400 meters, and a particle spectrometer. This paper discussed the key issues of accelerator physics and technologies. Also, the accelerator research progress of the projects are presented.
In order to produce a high luminosity at the interaction point, the Compact Linear Collider (CLIC) accelerators must preserve low emittance beams along both the main 22km linacs. A key factor in preserving a low emittance beam is the mechanical alignment and stability of the accelerator components.
The CLIC accelerators are divided into `Two Beam Modules’ (TBMs) which integrate a section of the power-delivering Drive Beam and the accelerating Main Beam. The Main Beam is accelerated within Acceleration Structures that require prealignment to within 14 µm of the Metrological Reference Network (MRN). To prevent a greater than 1% luminosity loss, the vertical jitter of the accelerator components must be kept below 1.4µm RMS when the TBMs are exposed to the ground noise within the tunnel, and other sources of vibration.
A design of the TBMs is presented which includes active alignment, passive prealignment, and sufficient mechanical stability to meet the specification. Finite Element Analyses (FEA) are used to demonstrate the suitability of this design. The results of the testing of prototype SAS prealignment and active TBM positioning systems are discussed and shown to meet the CLIC alignment requirements. Opportunities for future testing and areas for further optimisation are identified and discussed.
The FFA@CEBAF energy upgrade study aims to approximately double the final energy of the electron beam at the Continuous Electron Beam Accelerator Facility (CEBAF). It will do this by replacing the highest-energy recirculating arcs with fixed-field alternating gradient (FFA) arcs, allowing for several more passes to circulate through the machine. This upgrade necessitates the re-design of the vertical spreader sections, which separate each pass into different recirculation arcs. Additionally, the FFA arcs will need horizontal splitter lines to correct for time of flight and R56. This work will present the current state of the spreader re-design and splitter design.
The muon-dedicated linear accelerator is being developed for the muon g-2/EDM experiment at J-PARC. To suppress the decay loss during acceleration, the alternative phase focusing (APF) method inter-digital H-mode drift tube linac (IH-DTL) is adopted in the low-velocity region following a radio-frequency quadrupole linac (RFQ). We are planning to accelerate muons in 2024 using the RFQ and the IH-DTL which will accelerate muons from 8% to 30% of the speed of light with an operating frequency of 324 MHz. After the IH-DTL, a diagnostic beamline will be placed to measure the beam energy and quality after acceleration, and its design, which consists of magnets and bunchers, is underway. In this poster, we will report on the development status of the diagnostic beamline.
The Electron Ion Collider is adopting a crabbing scheme of 25 mrad crossing angle. The local crab cavity system designed to kick the bunches in the first interaction region (IR) also introduces higher order multipoles com-ponents in electric field which affect the dynamic aperture. We have studied the strength of each multipole up to n = 4, or octupole, with respect to the main dipole field in different operating scenarios. Dynamic aperture study has continued with a fundamental crabbing system at 197 MHz and its second harmonic system at 394 MHz. A comparison of multipole effect for different phase ad-vance between the two crab cavity systems across the IP is shown in this paper. Method of decreasing the sextupole component is investigated as a result of the dynamic aper-ture requirement.
An electromagnetic chopper is an important component of particle accelerators. It helps to provide users with different time structure beams. It is usually placed in the low energy beam sections of accelerators. In general, the chopper has rise and fall times of the order of a few nanoseconds. Due to this rise and fall time, post-chopper beam dynamics are affected. As part of this master thesis, the dependence of the beam parameter on the WNR chopper model (rise time, fall time, flat peak time) will be explored and CST software will be used for beam dynamics simulations.
A scheme for electron acceleration by self focused -Gaussian laser pulses in under dense plasma has been presented. The relativistic increase in the mass of plasma electrons gives nonlinear response of plasma to the incident laser pulse resulting in its self focusing. Under the combined effects of saturation nature of relativistic nonlinearity of plasma, self focusing and diffraction broadening of the laser pulse, the beam width of the laser pulse evolves in an oscillatory manner. An electron initially on pulse axis and at the front of the self focused pulse, gains energy from it until the peak of the pulse reaches. When the electron reaches at the tail of the pulse, the pulse begins to diverge. Thus, the deacceleration of the electron from the trailing part of pulse is less compared to the acceleration provided by the ascending part of the pulse. Hence, the electron leaves the pulse with net energy gain. The differential equations for the motion of electron have been solved numerically by incorporating the effect of self focusing of the laser pulse.
Circular Electron-Positron Collider (CEPC) is a 100 km circumference double-ring Collider, the high luminosity lattice in CEPC TDR is half lower emittance compared with the lattice in CEPC CDR. The dynamic aperture is strongly sensitive to the magnet misalignments and field errors. We present the study of the error correction for the CEPC TDR lattice and the dynamic aperture tracking after correction. The scheme of the correction and the resulting performance are discussed.
The Interaction Regions (IR) of many colliders benefit from the application of leading-edge technologies to ensure the highest possible luminosity delivered to the experiments. Leading-edge low-beta focusing magnets and crab cavities to handle individual bunches are critically important to increase the instantaneous and integrated luminosity in future Colliders.
The High-Luminosity LHC Upgrade, HL-LHC, with Nb3Sn Magnets (called MQXF) and Superconducting Radio Frequency (SRF) crab cavities (of two types, called DQW and RFD) is a world-wide collaborative project under construction in this decade to utilize the solutions mentioned above as key ingredients to increase tenfold the integrated luminosity delivered to the CMS and ATLAS experiments in the next decade. The HL-LHC AUP is the US effort to contribute approximately 50% of the low-beta focusing magnets and crab cavities for the HL-LHC.
In this contribution we present the valuable lessons learned by the US efforts in the procurement, construction, and testing phases of the Nb3Sn focusing magnets and SRF crab cavities. We will report on the experience gathered by HL-LHC AUP in the production of the first half of deliverables (magnets MQXFA03 to MQXFA13). We will also report on the test of the first cryoassemblies and the status of the cavities’ development, production and testing.
Both the technical and project management lessons-learned will inform applications of these technologies to future colliders and projects.
The FCC-ee project takes a step forward towards the discovery of new physical phenomena beyond the frontier of the standard model, by aiming at unprecedented center of mass energies and luminosities in a double-ring lepton collider. In order to explore potential improvements to the current lattice design, this paper looks at the use of combined function magnets within the short straight sections of the arc cells. The use of High Temperature Superconductors (HTS) with an operating temperature of 12 K and maximum field of 18.2 T for the combined function magnets allows increasing the bending radius and decreasing the synchrotron radiation. A first design is presented with comparisons to the current baseline.
During 2022, a dedicated study was undertaken at CERN, together with FCC Feasibility Study collaborators, aimed at proposing a robust configuration for the FCC-ee arc half cell. The proposed configuration takes into account integration aspects of the elements in the arc cross section, both for the booster and the collider, as well as aspects related to powering, cooling and ventilation, supporting and alignment, optics, instrumentation, handling and installation. The interfaces between the arc elements and the straight sections have also been analyzed. This paper summarizes the main conclusions of the assessment, and reports the preliminary engineering analyses performed to design the supporting system of the booster and of the collider. A proposal for a possible mock-up of the arc half-cell, to be built at CERN in the next years, is also presented.
The design of a muon collider complex requires to overcome challenges associated with muons short lifetime. To reach the expected luminosity for a multi TeV muon collider ring an interaction region with beta values of the order of a few millimetres is required. Resulting challenges are the development of a chromatic compensation section that is not degrading the physical and dynamical aperture, while allowing the control of the momentum compaction factor, as well as the control of the radiation due to muons reaching the earth surface. A preliminary version of a 10 TeV centre-of-mass energy muon collider ring fulfilling these requirements and taking limitations from the detector and magnet design into account is presented.
At LNL (Laboratori Nazionali di Legnaro), the vacuum system of ALPI (Acceleratore Lineare Per Ioni) accelerator includes about 40 pumping groups installed in the 90s. Obsolescence and rigidity of the used hardware and deficit of spare parts required a complete renovation of the system and relative controls. In 2022 we made the first steps of the system renovation with the development and installation of the new high level control system part based on EPICS (Experimental Physics and Industrial Control System) and CSS (Control System Studio). Meanwhile, we designed a new flexible and configurable low level control system part running on a Siemens PLC and exploiting MOXA serial server to control the renewed pump groups and pressure gauges. Moreover we extended the EPICS control system to support both HW configurations, providing to users the same information and graphic interface. The plan for the next years is to replace the legacy hardware with new racks running the new control system, provide service continuity, retrieve spare hardware, debug the PLC software and extend the EPICS control system with new features. This paper describes the adopted strategy and the upgrade status.
Chromaticity up to the third order in the LHC has been well observed in the LHC’s first and second operational runs, with regular beam-based measurements performed during commissioning and machine development. In previous runs however, no higher-order chromaticity could be observed. In 2022, dedicated collimators setups meant optics measurements could benefit from an improved range of momentum-offset for the chromaticity studies. This allowed the observation of fourth and fifth order chromaticity in the LHC at 450GeV for the first time. Measurements were performed for several machine configurations. In this paper, results of the higher order non-linear chromaticity are presented and compared to predictions of the LHC magnetic model.
A two-day test of operation with Pb ion beams was carried out in the CERN Large Hadron Collider (LHC) in 2022, with the aim of gaining experience in view of the future high luminosity heavy-ion physics runs from 2023 onwards. The LHC experiments received the first Pb-Pb collisions at a record energy of 5.36 TeV centre-of-mass energy per colliding nucleon pair (beam energy 6.8 Z TeV). Bunch trains created with a new production scheme in the injectors, including slip-stacking, were injected into the LHC, with the collimation of nuclear beams with bent crystals tested along with a new collimation scheme for collision products. This paper describes the conditions and outcomes of these tests, which are critical steps in the upgrade to higher luminosity.
The proposed FCC-ee machine is a high-energy, high-intensity and high-precision lepton collider which will require to reduce as much as possible the differential motions of its two beams at the interaction points. In this prospect, the vibration impacts of the quadrupoles in the region close to the interaction point are investigated. Considering the z-pole optics design and its dedicated optics simulation under MAD-X, the present paper describes the integration of the dynamics aspects (vibrations mitigation) to render the modelling more realistic towards operation. This simulation is based on the "particle tracking" mode. In this prospect, dynamic characteristics of the designed mechanical assembly are estimated according to an analysis in finite element models. Required transfer functions and realistic temporal sequences along the assembly are thus created and they can be implemented as inputs to the optical simulations to verify that this assembly allows the expected beam parameters. The obtained results on a dedicated cantilever mock-up are presented and the last optics simulations are discussed.
GaAs cathode is a unique device generating a spin-polarized electron beam by photo-electron effect with a circularly polarized laser illumination. Negative Electron Affinity (NEA) surface which is artificially made has an essential role in spin polarization, but the NEA surface has limited vitality. In this study, we activated GaAs as NEA cathode by evaporating Cs, K, and Sb metal on its cleaned surface. The experimental results including the quantum efficiency spectrum and the lifetime will be presented.
One of the design requirements to reach a high luminosity in the Electron Ion Collider (EIC) is the collision of matched spot sizes of hadron and electron beams at the IP, with a horizontal to vertical emittance ratio of up to almost 20. However, the natural vertical emittance of electron beams in the Electron Storage Ring (ESR) in EIC is a few orders of magnitude smaller than the horizontal one. Increasing the vertical beta function at the IP to reach the necessary vertical beam size may not be acceptable due to the associated growth of the beam-beam tune shift. We explore an approach to generate the vertical emittance through the transverse coupling using skew quadrupoles in one of ESR arcs, while keeping the rest of the ESR decoupled. In this paper, we present the study results on the modification of ESR optics, evaluation of the dependence of electron polarization on the excited vertical emittance and minimization of the depolarization through the spin match mechanism.
Studies of the beam spectrum of the Large Hadron Collider (LHC) have revealed the existence of harmonics of the mains frequency (50~Hz), ranging from 50~Hz to 8~kHz, in the form of transverse dipolar excitations. The restart of the LHC operation in Run 3 was accompanied by substantial improvements in the beam instrumentation. In particular, the upgrade of the transverse damper’s observation system (ADTObsBox), currently providing bunch-by-bunch and continuous position measurements, allows for the first time a systematic follow-up of the harmonics’ evolution during the run. In this paper, we present parasitic observations collected during the LHC physics operation, as well as results from dedicated experiments with the aim of providing further insights into the source of the perturbation, especially concerning the 50~Hz harmonics around 8~kHz. These tests include modifications in the operation mode of systems such as some of the Uninterruptible Power Supplies, while observing potential changes in the spectrum of the beam position data.
Travelling wave (TW) SRF accelerating structures offer several advantages over the traditional standing wave structures: substantially lower Hpk/Eacc and lower Epk/Eacc, ratios of peak magnetic field and peak electric field to the accelerating gradient, respectively, together with substantially higher R/Q. In this paper we discuss how a linear collider Higgs factory HELEN can be built using TW-based SRF linacs. We cover a plan to address technological challenges and describe potential ways to upgrade the collider luminosity and energy.
Energy recovery of residual ions may be needed to increase the energy efficiency of Neutral Beam (NB) injectors for fusion plants as DEMO while a deflection-based system has been proposed. A compact beam energy recovery system, composed of 2 Farady Cups (FC) with holes for D0 passage, based on space charge effects, very effective to recover ions with low residual energy, has been proposed recently to replace the Electrostatic Residual Ion Dump (ERID) designed for ITER to dump the residual D- and D+ before the NB injection in the tokamak plasma [1]. New more accurate simulations on the proposed recovery system, however, presented some collection efficiency problems for very high initial beam kinetic energy (Eki=0.5÷ 1 MeV) when a very low residual (few keV) energy in the planned device. In this contribution, all parameter tunings for optimized simulation results are described and discussed. The collection of high Eki ions at low energy (a few percent of the full neutral beam energy Eki) remain possible although it could be done with lower efficiencies.
Run 4 will be the first operational run of the LHC with full deployment of the upgrades from the High Luminosity (HL-LHC) project planned for 2026-2028 (Long Shutdown 3). The commissioning goals for the first run were defined to approach steadily the design beam current, while already fulfilling significant luminosity goals. Despite extensive operational experience already gained, intensity limitations due to electron cloud and/or impedance might require to further reduce beta* values from the very early stages. The paper presents various optics configurations considered under different Run4 scenarios together with their expected dynamic aperture.
The Spallation Neutron Source (SNS) recently took delivery of a third Radiofrequency Quadrupole (RFQ03) that will ultimately be installed on the front-end (FE) of the SNS Linac. The first RFQ (RFQ01) operated in the SNS FE for more than a decade before being replaced with the second RFQ (RFQ02). RFQ01 was relocated to the Beam Test Facility (BTF) where it operated for five more years. The RFQ02 was initially installed in the BTF for high power testing and used with H- beam for BTF operation. It replaced RFQ01 in the SNS FE in 2017 and has been operating for beam production since then. There are some differences between the three RFQs. RFQ01 has a square cross-section with pi-mode stabilizing loops (PISLs) with the structure being fabricated using two layers of materials, GlidCop outside and OFHC inside. RFQ02 and RFQ03 has an octagonal cross-section with end-wall stabilizer rods and was fabricated using OFHC only. RFQ01 suffered some field flatness distortion incidents that resulted in degradation in beam transmission efficiency and required RF tuning. RFQ02 has performed well but had a melted RF seal in the high energy end wall, that was ultimately mitigated by a redesign of the end flange seals. The SNS decided to order RFQ03 that has a design that followed that of RFQ02 closely, but end-wall contacts were modified to prevent RF seal failure. This report presents the testing, installation, high power RF operation, and design improvements of the RFQ03.
FCC-ee performance is challenged by magnetic errors and imperfections. Magnetic design simulations predict a systematic quadrupolar component in the arc dipoles significantly impacting the machine optics. This paper studies the impact of this component in the beta-beating and explores potential mitigations.
The Future Circular Electron-Positron Collider (FCC-ee) aims to achieve unprecedented energies and luminosities. This can only be achieved using complex insertion region optics that set high challenges for commissioning and operating the machine. In the following we discuss some of the optics correction methods anticipated to be used to achieve the targets of the FCC-ee.
The team at LANL continues efforts for the LANSCE Accelerator Modernization. This paper summarizes the progress in developing of the proposed concept of the modernization, and the major technical challenges that are expected in this concept. Separate subsystems are designed on the conceptual level, and the computer models for beam dynamics simulations are established and presented here. The technical details of the proposed subsystems are presented in the conceptual form, and the limited analysis of alternatives is performed and described.
The electron-ion collider will utilize a major portion of the existing RHIC rings for its hadron storage ring (HSR). This paper describes the lattice design of the HSR. Presently, RHIC consists of two rings, each of which contains 6 straight sections, and between those straights are arcs, each consisting of 11 FODO cells. The HSR uses 7 of the existing RHIC arcs which are unmodified, other than powering changes to allow the beam to travel opposite to its direction in RHIC in selected arcs. We select the arc in one sextant to keep the orbit period of the HSR the same as that of the new electron storage ring, depending on whether we are operating at hadron energies around 41 GeV/u or in the range of 100 GeV/u to 275 GeV/u. We describe the purpose and lattice design of the 6 straight sections of the HSR.
We present the lattice design for the interaction region (IR) for the Electron-Ion Collider. We specify the requirements that the IR must meet, both for the hadron and electron beams themselves and for the collision products and radiation that must be transmitted through the magnet apertures. We align the hadron magnets downstream of the detector to pass the collision products while minimizing stray fields in the electron line. We set the fields and gradients in the magnets near the IR to meet the required specifications at both the interaction point and the crab cavities. We describe how these magnet placements can be implemented in accelerator design codes. We match the hadron IR to the existing RHIC arcs, and describe the consequences for the spin manipulation snake and rotators.
The Electron Ion Collider (EIC) Hadron Storage Ring (HSR) will utilize the Relativistic Heavy Ion Collider (RHIC) arcs and modified straight sections. Due to these modifications in the straight section of the on project electron Proton Ion Collider (ePIC) experiment, a new injection system needed to be built one arc downstream of the existing RHIC injection system. The new injection system will have capability of injecting 290 bunches with a maximum rigidity of ~81 Tm. In addition to the new injection system, the hydrogen jet (HJET) and proton-carbon (pC) polarimeters will be located in the straight section downstream of injection. This paper will report the modifications required to the lattice, optics, and magnets.
The first year of Run 3 of the Large Hadron Collider (LHC) revealed significant changes in both linear and nonlinear optics errors with respect to Run 2. Several iterations of optics corrections were required to successfully bring the linear optics within operational tolerances. This paper presents the current status of optics corrections in the LHC and the challenges experienced in commissioning the optics to a beta* of 30cm in a single commissioning year after the Long Shutdown.
Local coupling correction in Interaction Regions (IRs) and global coupling correction based on Base-Band Tune (BBQ) measurement have been performed routinely for RHIC operation. However, one still observes significant residual local coupling measured by beam position data. For the Electron-Ion Collider (EIC) project, betatron decoupling for the hadron beam needs to be improved to maintain a large horizontal to vertical beam emittance ratio (12:1). In this paper, we will analyze the cause for noticeable residual coupling in RHIC and propose an integrated local and global betatron coupling correction based on beam position measurements and verify the new scheme with simulation and measurements.
To provide a more accurate and stable Radio-Frequency (RF) signal in conditioning and processing test progress, it is necessary to design an Low-Level Radio-Frequency (LLRF) control system which can provide high precision RF driving signal based on meeting the amplitude and phase stabilization requirement. Through Feed-Forward operation, accurate phase adjustment and amplitude adjustment are realized inside the pulse, to realize the precision and automation of phase-inversion, amplitude stabilization, phase stabilization, and waveform adaptation matching. An LLRF System integrated with feed-forward control and vector modulation output was designed and built, the long term working stability of the LLRF system was verified during a new 50MW S band Klystron conditioning progress.
The Advanced Sources and Detectors project is building an advanced multi-pulse linear induction accelerator capable of generating a 1.4 kA electron beam at energies up to 24 MeV. The accelerator, named Scorpius after the brightest known x-ray source in the sky, will be unique in its use of solid-state pulsed power (SSPP) to generate the voltage pulse for the injector and accelerating gaps throughout the accelerator, giving Scorpius unique control of the pulse shape by independently triggering 45 individual stages stacked in each of nearly 1,000 line replaceable units (LRUs). To take full advantage of the SSPP flexibility, automated optimization of the pulse shape to a desired waveform is currently under development. To demonstrate this capability, nonlinear surrogate circuit models of the SSPP have been developed using the hybrid transmission line/modified nodal analysis code, CASTLE, that include parasitics and a dummy load to generate reflections. Data-efficient Bayesian optimizations calling CASTLE directly for each iteration are compared with results from a convolutional neural network or other machine learning model trained on data generated by CASTLE, and the effect of the number of stages on pulse flattening is discussed.
We’ll introduce a high precision active motion controller based on machine learning (ML) technology and electric piezo actuator. The controller will be used for srf cavity active resonance control, where a data-driven model for system motion dynamics will be developed first, and a model predictive controller (MPC) will be built accordingly. Simulation results as well as initial test results with real SRF cavity will be presented in the paper.
In 2022, the Large Hadron Collider started its third operational run. Following the three-year Long Shutdown 2, a careful re-commissioning of the machine protection system (MPS) took place. The initial hardware and beam commissioning period was followed by a 30-day-long intensity ramp-up, during which the number of circulating bunches was successively increased to 2460 bunches per beam. After each pre-defined intensity step, a detailed analysis of the functionality of the MPS was performed before advancing to the next step. It paved the way to reach a record stored energy of 400 MJ per beam in 2022. This was achieved without observing any beam-induced damage, confirming the excellent performance of the MPS.
The paper reviews the strategy for the LHC re-commissioning and intensity ramp-up from a machine-protection perspective.
The CLIC Beam Delivery System (BDS) transports the lepton beams from the exit of the Main Linac to the Interaction Point (IP). The Final Focus System (FFS) is the last part of the BDS and its role is to focus the beam to the required size at the IP and to cancel the chromaticity of the Final Doublet (FD). MAD-X and MAD-NG are simulation codes for beam dynamics and optics that are used for particle accelerator design and optimization. This paper presents a comparison between the two codes to achieve the best performance of the design of the FFS, including the optimization methods, the speed performance and the physics accuracy.
The project of PolFEL free electron laser comprises 185 MeV cw-linac furnished with ASG electron gun and 4 Rossendorf-like cryomodules. Magnetic lattice has been designed applying alike air cooled quadrupole magnets. FODO quadrupoles in undulator section differ with trimmed coils. A variety of dipoles has been designed: 14 – degrees air and water cooled rectangular dipoles are used for low and high energy bunch compressors. 17 - degrees dipoles guide the beam towards a dump. The design of these dipoles bases on identical yoke, furnished with adequate coils and vacuum chambers. 45- degrees water cooled dipoles form a transfer section between FEL and Inverse Compton Scattering parts of the linac. Quadrupole poles design assumed parasitic multipoles strengths less than 10-4 relative to the main one. Dipoles field was assumed uniform within 10-4 of B0. Yokes and poles designs have been performed using 2D FEMM code and refined in 3D with Radia. Manufacturing of yokes and coils will be achieved in NCBJ workshop. Currently, the quadrupole prototype has been built and will be mechanically, electrically and magnetically verified.
An 800 MHz, Radio Frequency Quadrupole (RFQ) was designed to accelerate the proton beam to 2 MeV energy at a distance shorter than one meter in KAHVE-Lab, Turkey. A half-length test module was previously produced to investigate the local manufacturability of this RFQ cavity. The manufactured test module was subjected to mechanical, vacuum and electromagnetic tests to adjust the pressure, EM field and frequency parameters to the desired operational settings. Results from these tests were used to improve the final manufacturing process for the two modules of the RFQ which ended successfully in Q4 2022. The finished RFQ, after being fully assembled for the first time, will initially be subjected to vacuum tests followed by low-level RF and power tests. The KAHVE-Lab proton beamline is planned to be fully integrated and commissioned by the end of 2023. This study introduces a general framework about the current status of the 800 MHz RFQ, and discusses the ongoing commissioning studies.
Studies of third-order chromaticity in the LHC during its initial two runs have consistently demonstrated a substantial discrepancy between the expected Q''' at injection and that observed in beam-based measurements. In 2022 during Run 3, for the first time, studies of Q''' have been complemented by measurements of chromatic detuning, being the momentum-dependence of amplitude detuning, and the decapole resonance driving term 𝑓1004. In this paper, these beam-based measurements are presented and compared to the magnetic model. Potential sources of the previously identified Q”’ discrepancy are discussed.
During loss maps performed with beam at injection energy in the LHC with the high octupole and chromaticity settings used for multi-train operation, large beam losses were observed at an injection protection device (TDIS). Although these losses did not present a threat to machine operation or protection, reducing them is of high importance to improve machine performance. Various strategies were developed to mitigate these losses, such as octupole setting optimization at constant Landau damping and vertical tune reduction. Further optimization of collimator settings is also considered. Results of experimental tests and first simulations are reported here together with considerations for the future.
The largest current obstacle to SuperKEKB's luminosity goals is currently beam-related backgrounds occurring during accelerator operation. Thus, understanding the level of these backgrounds is of crucial importance for the future of the facility. In this work, we take advantage of the Belle II Electromagnetic Calorimeter's near-total coverage of the interaction region to create a spatial model of beam-induced backgrounds with the aim of providing fast feedback to improve accelerator conditions.
One of the most fundamental measurements since the Higgs boson discovery, is its Yukawa couplings. Such a measurement is only feasible, if the centre-of-mass (CM) energy spread of the e+e- collisions can be reduced from ~50 MeV to a level comparable to the Higgs boson’s natural width of ~4 MeV. To reach such desired collision energy spread and improve the CM energy resolution in colliding-beam experiments, the concept of a monochromatic colliding mode has been proposed as a new mode of operation in FCC-ee. This monochromatization mode could be achieved by generating a nonzero dispersion function of opposite signs for the two beams, at the Interaction Point (IP). Several methods to implement a monochromatization colliding scheme are possible, in this paper we report the implementation of such a scheme by means of dipoles. More in detail a new Interaction Region (IR) optics design for FCC-ee at 125 GeV (direct Higgs s-channel production) has been designed and the first beam dynamics simulations are in progress.
Utilizing short RF pulses ($\sim$9 ns) with Dielectric Disk Accelerators (DDA) is a way to improve the energy efficiency of a linear accelerator and decrease the required footprint while still achieving large energies. A DDA is an accelerating structure that utilizes dielectric disks to improve the shunt impedance while still achieving large accelerating gradients. A single cell clamped DDA structure was designed and high power tested at the Argonne Wakefield Accelerator, reaching an accelerating gradient of 102~MV/m. A multicell clamped DDA structure has been designed and fabricated. Simulation results for this new structure show a 108~MV/m accelerating gradient with 400~MW of input power with a high shunt impedance and group velocity. Engineering designs have been improved from the single cell structure to improve the consistency of clamping over the entire structure. The multicell structure has been fabricated, assembled, and low power tested with high power testing to come.
Muons circulating in a muon collider decay and generate neutrinos within a small solid angle, which reach the earth’s surface. One of the challenges of a high energy muon collider is to ensure that showers created by such neutrinos interacting close to the earth’s surface result in very low radiation levels. The neutrino radiation cone from a muon beam without divergence is estimated through a combination of analytical estimates and FLUKA simulations. Such neutrino cones have to be combined with the properties of the lattice to obtain the possible radiation levels at the earth’s surface. Studies of mitigation measures will be presented, combining the installation of the collider deep underground with a careful choice of the orientation, and with periodic variations of the muon beam trajectory either within the machine aperture or by deforming the whole machine in the vertical plane.
The Nuclotron-based Ion Collider fAcility (NICA) is under construction at JINR. The NICA project goal is to provide colliding beams for studies of hot and dense strongly interacting baryonic matter and spin physics. The NICA Collider includes two rings with 503 m circumference each and the injection complex. For the heavy ion mode, the injection complex consists of following accelerators: 3.2 MeV/u linac (HILAC), 600 MeV/u (A/Z=6) superconducting booster synchrotron (Booster) and main superconducting synchrotron (Nuclotron) with kinetic energy up to 3.9 GeV/u (A/Z=2.5). The injection complex has been under commissioning for more than 2 years. The latest half-year Run ended in February of 2023. It was devoted to preparations for the collider operation and also delivered slowly extracted 3.9 GeV/u xenon beam to the BM&N experiment.
Now the injection complex is shut down for its further development and an assembly of the collider. Cryogenic tests of the collider magnetic structure are expected at the end of 2023. The next run of the injection complex is aimed at an increase of ion flux by more than an order of magnitude and will be started at 2024.
To maintain polarization in a polarized proton collider, it is important to know the spin tune of the polarized proton beam, which is defined as the number of full spin precessions per revolution. A nine-magnet spin flipper has demonstrated high spin-flip efficiency in the presence
of two Siberian snakes. The spin flipper drives a spin resonance with a given frequency (or tune) and strength. When the drive tune is close to the spin tune, the proton spin direction is not vertical anymore, but precesses around the vertical direction. By measuring the precession frequency of the horizontal component, the spin tune can be precisely measured. A driven coherent spin motion and fast turn-by-turn polarization measurement are keys to the measurement. The vertical spin direction is restored after turning the spin flipper off. The fact that this manipulation preserves the polarization makes it possible to measure the spin tune during the operation of a polarized collider
such as RHIC and EIC.
As an energy frontier machine, the proposed Super Proton-Proton Collider (SPPC) will have the capability to explore a much larger region of new physics models with center of energy around 125 TeV and circumference 100 km.
The nonlinearity optimization of the SPPC collider ring lattice is essential to get a high peak luminosity and lifetime of the beams. In this paper, a collider ring lattice based on the CDR one will be presented. Then, the nonlinearity of the bare lattice was optimized using Lie map analysis and frequency map analysis. With the optimization, the lattice aberration at the interaction points and dynamic aperture of whole ring were improved.
Finally, the alignment tolerances and field error tolerances for the SPPC are evaluated. The correction scheme of the lattice with errors will be presented.
SuperKEKB suffers from sudden beam loss(SBL) during operation. It causes collimator damage, QCS quench and large beam background to the Bell-II detector. Beam aborts triggered by SBL hinder us from storing large beam current. Since cause of SLB is unclear, we launched an effort to investigate it and consider measures to be taken. In this paper, we discuss phenomena of SBL and various hypotheses to explain SBL.
The application of HTS coils as a matching device and a large-aperture L-band linac make it possible to transport a substantial part of positrons generated in a positron production target through a capture linac. It raises a question of how to manage their large phase space to provide bunches matched to the damping ring acceptance. This paper presents the beam dynamics studies of the FCC-ee positron linac consisting of an adiabatic matching device (AMD) with theoretical field distribution combined with constant solenoidal field along $\frac{9}{10}\pi$ large aperture L-band accelerating sections. AMD field drop rate, as well as the RF field phase and accelerating section length, were varied to find features of a bunch formation. It was shown that 5D normalized beam brightness is a useful parameter to optimize the initial part of the capture linac. A higher beam brightness can be obtained for the higher AMD field drop rate. Starting from some accelerating section length, two peak structure appears in the normalized brightness dependence on the RF field phase. The peaks correspond to the acceleration of the head or the tail of the initial positron longitudinal distribution. The last one provides a higher positron yield.
During the third run period of the CERN Large Hadron Collider (LHC), as well as for the future High-Luminosity LHC era, luminosity levelling by beta is a key technique to control the pile-up in the high-luminosity experiments ATLAS and CMS while maintaining Landau damping through the head-on beam-beam interaction. This implies changing the machine optics in the interaction regions while keeping high-intensity beams in collision and the experimental detectors in their data taking configuration.
This contribution summarizes the implementation and operational experiences obtained during the first year of operation with beta levelling at the LHC and provides an outlook for the following years, when the beta* levelling range will be further extended.
A non-negligible risk of magnet quenches occurring due to the reduced cleaning performance of the original LHC collimation system with lead ion beams was expected at an energy of 6.8 Z TeV beams. Crystal collimation has therefore been integrated into the HL-LHC upgrade baseline to overcome present limitations. The upgrade scope involves the installation of 4 new crystal primary collimators. Upgraded devices were installed based on the experience and experimental evidence gathered with a previously-installed test stand. In preparation to the new operational challenges, the controls of the new devices were integrated in the high-level LHC collimation control system, which is used to orchestrate the operation of these devices in harmony with all the other components of the machine. A dedicated application was also developed to address three main tasks: to find the main planar channeling of newly installed crystals using Machine Learning models developed at CERN; to optimise the angular orientation to maximise the channeling efficiency; to monitor that the optimal channeling orientation is kept throughout the fill. This paper will present and discuss all of these aspects.
In addition to the physics program with proton beams, the Large Hadron Collider (LHC) also provides collisions of fully-stripped Pb beams for about one month per year. When colliding Pb-Pb nuclei, electromagnetic interactions are the dominating processes because of the intense Coulomb field produced by the ions. These 'ultra-peripheral' interactions give rise to special losses in the machine that can impose limits on the luminosity. Among them, the bound-free pair production (BFPP) causes a localized power deposition downstream of each collision point, which could induce superconducting magnet quenches if not well controlled. These losses were studied and successfully mitigated for most LHC experiments, however the recent request by LHCb to increase the Pb-Pb luminosity requires a revision of BFPP collisional loss limitations. In this paper, the simulation of BFPP losses from Pb-Pb collisions around LHCb is presented. The loss patterns are discussed for different beam parameters. Finally, a mitigation strategy by means of an orbit bump is studied.
MINERVA entails the first phase of the MYRRHA programme, which aims at driving a nuclear reactor with a high-power proton accelerator, commonly referred to as an Accelerator Driven System(ADS). The purpose of MINERVA is to demonstrate the reliability requirements that are needed for a stable ADS, by the realization of a 100 MeV, 4mA proton beam.
In order to transport the proton beam with minimal losses, a strategic placement and usage of orbit correctors, i.e. steering magnets, and Beam Position Monitors (BPMs) along the accelerator is paramount. With this in mind, error studies were carried out with TraceWin to determine an optimal steering strategy and put forward requirements on magnet design and alignment. In addition, orbit correction studies were performed with an in-house developed beam dynamics simulation code, PyAccel. Comparison of the results obtained with both software packages serves as an important benchmark towards future developments.
A facility for a muon collider brings the big advantages of a compact lepton collider and a collision energy up to several TeV, well above the energy reach of conventional electron circular accelerators.
However, the short lifetime of muons drives the design of the accelerator complex and collider, which makes this complex unique. A high muon survival rate and luminosity requires an extremely fast energy increase in combination with intense and ultra-short bunches. The International
Muon Collider Collaboration proposes a chain of rapid cycling synchrotrons (RCS) for acceleration from several tens of GeV to several TeV.
The minimization of the muon decay during the acceleration process is driven by technological limitations like the maximum magnet ramp and field, and cavity gradient.
We will consider different scenarios to reuse as much as possible the existing infrastructure at CERN.
We will give some scaling laws for a hybrid RCS to evaluate the frequency shift due to a path variation and the trajectory variation.
Finally, we will propose a preliminary parameter range for the different stages of an RCS chain.
The Physics Beyond Colliders (PBC) studies at CERN address the possibility to utilise protons in the Large Hadron Collider (LHC) for a fixed-target program beyond the colliding-beam physics. As part of PBC, a double-crystal test stand is considered for installation in the LHC off-momentum collimation Insertion Region (IR) 3. In this PBC experiment, a first silicon crystal deflects beam-halo protons from the main beam onto a fixed-target. A second crystal, providing bending angles in the mrad range, is located immediately downstream of the target to deflect target-produced secondary particles onto a detector that will measure the electric and magnetic dipole moments of short-lived baryons. The LHC test stand will serve as a proof-of-principle machine experiment to assess the performance of new crystals at LHC energies and to address a number of critical machine aspects related to this complex setup. In this paper, simulations in MAD-X and SixTrack are used to predict the performance of the proposed double-crystal layout for the LHC Run 3 test stand and the LHC Run 4 final experiment.
A series of power outages during setup for RHIC Run 23 damaged two of the four helical dipole modules that comprised one of the full Siberian Snakes in RHIC’s Blue ring. The remaining two helical dipoles were reconfigured as a “partial” snake, one which rotates the spin by an angle less than 180 degrees. This partial snake configuration has a rotation angle and axis which both deviate from the ideal. We describe the compensatory measures taken to address the effects of these deviations. These include reconfiguring the other Blue snake to rematch the stable spin direction at injection and a change of the nominal store energy from 255 GeV to 254.2 GeV to improve the stable spin direction condition at store. Polarization transmission through RHIC acceleration was as good as with full snakes and we present some analytical and tracking results that corroborate the observed robustness with respect to deviations from ideal snakes.
Positron beams would provide a new and meaningful probe for the experimental program at the Thomas Jefferson National Accelerator Facility (JLab). The JLab Positron Working Group, formed in 2018 and now with over 250 members from 75 institutions, continues to develop an experimental program with high duty-cycle positron beams including but not limited to future hadronic physics and dark matter experiments. Critical requirements involve generating positron beams with a high degree of spin polarization, sufficient intensity and a continuous-wave (CW) bunch train compatible with acceleration to 12 GeV at the Continuous Electron Beam Accelerator Facility (CEBAF).
In this presentation we describe a start-to-end layout for positron beams at 12 GeV CEBAF utilizing the Low Energy Research Facility (LERF) at Jefferson Lab to build two new injectors. A GaAs dc high voltage photo-gun first generates >1 mA of polarized electrons which are then accelerated to 80-150 MeV and directed to a high-power spinning W target for polarized bremsstrahlung and positron pair creation. A second injector then collects, bunches and accelerates the positrons to 123 MeV. The positron beams are transported by a new beam line and injected into the CEBAF acceptance for acceleration to the end stations with energies up to 12 GeV. The layout is optimized to provide Users with positron spin polarization >60% and intensity greater than >100 nA, and with higher intensities when polarization is not required.
The Large Hadron Collider (LHC) is equipped with a betatron halo collimation system designed to prevent magnet quenches during periods of reduced beam lifetime. Protons subject to single diffractive scattering in collimators can nevertheless leak into the adjacent dispersion suppressors (DS). In view of the future high-luminosity (HL) upgrade of the LHC, a better understanding of the quench margin in these DS magnets is needed, considering the increased beam current and the resulting higher beam losses of up to 1 MW of power within a few seconds, which the collimation system is designed to withstand. In this contribution, we present FLUKA power deposition simulations for a controlled beam loss experiment at 6.8 TeV, probing the quench level of the superconducting magnets most exposed to collimation losses. The results are compared with the expected power deposition in HL-LHC operation, considering different collimator settings. In particular, we studied the power deposition for relaxed collimator gaps, which are considered as the baseline configuration for initial operation in Run 4.
In the Large Hadron Collider (LHC), corrections of local Interaction Region (IR) linear coupling are of importance to control beam sizes at Interaction Points (IPs) and hence the luminosity performance, as well as to prevent a significant impact on the beam dynamics. During the LHC Run 3, the skew quadrupole corrector magnets used on either side of IPs are expected to exceed their radiation dose limit. In this contribution, studies on the impact of operating with limited availability of these magnets are presented, should one or more become inoperable. Mitigation strategies for different scenarios are discussed.
We describe optics designs of the key components of proton and electron Recirculating Linear Accelerators (RLAs). They are presented in the context of a high-power hadron accelerator being considered at ORNL and a CEBAF electron energy doubling study, FFA@CEBAF, being developed at Jefferson Lab. Both concepts rely on the Fixed-Field Alternating gradient (FFA) arc optics designs where multiple beam passes are transported by a single beam line.
The muon linear accelerator is under development at J-PARC for precise measurement of muon anomalous magnetic moment and electric dipole moment. Four 2592 MHz disk-loaded structures (DLSs) operating in the TM01-2pi/3 mode take charge of the acceleration of high-velocity muon from 70% to 94% of the speed of light. They have disk-iris apertures tapered to generate a quasi-constant gradient of 20 MV/m. Gradual variation in disk space at each cell is one of the structural features of the DLS for muon to synchronize the accelerating phase with the changing speed of muon. Therefore, the dimensions of both end cells are significantly different. Two prototypes of RF couplers and two 9-cell reference cavities with shapes of the end cells of the DLS at the first stage have been fabricated and tested. We validate our design RF parameters and establish a method for tuning the DLS in this paper.
In recent years, there has been an increasing interest for experiments in the LHC complex that aim to push the frontiers of Physics, in locations that do not interfere with the normal operation of the machine while guaranteeing an acceptable signal-to-background ratio. This is the case with the Forward Search Experiment (FASER), which was approved in 2018, followed by the approval of the Scattering Neutrino Detector (SND) of the SHiP experiment in 2021. During the High Luminosity era, FASER and SND will continue to record data, for which a re-evaluation of the signal and background levels is required to prepare for the installation of the new detectors. Furthermore, there is a proposal for the construction of a Forward Physics Facility (FPF) at more than 600 m from the ATLAS interaction point to house far-forward physics experiments. These would benefit from a very low background due to the distance from the LHC tunnel and the more than 100 m of rock and concrete that serve as shielding, allowing the study of rare and exotic processes. Extensive calculations of physics signals, radiation levels and background conditions were performed by FLUKA Monte Carlo simulations and are summarized in this paper.
The European Spallation Source (ESS) project currently enters the final stage of installation. Since 2017, a group of engineers and technicians from The Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Science (IFJ PAN) are involved in the project. The contribution to the project can be divided into three main tasks: Radio Frequency Distribution System (RFDS), RF (Radio Frequency) Power Stations and Cryomodules.
The RFDS in ESS project is one of the largest installations of this type consisting of 155 RF high power systems. Engineers and technicians from IFJ PAN were responsible for preparation, installation and RF measurements of the above mentioned system. The team is also involved in preparation and conducting low and high power tests of the RF stations.
The IFJ PAN team is also responsible for the preparation as well as vacuum and cryogenic tests for 9 Medium and 21 High Beta Cryomodules, before they are installed in the tunnel.
The advanced quality control and quality assurance were mandatory for this work because the costs of failures, as well as potential delays, would have a huge impact in the project realisation. Therefore dedicated methods and approaches have been adapted to this work using experience gained by the IFJ PAN team on previous projects like LHC, XFEL and W7X.
The Future Circular Collider (FCC) study comprises two accelerators, namely a high-energy lepton collider (FCC-ee) and an energy-frontier hadron collider (FCC-hh). Both rings share the same tunnel infrastructure, analogous to LEP and LHC. We present the current design status of FCC-hh, updated from the Conceptual Design Report (CDR) and with recent developments including the new designs of the combined injection and dump insertion, combined injection and RF insertion, new collimation insertions, as well as the optimization of the arc cells and dispersion suppressors to increase the dipole filling factor.
Short pulsed proton beams of 8 ns has been extracted from FFAG accelerator in KURNS. Bunch rotation after adiabatic debunching was used at highest energy orbit.
The AAC community proposed linear collider concepts with energies extending to 15 TeV center-of-mass and luminosities up to 50E34 cm^-2 s^-1 as part of the Snowmass process. The beam power required to reach these energies and luminosities is prohibitive. We discuss the results of initial investigations of strategies to increase luminosity per beam power, a key figure-of-merit for linear colliders. We deploy a new tool for our studies, Particle-in-Cell simulations, in order to better understand collisions at high-energy and high-beamstrahlung parameters. The results of our studies will aid in the design of future linear colliders based on standard RF technologies and novel acceleration methods.
The strong field of the experimental solenoid around the interaction point has a considerable effect on the beam optics. Moreover, if the beams traverse the solenoid at an angle, as it is typically the case in a collider, the solenoid will also affect the closed orbit within and beyond the solenoid. Simulating these effects is not trivial. In the following we outline different philosophies of how this can be tackled and discuss how it is done in practice in various accelerator codes.
During about one month in every operational year, the Large Hadron Collider (LHC) works as a heavy-ion collider. Four one-month Pb-Pb runs have been executed so far, as well as two p-Pb runs. The LHC heavy-ion programme is scheduled to continue in the future, featuring increased luminosity and beam energy. Beam losses caused by ions fragmenting in the collision process risk introducing performance limitations. Losses occur immediately downstream of the collision points as well as at other locations in the ring, through multi-turn beam dynamics processes and interactions with ring collimators. This paper presents simulations of collisional loss patterns using a new simulation approach that relies on the SixTrack-FLUKA coupling. Simulations of the 2018 Pb-Pb and 2016 p-Pb runs are benchmarked against experimental data and the prediction of collisional losses for future Pb-Pb and p-Pb runs is shown.
Fixed Field Accelerators are a candidate for future hadron cancer therapy facilities as their high repetition rate and large energy acceptance enables novel treatment modalities such as high dose rate FLASH. However, conventional dose delivery mechanisms are still necessary, requiring continuous beam delivery over 1--30s. This work is the first study of slow extraction from a scaling Fixed Field Accelerator, using the LhARA facility for baseline parameters. At a horizontal tune of 10/3, the intrinsic sextupole strength of the nonlinear FFA magnetic field is sufficient to excite the resonance, although extraction is better controlled using an additional excitation sextupole at a tune close to 8/3, with radiofrequency knock-out extraction. Including considerations of issues due to nonlinear fields and limitations required to keep the tune energy-independent, slow extraction from Fixed Field Accelerators is successfully demonstrated.
There has been a recent explosion of interest for a Muon Collider (MuC) as evident by the number of journal publications, related workshops and white papers submitted for the 2021 Snowmass Study. In light of this strong interest and in order to provide input for Snowmass, a MuC Forum has created in 2020. It facilitated a strong bond and exchange of new ideas between the particle physics community and accelerator experts with the ultimate task to make a physics case for a MuC. This paper discusses three key achievements of this Forum. These were: (1) Highlight transformative new developments in detector and accelerators technologies that address many of past concerns about MuC feasibility. (2) Identify key areas where US can provide critical contributions to the global R&D efforts and, (3) present US sites that could host a MuC as well as the relevant R&D needed in order to achieve this.
The high precision measurement of the centre-of-mass energy in the Future Circular Collider e+e- (FCC-ee) at Z and W energies can be realized through resonant spin depolarization utilizing transversely polarized beams. This requires a guaranteed sufficiently-high spin polarization in the presence of lattice imperfections. Investigations of the impact of misalignments on the equilibrium polarization are conducted using analytical and Monte-Carlo spin simulations with Bmad. Potential optimization schemes to ensure high polarization using orbit bumps have been explored.
We describe methods for measuring the three-dimensional stable spin vector for RHIC stores at two locations in the ring, namely the proton-Carbon (pC) polarimeters and the interaction point at the STAR detector. Both the pC and STAR local polarimetry can only measure the two transverse components of the stable spin direction. Measuring the full spin vector requires making a local spin rotation at the measurement point. This is accomplished using the helical dipole spin rotators for STAR and a local horizontal orbit angle for the pC polarimeters, respectively. The stable spin direction at a third point, the hydrogen jet polarimeter is determined via spin tracking from the nearby pC polarimeter. We describe the measurement and analysis methods used and present results of the measurements made during RHIC Run 22.
The Drift Tube Linac (DTL) for the ESS Linac will accelerate H+ beams of up to 62.5 mA peak current from 3.62 to 90 MeV. The structure consists of five cavities. The first cavity (DTL1, 21 MeV) has been commissioned with beam in summer 2022. DTL2, 3 and 4 are installed in the tunnel since the end of 2022, ready for the conditioning and commissioning starting in 2023. DTL5 is under assembly and will be transported to the tunnel after the completion of beam commissioning up to 74 MeV. The paper wants to give an overview of the activities already done and ongoing on the five DTLs: from assembly to tuning, from conditioning to beam commissioning.
In the context of the FCC IS European study, which investigates the feasibility of a 100 km circular $e^{+}e^{-}$ collider for the future high energy physics research, we present the status of the High Energy Booster (HEB) ring. The HEB will be located in the same tunnel as the collider and should have the same circumference. The main difference is to have a bypass near the experiments to avoid perturbing the detectors. In order to perform precision measurements of the Z, W and H bosons, as well as of the top quark, unprecedented luminosities are required. To reach this goal and to fill the collider, it is mandatory to continuously top up inject some beams with a comparable emittance and bunch length to the collider ones.
One challenge of the HEB is in the fast cycling time allowing to reach the collider equilibrium emittance, especially for the Z mode. We present the status of the layout and optics design of the HEB taking into account these challenges. A special focus will be made on the cycling considerations.
In this work, we examine the beam correction requirements for the FFA@CEBAF energy upgrade. Both hardware and software diagnostic and corrector components are under investigation; in particular the relationship between hardware and software optimization will be developed. To generate a representative sample of errors---from the machine lattice and other beam properties---we construct a Markov Chain Monte Carlo (MCMC) sampler which considers different probability distributions for different types of errors. This sample is used to investigate the statistical sensitivity of the beam to various diagnostic and corrective schema. Once statistics are acquired, we plan to use a variety of optimization techniques to minimize correction time for the electron beam in the FFA arcs designed for the CEBAF upgrade.
Two High Luminosity Large Hadron Collider (LHC) type crab-cavities have been installed in the CERN SPS for testing
purposes. A first partially successful attempt to characterize the skew-sextupolar component of the radio frequency field of the crab-cavity
by means of beam-based techniques has been carried out in 2018.
The large orbit distortion produced by the crab cavity dipolar field combined with the multipolar errors in the SPS optics
resulted in some systematic errors that cannot be easily accounted for. After a major overhaul of the SPS turn-by-turn
BPM system a second attempt was carried out in 2022. In the attempt to keep under control systematic errors,
orbit correctors have been used to compensate the large orbit excursion produced otherwise by the crab cavity.
The results of the new measurement are here discussed.
High intensity heavy ion beams are a main constituent of the FAIR research program. They will be provided by the UNILAC via the high current injector HSI. Generated in high current sources, these ions originally have low charge states. To allow for efficient acceleration in the UNILAC and SIS18, a gas stripper is located at the end of the HSI to reduce the mass-to-charge ratio below 8.5. An effort has been made to enhance the stripping by introducing hydrogen instead of nitrogen as stripping target, thereby increasing the stripping efficiency by up to 60%. The main focus of the project is now on transforming the experimental setup into a system suitable for regular operation.
In 2022 the main effort was on the finalization of the technical and safety concept, which had been thoroughly revised last year and was awaiting final risk assessment. Additionally, solutions to some details had to be left open for discussion and decision with the help of external specialists. Both objectives were achieved and the technical and safety concept was approved with some modifications. Some of the planned safety measures were found to be unnecessary, resulting in a minor reduction of complexity and cost. The risk assessment was documented and the explosion safety document, relevant for later operation, compiled. Based on the design now being approved, the residual parts necessary for the gas stripper facility may be specified and procured and will be presented in this publication.
Wakefields kick the electron bunch to a non-linear tilt causing emittance growth. Any additional correlation like an energy chirp (energy vs z dependence) will filament the disturbance further causing a nearly unrecoverable bigger emittance. For C3 (Cool Copper Collider) the emittance preservation numbers seems to be about 1000 times more stringent than achieved. It is actually "only" about 30 times trickier (square root of 1000) which is still a big number. During two-bunch setups for LCLS (Linac Coherent Light Source) it was observed that the same transverse beam offset reduced the wakefield kick and at the same time the RF kick from the most probably misaligned accelerating structure. To turn this around an RF kick can be easily measured with RF on and off, or a phase scan using a single bunch. The plan is to test this at FACET-II where the emittance growth is quite high due to a high charge. Experimental results where RF kicks are locally minimized and therefore give a better starting value for emittance tuning will be presented in a later paper.
The Electron Ion Collier (EIC) will utilize highly polarized electron and ion beams. To preserve polarization through numerous depolarizing resonances over the whole EIC hadron accelerator chain, harmonic orbit correction, partial snakes,horizontal tune jump system and full snakes have been used. A new scheme using skew quadrupoles to compensate horizontal intrinsic resonances is under development. In addition, close attentions have been paid to betatron tune control, orbit control and beam line alignment. The polarization of 60% at 255 GeV has been delivered to experiments with 1.8E11 bunch intensity. For the EIC era, the beam brightness has to be maintained to reach the desired luminosity.This will be achieved by electron cooling at injection of EIC hadron storage ring. Since we only have one hadron ring in the EIC era, existing spin rotator and snakes can be converted to six snake configuration for one hadron ring. The number of snakes can be increased. With properly arranged snakes in EIC and reduction
of emittance, the polarization can reach 70% at 275 GeV. The general strategy of polarization preservation scheme in the injectors and hadron ring of the EIC is described in this paper.
To further enhance the accelerating gradient of accelerators, we designed a cryogenic C-band standing wave bi-periodic accelerating structure for the Shanghai Soft X-ray Free Electron Laser Facility (SXFEL). According to the low-temperature environment, material characteristics and technological conditions, the design is completed and it is decided to design the accelerating structure into a bi-periodic magnetic coupling structure. It is a 17-cell structure consisting of 9 accelerating cavities and 8 coupling cavities. To guarantee the symmetry of the field, the structure is doubly-fed. Operating with the $\pi/2$ mode standing wave, it is much less sensitive than the standing-wave structure of $\pi$-mode. Additionally, the microwave mode is TM02 in coupling cavities that are larger and even less sensitive than the traditional bi-periodic structure. The shape of the coupling cavity can be redesigned to make it tunable.
A SLED (SLac Energy Doubler) RF pulse compressor is a passive RF component which increases the peak RF power level at the cost of reducing the pulse length. The Canadian Light Source (CLS) plans to replace the current 250 MeV Linac with a new one in mid-2024 by RI Research Instruments GmbH. The new Linac has a similar energy and two of its three 5.3 m TW constant-gradient accelerating structures are connecting to a SLED. Since a SLED output is not flat, this introduces additional energy variation along a bunch train, increasing the total energy spread. In addition, the energy spread acceptance of the CLS booster ring is below 0.5% FWHM, and it is critical to minimize the SLED non-flatness output effect by different methods. This paper will study the SLED effect on a multi-bunch train energy variation and consider the transient beam loading effect. Finally, we will show that by selecting proper RF phase switching and beam injection timing, and by alternating energy gain slope between the SLED-ed and non-SLED-ed Linac cavities can achieve the required energy spread.
The Electron-Ion Collider has an electron storage ring (ESR) and a hadron storage ring (HSR) with beams traveling in opposite directions that collide initially at one but eventually at two interaction points. Our desired machine configurations require a wide range of energies for both rings: 5 to 18 GeV in the ESR, and 41 to 275 GeV/u in the HSR. The range of velocities in the HSR requires that we have a radial position in the arcs which depends on energy for energies from 100 to 275 GeV/u, and that we use a separate arc for a 41 GeV/u beam. We describe the requirements placed on our design to ensure synchronization for all these energies. When there are two detectors, the large beam-beam forces will not support having bunches colliding at both detectors simultaneously, so the design must ensure that bunches collide at only one IP. We describe the constraints this places upon our machine design and the bunch patterns that we use. We discuss the impacts on the timing of orbit manipulations that we expect to make in the ESR: the superbends that increase the radiation at 5~GeV and and orbit shifts to adjust damping partition numbers.
Recently, we completed a performance upgrade of Test Lab klystron-modulator system for PLS-II RF Linac as well as new developed S-Band 80-MW klystron test. PLS-II main linac system are under an operation of 17 RF stations including S-Band 80-MW klystron. It will be used as a test station for a performance test of RF components for PLS-II RF Linac. Klystron as RF sources is one of critical components for stable beam energy control since its RF power output affects the electron beam energy. Pulse-to-pulse stability of RF linac klystron modulators is one of important issues in 3rd generation synchrotron machine for the top-up operation of the PLS-II linac. This machine requires highly stable RF sources with a stability of 0.01% rms, to meet the beam stability requirements. By adopting a precision capacitor charging power supply (CCPS), we achieved the beam voltage with less than a 100 ppm stability for the MK system. This paper discusses an operational characteristics and measurement results of the Test Lab pulsed MK system.
The CERN Linear Accelerator for Research (CLEAR) is a test facility delivering an electron beam in the 30-220 MeV energy range to a diverse user community. In 2022, several hardware and software upgrades were done to the main installation, and procedures and methods were developed to address specific user requirements, including a further extension of the beam parameter ranges. In the paper, these improvements are described and the experimental activities during 2022/2023 are outlined. An outlook on future potential upgrades and on the planned experimental activities in the next years is also given.
The Electron-Ion Collider polarized pre-injector is designed to generate a 7 nC with eight bunches every second to inject into the Rapid Cycling Synchrotron. The pre-injector includes the polarized electron source, bunching section, traveling wave plate (TWP) LINAC, and longitudinal phase space manipulation. A compact zig-zag chicane, and dechirp cavity are used to rotate the bunch in longitudinal phase space to reduce the energy spread and increase the bunch length. In this proceeding, we present the RF frequency selection and the progress of the recent pre-injection design. We will also discuss the wakefield and coherent and incoherent synchrotron radiation impact on the beam quality.
The European Spallation Source neutrino Super Beam plus (ESSνSB+) project has recently been approved by the EU for a 4-year design study. It aims at measuring the neutrino-nucleus cross-section, which represents the dominant systematic uncertainty in the measurement, in the energy range of 0.2 – 0.6 GeV, as well as perform searches for sterile neutrinos using a Low Energy nuSTORM (LEnuSTORM) and a Low Energy Monitored Neutrino Beam (LEMNB). ESSnuSB+ follows the ESSnuSB design study project 2019-2022 that resulted in a conceptual design of ESSnuSB and an evaluation of its high performance for leptonic CP violation measurements which is due to that the measurements will be made at the second, rather than the first, oscillation maximum, where the sensitivity of the experiment is close to 3 times higher than at the first maximum. This paper reviews the ESSnuSB design-study results and presents the planned ESSnuSB+ design study.
The Frascati linear accelerator was used as electron and positron source for the DAFNE collider and the Beam Test Facility (BTF) where the fixed target experiments as PADME or irradiation test for space components are ongoing.
Builded in 1996 an upgrade of the L-C traditional resonant charging system is started in 2018 and today 3 of the 4 RF power stations modulator are upgraded from the 3-phase variable phase control (SCR) based on a full-wave bridge diode assembly to a new 2 constant-current capacitor charging power supplies.
This paper will discuss the design of the upgrade and the performances of the systems in operation
The IFMIF RFQ has to accelerate a D+ beam of 125 mA
from the source energy of 100 keV to its final energy of 5
MeV. For such a purpose, the needed RF power
(approximately 600 kW dissipated power and 600 kW beam
power) is injected in the RFQ from 8 amplifier chains with
8 coupling loops. In order to quantitatively understand the
different circumstances which can occur, an equivalent
circuit of the RFQ (that can be generalized to a generic multple-feed cavity) with all the feed lines and couplers will
be described, and the expressions for cavity and reflected
voltages and powers will be derived. Moreover, some operational
scenarios that can occur will be analyzed. In particular
errors in amplitude phase and coupling of each of the 8 feed
lines of the RFQ itself will be introduced. This analysis is also useful as a guideline in determining the basic architecture of the amplitude/phase controls of the cavity feeds, for a given set of amplifier amplitude/phase characteristics.
Following a 3-year long shutdown for upgrade and consolidation work, the LHC was re-commissioned in spring 2022, achieving a new record of 6.8 TeV per beam. This paper will describe the beam commissioning phase, the electron cloud conditioning, and the intensity ramp-up bringing the machine to a steady production state. The main issues and achievements will be presented, including the fully automated luminosity levelling via β* adjustment. The limitations for beam intensity and peak luminosity will also be discussed.
The existing post-stripper Drift Tube LINAC (DTL) of the GSI UNILAC will be replaced with the new Alvarez 2.0 DTL to serve within the injector chain for the Facility for Antiproton and Ion Research (FAIR). The 108.4 MHz Alvarez 2.0 DTL accelerates intense ion beams along five individual cavities with a total length of 55 meters from 1.36 MeV/u to 11.32 MeV/u. The design of the Alvarez 2.0 DTL has been completed and a 1.9 meter First-of-Series cavity section has been successfully RF-conditioned at nominal uranium operation including power margin. The prototype of the shortest drift tube (DT) with an internal pulsed quadrupole magnet operated successfully and a study of the longest DT is in fabrication. The Alvarez 2.0 cavity will be delivered in spring 2023 and the DTs of the first cavity AI have been ordered. Additionally, all add-on parts like the adjustment frame of the drift tubes or the plungers are partially in tender, production, or have been already delivered. The copper-plating of all cavities will be done on-site, while all add-on parts will be copper-plated externally. The current status of the Alvarez 2.0 DTL project will be presented in this contribution.
The Future Circular electron-positron Collider, FCC- ee, is designed for unprecedented precision for particle physics experiments from the Z-pole up to above the top-pair-threshold, corresponding to a beam energy range from 45.6 to 182.5 GeV. Performing collisions at various particle-physics resonances requires precise knowledge of the centre-of-mass energy (ECM) and collision boosts at all four interaction points. Measurement of the ECM by resonant depolarization of transversely polarized pilot bunches in combination with a 3D polarimeter, aims to achieve a systematic uncertainty of 4 and 100 keV for the Z-pole and W-pair-threshold energies respectively. The ECM itself depends on the RF-cavity locations, beamstrahlung, longitudinal impedance, the Earth’s tides, opposite sign dispersion and possible collision offsets. Application of monochromatization schemes are envisaged at certain beam energies to reduce the energy spread. The latest results of studies of the energy calibration, polarization and monochromatization are reported here.
A new electron cooling experiment is being planned at the Integrable Optics Test Accelerator (IOTA) at Fermilab for cooling ~2.5 MeV protons in the presence of intense space-charge. Electron cooling is integral to the study of beam dynamics and has valuable applications for producing high-intensity hadron beams in particle accelerators. For such goals, an electron lens to be placed in the IOTA ring will be used for electron cooling, space-charge compensation, and non-linear dynamics. Here we present the simulations and designs of two thermionic electron sources for the cooling at IOTA. One cooler is a basic electron source and will be used for cooling the proton beam and as a tool for other experiments at IOTA. The other cooler is a strong electron source, which will be used for studying effects of electron cooling in ion beams with intense space-charge. We particularly discuss parameters of the thermionic sources’ electrodes, as well as the simulation results. We also present a new electron source test-stand at the University of Chicago, which will be used to test the thermionic electron sources. We also discuss the results from analyzing the test stand operations with a currently existing electron source. Furthermore, we present future steps for production and commissioning of these thermionic sources at IOTA.
Ionization cooling is the only suitable approach to reduce the phase space volume occupied by a muon beam on a timescale compatible with the muon lifetime. Small normalized transversal emittances can be achieved by using hydrogen (H) as an absorber and high solenoid fields at low beam energy. The strong focusing suppresses emittance growth due to scattering occurring from muon beam interaction with nuclei in the absorber's atoms. This leads to very small beam sizes and therefore the deposition of energy in small volumes causing a high peak energy density. Temperature changes in H can cause pressure rises that may damage the absorber's H containment windows. This work presents the acceptable temperature ranges in liquid H and discusses an alternative method with low density H-gases.
The SuperKEKB accelerator is currently in operation in Tsukuba, Japan, with a planned long shutdown in 2026. Among the possible upgrades being considered during this period is the change to a polarized electron beam in the High Energy Ring. Such a change would require modifications in the source generation and transport, geometrical and lattice variations to provide spin rotation, and polarimetry. A Polarized SuperKEKB Working Group has been formed from members of the Belle II experiment and the SuperKEKB accelerator team to investigate the possibilities and challenges of these modifications. This talk lays out the goals of the proposed upgrade, considers the necessary changes to the existing accelerator and their feasibility and lays out the physics motivation behind such an effort.
During the injection phase of the Higgs mode of CEPC, the stored energy of the cavity is low and beam loading is relatively high. The synchrotron radiation damping is weak compared to the growth rate of the untidamped mode. This will cause two types of trouble. Firstly, the transient beam loading caused phase-shift between the head and the tail of the beam will be too much. Secondly, the untidamped mode will grow too fast. Therefore, we performed a series of studies in order to put a quantified requirement on the strength of the damping mechanism and the power overhead.
During the on-axis injection process under the Higgs model, the transient beam loading in the CEPC storage ring will cause a phase shift between the head and the tail of one beam. Since the missing bunches are only extracted from one of the beams at a time, there will be a misalignment between the colliding bunches at the IP. In this paper, we presented the results of the study on this transient beam loading under different initial and extraction patterns and gave the preliminary analysis of the average luminosity loss due to this effect.
The performance requirements for next generation electron accelerators put ever increasing demand on the photocathode performance, where it fundamentally limits the achievable beam quality. Metal photocathodes are limited by their high work function and relatively low quantum efficiency, necessitating the use of high powered deep UV lasers. Metal oxide thin film interfaces have been shown to reduce the work function of the underlying metal photocathode, whilst maintaining the ease of use, high durability and fast response time. This leads to an improvement in quantum efficiency and spectral response to desirable incident laser sources. We present the characterisation of a thin film yttria (Y2O3) enhanced Au photocathode at various film thicknesses. Quantum efficiencies were measured at 265 nm along with surface compositions via X-ray photoelectron spectroscopy.
The studies and R&D on the high-intensity positron source for the FCC-ee have been initiated for a while. The positrons are produced by a 6 GeV electron drive-beam incident on a target-converter at 200 Hz. The drive beam comes in 2 bunches spaced by 25 ns with a maximum charge of ~5 nC per bunch. Two scenarios using conventional and hybrid targets are being studied for positron production. According to the FCC CDR, the Flux Concentrator is used as the matching device for the capture system, followed by several accelerating structures embedded in the solenoidal field. Then, the positrons are further accelerated to be injected into the damping ring. Recently, the feasibility study on using a SC solenoid for the positron capture has been started, and the design based on the HTS technology is under investigation. In addition, the large aperture 2 GHz RF structures, which have been specially designed for the FCC-ee positron capture system, are used with the goal of demonstrating accepted positron yield values well beyond the values obtained with state-of-the-art positron sources. The purpose of this paper is to review the current status of the FCC-ee positron source design, highlighting the recent research into the positron production, capture system, primary acceleration, and injection into the damping ring.
This publication builds on previous studies that explore the use of MAD-X and SAD to simulate FCC-ee. In particular, we examine further optics properties as well as single particle tracking. Compared to previous iterations, this work also introduces a comparison to XSuite and discusses how the different codes fit in a cohesive FCC-ee strategy.
A matching device with a strong magnetic field is used to capture positrons in the positron source of future e+e- colliders such as the Compact LInear Collider (CLIC) and the Future Circular Collider (FCC-ee). Compared to conventional matching devices such as flux concentrators, superconducting (SC) solenoids can have a much higher peak field, improving the capture efficiency and the positron yield. In this paper, we tested an analytic SC solenoid field and simulated the matching device for the CLIC positron source. Furthermore, we optimised the coil parameters for maximum positron yield. The results from a study of the latest high temperature superconductor based solenoid designed by PSI for the FCC-ee positron source is also presented.
V3Si is an A-15 SC that has a relatively higher Critical Temperature Tc (17 K), compared to niobium (Nb) and can maintain a higher critical field than Nb [1]. These properties would in theory allow thin film V3Si superconducting RF-accelerator (SRF) cavities to operate at higher temperatures and with greater accelerator voltages, compared to Niobium cavities. However, this would require the deposition of V3Si thin films with superconducting (SC) properties intact.
The SC properties of V3Si (as measured by RRR and Tc) is closely linked to the stoichiometry, which in turns depends on substrate composition and deposition temperature[2]. It has been shown that HiPIMS is capable of ion bombardment, during deposition, and this ion bombardment has been shown to have similar effects to sample heating[3] in allowing greater control of stoichiometry at lower temperature.
Here, for the first time, we report on the use of HiPIMS to deposit superconducting V3Si films: additionally, films are deposited from a single target rather than co-deposited. V3Si samples with a Tc of 15.1 K without the need of post-deposition annealing have already been deposited using HiPIMS. Additionally, DC and HiPIMS has been used to deposit samples under the same conditions and the use of HiPIMS increased the Tc by 2-3 K. This reopens the possibility of viable V3Si coated cavities produced by magneton sputtering .
Alongside the new LCLS-II facility, a new electron beamline known as Linac to End Station A (LESA) is under construction at SLAC. LESA will use field-emitted dark current from the new superconducting accelerator to search for MeV- to GeV-scale dark matter. To predict the behavior of the dark current in LESA, we must account for the effects of wakefields. In the conventional analysis of long-range wakefields, the bunches are both the sources and subjects of collective effects. Since the contribution of dark current to the wakefield is negligible, the dark bunches are passive recipients of the wakefield kicks. However, we also lose some simplifying assumptions. In contrast to the main bunches, which are generated at a low subharmonic of the RF frequency, dark current is generated on every RF cycle of the source cavity. The dark current bunches may also occupy a much larger proportion of each RF bucket – possibly the entire longitudinal acceptance of the accelerator. These complications lead to effects that are not seen in the main bunches, such as “beating” of the betatron amplitudes along the dark bunch train. In this work, we present the theory behind this interaction and apply it to LESA.
At MAXIV Laboratory we are continuing the efforts to reduce the emittance of 330 pm.rad of the larger storage ring (SR) operating at an energy of 3GeV. This paper details the techniques used to improve the characterization of the optics, and to optimize the injection into the SR with an emphasis on the difficulties encountered during the process and the strategies adopted to overcome them.
The far-infrared linac and test experiment (FLUTE) serves as an accelerator test facility for a variety of accelerator physics studies. FLUTE is foreseen to provide coherent radiation in ultra-short, very intense light pulses in the terahertz (THz) and far-infrared spectral range. A superconducting undulator in the accelerator structure after bunch compression offers the possibility to generate high-energy, pulsed radiation between 4 THz and 12 THz corresponding to photon energies between 16.5 meV and 50 meV. This energy range, for instance, is of high interest for interaction and reaction studies of liquids, especially in water, and thus for materials and medical research.
In this contribution we describe the specific design parameters and the general layout of the THz superconducting undulator to reach the envisioned scientific goals.
An in-vacuum Hall probe measurement bench was designed, built, and used to measure four Cryogenic Permanent Magnet Undulators (CPMUs) at 77 K at Diamond Light Source. The devices were tuned to correct the phase error at cold temperatures based on the measurements from the in-vacuum bench. The in-vacuum bench consists of a stretched wire system supplied by Danfysik and the in-house Hall probe bench. The Hall probe bench has gone through two iterations: the first was prone to deforming with temperature changes; the second was made thicker following design changes to the magnet holders and girders of the CPMUs which allowed more space for the bench inside the vacuum vessel. The design and commissioning of the bench will be presented, along with some measurements of the CPMUs at room temperature and at 77 K. Details such as height compensation, temperature compensation, and triggering of the Hall probe measurements will be covered.
A third family of sextupole magnets was recently in-corporated at the KIT storage ring KARA (Karlsruhe Research Accelerator). Computer studies of beam dy-namics were performed with an objective to estimate benefits of operation with three sextupole families and possibility of new configuration of ring lattice to con-trol slope and curvature of momentum compaction factor as function of energy offset of particles in a bunch. Adjustment of high order terms of alpha would allow to shorten bunch further down. Simulations of KARA ring model have been bench-marked on exist-ing experiments at Metrology Light Source (MLS) in Berlin (Germany) and SOLEIL (France).
A 7 MeV Alvarez-type drift tube linac (DTL) had been designed and machined in the past few years for Xi'an 200 MeV proton application facility (XiPAF). This paper presents the assembly, alignment, error analysis and tuning results of the DTL. After all these tasks were completed at Tsinghua University, the DTL cavity had been transported to Xi'an for repetition measurement and test. It has been aligned on the beamline for RF conditioning and beam commissioning.
Due to various errors, the beam does not pass through the center of magnets in a storage ring. The beam orbit is affected by additional dipole fields since magnetic field feed-down. To obtain a reference orbit, on which the beam circulates along the quadrupole axes, the beam-based alignment (BBA) is performed in the ring. In this work, a novel method based on a neural network is proposed to find the golden orbit. This golden orbit can be directly used for operation, or can be adopted as the starting point for the conventional BBA. The development of this new method and corresponding experiments are reported in this paper.
The single nonlinear kicker (NLK) injection has been adopted by several synchrotron radiation light source facil- ities or their upgrades. The injected beam receives a kick from an NLK and goes into the acceptance of the storage ring while the stored beam passes through the center of the NLK where the magnetic field is almost zero. Compared with the local-bump injection, NLK injection requires less space for kickers and causes less oscillation amplitude for the stored beam during injection. Currently, a conventional local bump injection including four pulsed dipole kicker magnets is adopted in the HLS-II storage ring. In this paper, we propose an NLK injection scheme by only replacing one kicker with a pulsed NLK for HLS-II. The simulation result is also presented.
Compared to the conventional injection scheme, the three-kicker bump injection scheme with an anti-septum has two advantages. One is less requirement of dynamic aperture thanks to the thin blade of the anti-septum, the other is less installation space requirement of the injec-tion system. Both are beneficial to the beam injection for the fourth generation light sources. In this study, the application of this injection scheme to the HALF storage ring is presented. The layout and parameters of the injec-tion system are designed and the injection process is simulated. The results of the injection efficiency and the effect on the stored beam during beam injection is shown in this paper.
Wuhan Advanced Light Source (WALS) is a fourth generation diffraction limit synchrotron radiation facility, which is composed of a full energy 1.5 GeV LINAC, a 1.5 GeV Storage Ring and 10 beamlines for its phase I project. The LINAC is 6 meters lower than the storage ring, which is connected by a 46 meters beam transfer line. The beam transfer line includes three parts, one ver-tical line between two horizontal lines. Four achromat sections are used, the first three are 30 degrees with exact same settings and the last one is matched with the storage ring injection septum and non-linear kicker. In this paper, the optic and error correction results are described in brief, especially the dispersion correction. Since there are horizontal and vertical dispersions at the same time, the correction process must correct both of them at the same time.
Large initial beam position monitor (BPM) offsets have to be reduced by one order of magnitude by means of beam-based calibration (alignment) (BBA) in order to match the element-to-element magnet alignment error. At SLS 2.0 the BBA will be performed with respect to adjacent auxiliary quadrupole magnets, which are also employed for optics and tune correction. Different static and dynamic techniques can be applied to determine the offsets. The error of the individual measurements needs to be at the micrometer level to guarantee the necessary reproducibility of position and angle at the beamline source points on medium- and long-term time scales.
Top-up operation at BESSY II is performed with average injection efficiencies of 98 %. However, the four-kicker bump and the septum, that form the present injection system, both contribute to a distortion of the stored beam with an amplitude of about two millimeters for several thousand turns after injection. A non-linear injection kicker (NLK) could be used to reduce the distortion due to the kicker bump by a factor of approximately 30 - a necessary condition for transparent injection. Studies with an NLK and optimized sextupole settings have shown that it is also possible to achieve injection efficiencies of up to 97 %. The NLK was characterized beam-based with regards to the application of the NLK for BESSY II user operation, a possible injection method for BESSY III and to get a better understanding of the limiting effects of the injection efficiency. Additionally, measurements and simulations were compared.
To harness the major advances that have been done in the field of synchrotron light research, Elettra synchrotron radiation facility is being updated. Presently in its design phase, the Elettra 2.0 project will allow new and better research to be performed at the facility. In the upgrade of the storage ring, the new 6BA lattice brings challenges in terms of available space and radiated power. This paper presents the bending magnet photon absorber designed to cope with the new requirements. The absorber concept created for ESRF-EBS has been revised and re-engineered to make it suitable for the specific features of Elettra’s sources. To reduce the high-power densities induced by the short source-absorber distance, the one-jawed, toothed profile was obtained via a robust optimization, considering possible misalignments or beam miss-steering. Novelty of the approach is the absorber insertion in the vacuum chamber from the inside of the ring. Finally, presented are the thermo-mechanical and computational fluid dynamics simulations (ANSYS) performed to validate the design, comprehensive of a monte-carlo, ray-traced simulation to evaluate photon reflections (SYNRAD) and their effects.
Due to the reduced diameters of the vacuum chambers and of the other equipment, the performance of the next generation light sources can be greatly affected resulting in a reduction of the intensity in both single and multi-bunch operations. This is particularly important for Elettra 2.0 since there are plans to incorporate bunch compression schemes for providing very short photon pulses. In this study, the resistive wall and single bunch instabilities are investigated by tracking in order to define their thresholds.
At SPring-8, the injector was changed from the booster synchrotron to the XFEL linear accelerator. Accordingly, we have developed a new bunch cleaning system in the storage ring to ensure high bunch purities required by photon beam users since unwanted electrons were observed behind the injection bunch even after some countermeasures were taken in the injector to eliminate unwanted electrons. The bunch cleaner in the ring resonantly excites the vertical betatron oscillation on a targeted satellite bunch so that it is lost at the minimum aperture location without perturbing other bunches delivering photon beam to user experiments. The developed bunch cleaner has proved to achieve a bunch purity better than 10^(-10), which is already provided to a variety of user experiments demanding high bunch purities. The versatile system can work for all the bunch filling patterns with the regular top-up injection mode at SPring-8.
Inverse Compton Scattering is a promising technique to deliver compact, high brightness and high rate sources of photons ranging from few keVs to several MeVs. Current projects either focus on producing high rates of photons thanks to high-power (up to 300kW) enhancement optical cavities and electron storage rings or on providing low bandwidth photon sources based on room-temperature linacs. Burst mode operated optical enhancement cavities coupled to pulsed RF muti-bunch linac systems have the potential to provide high quality and high rate at the same time. To this end we concentrate on realizing innovative systems operated at GHz frequencies with repetition rates of several hundreds of hertz corresponding to linac RF-pulsing capabilities. Recent experimental advances, made within a collaboration between Amplitude and IJCLab, in the realization of a compact enhancement cavity seeded by a GHz laser and operated in burst mode are described. Performance will be reported along with prospects for improvements.
The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory is one of the most powerful accelerator-driven neutron sources in the world. The intense protons strike on SNS’s mercury target to provide bright neutron beams, which also leads to severe fluid-structure interactions inside the target. Prediction of resultant loading on the target is difficult particularly when helium gas is injected into mercury to reduce the loading and mitigate the pitting damage on vessel walls. A 2-phase material model that incorporates the Rayleigh-Plesset (R-P) model is expected to address this multi-physics problem. However, several uncertain parameters in the R-P model require intensive simulations to determine their optimal values. With the help of machine learning and the measured target strain, we have studied the major uncertain parameters in this R-P model and developed a framework to identify optimal parameters that significantly reduce the discrepancy between simulations and experimental strains. The preliminary results show the possibility of using this mercury/helium mixture and surrogate models to predict a better match of target strain response when the helium gas is injected.
Optical enhancement cavity (OEC) provides the high intensity and high stability modulation laser field in steady-state microbunching (SSMB) light source. An SSMB extreme ultraviolet (EUV) light source targeted for lithography application is currently being developed at Tsinghua University, which demands for megawatt scale intra-cavity power for OEC. Cavity mirrors are the key components of the OEC to realize its designed parameters. Here we report the development progress of the cavity mirrors.
The fourth generation of synchrotron radiation sources will be constructed in Wuhan. The RF system of the storage ring provides 600kV voltage to the beam through a 500MHz normal conducting cavity. A coaxial coupler is designed for the 500 MHz cavity to input 150kW power. The coupler was modified from KEK-B. We use a high-power ceramic disk window design and under over cut window structure. The fabrication of the coupler is underway.
The RF system of the ThomX storage ring consists in a 500 MHz single cell copper cavity of the ELETTRA type, powered with a 50 kW CW solid state amplifier, and its associated Low-Level RF feedback and control loops. The low operating energy of 50 MeV makes the impedances of the cavity higher order modes (HOMs) particularly critical for the beam stability. Their parasitic effects on the beam can be cured by HOM frequency shifting techniques, based on a fine temperature tuning and a dedicated adjustable plunger. A cavity temperature stability of ± 0.1 °C within a range from 30 up to 70 °C is achieved by a precise control of its water-cooling temperature. On the other hand, the tuning of the cavity fundamental mode is achieved by changing its axial length by means of a mechanical tuner. This report describes the setup of the facility and the results of the commissioning.
We will report on the ongoing ThomX ring commissioning, its status, its main challenges, our results and our planning.
ThomX is a compact Compton-based X-ray source under commissioning at IJCLab in Orsay (France). This facility is composed of a 50-70 MeV linac, a transfer line and a storage ring whose closed orbit is 18 m long. Compton scattering between the 50 MeV electron bunch of 1 nC and the 30 mJ laser pulses stacked in a Fabry-Perot cavity results in the production of X-rays with energy ranging between 45 keV and 90 keV. We aim at a total flux of about 10^13 X-rays per second.
The injector commissioning started in the spring of 2021. The ongoing storage ring commissioning faces many challenges due to the ring’s low energy, its compactness, its non-linear beam dynamics, the time-limited beam storage and the need to achieve a very accurate and stable geometry of the collision region between the laser pulses and the electron bunch. The commissioning and operational experience is of great importance for the future Compton sources.
We presented a novel concept of longitudinal bunch train compression capable of manipulating relativistic electron beam in range of hundreds of meters. It has potential to compress electron beam with high ratio, and raise its power to ultrahigh level within compressed duration of nanoseconds. Electron’s spiral motion in uniform magnetic field is utilized to fold the hundreds of meters long trajectories into a compact setting. Helix angle of bunches’ spiral track are adjusted by a local time-varying magnetic field. Spiral pitch of each bunch gets gradually increased from the leading edge toward trailing edge of the train. After the spiral procedure, interval between bunches is redefined and the compression is realized. The method is explored both analytically and numerically. Compared to microbunching or chicane modulation, this method could compress bunches at distinct larger scales, opening up new possibilities for generation of beam with ultra-large power storage.
Over the last three years (2020-2022) Diamond Light Source has installed four in-house designed, built, and measured Cryogenic Permanent Magnet Undulators (CPMUs). All four are 2 m long with a 17.6 mm period and have a minimum operating gap of 4 mm. These have replaced existing 2 m long in-vacuum pure permanent magnet (PPM) devices to improve the flux to several of Diamond’s MX (Macromolecular Crystallography) beamlines by a factor of 2-4. In this paper we present the mechanical and cryogenic design considerations, and the shimming procedures and tools developed to produce these devices. The performance of the CPMUs compared to their PPM counterparts will also be reviewed.
A degrader device is being built at the CEBAF injector to degrade the electron beam phase space for machine acceptance studies. The electron beam is degraded through multiple scattering in a thin target before further transport in the injector beamline for injection into CEBAF. The degraded electron beam will approximate phase space distributions expected from a bremsstrahlung-based polarized positron source as in the PEPPo method. The effort is in broader support of the Ce+BAF positron capability that is currently under study. Two options for the degrader device are considered, and simulation results are presented.
A test station for the THALES 300kW transmitter PSM has been successfully constructed in NSRRC. Integrating the modules of power supply, control interface, interlock protection, and accessories into a single rack simplifies the examination procedure and makes signal observation easier. The layout and hardware realization of this test station, as well as important considerations and proper examination procedure in place to ensure safe and accurate operation are all presented in this article.
High power input often leads to frequency deviation that cannot meet the high-precision frequency control requirements of keV Ultrafast Electron Diffraction (UED) compression cavities. In this paper, we propose new solu-tions for reducing heat generation and frequency devia-tion based on modifications to the cavity design and power input method, building upon the design of the orig-inal elliptical cavity. These solutions have been verified through simulation calculations. In pulsed input mode, the cavity temperature rise is within 2℃, and in continu-ous wave mode, the new cavity design can withstand temperature rises of up to 20℃, both of which meet the requirements of practical engineering.
With the growing interests and new experimental development in time-resolved studies at Stanford Synchrotron Radiation Light Source (SSRL), we are motivated to develop the Pseudo Single Bunch (PSB) operational mode to address the requirements from time-resolved and regular user experiments simultaneously. In this paper, we will present the physics design for this new mode. Beam line simulations for performance evaluation of the user experiments are also reported.
The Advanced Light Source (ALS) at the Lawrence Berkeley National Laboratory (LBL) is going through an upgrade (ALS-U), where the ALS triple-bend achromat is replaced by a nine-bend achromat storage ring (SR) with on-axis injection using beam swapping from a triple-bend achromat accumulator ring (AR). The small beam size at the straight sections of the ALS-U has opened the possibility to use small-diameter circular vacuum chambers for insertion devices. An elliptically polarizing X-type undulator with a small circular vacuum chamber and symmetric placement of the magnet rows around the vacuum chambers is being developed at LBL. This type of undulator is suitable for the ALS-U and other fourth generation light sources. Salient features of the X-type undulator include the mechanical construction with compact crossed roller bearings and fully hydraulic motion control system. These are described together with a status report of the progress of the prototyping work.
With the high accelerating gradient, radiofrequency (rf) gun has a significant feature of suppressing the growth of transverse emittance caused by space charge. Field emission cathodes were first used in vacuum electronic devices, which do not require the high electron beam intensity, but the cathode size and integrality. A new X-band (11.424 GHz) rf electron gun has been proposed with the highlight of four-feed coupler, which can eliminate the quadrupole field component observed and analyzed from the imagine experiment, which have affected the resolution of the imaging system to some content.
The PETRA IV storage ring currently under development at DESY will require a third harmonic 1.5 GHz RF-system to prevent negative effects on both, lifetime and emittance, caused by Touschek effect and Intrabeam scattering. These cavities lengthen the bunches and thereby reduce their charge density.
For this 3rd harmonic system, a one-cell single-mode cavity with a simple mechanical and electrical structure is under design that should also reduce Higher Order Modes (HOMs) to a quality factor less than 100. Therefore, the well-known approach of the Choke Mode Cavity was chosen, that use a radial line damper to attenuate the HOMs and a radial choke that traps the acceleration mode.
The general behaviour of the choke mode structure was simulated, discussed and optimized for the requirements of a one-cell cavity with high effective shunt impedance, high-quality factor and simple manufacturing.
The PETRA IV project will have a storage ring with an ultra-low natural emittance of 20 pm rad [1]. For an off-axis injection scheme with working points at the difference resonance it is important to assure the vertical excursion arising due to transversal coupling such, that injection efficiency is not compromised. In this contribution we present simulations results of an off-axis injection near the coupling resonance, which provides equal equilibrium emittances. Advantages and disadvantages of such a scheme are discussed.
The FEL performance strongly correlates with the undulator field quality. The definition of mechanical tolerances for the undulator magnets allows us to achieve the wished field quality. These mechanical tolerances should be defined both on short and long-range errors. With long-range errors, we address problems like deformations of the yoke caused by the support structures or unwanted tapering, which can arise in the positioning procedure of the parallel undulator coils. In this contribution, we quantify the effect and set tolerances of a few types of long-range errors on the FEL radiation generated specifically from superconducting undulator coils.
Elettra will be upgraded between 2025 and 2026 and the storage ring lattice will be totally different to enhance the emittance and improve the coherence of the machine.
The storage ring design requires a stiff support system to reduce the impact of vibrations on the electron orbits, a high thermal stability as well as low static deformations. The magnets support system must be easy to transport, align and must be cost effective. In order to achieve these requirements, the magnets supports of each synchrotron cell are granite blocks long from 0.8 to 1.57 m and the girder alignment system consists of 3 main adjustment feet and 2 stiffeners. An optimization study was conducted de-fining the most effective location of the feet. Each magnet can be aligned on the girder by means of 3 levelling wedges that can be moved both manually and automatically by means of motorized actuators.
A FEA calculation was carried out to optimize the design in order to achieve a target stiffness and an experimental test was performed on a prototype girder in order to verify the numerical results.
The European X-ray Free Electron Laser (EuXFEL) is a user facility delivering soft and hard X-ray FEL radiation. It provides X-rays with high brilliance and intensities in the photon energy range of 0.5 keV to 25 keV. 2700 pulses at 10 Hz with femtosecond up to 4.5 MHz pulse repetition rate. The FEL radiation which is created by the Self Amplified Spontaneous Emission (SASE) process, whose stochastic nature gives rise to shot-to-shot fluctuations of the pulse energy and spectrum. In order to cover these variations, the HIgh REsolution hard X-ray single-shot (HIREX) spectrometer has been installed in the Hard X-ray beamlines SASE1 and SASE2. The HIREX spectrometer is an online device, based on a bent diamond and Silicon crystal as a dispersive element and a MHz-repetition rate GOTTHARD strip detector. The SASE2 HIREX spectrometer is identical to the HIREX spectrometer installed at SASE1 with the difference that it does not provide gratings that can be used as a beam splitter. Thus, the spectrometer crystal has to be placed in the direct beam to collect energy spectra. In this contribution, we will present the measurement results of central photon energy and bandwidth jitter of the SASE-FEL beam at different photon energies. Further, we will also focus on the automation of the HIREX spectrometer for instrument beamlines with a single push button.
Sharing of emittances between transverse planes has potential benefits in storage ring light sources. The larger vertical emittance significantly increases the Touschek lifetime, while the smaller horizontal emittance helps to mitigate the loss in brightness at high photon energies due to the larger vertical beam size and divergence. A fully coupled beam is considered as an optional operation mode for the SLS 2.0, should a longer beam lifetime be required.
In this paper, we investigate the feasibility of having round beams in SLS 2.0 by operating on the linear difference resonance. We analyze the impact on the linear- and nonlinear performance of the machine, in particular the impact on Touschek lifetime when all apertures are included.
Rapid commissioning and automated start up procedures are crucial for many upcoming 4th generation storage ring light sources as their downtime demands are very challenging given their increased operational complexity. Detailed commissioning simulations as a tool of error analysis are not only used to guide the design process of new machines but also a prerequisite to implement an automated commissioning and start up procedure for the final machine. The current ALS can be used effectively to test the developed automated commissioning procedures for the ALS Upgrade because the lattice is very similar to the ALS-U Accumulator Ring, of which detailed commission simulations have been carried out. In this study we present first results including first turn beam threading and turn by turn beam based alignment procedures.
A Multipole Injection Kicker (MIK) has been successfully designed, constructed, installed and commissioned with beam in the MAX IV 1.5 GeV ring. This device allowed reaching injection efficiencies as high as those obtained with the previously used conventional dipole injection kicker scheme, while at the same time providing an order of magnitude reduction in the perturbations to the stored beam resulting from the injection process. In addition, the device has had a major positive impact in allowing effective top-up injection under the strong optics perturbations generated by long-period elliptically polarizing undulators. In this paper we describe the first operations with the device and detail the process of optimisation and commissioning.
Superconducting undulators provide a possible means of broadening the range of wavelengths that can be covered by an XFEL facility by generating larger magnetic fields at shorter periods than can be achieved using permanent magnet undulators.
As part of ongoing prototyping work at STFC to develop a superconducting helical undulator with 13 mm period and 5 mm magnetic gap, a test cryostat has been designed and built to investigate the performance of 325 mm long prototype magnets. The test cryostat is used to cool prototypes to 4.2 K and to power them to a full operational current of 250 A. Cryogenic Hall sensors measure the field in the magnet bore during testing.
Techniques to measure the field profile and the integrated field components inside the small, closed magnet bore have also been developed. These measurements are crucial for understanding the magnetic performance of the prototype magnets and identifying and implementing suitable corrections to the field integrals. We present here the first cooling and magnetic field measurement results of the prototype undulators.
The High Energy Photon Source (HEPS) is a 4th generation synchrotron radiation source being built in China. An APPLE-Knot undulator with a new configuration is designed for the XCMD beamline of the HEPS. It is the first time to apply four-row APPLE-Knot undulator in storage ring based light sources. The main differences between the novel design and the conventional design of the APPLE-Knot undulators are discussed. Furthermore, the influences of the APPLE-Knot undulator on storage ring optics, as well as the dynamic effects during the process of gap variation at different polarization modes, are investigated and will be introduced in this paper.
We are developing gamma-ray-induced positron annihilation spectroscopy (GiPAS) using ultra-short pulsed gamma rays at the UVSOR synchrotron facility in Japan. The gamma rays with the pulse width of picosecond range are generated by 90-degree inverse Compton scattering between a 750 MeV electron beam and an 800 nm laser. As the energy of the gamma rays is 6.6 MeV, gamma-ray irradiation produces positrons by pair production inside the material. Generated positrons localize on atomic-scale defects in solid crystals, such as vacancies, dislocations, and vacancy clusters. Positronium, the bound state of an electron-positron pair, localizes in vacant space caused by the free volume in polymers. Therefore, positrons are excellent probes of the nanostructure of these materials. Furthermore, the circularly polarized gamma rays generated by a circularly polarized laser can produce spin polarized positrons. The spin polarized positrons provide additional information about the electron spins around defects. GiPAS is currently available for users in UVSOR-III. In this conference, we will present a generation method of the ultra-short pulsed gamma-rays and details of GiPAS*.
A laser-driven storage ring is proposed to generate steady-state, nanometer-long electron bunches. A ring of this type can produce coherent EUV radiation with greatly enhanced power and photon flux, benefiting a wide range of scientific and industrial communities, including condensed matter physics and computer chip fabrication. The underlying mechanism is called generalized longitudinal strong focusing (GLSF), which invokes precise transverse-longitudinal coupling dynamics and lowers the required laser power significantly by exploiting the ultrasmall vertical beam emittance. A practical instance indicates that kW-level coherent EUV radiation is attainable in a GLSF ring with a modulation laser power as low as 1 MW, allowing for continuous-wave operation of up-to-date optical cavities.
Iranian light source facility (ILSF) is a 4th generation synchrotron with a nominal horizontal emittance of 270 pm.rad. Storage ring magnet-girder support stability is essential for beam stability. The support system of storage ring girders is essential to achieve the accuracy of adjustment and vibration stability. After studying different girder support systems and considering the stability requirements of the ILSF machine, the wedge and screw support system was selected for vibration analysis. In the vibration analysis, the wedge system was better than the screw one. The wedge system improves the magnet-girder stability, which caused an acceptable increase in the vibration frequency modes in the modal analysis.
Inverse Compton scattering (ICS) is a method used for X-ray production that has been possible in recent years due to the rapid development of ultra-fast, short, and stable oscillators. In addition, the research and development of high Finesse Fabry-Perot Cavities to store high average power inside it. ThomX is a new generation of compact X-ray source which implements the ICS method. It will produce higher flux and better quality X-rays than the traditional sources such as X-ray tubes and be cheaper and more compact than synchrotrons. ThomX is currently being commissioned in IJCLab ( Laboratory de physique des 2 infinitis – Irene Joliot Curie ) at the Orsay campus. It is composed of a linear accelerator that can accelerate the electron bunch up to 50 MeV, an electron ring to store it over multiple revolutions at 16.66 MHz, and a Fabry Perot cavity to maintain the photon pulse at 33.33 MHz. The first electron beam produced was in October of 2021, and then it had a full round in the storage ring in 2022. It is expected to produce x-rays in mid-2023 when its Optical cavity has power stored in it. It is a high Finesse Fabry-Perot cavity that can store up to 1 MW. Such cavities face many problems, from high power stability to heating up of their reflecting mirrors. Here, we will describe the optical cavity commissioning of ThomX and the challenges faced throughout the preparation for the production of X-rays.
The layout of Elettra 2.0 preserves the useful length of the long straight sections so that all the existing insertion devices (IDs) could in principle be maintained in the upgraded machine. However, new high-performance beamlines are planned that will take advantage of the much lower electron beam emittance. Therefore new undulators are being designed and constructed for these beamlines. Space is also available in some of the short straight sections, and we’re developing compact undulators and wigglers to make optimal use of them. In this contribution the parameters and characteristics of the new IDs will be presented.
As preparation for the upcoming Diamond-II upgrade, provisions for timing-users (those who predominantly care about the timing characteristics of the synchrotron radiation) are being investigated. Although ‘Hybrid bunch’ modes are currently employed at Diamond, such operation presents challenges for Diamond-II that merit investigating alternative approaches. PPRE, one such approach, involves resonantly exciting a targeted electron bunch using a Transverse Multi Bunch Feedback system (TMBF). We report on the efficacy of the TMBF for driving one (or few) bunches, focusing on studying the charge-dependent effects and the achieved vertical emittance, and also by considering the effect of long range impedance between bunches. Furthermore, to test experimentally the use of PPRE, we present our first results from a representative beamline. The work is also discussed in context of the proposed operational requirements for Diamond-II.
Ion instabilities are a major concern in diffraction-limited storage rings. ELEGANT offers a `strong-strong' model for ion simulations that describes both the beam and ions using multi-particles. To balance accuracy and computing resources, a simplified model using ILMATRIX and one IONEFFECTS element per turn is employed to study the ion effects of the Diamond-II storage ring. After benchmarking, it was found that the simplified model overestimates the ion instability compared with element-by-element tracking by a small amount. A preliminary vacuum conditioning process has been studied, and ion instabilities have been analysed at different stages for various filling patterns. This paper outlines the simulation settings and presents preliminary results, including the filling patterns to be used at each stage of vacuum conditioning. The ion instability for hybrid filling patterns at the expected operational vacuum condition is also studied.
In this paper, we present our thinking on how to keep the modulation laser and electrons phase-locked in a steady-state microbunching storage ring.
Diffraction-limited light sources have garnered significant interest -- yet the smaller equilibrium size of their electron bunches also reduces the beam-lifetime. One remedy is to vertically excite the electron beam, for instance using a Multi Bunch Feedback (MBF) system. Previous work has demonstrated that this approach can safely increase the vertical emittance, thus beam-lifetime. However, not all operational vertical emittances are created equal. Driving the beam at frequencies near resonances can generate large coherent beam-centroid motion that results in an enlarged apparent photon-source. In this work, we present a methodology, justified with theoretical reasoning and simulation, that finds the optimal combination of frequency and kick strength that satisfies both the operational requirements and the beamline interests. The methodology is then demonstrated for the Diamond-II lattice, including short-range wake effects.
X-ray beamlines—essential components of all synchrotron light sources—transport emitted radiation from the stored electron beam to an experimental station. One may describe the linear optics of the beamline via an ABCD matrix computed using a ray-tracing code. Furthermore, one may then include diffraction effects and arbitrary wavefront structure by using that same information in a Linear Canonical Transform (LCT) applied to the initial wavefront [1]. We describe our implementation of a Python-based LCT library for 2D synchrotron radiation wavefronts. We have thus far implemented the separable case and are implementing algorithms for the non-separable case. Our code base also includes rectangular apertures. We have tested our work against corresponding wavefront computations using the Synchrotron Radiation Workshop (SRW) code [2]. We present benchmark comparisons of LCT vs. SRW for both undulator and bending magnet sources of radiation. Finally, we describe our plans for extending this work to partially coherent radiation.
In the fourth-generation storage ring light sources, the dynamic acceptance is usually small related to the extremely strong nonlinearity inherent in the multi-bend achromat design, making it difficult to implement traditional off-axis local-bump injection. It was found that a double-frequency rf system can be used for longitudinal injection with the help of rf gymnastics. However, such schemes require tuning the RF parameters during injection, which would challenge the RF hardware system and cause the bunch length shrinking of the circulated bunch. In this paper, we find that with proper parameters optimization, a double-frequency RF system with static parameters can be used for longitudinal injection. A detailed design of this scheme for the application in the Southern Advanced Photon Source (SAPS) is presented.
For a reliable determination of the single bunch stability threshold, the broadband impedance budget needs to be analyzed for all resistive and inductive contributions. The completely new design of the arc vacuum chamber of SLS 2.0 with respect to SLS - now with a reduced beam pipe diameter, and coated with layers of copper and NEG - requires special focus on the resistive wall impedance.
Higher Order Modes (HOMs) of vacuum components were also investigated. Since they stay trapped in specific positions of the ring, they can be the source of power heating and related mechanical stress, as well as the cause of Coupled Bunch Instabilities (CBI). The impact of the HOM impedance spectrum can become very important, notably if the device responsible of the resonance recurs several times in the ring or if it is located at positions with high beta values. We show some examples of HOM analysis and their related optimization, which were adopted for cavities appearing also in valves, bellows and diagnostic components.
The Shenzhen Innovation Light-source Facility (SILF) is a 4th generation diffraction limited storage ring project with an operating energy of 3 GeV, which is prosed by the Institute of Advanced Science Facilities, Shenzhen. For the storage ring, hybrid seven-bend achromat (H7BA) lattice is used in order to achieve a low electron beam emittance. There are longitudinal gradient bends (LGB), strong dipoles with longitudinal gradient (SUPB), dipole and quadrupole combined function magnets, strong quadrupoles with large vertical gaps, strong sextupoles, octupoles and corrector magnets in each unit cell. The field requirements of these magnets and the limited space available pose several design challenges. This paper presents a summary of magnet designs for the various magnet types.
One of the design challenges of Superconducting undulators (SCUs) is the fulfilment of tight mechanical tolerances. Simulations show that to guarantee high quality of the emitted radiation local mechanical errors must be below a few tens of micrometres. Such requirements are at the limit of the most precise machines and techniques for mechanical manufacturing. In addition, once the SCU is assembled with the support structure, mechanical deformations can affect the device in the long range.
In this contribution, we describe the possible long and short-range errors that can arise in the SCU and we present various schemes based on shimming coils to correct the short-range errors.
The Tapered undulator provides interesting possibilities for keeping the undulator in resonance with the electron beam along the length of the undulator. The U50-II [1,2] undulator at Laser and Insertion Device Application Laboratory of DAVV, India is a 1000mm length, 50mm period length undulator. The four heavy-duty precise lead screw attached to the mechanical girder allows its gap to be tapered. In this paper, we report the field integral, phase error measurement of the tapered U50-II PPM undulator by Hall probe method and compare its accuracy by stretched wire result [3].
The High Energy Photon Source (HEPS) is a 34-pm, 1360-m storage ring light source being built in the suburb of Beijing, China. In the HEPS storage ring, a proportion of quadrupoles and sextupoles are equipped with trim coils for horizontal and vertical orbit correction. For these magnets, the main field and corrector fields may have non-ignorable impact on each other. We have carried out detailed measurements and subsequent data analysis of these magnets. It is observed that changing the corrector currents in the presence of constant main current, can lead to a relative deviation of the main field of 0.1 percent level. In this paper, we will report the measurement procedure and main results.
Gaussian lasers with temporal or spatial chirp have been used in the manipulation of the electron beam in the high-gain harmonic generation or echo-enabled harmonic generation in free-electron lasers. This paper presents the Mathematica expressions of these lasers. This work is a first step for novel laser-electron manipulation technique in presence of temporal or spatial chirp.
Numerical simulations of the beam dynamics with the Coherent Wiggle Radiation (CWR) impedance for the preliminary EIC back-up ring cooler parameters and positive and negative momentum compaction are discussed in detail. We show the microwave instability threshold dependence on low-frequency CWR impedance in free space and for parallel plates. The numerically simulated results performed by the Vlasov-Fokker Planck solver and the ELEGANT code have been compared with a new analytical approach to cross-check the microwave instability threshold.
Ultra-high brightness and ultra-low emittance electron beams can great enhance the radiation power in light sources, but the electron beams are prone to nonlinear effects in the velocity compression, which leads to the asymmetry of the beam. In this paper, a multi-objective optimization method based on NSGA-III is proposed to achieve a good symmetry in the C-band photocathode injector with an emittance lower than 0.5 mm mrad and a peak current higher than 100 A.
In beamline design, there are many floating parameters that need to be tuned; manual optimization is time-consuming and laborious work, and it is also difficult to obtain well optimized results. Moreover, there are always several objectives that need to be considered and optimized at the same time, making the problem more complicated. For example, asking for both the flux and energy to be as large as possible is a usual requirement, but the changing trends of these two variables are often contradictory. In this study, a novel optimization method based on a multi-objective genetic algorithm is introduced, the first attempt to
optimize a beamline with multiple objectives. In order to verify this method, beamline ID17 of the European Synchrotron Radiation Facility (ESRF) is taken as an example for simulation, with energy and dose rate as objectives. The result shows that this method can be effective for beamline optimization, and an optimal solution set can be obtained within 30 generations. For the solutions whose objectives are both improved compared with those of ESRF beamline ID17, the maximums of energy and dose rate increase by around 7% and 20%, respectively.
(The corresponding paper is published: https://journals.iucr.org/s/issues/2023/01/00/ve5159/ve5159.pdf)
We have developed numerical method to calculate temporal structure of synchrotron radiation in arbitrary magnetic field. Using this method, spectral phase of synchrotron radiation can be calculated, which is important in the reconstruction of temporal structure of radiation. It is also interesting that it reflects the symmetric property of magnetic field from which radiation is generated. Recently an experiment to deduce the spectral-phase structure of undulator radiation using ‘spectral phase interferometry for direct electric field reconstruction (SPIDER)’ was carried out at UVSOR-III. The experimental result was compared with the numerical calculation in the regard. We will also discuss the effect of the magnetic field error to the spectral phase.
The electron storage ring DELTA which is operated by TU Dortmund University can be run at a reduced beam energy down to 500 MeV instead of 1.5 GeV. If a single bunch at low energy is stored, the bunch charge threshold for the emission of THz bursts is exceeded. Using a fast Schottky-barrier detector, coherent synchrotron radiation bursts of THz radiation were detected. Turn-by-turn data of the THz bursting behavior as function of the bunch charge and bursting spectrographs are presented.
In this study we investigate the advantages and challenges of applying the two frequency crab cavity short pulse scheme to multi-bend achromat (MBA) lattice based fourth generation synchrotron light sources. Using the Advanced Photon Source Upgrade (APS-U) lattice as a concrete example, we show that short pulses with duration of 1~10 ps (FWHM) can be generated with modest deflecting voltages. A longitudinal radio-frequency (RF) cavity whose frequency is a half-integer multiple of the fundamental RF frequency is used to provide bunch lengthening and shortening for certain buckets. The proposed system parameters and the expected performance are shown.
The strong intra beam scattering effect and the increase in horizontal emittance become common issues for next-generation ultra-low emittance storage rings. The round beam can be an effective method to solve these problems. Moreover, the produced round synchrotron radiation is suitable for optical matching. The on-resonance tune is an easier method to achieve round beam. In this paper, simulation and experimental results are introduced based on the nominal lattice of the HLS-II storage ring.
The Swiss Light Source (SLS) will shut down in October 2023, entering the dark time period for installation of the upgraded SLS 2.0 synchrotron. The commissioning of the new electron storage ring is planned for early 2025. The upgraded storage ring features a lattice based on modern 7-bend achromats with lower momentum compaction factor, NEG coated vacuum pipes of smaller aperture and an increased beam-energy from 2.4 GeV to 2.7 GeV.
To guarantee full performance, a careful analysis of the effects induced by the machine broadband and geometrical impedances and ions is mandatory. In addition to the potential well distortion due to the wake fields, the analysis must also include the transient beam-loading effects on the bunch lengthening of the passive superconducting harmonic cavity.
We provide an overview of the collective effects studied for SLS 2.0, including single bunch instabilities from the broadband impedance budget, coupled bunch analysis and ion effects. For each kind of such instabilities, the main threshold curves are presented, as well as the related safety margins of operation and the tracking procedures followed.
The prototyping accelerator based on laser-plasma technology (PALLAS) project aims to build a laser-plasma injector accelerator (LPI) test facility to deliver within a few years electron beams of 150-250 MeV, >30 pC, <1 mm.mrad emittance beam at 10 Hz with control and stability comparable with RF accelerator. The project is, among others, built in the framework of the technical preparatory phase of the EuPRAXIA [1] project's TDR. The development approach is based on three axes: advanced laser control, plasma target development and electron beam characterization. After a quick overview of the installation, the recent progress and results in plasma targetry and laser-plasma injector modelling will be reported. Advanced laser driver control development implementation for online monitoring will be presented. The recent progress in the electron beam characterization line will be discussed.
Undulators containing magnetized rare-earth helices can provide a significantly higher oscillatory electron velocity than the widely used planar Halbach undulators. Using Wire Electrical Discharge Machining (WEDM) and combining planar tool with rotary work piece motion, it is possible to manufacture NdFeB helices with a period of 1 mm or less with high accuracy. In this work, we describe the results of manufacturing, theoretical and experimental studying prototypes of micro-undulators in the form of one or two longitudinally magnetized helices. Also shown are more efficient hybrid systems of two longitudinally oppositely magnetized and two steel pre-non-magnetized helices with a field on the axis of the order of 1 T. Such micro-undulators can significantly increase the efficiency of X-ray Free Electron Lasers and Inverse Free Electron Lasers.
Research and development of an accelerator-based THz source prototype for pump-probe experiments at the European XFEL are ongoing at the Photo Injector Test Facility at DESY in Zeuthen (PITZ). Proof-of-principle experiments have been performed to generate a high-gain THz Free-electron Laser (FEL) based on the Self-Amplified Spontaneous Emission scheme. The FEL radiation pulses with a central wavelength of about \SI{100}{\micro\metre} (\SI{3}{\tera\hertz}) and single pulse energy of several tens~\SI{}{\micro\metre} can be generated. In this paper, we present and discuss the photon diagnostic setup for the THz FEL together with examples of diagnostic results, including pulse energy and an FEL gain curve. The upgraded photon diagnostic setup, capable of measuring pulse energy, transverse distribution, and spectral distribution, is expected to be operational in the spring of 2023.
Hefei Advance Light Facility (HALF) is a 2.2 GeV diffraction-limited storage ring, which is developed by National Synchrotron Radiation Laboratory in China. It has 20 long straight sections and 20 middle straight sections. All the experimental stations in the first stage will employ undulator as the light source. In this paper, we introduce the preliminary design of insertion devices of HALF, which includes 11 undulators and 2 wigglers. The undulator design is carefully optimized based on the current undulator technology and experiment user demands. The photon flux of these undulators can cover the photon energy from 5 eV to 10 keV with the flux greater than $10^{14}$ phs/s/0.1\% B.W. It can reach an ultra-high brilliance at the soft X-ray wavelength region. Most of the insertion devices are the elliptically polarized undulators and the in-vacuum undulators, therefore the light source of HALF will be charactered by a flexible tunability on polarization state and a broad range of photon energy from VUV to X-ray wavelength region.
The Steady-State Microbunching (SSMB) mechanism, which combines the benefits of high repetition rate of a storage ring and coherent radiation, has the potential to produce high average power short wavelength light. In order to generate kilowatt level radiation, the electron injector should have the ability to provide a 1 A average current, 100 ns long DC beam, with the requirements of small emittance (<1~mm$\cdot$ mrad), and very small energy spread (<$5\times 10^{-4}$) for the SSMB storage ring. This paper presents an overview of the physical design of the electron gun, linac, and stretching ring components of the injector, as well as the beam loading compensation methods employed in the electron gun and linear accelerator.
The potential future Soft X-ray (SXL) FEL beamline at the linear accelerator at MAX IV will require a series of undulators with distinct properties: It must be cost-effective and compact. Furthermore, it needs to have a small and round magnetic gap and provide elliptically polarized light under full polarization control. This undulator of a compact APPLE X type is currently being prototyped in the Insertion Device group at the MAX IV Laboratory. In this paper, we present the technical requirements of both, the mechanical and magnetic challenges that follow with the compactness and complexity of the device. Thereafter, we outline the assembly procedure of the undulator and present the methods we intent to use for magnetic measurements to evaluate the prototype's performance.
The High Energy Photon Source (HEPS) is a 34-pm, 1360-m storage ring light source being built in the suburb of Beijing, China. The construction of HEPS started in mid-2019. Later, to deal with challenges emerging from the technical and engineering designs, the HEPS accelerator physics design was modified and had been finalized in 2020. Afterwards, studies on related physics issues were updated and have been basically finished. Besides, preparing studies for commissioning of the HEPS Linac, booster and storage ring were started almost at the same time, and are still underway. The commissioning of the Linac has been launched since early of 2023. In this paper, we will briefly introduce the updated studies on related physics issues and present the results of the Linac commissioning.
The Hefei Advanced Light Facility (HALF) is a soft X-ray and VUV diffraction-limited storage ring to be built in the Hefei city of China. This paper reports the recent progress on the physics design of the HALF storage ring, including lattice modification and optimization, error and insertion device effects, collective effects, injection scheme and collimation.
An in-vacuum undulator is important for synchrotron radiation. An in-vacuum undulator with a permanent-magnet is used by the Taiwan Photon Source (TPS) in the National Synchrotron Radiation Research Center (NSRRC). Before installation in the storage ring, the magnetic field of the undulator is measured at the oper-ational gaps. The magnetic-field for an in-vacuum un-dulator is measured using a Hall-probe and a stretched-wire measurement system. This study uses a pulsed wire magnetic field measurement system for an in-vacuum undulator. A reference magnet with a known magnetic field is used to determine the magnetic field profile for an in-vacuum undulator and it is demonstrat-ed that the oil dampers crucial to eliminating dispersion waves for the pulsed wire measurement. The results are used to compare the magnetic field measurements that use a pulsed wire with those that use a Hall probe.
The user community of the Angle-Resolved Photoemission Spectroscopy (ARPES) beamline in Diamond Light Source (DLS) is strongly interested to use the lower photon energies down to 10 eV compared to the current 18 eV in both Diamond and the future 3.5 GeV machine Diamond-II. The high level of the heat load on the first optic as well as the undesired higher harmonics contamination are two major challenges for the beamline operation. The Quasi-Periodic APPLE-KNOT (QP-AK) undulator is a potential candidate to resolve these two issues. This paper presents the magnetic design and reports the overall performance of the undulator in terms of flux, polarisation degree and partial power. The linear and non-linear beam dynamics effects of the undulator are investigated by the kick-map approach. Active shims will be used to suppress the dynamic multipoles of the device, as used with the current APPLE-II device. The beam dynamics studies show the minimal impact on beam lifetime and injection efficiency and residual beta-beat in Diamond and its upgrade.
Shanghai Laser Electron Gamma Source (SLEGS) beamline, based on laser Compton scattering (LCS), as one of beamlines of Shanghai Synchrotron Radiation Facility (SSRF) in phase II project, has been construct-ed and started test commissioning from July 2021. The results of the commissioning already show a steady experimental proof that SLEGS can produce gamma rays with adjustable maximum energy by consecutive-ly changing the interaction angle between laser beam and electron bunches.
In this paper, the recent progress of SLEGS is given. The newly measured gamma-ray’s spectra and flux are presented. The resolution of the gamma-rays is im-proved with the application of external collimator. A gamma spot monitor is setup to measure the spatial distribution of LCS gamma ray. A 4π flat-efficiency 3He neutron detector (FED) array and the neutron time-of-fight (TOF) spectrometer are also designed and installed. Some preliminary results of these devices is introduced.
The Taiwan Photon Source (TPS) experimental facility has experienced vibration interference at approximately 16.8 Hz during experiments at the end station of the TPS 23A beamline, which was traced back to the air handling units (AHUs) located on the second floor of the outer ring area of TPS. The vibration of the AHUs not only affects the TPS beamline 23A end station but also all experimental areas. In this paper, we present two methods to reduce the floor vibration of the experimental hall caused by the AHUs. Firstly, we adjusted the operating frequency of each AHU fan to avoid resonance and reduce the vibration of the nearby experimental area floor, which can be reduced by up to 40%. Secondly, we installed additional air isolation mounts outside the AHU to further reduce the impact of the fans on floor vibrations, which resulted in a reduction of vibration transmission by about 30%. Our findings provide useful information for those dealing with vibration interference caused by AHUs and can help improve the experimental accuracy and efficiency in similar facilities.
The Diamond-II storage ring will utilise normal conducting main cavities and a passive superconducting harmonic cavity in its RF system. To evaluate the effects of bunch lengthening and lifetime gain from the harmonic cavity for different filling patterns, transient beam loading effects need to be studied. When simulating these effects with ELEGANT, RF feedback for the main cavities must be defined using sets of infinite impulse response (IIR) filters. This paper describes the method used to convert proportional-integral (PI) feedback parameters representative of the RF feedback implemented at Diamond into equivalent ELEGANT settings and presents simulation results demonstrating the effectiveness of the RF feedback. Transient beam loading effects for the standard and hybrid filling pattern are also studied.
The Siam Photon Source, a synchrotron light source in Thailand, has undergone multiple improvements in recent years, including the installation of up to four insertion devices in the storage ring. The machine has operated at maximum capacity for a significant period of time. This study presents a statistical analysis of the machine's operation over the past seven years, including the number of beam service hours, machine downtimes, and repair times. The paper also discusses critical incidents that occurred during this period, such as faults with a booster ring bending magnet power supply, superconducting magnet cool-down problems, and issues with a cryogenic plant's liquefaction process. Furthermore, this report highlights major upgrades and improvements made over the past seven years to enhance beam quality.
The feasibility of performing sextupole injection at TPS (Taiwan Photon Source) storage ring has been demonstrated in November 2021 with 300 mA stored electron beam. In order to carry out the experiment, a sextupole and its associated pulser were fabricated according to the specifications required. The sextupole was installed during a short break in September 2021 by making use of a ceramic unit located between kicker-3 and kicker-4 at the injection straight section. Moderate adjustment of the beam injection trajectory at the BTS (booster-to-storage ring) transfer line is needed so as to avoid beam scraping off at the injection septum. A brief description of the preparation work is given and the experimental results are summarized in this report.
A new in-vacuum undulator (IVU) with varying gap width is being developed for the new X-Ray source, PETRA IV at DESY. Its electromagnetic properties need to be investigated. These include, especially, the losses in the flexible taper transitions between the beam pipes and in the magnet array, as well as the impact of the IVU's impedance on beam stability. To assess the impedance of the structure, we employ numerical simulations. The challenges lie in the large size of the IVU, the wide frequency range due to the short bunch length, the highly resonant response of the system, and in the complex geometry of the structure. In a first step, wakefield simulations are carried out using CST Studio Suite. Subsequently, the shunt impedances are calculated by eigenmode simulations with the CST Studio Suite and a specialized in-house frequency domain impedance solver.
The periodic orbit change caused by the temperature fluctuation of the cooling water at the SAGA-LS storage ring was suppressed by the slow orbit feedback correction system using newly equipped extra-windings on 8 steering magnets.
In recent years, the amplitude growth of temperature fluctuation of the cooling water caused maximally 40 micrometer periodic orbit change at the SAGA-LS storage ring, which affected some synchrotron radiation experiments. We equipped new extra-windings on 8 steering magnets to compensate the periodic orbit change, since the existing steering magnets for global orbit correction did not provide sufficient resolution for this small orbit change. By applying the slow orbit feedback correction system using the extra-windings, the periodic orbit change was suppressed satisfactorily.
In this conference, we will also discuss about the mechanism by which the temperature fluctuation of the cooling water causes the orbit change at the SAGA-LS storage ring.
The extraction inefficiency of the slow extraction process induces radioactivity in the area surrounding the electrostatic septum. Studies at the CERN Proton Synchrotron (PS) are investigating beam loss reduction techniques to improve the efficiency of the beams provided to the experiments of the East Area. Powering octupoles distorts the transverse phase-space of the extracted beam which can be exploited to maximize the number of particles in the field region of the septum with respect to the number lost on the septum. The effect of octupoles on the separatrices near the third-order resonance is simulated with MADX-PTC tools to observe phase space folding and to predict the multipole parameters needed to minimize beam loss. Experimental studies are performed to confirm the validity of the simulation models and to quantify the net benefit of using octupoles to improve the extraction efficiency.
The beam abort system for the current Swiss Light Source (SLS) is based on inverting the RF phase to decelerate the stored beam. The losses are localised at longitudinal positions where the dispersive orbit encounters the machine aperture. For the SLS, these losses mainly occur at the septum and in the arcs. For the SLS 2.0* with its multi-bend-achromat lattice and thus much lower dispersion in the arcs, tracking simulations show that these losses are localised at superconducting super bends and in-vacuum insertion devices. Due to this unfortunate loss distribution and the fragile vacuum chamber combined with the small beam size and stored beam energy of 1 kJ, a more controlled beam abort is desired. In case of an RF failure, the beam abort system must dump the beam safely before the critical dispersive orbit is reached. A fast beam dump controller with dedicated inputs for fast systems such as the low-level RF and fast feedback systems is foreseen for triggering the required emergency beam dump. The majority of the well over 6000 machine interlock signals will be monitored by the slow, programmable-logic-controller-based machine interlock system (MIS). For the MIS the sheer amount of signals poses a challenge.
The Swiss Light Source SLS will have a 15 months long shutdown starting in October 2023 in order to install the new storage ring SLS 2.0. While the procurement of large series of components like magnets, power supplies, RF, vacuum chambers, … has started, the design of more specific components like the thin septum, undulators or collimators, is close to completion. The main difficulties and challenges of SLS 2.0 are common to other diffraction limited storage rings: cross talk issues due to the very short distances between magnets and especially with permanent magnets, heat dissipation issues in the small aperture vacuum chambers due to synchrotron radiation and RF heating and in general beam instabilities issues due to wakefields perturbations. Components have been designed to withstand these constrains and this paper will give an overview of the key components design and first tests before installation.
The synchrotron SOLEIL is both a 2.75 GeV third-generation synchrotron light source and a research laboratory at the forefront of experimental techniques dedicated to matter analysis down to the atomic scale, as well as a service platform open to all scientific and industrial communities. We present the performance of the accelerators delivering extremely stable photon beams to 29 beamlines. The beam delivery schedule and the operation have been affected by the energy crisis. Shortages of cryogenic fluids and electronic components, coupled with a high inflation, are impacting the operation budget and the related projects. The update on the construction of the new low-energy footprint cooling station is presented. Finally, new developments and testing of prototype equipment related to the upgrade of the injector complex and the main storage ring are discussed.
At DELTA, a 1.5-GeV synchrotron radiation source at TU Dortmund University, ultrashort radiation pulses are generated using CHG (coherent harmonic generation), where the interaction with laser pulses in an undulator (modulator) causes a periodic electron energy modulation within a 50-fs slice of a 2000-times longer electron bunch. A dispersive chicane creates a density modulation giving rise to the coherent emission of ultrashort pulses at harmonics of the seed pulse in a second undulator (radiator) exceeding the incoherent background from the whole bunch. In summer 2022, the electromagnetic insertion device U250, which included both undulators and the chicane, was reconfigured to demonstrate EEHG (echo-enabled harmonic generation, originally proposed for linac-based free-electron lasers) at a storage ring and to reach higher harmonics. The U250 coils were rewired to create two modulators for a twofold laser-electron interaction, two chicanes to manipulate the electron density, and the radiator, each comprising only a few undulator periods. The two seeds are a frequency-doubled Ti:sapphire laser pulse at 400 nm and its residual at 800 nm wavelength. EEHG pulses are detected using an in-vacuum grating spectrometer. In addition, the coherent emission of THz radiation is monitored. The paper presents first results of this project termed SPEED (Short-Pulse Emission via Echo at DELTA) which, to our knowledge, is the worldwide first attempt to perform EEHG at a storage ring.
High Energy Photon Source (HEPS), a 6 GeV diffraction-limited synchrotron light source, is currently under construction in Beijing. The double-frequency RF system is being developed to deliver 6 MV of RF voltage and 850 kW of beam power with an active third harmonic system. The prototypes of the higher-order-mode damped 166.6 MHz quarter-wave superconducting cavities, as well as the 499.8 MHz harmonic superconducting cavities, have been manufactured and vertical tested, while the cryomodules for these cavities are being developed. All six normal-conducting 5-cell cavities were high-power tested and three of them have been installed in the booster tunnel for initial beam commissioning. Following the success of the prototype 166.6 MHz 260 kW and 499.8 MHz 150 kW solid-state power amplifiers, the series production of the amplifiers is underway. The new low-level RF control system based on Xilinx FPGA is in the prototyping phase and the first lab test results fulfill the HEPS requirements. This paper presents the status and progress of the RF system for HEPS.
The ALS-U project is an upgrade to the Advanced Light Source (ALS) at the Lawrence Berkeley National Laboratory that aims to deliver diffraction-limited x-ray beams with an increased beam brightness of two orders of magnitude for soft x-rays compared to the current ALS facility. A nine-bend achromat lattice Storage Ring (SR) and a three-bend achromat Accumulator Ring (AR) will be installed in the facility. The project has recently received federal approval to start construction for the new storage ring. The accumulator ring (AR) has received early funding and is currently being installed in the ALS facility during its regularly planned shutdowns. This paper describes the status of the accumulator ring installation.
The implementation and further improvements of superconducting undulators is part of the European XFEL facility development program. Within this program, a magnetic field test facility is being developed. Named SUNDAE2 (Superconducting UNDulAtor Experiment 2), it aims to perform in-vacuum magnetic field measurements of superconducting undulators (SCUs) with three techniques: Hall probe, moving wire, and pulsed wire. This contribution presents the updates and status of SUNDAE2.
RadiaBeam, in collaboration with UCLA and Fermilab, is developing a strongly tapered helical undulator system for the Tapering Enhanced Stimulated Superradiant Amplification experiment at 515 nm (TESSA-515). The experiment will be carried out at the FAST facility at Fermilab as a Gamma-Ray high Efficiency ENhanced Source (FAST-GREENS). The undulator system was designed by UCLA, engineered by RadiaBeam, and will be installed on the beamline at Fermilab. The design is based on a permanent magnet Halbach scheme of four 1-meter long undulator sections; two of which have been completed and installed. The undulator period is fixed at 32 mm and the magnetic field amplitude can be tapered by tuning the gap along the interaction. Each magnet can be individually adjusted by 1 mm, offering up to 25% magnetic field tunability with a minimum gap of 5.58 mm. This paper discusses the design and engineering of the undulator system and the stage 0 installation status.
Wuhan Advanced Light Source (WALS) is the low-energy 4th generation advanced light source, which is proposed by Wuhan, China. WALS includes a 1.5 GeV full-energy LINAC injector, a 180 m circumference, 1.5 GeV low-emittance storage ring, and a series of start-of-the-art beam lines. The standard 7BA magnetic focusing structure is adopted for the storage ring to lower the beam natural emittance and the lattice has been well- designed and optimized by multiple-objective genetic algorithm to maximize the dynamic aperture and energy acceptance. The dynamic aperture of the storage ring at injection can reach up to 8 mm in the horizontal plane, which makes the off-axis beam injection method possible. An off-axis beam injection scheme based on the pulsed nonlinear magnet is to be employed for the storage ring. Detailed studies about the beam injection scheme, including the beam optical design, nonlinear magnet design and optimization, have been performed and multi-particle simulations have also been carried out to study the beam injection procedure, which will be presented in this paper.
The South Advanced Photon Source (SAPS) is a newly proposed storage ring (SR) based photon source project operating at the beam energy of 3.5GeV. To achieve X-ray diffraction-limited in the SR with high density bunch, larger coupling impedance brought by more compact beam pipe structure is inevitable, which makes the beam collective effects be one of the major challenges to the physical design. By impedance modelling and beam dynamics simulations, the longitudinal and transverse beam instabilities in SR have been studied.
The Diamond-II storage ring has been designed to increase photon brightness by up to two orders of magnitude compared to the existing Diamond facility. A single-bunch aperture sharing injection scheme using short stripline kickers applied with high-voltage nano-second pulsers was proposed to provide both high injection efficiency and high photon beam stability in top-up mode [1]. The quasi-transparent injection process has been optimised and studied using Accelerator Toolbox. The results of these study will be presented.
A fourth generation storage ring with an energy of 3 GeV is proposed by Institute of Advanced Science Facilities, Shenzhen. After repeated optimization, the storage ring achieved a dynamic aperture of 15mm. With a relatively large dynamic aperture, Off-axis injection scheme is possible for SILF storage ring. We first considered conventional local bump injection as a candidate. The nonlinear kicker injection, which reduces perturbations on stored beam, is also a promising scheme. In this paper, we studied the feasibilities of these two injection schemes on SILF storage ring, and discussed the advantages and disadvantages of them. Through simulation work, we showed the way to achieve a higher injection efficiency for nonlinear kicker injection.
SIRIUS is the 4th generation synchrotron light source built and operated by the Brazilian Synchrotron Light Laboratory (LNLS). SIRIUS is currently operating with six beamlines and eight others are at different stages of deployment. In this work we report on the development of simulation tools to analyze the impact of insertion devices (IDs) on SIRIUS beam orbit, optics and dynamic aperture (DA), aiming at defining their specifications for external suppliers and verifying the feasibility of installing existing IDs. In particular, we analyze the fields of two IDS used in the previous LNLS synchrotron light source (UVX), now decommissioned: one planar 2T hybrid wiggler and one EPU of the type Apple-II. These IDs were installed in SIRIUS in 2022 and are now temporarily serving as light sources for the commissioning of PAINEIRA and SABIÁ beamlines.
Furthermore, we also analyze the effects of two new IDs that will be used as titular light sources for CARNAÚBA, CATERETÊ, EMA, and PAINEIRA beamlines. One is an In-Vaccum Undulator (IVU) and the other is a Vertically Polarizing Undulator (VPU). An undulator built In-house will be used as a temporary light source for the SAPUCAIA beamline commissioning and its effects on SIRIUS beam parameters are also reported.
The Korea fourth generation storage ring (Korea-4GSR) is a 4GeV, low emittance light source to be built in Ochang, Korea. The booster ring, which consists of 26 FODO standard cells and 2 dispersion-free cells, ramps the beam energy up from 200 MeV to 4 GeV as part of the injector. The circumference and repetition rate of the booster ring is 772.9 m and 2 Hz, respectively. In this paper, the injection scheme, energy ramping curve, eddy current effect, beam parameters changing curve, and RF voltage during the energy ramping in the booster ring will be presented in detail.
Laser Compton Scattering (LCS) is a technique to produce quasi-monochromatic X-rays and gamma rays by colliding a laser with a high-energy electron beam produced by an accelerator. Although LCS light sources are expected to produce photons of the same quality in a small (6m x 8m) device as those from large synchrotron radiation facilities , the low number of scattered photons is an issue for practical use. To solve this problem, we have developed an optical cavity to generate colliding lasers with high repetition rate and high peak power. However, the operation of an optical cavity in an accelerator environment with high noise limits the stored optical power by maintaining resonance through resonator length control. Therefore, we have devised and are developing a self-resonating optical cavity in which the resonance is maintained spontaneously by connecting the optical storage resonator and the laser oscillator in a closed loop. In this talk, I will report on the current status of self-resonating optical cavity and its temperature dependence.
The High Energy Photon Source (HEPS) is a 1360.4-m, 6-GeV, ultralow-emittance light source, being built in the suburb of Beijing, China. The HEPS booster contains 128 dipoles,148 quadrupoles and 68 sextupoles, which are divided into several groups. The magnets in one group are connected in series, and powered by a single power supply. To minimize the impact on beam dynamics, magnets sorting needs to be done. The RMS values of closed-orbit distortion and beta-beating were used as the merit functions of dipole sorting and quadrupole sorting, respectively, and the sextupoles were grouped with the integral field differences between magnets. This paper will present the sorting process and the results of beam dynamics after sorting.
One of the main characteristics of the future light sources like Elettra 2.0 is the small vacuum chamber cross section. In fact, the resistive-wall (RW) impedance due to the small vacuum chambers cross section enhances transverse coupled-bunch instabilities. In this study, the effect of the RW in the multi-bunch case is investigated versus chromaticity. The threshold currents in the presence of broad-band and RW impedances are estimated for the Elettra 2.0 storage ring at different values of chromaticity using macroparticle tracking and frequency domain semi-analytical calculations. In particular, it is found that, above a certain chromaticity, the threshold current is determined by the radial head-tail modes. In view of mitigating these instabilities, the effectiveness of the transverse bunch-by-bunch feedback system as well as bunch-lengthening harmonic cavities is also useful.
Previous TDR studies for the SOLEIL II Upgrade project have converged towards a lattice alternating 7BA and 4BA HOA type cells providing a low natural horizontal emittance value in the 80 pm.rad range at an energy of 2.75 GeV. This lattice adapts to the current tunnel geometry as well as to preserve as much as possible the present beamline positions. The new TDR lattice is an evolution including perfect straight sections alignment, better relative magnet positioning and more space for accommodating photon absorbers, BPMs and other mandatory diagnostics. The SOLEIL upgrade TDR lattice is then composed of 20 HOA cells with a two-fold symmetry, and provides 20 straight sections having five different lengths of 3.0, 3.6, 4.2, 8.0, and 9 m. This last long straight accommodates a triplet of quadrupoles to set the two low vertical beta functions and an additional canting for the two long beamlines. This paper reports the linear and the non-linear beam dynamic optimizations as well as future directions for performance improvement.
High-intensity, monochromatic X and 𝛾-rays are a powerful tool for applied science in all fields. Free-Electrons Lasers can generate soft X-rays. A magnetic undulator's shortest possible oscillation period is ~1 cm, which restricts the photon energy to hundreds of keV at GeV-range electron energies. Inverse Compton Scattering, which needs powerful lasers, may provide hard X-rays and 𝛾-rays.
An interesting alternative is crystalline undulators (CU), i.e., a periodically bent crystal in which channeled charged particles follow the bending of the crystalline planes, thus generating e.m. radiation in analogy with standard magnetic undulators. The oscillation period can be lowered to sub-millimetric size, resulting in tens of MeV in photon energy using GeV electron beams[1]. A CU has the great advantage of being a passive and highly sustainable element, requiring neither magnets nor intense lasers.
Different techniques for producing CU, by taking advantage of modern technologies, will be illustrated. The grooving method[2], low-pressure chemical vapor deposition[3], ion implantation, and pulsed laser melting can provide a periodic deformation field that leads to a periodic bending of the crystal structure.
References:
[1] Novel Light Sources Beyond Free Electron Lasers, A.Korol; A.V. Solov’yov, Springer Cham, (2022)
[2] R. Camattari et al., Phys. Rev. Accel. Beams 22 (2019) 044701
[3] L. Lanzoni et al., International Journal of Engineering Science 46 (2008) 917
Polarization control of undulator radiation attracts a great attention due to its application prospects in material and biology. Various undulators have been developed to obtain radiation of specific polarization states. In the electron storage ring light source, different methods have been proposed to realize a specific polarization switching. However, there is still a strong demanding to improving the switching speed and/or increasing the available polarization state in a single beam line.
This paper gives systematic analysis of simple schemes to obtain the polarization switching by using the segmentation of the undulators with the phase shifter placed between each adjacent undulators. Through switching the polarization state of each undulator and the phase shifts, the polarization state can be fast switched between different polarization states in a same undulator line. The theoretical analysis for the radiation characteristics under different undulator configurations are demonstrated to reveal the basic principle of this simple method.
The Korea-4GSR with low emittance of 60 pm-rad provides the photon beam that is 100 times brighter and 100 times more coherent than PLS-II. Despite these powerful advantages, the new source imposes high power density on beamline optics. In particular, the first mirror M1 receiving broadband white beam will be directly affected. To check this, we calculated the power density by introducing a new ray-tracing algorithm. And this result is converted to temperature through Ansys steady-state thermal. The consistency of this calculation was evaluated as the measured value of M1 being monitored in PLS-II BL8A. This paper shows the results of the above.
Transverse Resonant Island Buckets (TRIBs) can be established by moving the horizontal tune close to a third order resonance. In this case the TRIBs correspond to a second stable orbit, longitudinally winding around the core orbit in the transverse x-x’-phasespace and closing after three revolutions. TRIBs provide many potential application possibilities ranging amongst others from simple bunch separation over dedicated multi-colour- or multi-polarization-experiments* to injection/extraction to/from the island orbit. For Leptons the synchrotron radiation damping attracts excited particles on the island orbit to the island fixed point, enabling non-adiabatic methods for population of the island orbit. Modern bunch by bunch feedback systems thus enable arbitrary filling patterns of the core and island orbits. Optics for TRIBs at the SLS are implemented successfully, enabling further studies of the TRIBs and the corresponding island orbit at the SLS.
The concept of Transverse Resonance Island Buckets (TRIBs) has recently gained attention in the storage ring light source community, and has found usage to, e.g., serve timing users and can enable fast polarity switching of the light in undulators.
This contribution introduces two options for creating TRIBs in SLS 2.0 using either 3Qx or 4Qx resonances. Options for control of the islands using sextupoles and octupoles in SLS 2.0 are evaluated. The optics and equilibrium emittance within the islands are calculated and checked using tracking simulations. Furthermore, the diffusion of particles from the islands due to radiative effects and Touschek scattering is discussed.
Inverse Compton Scattering (ICS) is an ideal source of tunable monochromatic gamma rays. These gammas have uses for Nuclear Resonance Fluorescence, and production of novel medical radioisotopes. The gamma energy can be tuned by changing the electron energy. An ICS source can be made quasi-monochromatic by using low energy spread electron and laser beams, and using a collimator.
Currently ICS gammas are only available from large synchrotron driven electron sources. These sources suffer from a smaller flux in the desired bandwidth than ERLs or linacs. A new planned gamma source is under consideration as part of the proposed UK-XFEL project, this would involve part of the XFEL linac being enabled for an energy recovery mode.
A demonstrator experiment to support the UK-XFEL project is being discussed for the upgraded CLARA facility at Daresbury Laboratory. The experiment will scatter Ti:Sapphire laser pulses at 800 nm off 250 MeV electrons. The gammas will be collimated. This experiment will characterise the source to determine the bandwidth and flux of the source. The maximum energy of the gamma photons in this experiment is 1.48 MeV and the bandwidth of the collimated source is 3.2%.
In this work I will present simulations of the planned experiment, showing the scattered gamma energy, bandwidth and tunability of the source.
HZB is in the process of developing a concept for a successor to the BESSY II synchrotron facility. The new facility will build on the strengths developed in Berlin over the last twenty years in delivering flexibly polarised soft X-Rays to dozens of beamlines. The successor facility BESSY III is planned to operate at 2.5GeV, in comparison to the 1.7GeV operation of BESSY II. This makes it easier to achieve the goal of delivering 1keV photons to beamlines on the first harmonic of our APPLE II Insertion Devices. It also makes it easier to achieve the aspiration of delivering tender X-Rays up to 10keV more routinely to users utilising in-vacuum APPLE II devices*, Cryogenic Permanent Magnet Undulators (CPMUs) or Cryogenic APPLE devices[2]. However, it also presents challenges in delivering the low energy photons below 10 eV, as period lengths of the relevant undulators must be increased, which in turn increases on-axis power. APPLE-KNOT designs will be pursued to overcome this issue.
The undulator group will also be planning Double Period Undulators[3] to offer beamlines broad spectrum coverage from 50eV to 10keV on the 1st and 3rd harmonics.
This paper outlines the first choices of undulators to be available to the successor facility BESSY III.
The codes UNDUMAG and WAVE have been developed at HZB/BESSY. They are used
intensively to design undulators, and to understand their magnetic and
synchrotron radiation properties, as well as their impact on the storage ring.
Recent extensions will be presented. A more intuitive input file to define
undulator geometry has been developed, as well as a Python based GUI that
allows the set-up of common undulator types. This GUI also allows the
visualization of results. The magnetization of permanent magnet blocks can
now be defined in terms of polynomial coefficients to simulate and study
magnet inhomogeneities.
WAVE has also been interfaced to UNDUMAG to calculate the real magnetic field
of insertion devices. A second undulator mode has also been developed that
calculates undulator synchrotron radiation by summing the radiation field
amplitudes of a single period with appropriate phase advance and depth of
field effect corrections. Field and phase errors can be included in this mode,
which has seen a speed performance increase of an order of magnitude.
Siam Photon Source (SPS) is an existing synchrotron light source in Thailand, which has been operated and provided synchrotron radiation for user beam service for more than 20 years. The SPS accelerator system con-sists of a 40-MeV linac, a 1.2-GeV booster synchrotron and a storage ring with double bend achromat (DBA) lattice. The linac is one of the most critical parts of the SPS machine in which its performance affects beam injection and hence to the beam service. Beam diagnostics of the SPS linac has been upgraded in order to allow better beam monitoring and become a crucial part for linac optimization to achieve higher machine performance. In this paper, upgrades of beam diagnostics of the SPS linac will be discussed.
The main accelerator of WALS (Wuhan Advanced Light Source) is a 1.5 GeV, 180 m storage ring with emittance 222.8 pm.rad, which reaches soft X-Ray diffraction limit. To achieve such low emittance, the magnet system is designed very compact with very small aperture. And this results in a narrow transition structure and a low flow conductivity vacuum chamber. In consideration of the beam lifetime, the vacuum system requires the average static and dynamic pressures to be better than 5×10-10 Torr and 1×10-9 Torr, respectively. And the distributed pumping and proper absorption of synchrotron radiation load are required. In this paper, oxygen-free high-conductivity copper (OFHC) is used as the main material of storage ring vacuum chamber. And the radiation load in the storage ring was solved by providing water along the illuminate of synchrotron radiation surface and area. The Non-evaporation getter (NEG) coating provides a distributed pumping which can acquired by vacuum magnetron sputtering plating, significantly reduce the cost and complexity of storage ring vacuum system construction.
In intraoperative radiation therapy (IORT), accelerators typically consist of two or more tubes to achieve adjusta-ble electron energy. To simplify the accelerator structure and meet the demand for convenient adjustment of elec-tron energy, we propose an X-band electron linear accel-erator for IORT, composed of 102 cavities. This accelera-tor can adjust the output electron energy over a large range solely by varying the input power, providing elec-trons with energy exceeding 13MeV at maximum and approximately 5.5MeV at minimum, which satisfies the requirements of electron IORT. We also measured the field distribution and S-parameters at low power, and the ener-gy spectrum distribution also was measured at different input powers. This accelerator design provides a feasible and simple solution for IORT-specific accelerators.
A method is described whereby any desired longitudinal electron bunch profile may be generated in a storage ring by tailoring the wake potential. The required wake function is found by implicitly solving the Haïssinski equation through the usage of a regularization parameter. For two coveted longitudinal profiles—a lengthened profile and a triangular profile—the required solutions are obtained and verified through particle simulations in longitudinal phase space, as well as through full particle tracking simulations. Auxiliary variables such as energy spreads/chirps and transverse phase-space distributions are found to be unaffected by the additional potentials. A possible implementation means is discussed in the context of using multiple harmonic cavities.
The main ring synchrotron (MR) of the Japan Proton Accelerator Research Complex (J-PARC) has provided high-intensity proton beams to the T2K long-baseline neutrino experiment, which requires high statistics to confirm the existence of CP violation. We plan to increase the beam power from 0.5 MW in 2021 operation to 1.3 MW by 2028 in the fast extraction mode of the MR. This upgrade supports higher statistics for T2K and the Hyper-Kamiokande long-baseline project, which will start from 2027.
The scheme of the upgrade is to quicken the repetition period by a factor of two from 2.5 s in 2021 operation, and to increase the number of protons per pulse 30% more. This scheme requires hardware upgrades on the power supplies of the main magnets, high gradient RF system, collimator system, injection and fast extraction systems, and beam monitors. The upgrade of the MR is on schedule. The hardware upgrade for high-repetition operation was completed by 2022. The remaining upgrades will be accomplished in following several years to increase the number of protons per pulse. The improvement of the beam dynamics in the MR is also necessary to manage higher space charge effects due to increase of the beam intensity, and to localize beam losses at the collimator section in the MR more efficiently. This presentation reports the first results of the MR beam operation in the high repetition rate and the strategies to 1.3 MW operation based on beam study results.
We propose a novel method to suppress the emittance variation caused by the opening and closing of the gap of insertion devices (IDs) in extremely low emittance light source storage rings. The core idea is to leak a small amount of dispersion into the straight section where IDs are installed and optimize its value so that the radiation excitation and damping caused by IDs are balanced [1]. A typical value of the leaked dispersion is about 10mm or less, and the storage ring can be considered quasi-achromatic. To carry out the optimization, we introduced a concept of “average ID peak field” over the ring as an indicator of the ID operating condition in user time. This concept allows us to represent a complex ID gap status with a single parameter and is very effective in deriving an equation for determining the optimum value of the leaked dispersion. The proposed method is passive and applicable to any light source storage ring, and the emittance variation is potentially expected to be less than 1% by carefully optimizing dispersion leakage. In this work we show how this scheme works for suppressing the emittance variation using the SPring-8-II storage ring [2] as an example.
Measurements of the very long single bunch spectrum with RF off, were started in the SPS in 2012 to identify the main impedance sources responsible for both single and multi-bunch beam instabilities observed during operation. The impedance of the vacuum flanges with a strong peak at 1.4 GHz was identified and proven from simulations to limit the beam intensities required for the High-Luminosity LHC (HL-LHC). A shielding campaign was then initiated and applied during the long shutdown period in 2019-2020 to reduce their impedance. The same measurement technique was used recently to verify and evaluate the impedance reduction, as well as to identify other impedance sources. In this paper, the results of the new measurements are presented and compared with those found in 2012. The comparison shows that the strong impedance peak at 1.4 GHz has been fully suppressed and that the instability threshold largely increased in both optics used in measurements. Furthermore, the beam spectra evolution during the de-bunching is driven by the main 200 MHz cavity impedance, and no other dominant peak for the measured intensity range was observed.
The superconductive quarter wave cavities hadron Linac ALPI is the final acceleration stage at the Legnaro National Laboratories. It can accelerate heavy ions from carbon to uranium up to 10 MeV/u for nuclear and applied physics experiments. It is also planned to use it for re-acceleration of the radioactive ion beams for the SPES (Selective Production of Exotic Species) project. The linac was designed in 90’ with the available techniques and it was one of the peak technologies of this kind in Europe at those times. However, the improvements on the cavity fields increased the real-estate gain and the energy output, at the price of lattice periodicity and non-linear RF defocusing. This fact turned out to be troublesome for the operations and delayed the nominal transmission achievement. In this paper we will present the innovative results obtained with swarm intelligence algorithms, in simulations and commissioning. In particular, the increment of the longitudinal acceptance for RIB (Radioactive Ion Beams) acceleration, managing 84 independent cavity phases, and beam orbit correction without the beam first order measurements will be discussed.
A realistic laser assisted charge exchange (LACE) scheme for 1.3~GeV H- beam injection into the Ring for Spallation Neutron Source is under development. The design considered here is supposed to demonstrate the possibility of H$^-$ charge exchange injection into the SNS ring as an alternative to carbon foil stripping. A realistic stripping magnet design is considered as an integrated part of the injection area. Beam dynamics at the injection area are optimised. Laser assisted stripping, painting and beam dynamics of protons in the ring is simulated. Several alternative stripping schemes are evaluated.
Recent storage ring experiments have demonstrated the power and the potential of laser cooling of bunched relativistic ion beams. Encouraged by this, the heavy-ion synchrotron SIS100 at FAIR (Darmstadt, Germany) will be equipped with a truly unique laser cooling facility. A sophisticated combination of 3 newly developed UV (257 nm) laser systems and modest rf-bunching will allow for fast cooling of injected intense heavy-ion beams. There will be two powerful pulsed laser systems with MHz repetition rates and variable pulse duration (1-50 ps and 50-740 ps) and one powerful tunable cw laser system. The picosecond laser pulses are broad in frequency and will enable fast cooling of injected ion beams with a large initial longitudinal momentum spread. The cw laser can be rapidly tuned over a large frequency range and has high spectral power density, forcing the ion beams to remain cold during storage. This combination of 3 UV laser beams should be up to the challenge of suppressing intra-beam scattering and space charge effects. We will present new experimental results from the ESR storage ring and the status of the SIS100 laser cooling facility.
In high intensity proton synchrotrons, space charges effects will cause tune shift of the beam. When the betatron tune spreads over a resonance line, the betatron oscillation amplitude will get larger, causing large beam loss. Through the quadrupolar beam transfer function, the coherent space-charge tune shift of quadrupolar beam oscillations can be derived with quadrupole oscillating frequency.
China Spallation Neutron Source (CSNS) is a high intensity accelerator based facility consists of linear accelerator and the Rapid Cycle Synchrotron (RCS). A quadrupolar BPM is already installed at RCS for obtaining quadrupolar beam oscillating information this year. This paper will present the experimental data during accelerator commissioning and how to obtain the quadrupole beam oscillating frequency on CSNS/RCS.
Cylindrical corrugated waveguides (CWGs) for accelerators and light sources have actively been studied in the past decade theoretically and experimentally. CWGs with a planar geometry have been successfully employed to cancel linear energy correlation in the electron bunch and thus to enhance the performance of free electron lasers (FELs). Cylindrical CWG have been proposed as a passive streaker for a time-resolved diagnostic of the electron bunches, for a subterahertz FEL, and for a compact high repetition rate multi-user X-ray FEL This paper will describe the fabrication of a small-size precision cylindrical CWG and comparison of beam measurements with predictions.*
* Phys Rev Accel Beams 25, 031302 (Feb 2022)
The High-Luminosity LHC project aims at increasing the LHC luminosity by an order of magnitude, and support LHC operation till the early 2040s. This presentation will review the overall HL-LHC project status. Many HL-LHC achievements will be available for reporting by mid 2023, starting with the finalisation of the Civil Engineering and extending up to the triplet magnet prototype demonstration.
Dielectric wakefield acceleration (DWA) is a high gradient novel acceleration concept. To realise this concept for future high energy facilities, scalable models of the transverse and longitudinal beam dynamics from these wakefields must be created and experimentally verified. We present a summary of results from the recent experimental run at the CLARA facility. This study used both circular and planar quartz DWA structures and was performed with 100 pC bunch charge and 35 MeV beam energy. The effect of dipole-like and quadrupole-like wakefields from both structures were studied in detail for a variety of beam distributions. These results were used for the benchmarking a highly scalable simulation code which was developed in-house.
For the purpose of indirect search of dark matter, we designed laterally driven Dielectric Laser Acceleration (DLA) structure that achieves 1.2 MeV energy gain in 6 mm length together with 6D confinement. The design originated from a relativistic DLA structure and was supplemented with non-homogeneous shapes following the APF segments and optimized using a genetic algorithm together with the DLAtrack6D tracker. The achieved throughput could be increased to 98%.
For the first time, photoemission of spin-polarized electron beams from gallium nitride (GaN) photocathodes are observed and characterized. The spin polarizations of the emitted electrons from epitaxially grown hexagonal and cubic GaN photocathodes activated to Negative Electron Affinity (NEA) via cesium deposition are measured in a retarding-field Mott polarimeter.
SuperKEKB is a positron-electron collider with a nano-beam scheme and continues to achieve the world’s highest luminosity for the production of B meson pairs. The luminosity performance has been improved by the adoption of the crab-waist scheme. The nano-beam scheme allows the vertical beta function at the interaction point (IP) to be much smaller than the bunch length. The vertical beta function and the beam size at the collision point are the smallest in the world among colliders. As the result, the peak luminosity which is larger than twice the predecessor KEKB record has been achieved in 2022. Recent progress will be presented, and then the problems and issues to be overcome will be discussed for further improvement of the luminosity performance. We had a long shutdown (LS1) since 2022 summer to upgrade both the Belle II detector and the machine. We will report the strategy of luminosity improvement after LS1.
The environmental credential of future colliders are increasingly in the spotlight, because of their size and complexity, and will be under scrutiny for their impact on the climate. Therefore, sustainability has become a prioritized goal in the design, planning and implementation of future accelerators; approaches to improved sustainability range from overall system design, optimization of subsystems and key components, to operational concepts. A direct quantification of the ecological footprint, be it greenhouse gas emissions during construction and operation, or consumption of problematic materials, is currently performed only sporadically, mostly through translation of electricity consumption into equivalent CO2 emissions. Two large electron-positron linear colliders are currently being studied as potential future Higgs-factories, CLIC at CERN and ILC in Japan. These projects are the central elements of the recently approved EU / EAJADE (Europe-America-Japan Accelerator Development and Exchange) program. A direct societal impact is expected through EAJADE WP4 (Sustainable Technologies for Scientific Facilities), where methods to reduce the power consumption of accelerator technologies and systems will be studied, and smart integration of future accelerator infrastructure with the surrounding site and society (e.g. Green ILC concept). This contribution will highlight past achievements and address the EAJADE WP4 future program.
A novel technique, called a spin transparency mode, for preservation and control of electron and ion spin polarization in colliders and storage rings has been proposed. The beam polarization can then be fully controlled by small adjustments of the snake axis orientations and snake strengths. An experiment has been carried out recently to test the concept. One of the RHIC rings is set to be “transparent” to the spin by making the axes of its two Siberian snakes nearly parallel. The polarization was rotated from vertical to radial and from up to down by varying the snake currents. This paper summarizes the recent experiment results and discusses the comparison with simulations.
Superconducting undulators (SCUs) can produce higher photon flux and can cover a wider photon energy range compared to permanent magnet undulators (PMUs) with the same vacuum gap and period length. The operational experience of SCUs in accelerators as well as future plans of deploying SCUs in free electron lasers, diffraction limited storage rings and compact light sources will be presented.
SASE studies in the sub-ångström regime, using optimized electron beams, are carried out at varied energy levels according to the present state of the facility, that is, a pulsed mode operating with a 10 Hz repetition 0.6 ms-long bunch train with beam energies between 14 GeV and 17.5 GeV. From simulations nearly Millijoule-level SASE intensity is obtained at a photon energy of 30 keV at 16.3 GeV electron beam energy using a gain length of about 8 m. Experimentally this energy has been achieved with 300 µJ intensity at the EuXFEL at DESY. The setup for the machine and the photon beamlines to reach this point will be presented. The prospects to reach even higher photon energies will be illustrated.
Business association for large supplies
The company D-Beam Ltd was established in 2015 to capitalize on the beam diagnostics R&D carried out in the QUASAR Group at the University of Liverpool/Cockcroft Institute. The start-up was one of the first companies to join the STFC CERN Business Incubation Centre (BIC) at Sci-Tech Daresbury. D-Beam has since become the partner of choice in a number of national and European projects.
The company's optical-fiber beam loss monitor (oBLM) was selected as an ASTeC technology highlight of the year in 2018/2019, D-Beam's research was highlighted as an STFC Impact Acceleration Account success story in 2020, and work into adaptive optics based monitors was recognized as an ARIES success story.
This talk will discuss the challenges related to setting up a spin-out company and present ideas of how to successfully engage with funders and research partners.
Spin-off company – the main challenges
Innovative approaches in procurement procedures
Aberration correction electron optics and cold field-emission electron source made the transmission electron microscope (TEM) a popular tool to image atomic and nano-scale objects. Cryogenic electron microscopy (Cryo-EM) revolutionized the bio-structure science, and recently it is explored to investigate radiation-sensitive battery and energy materials. But non- physiological environments, sample damage and electron beam induced sample movement greatly limit the science impact of both TEM and Cryo-EM. To address those challenges, we propose to develop ultrafast electron microscope based on megaelectron electron beams (MeV-UEM). The development of high-brightness electron sources made it feasible to explore megaelectronvolt electrons for Ultrafast Electron diffraction and Microscope (MeV-UED/UEM) [1-2]. MeV-UED had broad and transformative impact on ultrafast science, such as the first 2-D materials ultrafast structure dynamics, light-induced transient states, molecular movies of canonical interception & ring-opening, and the first hydrogen bond structure dynamics in liquid water [3]. The proposed MeV-UEM will capable of single-shot imaging with atomic spatial resolution (0.3 nm) and sub-nanosecond temporal resolution. We will present the plan of employing accelerator technologies, such as high-brightness MeV electron source, novel electron optics and high field magnet, to realize the MeV-UEM.
FERMI is the seeded Free Electron Laser (FEL) user facility at Elettra laboratory in Trieste, operating in the VUV to soft X-rays spectral range. In order to extend the FEL spectral range to shorter wavelengths, an upgrade plan for increasing the Linac energy from 1.5 GeV to 2.0 GeV is actually going on. After the successful testing of the short prototype of the new high gradient (HG) S-band accelerating structure up to an accelerating gradient of 40 MV/m, two full-length 3.0 m HG structures have been built and installed at the FERMI linac. In this paper, we report the low power measurement, conditioning results, and commissioning with the beam of the first HG module.
The Hard X-ray Self-seeding system at the European XFEL started to be available for user delivery in summer 2021. A large number of user requests of HXRSS showed the interest and the importance of longitudinally coherent X-ray FEL pulses with narrow bandwidth for different applications. In this paper, we will summarize user requirements, tuning procedures and performance we achieved during user delivery.
The Ion Beam Centre at Kurukshetra University is the first facility established by Department of Science and Technology, Govt. of India by funding and supporting Accelerator based research programs in university system. The facility has been providing accelerator-based research facilities to researchers of host university as well as researchers from all over India. The air insulated high current 200 kV Ion Accelerator, with the high voltage in the range of 30-200 kV is designed for ion implantation to provide ion beams of variable energy. It is equipped with SO-55 ion source, which is a hot filament, hollow cathode type ion source providing beams in the range of 10 nA to 120 µA. The ion source is operated at +30kV and depending upon the experimental requirements, the source is operated as it has High temperature oven (600-1700), Medium temperature oven (400-700) and Low temperature oven (100-400) all equally capable of running gas with the choice of using charge material either in elementary form or in gas form. The overall facility has been utilized for part of Engineering and Technology based teaching of students pursuing semiconductors developments. The present presentation provides an overall development performance of modifications for the improvements in the experimental setup. The performance of the source has been tested by running argon, boron and gold beams at maximum energy of 200 keV regularly at the optimum performance of the ion sources.
A Structured Laser Beam (SLB) is a type of optical beam with spatially inhomogeneous 3D polarisation structures. Generating SLBs from vector beams allows the creation of Hollow Structured Laser Beams (HSLB) with a dark central core. In this way, atypical electric and magnetic field vectors, which are purely longitudinally polarized in the dark zones of the beam, are obtained. The SLB spatial distribution can also include regions with both the electric and magnetic fields longitudinally polarized and oriented in the same or opposite directions. The SLB has a transverse distribution similar to that of a Bessel beam but can theoretically propagate to infinity, therefore giving the potential to generate strong, longitudinally oriented electric fields over long distances, which could possibly allow the acceleration of charged particles. The results of the study of this phenomenon, including simulations of the spatial distribution of the electromagnetic field components, are presented in this paper.
A 1–2 GHz stochastic cooling system is being de-veloped to provide fast 3D cooling of hot secondary beams (antiprotons at 3 GeV and rare isotope ions at 740 MeV/u) at intensities up to 10^8 particles per cycle. For antiproton cooling, cryogenic plunging pick-up electrodes will be used to improve the ratio of Schott-ky signals to thermal noise. To cool hot rare isotope beams quickly, a two-stage cooling (pre-cooling by the Palmer method and main cooling by the notch-filter method) has been decided. This paper presents the recent R&D highlights of this unique stochastic cool-ing system especially the main sub-systems i.e. two cryogenic plunging slotline pick-ups, one Palmer pick-up, and two slot-ring kickers.
Purpose: In the effort to develop a compact dielectric wall accelerator (DWA) system for proton radiotherapy, this work aims to demonstrate the feasibility of a drift step recovery diode (DSRD) based pulse forming network (PFN) to generate high magnitude, nanosecond scale voltage pulses at high repetition rates.
Methods: An initial numerical feasibility study was conducted in order to demonstrate the possibility of generating a 17 kV, nanosecond scale pulse with a DSRD-based standard PFN (forward and reverse current branch). Then, a DSRD-based PFN was designed using a magnetic switch, seen in Figure 1 (https://bit.ly/3iMCOHs). Saturation of a transformer discharges a storage capacitor. At maximum current, the DSRD turns off, commuting stored energy to a load. A low energy prototype was developed at SLAC. A 20 kV, high repetition rate (1-10 kHz) prototype is currently being developed.
Results: The numerical study demonstrated that a max output of 16505 V with a rise time of 1.11 ns can be generated with a stack of 19 DSRDs. Figure 2 (https://bit.ly/3VGPuhS) presents a 4.9 kV pulse of the low energy prototype.
Regarding high current e+ sources, the almost universal usage of target-based production schemes combined with conventional capture technology has led to poor transmission efficiencies. This long-standing difficulty to handle the extreme e+ transverse emittance and energy spread has been a major impediment for future, high luminosity lepton collider designs. The PSI Positron Production (P-cubed or P$^3$) experiment, framed in the FCC-ee study, is a demonstrator for a e+ capture system with potential to improve the state-of-the-art e+ yield by an order of magnitude. The experiment will be hosted at the SwissFEL facility at PSI as of 2025, where installation works are ongoing. This paper is an overview of P$^3$, with a particular focus on the novel capture system and its effects on the beam dynamics. A concept for the experiment diagnostics is also introduced.
Muons have been playing an important and unique role in both fundamental physics and applied sciences; Recent results of the muon magnetic anomaly hint at physics beyond the Standard Model; Muon spin rotation techniques have been widely applied to the study of superconductivity and magnetic materials. A typical muon experiment measurement time of 10 muon lifetimes means that an ideal muon source should operate at around 50 kHz in the pulsed mode. However, current muon sources are either driven by several 10 Hz pulsed proton accelerators (e.g. J-PARC) or DC proton accelerators (e.g. PSI), resulting in low-duty cycles for many types of muon experiments. Here we explore the use of a high-repetition-rate pulsed electron beam at the Shanghai SHINE facility as a muon source driver. SHINE is based on an 8-GeV CW superconducting RF linac, with a bunch rate of 1 MHz and a bunch charge of 100 pC. Downstream of undulators, the electron beam is deflected and absorbed in a beam dump. Based on a GEANT4 Monte Carlo simulation, we estimated the maximum intensity of the muon beam to be around $10^{9}$. The main production channels are photo-nuclear and Bethe-Heitler processes and each of these processes generates muon beams with different kinematics and time profiles. Such muon beams can improve the performance of current muon physics experiments such as the muonium to anti-muonium conversion and the muon spin rotation technique.
In a subcritical assembly, heavy metals are used to generate additional photo-neutrons using high-energy electrons. One of the options for a neutron-generating target is a set of tungsten plates coated with tantalum. It is promising due to the high neutron yield upon irradiation with high-energy electrons.
The operating conditions of a tungsten target exposed to electron beams with an energy of 100 MeV, a pulse beam current of 600 mA, and a power density of 2.5 kW / cm2 impose high demands on the target's tightness, in terms of the release of radioactive products from tungsten to the cooling target water.
To protect against chemical corrosion and the ingress of radioactive products of the irradiated material into cooling water, the tungsten target plates are coated with a protective layer of tantalum. The tungsten target worked on a high-energy electron accelerator for 6 months. No radioactive products were detected in chilled water.
High gradient radio-frequency structures are of considerable interest in ongoing structure wakefield acceleration research. The prospect of economical accelerators with a small footprint in the sub-terahertz regime shows promise in achieving high gradient and high efficiency, and in that vein, we present a design for a metallic corrugated waveguide designed at 110 GHz. This W-band structure has been optimized in the CST Studio Suite for the maximum achievable gradient of 84.6 MV/m from a nominal Argonne Wakefield Accelerator (AWA) electron bunch at 65 MeV, with a charge of 10 nC and an RMS length of 0.5 mm. When the developed structure is excited with a shaped electron bunch, higher gradient and longer beam propagation distance could be achieved. Simulations are ongoing to test the effects of bunch shaping on the structure's performance, and structure fabrication and cold tests are underway in preparation for a collinear wakefield acceleration experiment at AWA.
The Facility for Rare Isotope Beams (FRIB), a major nuclear physics facility for research with fast, stopped, and reaccelerated rare isotope beams, started operation in May 2022. Since then, five nuclear physics experiments have been successfully accomplished. The experiments with rare isotope beams typically last within 1-2 weeks. Each experiment requires a different primary beam and its energy. It is critical to shortening the accelerator and fragment separator setup time to meet the requirements of the FRIB Users community. Currently, the primary focus in the linac is to reduce the accelerator setup time and ramp up beam power. Many physics applications, including Machine Learning, have been developed and used to set up the accelerator and beamlines. The simultaneous acceleration of multiple charge states of heavy ion beams is routinely used to minimize the beam power deposition on the charge selector slits after the stripper. The challenges in the fragment separator are related to the highly non-linear beam physics due to the large emittance and momentum spread of the isotope beams. Since the iron-dominated SC magnets operate near saturation, the optimization process includes field distributions at different excitation currents. This paper discusses the theoretical and experimental procedures to improve the linac and fragment separator performance.
Beam-driven plasma-wakefield acceleration has the potential to reduce the size and construction cost of large-scale accelerator facilities, by providing accelerating fields orders of magnitude greater than that of conventional accelerating structures. To keep the running costs affordable, high energy-transfer efficiency from the wall-plug to the accelerated bunch has to be demonstrated. For this, drive bunches must be efficiently produced, strong decelerating fields must be sustained for the drive bunches until their energy is depleted, and the resulting accelerating fields must be strongly beam loaded by the trailing bunches. Here we address the state-of-the-art in all three phases by reviewing the expected klystron efficiencies at future facilities, reporting on recent measurements performed at FLASHForward whereby 50% of the drive-beam energy is transferred to the wake, and laying the groundwork for how these results can be combined with previous record results in the transfer of energy from the wake to the accelerating beam. With this expected level of energy-transfer efficiency it is shown that plasma accelerators hold the potential to become competitive with conventional accelerators.
To complete the Italian In-Kind contribution to the ESS SRF Linac, we are working on the qualification of the last eight missing cavities. To achieve this, we are proceeding with reprocessing of not yet qualified cavities and, as a mitigation, we are constructing at the vendor four more cavities. In this paper, we report on the actual status of both of these activities with the most recent results.
The design and construction of continuous wave (cw) superconducting (sc) high intensity linacs is a crucial goal of worldwide accelerator technology development. The standalone sc cw heavy ion HElmholtz LInear ACcelerator (HELIAC) is a common project of GSI Helmholtz Centre for Heavy Ion Research and Helmholtz Institute Mainz (HIM) under key support of Goethe University Frankfurt (IAP). In 2017 the first section of the linac has been successfully commissioned and extensively tested with heavy ion beam at GSI, featuring the capability of 216.816 MHz multi-gap Crossbar H-mode (CH) DTL-structures. At present, the first fully equipped cryomodule of the HELIAC is under construction. Six further superconducting CH cavities are being procured. The HELIAC beam dynamics concept foresees a total of twelve CH-cavities in order to accelerate ions with a mass-to-charge ratio of 6 up to a smoothly variable energy in the range 3.5 - 7.5 MeV/u. In this paper, an advanced compact and less complex layout is presented, where the same number of accelerating cavities can be accommodated in three instead of four cryomodules, thus also reducing the number of solenoids and rebunchers, required for beam focusing. In addition, the integration and linking of the HELIAC to the GSI accelerator facility will be outlined.
The Advanced Ion Source for Hadrontherapy (AISHa) is an ECR ion source operating at 18 GHz, developed with the aim to produce multiply charged ion beams with low ripple, high stability and reproducibility, low maintenance. Due to its unique peculiarity, it is a suitable choice for medical applications, but also to nuclear-physics and material experiments.
Two AISHa sources have been realized up to now: the first at INFN-LNS, as a prototype, and the second at the Centro Nazionale di Adroterapia Oncologica (CNAO).
The first one, fully commissioned at INFN-LNS, will be used as testbench for the preparation of new beams for Nuclear Physics; R&D activities are also planned within the IONS experiment in order to increase plasma confinement and to refine techniques of non-invasive plasma diagnostics aimed to correlate plasma parameters and beam parameters.
The second one recently produced the first beam and it will permit to increase the opportunities provided by the CNAO hospital, with the long-term goal of introducing new ionic species into clinical practice such as helium, oxygen and later also iron and lithium, either useful for bio-spatial research and for experimental and industrial research. In this presentation, the key peculiarity and the experimental results of the Aisha ion source will be presented.
The high Quantum Efficiency (QE) and low Mean Transverse Energy (MTE) of alkali antimonide photocathodes enable the production of bright electron beams for a variety of accelerator applications. Growing alkali antimonide photocathodes requires an elaborate growth chamber and an operator with considerable expertise. Moreover, their sensitivity to chemical poisoning requires storage in an ultra-high vacuum environment, which poses a significant challenge to their commercialization. As a step towards commercialization, we developed a “cathode-in-a-can" system to provide photoinjector facilities with high performance, air sensitive photocathodes. This system allows for a cathode to be grown at one facility, shipped in a compact vacuum-sealed canister to another facility, then removed from the canister and transferred to the photoinjector to preserve the cathode’s excellent photo-emitter qualities.
A first beam dynamics and RF design of an Alvarez-type drift tube linac (DTL) has been defined in the framework of the EU project, HITRIplus. Its main application is to be exploited as a carbon (12C4+) and helium (4He2+) ion injector into a compact synchrotron for patient treatment. As a second implementation, helium particle acceleration with a higher duty cycle of 10% enables the possibility for radioisotope production. The 352.2 MHz structure efficiently accelerates two ion species, for A/q=3 and 2, in the energy range of 1÷5 MeV/u and for a beam current of ~0.5 mA. The design extends to a full length of ~7 meters. Permanent magnet quadrupoles are utilized all along the DTL for focusing both ion beams. This paper presents a first-phase analysis towards a realistic DTL design capable of providing full beam transmission and minimum overall emittance increase for two ion beams.
A new type of accelerator called Harmonytron has been proposed. The Harmonytron is based on a scheme of vertical Fixed-Field Alternating gradient (vFFA) focusing with harmonic number jump beam acceleration. An electron model of vFFA accelerator is under development at Kyushu University. The current status of the vFFA accelerator will be discussed.
Energy matching between two hadron synchrotrons is the adjustment of the magnetic bending fields and beam momentum to obtain a correct transfer between the two. Conventionally, energy matching is achieved by turning off the RF system and measuring the revolution frequency of the de-bunching beam in the receiving accelerator. For an ideal circumference ratio, the orbits would then be centred in the two rings. However, this procedure is non transparent, seen that the de-bunched beam cannot be accelerated anymore. Thanks to the Low-Level RF (LLRF) upgrade in the Super Proton Synchrotron (SPS) during the 2019-2021 long shutdown, most LLRF signals have become available in digital form, allowing easy online display, analysis, and storage. In this contribution, we look at the possibility of performing energy matching between the PS and the SPS in a more transparent way, without disabling the RF system. The signals from the beam phase and synchronization loops reveal information on the energy of the beam injected into the SPS. This allows to continuously monitor the transfer frequency error, as well as identify and correct potential long-term drifts.
The ESS cavity operation is challenging due to long RF pulse, high gradient, high beam power and high demands for energy efficiency and availability. These require a better understanding of RF-cavity dynamics and insight into RF-cavity interaction. RF and cavity dynamics identification relies heavily on high precision measuring and characterizing basic cavity parameters (Ql, dynamic detuning, phase, amplitude, etc). Thanks to advanced hardware capabilities and software intelligence, cavity basic parameter measurement has achieved good precision at ESS and played important role for different cavities. It enables us to observe some critical RF-cavity dynamics during ESS cavity testing and conditioning. Application of high precision measurement of cavity basic parameters will be introduced. Some RF-cavity interaction and dynamics such as Lorentz Force Detuning and quench detection will be reported. Further application development of high precision measurement for cavity with heavy beam loading will also be discussed.
AWAKE is the first proof-of-concept proton-driven plasma wakefield acceleration experiment. AWAKE’s first phase concluded in 2018, with controlled acceleration of electrons to energies of 2 GeV in a 10-m long plasma cell. AWAKE’s second phase operates since 2021. It has been divided into four stages (Run 2a, Run 2b, Run 2c and Run 2d) to prove step by step good that the required electron beam parameters can be obtained reliably and consistently. The transition from Run 2a to Run 2b, which is scheduled for the first semester of 2023, includes the decommissioning of the current vapor source as well as the installation of a new 10-meter-long step density plasma source. After summarising the motivation for the AWAKE Run 2 programme, this paper will describe the preparation works for such an installation, the challenges linked to the infrastructure and the implementation of scheduling tools for the coordination of the facility.
High-energy proton bunches offer the potential to drive wakefields over very long distances in plasma. An externally-injected electron bunch can thus in principle experience very large energy gain (hundreds of GeVs to TeVs) in a single plasma with GeV/m accelerating gradient. AWAKE explores this potential with 400GeV proton bunches from the CERN SPS. Based on the succesful demonstration of seeded self-modulation of the proton bunch and of acceleration of test electrons, a plan was devised to produce 10-200GeV electron bunches with parameters suitable for application to particle physics**. We will outline key experimetal results and the general plan for the experiment.
ARES is an electron linear accelerator at the SINBAD facility at DESY. It aims to deliver reliable high-brightness beams with energy in the range of 100 to 150 MeV having fs to sub-fs bunch lengths. This is ideal for injection into novel high-gradient acceleration devices such as dielectric laser accelerators and laser-plasma accelerators which feature fields with fs to ps period. The ARES linac has been successfully commissioned. Here we report the results of the beam-based alignment of focusing solenoids of ARES. The alignment is an important part of commissioning and is crucial for the beam quality.
Neutrons are an essential tool for studying the structure and dynamics of matter. The High Brilliance neutron Source (HBS) project aims to develop a scalable Compact Accelerator-driven Neutron Source that will enable neutron fluxes at the corresponding instruments comparable to existing fission-based or spallation neutron sources. The full-scale HBS facility is characterized by the simultaneous operation of a suite of neutron instruments subdivided into three target stations, each efficiently operated to deliver different neutron spectra. This is realized by different proton beam timing schemes distributed to the target stations. A corresponding beam line design has been worked out in detail. It will deliver proton beams of up to 100mA and 70MeV from the proton Linac via the target beamlines to the neutron production targets. To ensure the complex pulse structure of the proton beam, a multiplexer magnet system will be installed to generate and distribute the different proton pulse schemes to the target stations. The three individual target stations will be operated at different proton pulse frequencies, where the corresponding proton pulse length is coupled via a fixed duty cycle. Major development steps of this project are the development of a three-field septum magnet, which is an essential part of the multiplexer magnet system, the beam dynamics integration of the multiplexer magnet system into the beamline, and the ion-optical layout of the individual target beamlines.
Beam intensities and powers being increasingly strong, installations increasingly large, the need to reduce losses and costs (i.e. dimensions) becomes essential. Improvements are possible by increasing the acceptance in the two transverse planes. For example for LEBT lines and radioactive beams, a large geometric acceptance allows efficient transport of reaction products that have large phase space dimensions downstream of the TIS. For low intensities, the flux is preserved to allow maximum intensity on target (reactions with low cross section). We investigate the solution to control the beam line acceptance by measuring the emittance growth and a feedback with the design, e.g. pole shape and high-order modes of the fields. This is possible with detection of very low intensities of the halo and beam loss monitoring.
The injectors for the LHC at CERN underwent a major upgrade during a recent two-year long shutdown in the framework of the LHC Injectors Upgrade (LIU) project. Following this upgrade, the Proton Synchrotron (PS) was restarted in 2021, with the same beam quality as before the upgrade quickly achieved or surpassed. This contribution details the current beam performance for fixed-target and LHC-type beams in the PS and the ongoing activities to improve the operational efficiency by means of automating routine operational tasks.
Plasma wakefields can produce broadband electron spectrums that can mirror the characteristics of the electron fluxes that exist in the planetary radiation belts. The SAMURAI RF facility which is currently being constructed and commissioned at UCLA, will be capable of producing beams with 100s pC of charge with bunch lengths in the 100s of fs range with low transverse emittances in the 3-80 MeV range. We explore the production of broadband electron energy spectra from the beam plasma interaction of these beams. The beamline transport and diagnostics preceding and proceeding the interaction are discussed in this paper.
The HL-LHC project covers the upgrade of the LHC, aiming at collecting an integrated luminosity of 3000 fb-1 equal to a 10-fold increase of the nominal LHC performance. Approved in 2016 for a 950 MCHF budget, the project is shaped by 19 work-packages, covering all expertise areas, from beam dynamics to technical infrastructures. A truly international effort is deployed, where 38 institutes collaborate to supply key technologies, equipment, and manpower. Compensating overcost with saving and descoping, Budget-at-completion has been limited within ~10%. The Make or Buy plan drives procurement, ensuring optimal and timely acquisition conditions through transparency, equality, and competitiveness in accordance with CERN Procurement Rules. Differently from US DoE projects, HL-LHC features no risk contingency, whilst being a technology driver, hence exposed to non-negligible intrinsic risk. Risks are catalogued and followed up, aiming at building resilience, supporting decision making, and applying appropriate cost and schedule risk mitigation measures. The paper describes the methods used in cost, procurement, and risk management, as well as the evolution and challenges in these areas.
The generation of high--brightness electron beams is a crucial area of particle accelerator research and development. Photocathodes which offer high levels of quantum efficiency when illuminated at visible wavelengths are attractive as the drive laser technology is greatly simplified. The higher laser power levels available at longer wavelengths create headroom allowing use of manipulation techniques to optimise the longitudinal and transverse* beam profiles, and so minimise electron beam emittance.
An example of this are bi-alkali photocathodes which offer quantum efficiency ~ 10% under illumination at 532 nm. Another solution is the use of modified photoemissive surfaces. Caesium has a low workfunction and readily photoemits when illuminated at green wavelengths (~532nm). Caesium oxide has an even lower workfunction and emits at red wavelengths (~635nm).
We present data on our work to create a hybrid copper photocathode surface modified by implantation of caesium ions, measuring the surface roughness and probing its structure using MEIS. We measure the energy spread of photoemitted electrons, the QE as a function of illumination wavelength, and the practicality of this surface as a photocathode by assessing its lifetime on exposure to oxygen.
Novel particle accelerators based on plasma technology allow a drastic reduction in size, due to the high accelerating field established inside plasmas, which are created and confined by specific devices. Plasma Wakefield Acceleration experiments are performed at the SPARC_LAB test facility (Laboratori Nazionali di Frascati - INFN) by using gas-filled capillaries, in which the plasma formation is achieved by ionizing hydrogen gas through high voltage pulses.
In this work, the characterization of gas-filled plasma-discharge capillaries is presented. Several geometrical configurations are tested, including capillaries with different channel shapes and arrangement of inlets positions for the gas injection. Such configurations are designed in order to enhance the uniformity of the plasma density distribution along the plasma channel, which is necessary to improve particle beam acceleration. Plasma sources are characterized by means of the spectroscopic technique based on the Stark broadening method, which allows to measure the evolution of the plasma density profile along the channel. In addition, the CFD software OpenFoam is used to simulate the dynamics of the neutral gas during the filling of the capillary.
LCLSII 1-MeV CW electron source was successfully commissioned 2018-2020. 100MeV injector system is being commissioned since summer 2022. CW RF operations for injector system is routinely established and e-beam is being ramped to very high rate. Ultra-low emittance has been achieved for desired charges. Dark current along the injector beam line is systematically characterized and mitigations are placed. We will present operational experience for CW RF gun/buncher and high rate (up to 1MHz) e-beam operations. 100MeV injector beam performance including ultra-low emittance and bunch length for desired charges, and dark current measurement and mitigation will be discussed.
The Offline 2 mass separator laboratory is part of the CERN-ISOLDE Offline facilities - a suite of installations required to perform essential quality control on target and ion source units before irradiation at CERN-ISOLDE. The facility is also used for offline studies as a prerequisite before conducting any beam development on-line, especially establishing systematic effects. The Offline 2 separator resembles the online CERN-ISOLDE Frontend and employs identical services such as beam instrumentation, gas system, laser ionization and the equipment control system. The facility is able to generate dc as well as bunched non-radioactive beams up to an energy of 60 keV. The ion beams can be cooled and bunched in an unmodulated RFQ. In order to study effects of the RFQ buffer gas on the formation of molecular species, a dedicated identification setup is required.
This work presents the current status of the commissioning of RFQ and results of its first operation. Furthermore, we show the first results of beam emittance measurements, which are compared to 3D beam dynamic simulations. We present the ongoing installation of a Magnetof ion and Wien filter behind the RFQ, respectively.
Recent demonstrations of terahertz (THz) powered accelerators and beam manipulators have opened a pathway towards miniaturized accelerators that promise to enable new science due to unique features such as reduced timing-jitter and reduced space-charge broadening of the electron bunches. Here, we present on the development of a matchbox sized multi-layered accelerator structure powered by a single few-cycle terahertz pulse and designed to boost the output of a 55 keV DC electron gun to energies up to ~ 400 keV. An integrated actuated mirror is used to interfere the transversely injected THz pulse with itself, creating a transient standing wave optimized for efficient acceleration of the electrons. In contrast to a double-side-pumped approach this reduces the complexity of the optical setup by using the available THz energy more efficiently. We demonstrate first acceleration and map out the booster performance by varying the injection timing of the electrons and fine-tuning of the transient THz standing wave. Such a table-top source is promising for ultrafast electron diffraction experiments as well as precursor for subsequent acceleration to MeV energy by THz-driven LINACs.
In the frame of ongoing initiatives for the design of a new generation of synchrotron-based accelerators for cancer therapy with ion beams, an analysis of linac designs has been started, to address a critical element with strong impact on performance and cost of the accelerator. The goal is to identify alternatives at lower cost and similar or possibly smaller footprint than the standard 217 MHz injector presently used in all carbon therapy facilities in Europe. As an additional feature, a new linac design can be tailored to produce radioisotopes for treatment and diagnostics in parallel with operation as synchrotron injector.
In this paper is analysed the attractive option of moving to 352 MHz frequency, to profit of reliable mechanical designs already developed for protons and of the cost savings that can be obtained using as RF power sources klystrons with a much lower cost per Watt than tubes or solid-state units.
The paper will present a Quasi-Alvarez Drift Tube Linac (DTL) version of an injector linac for carbon ions at q/m=1/3 and compare it with recently developed DTL and IH designs. The option of a separated-IH type linac will be also discussed, together with a standard IH design at 352 MHz. Finally, a DTL design at 352 MHz for injection of fully stripped helium ions into the synchrotron will be presented.
The electron source is a critical component of the RUEDI (Relativistic Ultrafast Electron Diffraction & Imaging) facility, which needs to provide beam to match the re-quirements for performing both electron microscopy and ultrafast electron diffraction. To meet these demands, different operational modes are needed, to deliver ultra-short, ultra-bright and highly temporally and energy stable electron pulses with a charge varying from 0.2 pC to 20 pC and a kinetic energy of 4 MeV, with a repetition rate with 100 Hz (and higher). The dark charge produced by the electron source should be minimised to avoid significant noise in the image. Analysis of existing elec-tron sources suggested that the optimal solution is a normal-conducting S-band RF photocathode gun operat-ing with a metal photocathode, illuminated by an ultravi-olet laser. A number of critical design decisions were identified to reduce gun dark charge which are discussed in this paper. These include the gun RF design (number of cells and type of coupling), beam generation scheme (that includes the type of the photocathode), reducing duration of RF drive pulse and methods of maintaining good RF field stability.
Laser wakefield acceleration (LWFA) using metal targets has been developed for high-vacuum and high-repetition rate operations compare to the gas targets[1-2]. However, the ionization effect due to high intensity fs laser should be considered as propagating through the plasma and the difference of LWFA mechanisms between aluminum plasma and helium plasma has been investigated with the simulation. The partially ionized aluminum ions are ionized to higher charge state up to Al11+ as the main laser is propagating through the metallic plasma. As comparing to helium plasma case, a lot of electrons are injected into the wake cavity even at lower laser power and the energy of accelerated electrons are decreased. By increasing the plasma density, the charge and the oscillating amplitude of injected electrons can be optimized for betatron radiation.
We proposed a structured metal target using a thin Ti or Cu wire in aluminum to improve the beam quality. The aluminum plasma with a thin Ti or Cu plasma zone can be produced by laser ablation. When changing the focal position of fs laser pulse with respect to the position of the thin-layered zone, the injection timing of electrons depleted from Ti or Cu ions can be adjusted. We present and discuss the simulation results depending on the thickness and the position of the thin layer.
During the last run, the CLARA accelerator ran with a 2.5 cell 10 Hz S-band RF gun which had a modified back plate to allow the use of INFN-style photocathode pucks. Previously this gun had used a solid wall back plate that also acted as the photocathode*.
This presentation describes the different photocathodes that were used during the run and the various methods employed to prepare them for use. An initial cathode which was based on a solid Mo puck with the thin film of Cu grown using magnetron sputtering was seen to give high initial QE but a very fast degradation rate. Subsequent cathodes were hybrids with a Mo body and a solid copper tip for the active area. Several cathodes prepared using alternative techniques were employed, giving varied initial QE and lifetime. The final cathode used had satisfactory QE and a long enough lifetime to deliver a six month period of beam exploitation for external facility users.
Surface nanostructuring is a promising approach when it comes to improving the quantum efficiency (QE) of materials for electron accelerator purposes at CERN. This is due to the plasmonic effect taking place in metallic materials at the nanoscale, when an electromagnetic wave interacts with a sub-wavelength feature. Ultrafast laser surface nanopatterning can be an efficient and times saving method for producing such nanostructures. We conducted a study of nanostructuring of copper surfaces with a deep-UV femtosecond laser. A wide range of fabrication parameters (speed, laser fluence and repetition rate) were tested. At different energy regimes we were able to produce Laser Induced Periodic Surface Structures (LIPSS), as well as spherical nanoparticles of tunable size and other types of periodic nanoscale features. Sub-wavelength periodic structures yield higher exaltation of surface plasmons under matching excitation wavelength, resulting in a potentially significant increase in QE of copper photocathodes. Moreover, by using the same laser source for nanomachining and photoemission, one can easily integrate the technology in and existing photoinjector.
Alkali antimonide photocathodes are promising candidates for many high-brightness electron sources due to their low-emittance and high quantum efficiency. However, these materials require ultra-high vacuum (UHV) storage and transport to avoid oxidation, which affects their performance. In this proceeding, we report the synthesis of cesium antimonide cathodes with different stoichiometric ratios. These cathodes are compared in terms of photoemission properties (QE and spectral response) and crystalline structure. The results show that the change in the stoichiometry of the cesium antimonide leads not only to a different spectral response but also demonstrate that cathodes with a lower ratio Cs:Sb are highly resistant to oxygen which makes them great candidates for applications where UHV conditions are not obtainable.
The so-called “green photocathodes”, based on alkali antimonide compounds, are characterized by high efficiency at green light wavelengths (1-10% at 500-550 nm) and excellent charge lifetime, but are easily poisoned in poor vacuum and are usually grown in form of disordered polycrystalline layers. Surface disorder is an extrinsic factor significantly contributing to reduce the transverse beam brightness at the photocathode. State-of-the art deposition techniques have been successfully employed to create smooth and ordered alkali antimonides; for example, epitaxial Cs3Sb photocathodes have been grown by electron diffraction monitored molecular beam epitaxy.* By focusing on structure rather than efficiency, we discovered that atomically smooth films of CsSb can be reproducibly grown on selected substrates. While the quantum efficiency at 505 nm is significantly lower than the Cs3Sb counterpart, this material is still a visible light photocathode (with QE~0.5-1% at 405 nm) and appears to be more robust against contamination. We report a detailed characterization of this phase via x-ray and UV photoemission spectroscopy, angle resolved photoemission spectroscopy and scanning tunneling microscopy.
Abstract: Electron Cyclotron Resonance Accelerator (eCRA) simulation results are presented for realistic TE111 cavity geometry and finite space-charge beams that confirm the single-particle idealized solutions. The simulations include cavity openings for RF inputs, beam injection, and pumping; RF input couplings that maximize efficiency; a thin window for exit of the accelerated beam; realistic magnetic field profiles; finite diameter multi-Ampere beams. One simulated example is for a copper cavity with Q0 of about 19,000, with RF input power at each port of 12.5 MW, an 8.0-A, 100 keV beam was found to be accelerated to 2.2 MeV, for a pulsed beam power of 17.6 MW at an efficiency of 67%. A wide variety of applications can be envisioned for MW-class eCRA beams with energies in the range 1-10 MeV. Our first proof-of-principle demonstration of eCRA is to provide beams to generate intense X-ray fluxes to enable the replacement of radioactive sources now widely used for sterilization of medical supplies and foodstuffs. This demonstration will be based on use of available S-band components, although the optimal operating frequency for eCRA could be about 1000 MHz. In any case, the possibility of MW-level average power eCRA beams—even with predicted efficiencies >80%--will depend upon the availability of the required RF sources to drive eCRA.
Dielectric wakefield acceleration (DWA) is a promising approach to particle acceleration, offering high gradients and compact sizes. However, beam instabilities can limit its effectiveness. In this work, we present the result of a DWA design that uses alternating gradients to counteract quadrupole-mode induced instabilities in the drive beam. Through simulation and experimental results, we show that this approach is effective at suppressing beam breakup, allowing for longer accelerating structures.
We have designed and fabricated a new apparatus for positioning the DWA components in our setup. This allows us to precisely and independently control the gap in both transverse dimensions and consequently the strength of the destabilizing fields.
Our results show that the use of alternating gradient structures in DWA can significantly improve its performance, offering a promising path forward for high-gradient particle acceleration.
A planned experiment at the Argonne Wakefield Accelerator (AWA) facility will demonstrate the plasma photocathode concept, wherein precise laser-based ionization of neutral gas within the wakefield driven by a relativistic particle beam generates a high brightness witness beam, which is accelerated in the wakefield. Replacing the plasma wakefield acceleration component with a dielectric wakefield acceleration scheme can simplify experimental realization by relaxing requirements on synchronization and alignment at the expense of accelerating gradient. However, this places rigorous constraints on drive beam dynamics, specifically charge, size, and relative separation. This paper presents progress on the design of such a hybrid scheme, including improved simulations accounting for anticipated beam properties and revised structure characteristics.
The Japan Atomic Energy Agency (JAEA) is designing a 30 MW continuous wave (cw) superconducting proton linear accelerator (linac) for the Accelerator Driven Subcritical System (ADS) proposal. The JAEA-ADS linac's source must provide a proton beam over 20 mA with an energy of 35 keV and a normalized rms emittance of less than 0.1 π mm mrad. As the extraction system determines the beam properties and quality, systematic optimizations in the geometry and input values of the extraction system design were conducted using the AXCEL-INP 2-D simulation program to satisfy the goal requirements. This work describes the extraction system design and reports the beam dynamics results of the first study for the proton source of the JAEA-ADS linac.
Structure-based wakefield acceleration with nanosecond-long RF pulses is a promising advanced accelerator concept to mitigate the risks of RF breakdown. Advanced structures are required to satisfy the need of a high transient gradient with a short pulse length. A metamaterial (MTM) structure, as a subwavelength periodic structure exhibiting a negative group velocity, could have a higher shunt impedance, thus a higher gradient, compared to structures with the same but positive group velocities. An X-band ‘wagon wheel’ structure has been designed and tested as an accelerating structure for two-beam acceleration. Up to 200 MV/m of gradient has been achieved with an input power extracted from the 65 MeV drive beam at AWA, with a peak power of 115 MW, and a pulse length of 6 ns (FWHM). Evidence has been found towards a new accelerating regime, the breakdown insensitive accelerating regime (BIAR), where breakdown was only observed in the secondary pulse of the transmitted RF signal while the primary pulse (useful for acceleration) was not interrupted. This experiment could lead to high-gradient wakefield acceleration and new knowledge in the breakdown physics in the short-pulse regime.
Accelerators operating in the mm-wave regime can reach much higher gradients than conventional accelerators due to the favorable scaling of the breakdown threshold with frequency. These structures also have the potential to achieve a much higher shunt impedance, enabling the efficient use of RF power that is critical given the current limitations on high power RF sources in this regime. We report on the design, fabrication, and testing of a 95 GHz linac. Simulations predict this π-mode standing wave accelerator composed of 16 cells will produce an energy gain of 3 MeV for an input power of 1 MW. We report on cold test results characterizing the fabricated prototype, as well as techniques for tuning the cavities. We discuss the outlook for beam tests of this mm-wave accelerator utilizing a field emission gun and injector, as well as extending this approach to higher beam energies.
The High Intensity and Energy ISOLDE facility (HIE-ISOLDE) at CERN has unprecedentedly expanded the research capabilities to investigate the structure of the atomic nucleus and the nuclear interaction. In this context, to meet the high-resolution mass spectroscopy required by the HIE-ISOLDE physics program, an innovative spectrometer is currently being designed, the ISOLDE Superconducting Recoil Separator (ISRS). The ISRS is based on a compact storage ring formed of iron-free superconducting multifunction Canted-Cosine-Theta (CCT) magnets. In this contribution, we report on the current status of the ISRS design, paying special attention to its optics configuration and beam dynamics aspects.
The generation of electron sources by high gradient laser wakefield acceleration (LWFA) has already demonstrated its feasibility. This acceleration technique is on the way to be implemented for practical uses by well-defined user communities. However, obtaining the required outstanding high-quality beams is a difficult challenge. Several key parameters, such as the laser distribution (including intensity, waist, and shape) and plasma profile (including max density, length, and composition), must be selected carefully to control the final electron beam properties and generate a high-quality electron beam (200 MeV, > 100 pC, 1$\mu$m, 1%) via a localized ionization injection scheme. We will present results of particle-in-cell simulations carried out to investigate the role of the plasma and laser characteristics in reducing the energy spread and the emittance while increasing the electron beam charge and energy. We search to have appropriate Twiss parameters to enable beam transport to users, as well as determine the best configuration for the EARLI project, a LWFA expected as an electron injector for the AWAKE experiment.
Chopper systems are typically used to provide beam time structure and ensure the safety of accelerator operations by deflecting the beam away. The reliability of conventional chopper is entirely based on high-voltage (HV) pulsed power supplies, and when it fails to charge the electrostatic deflection plate, the beam cannot be cut off and will enters the downstream accelerator. To meet the strict beam stopping time requirements of the China Initiative Accelerator Driven System (CiADS), improvements in safety are necessary. To address this issue, a novel E × B chopper has been physically designed, which is based on a permanent magnet and an electrostatic deflection plate. This design ensures the safety of the accelerator while providing the necessary pulse waveform. The device is small and highly reliable, making it suitable for use in most accelerators. The device is small and highly reliable, making it suitable for use in most accelerators. Moreover, beam dynamics simulations of the chopper have been conducted to determine its influence on beam quality, and beam cutting capability analysis has been performed.
This poster will describe the design of the photocathode plug for CARIE. Photocathodes are used to produce beams for a variety of accelerator applications, including colliders, UED, and FELs. Thin film semiconductors offer ways to increase QE, reduce MTE, and increase beam brightness, but are very sensitive to chemical contamination and have never been tested under high gradients or successfully integrated into a high gradient injector. LANL is developing CARIE, which will serve as a high gradient photocathode test stand, and will consist of a cryo-cooled high gradient injector with beam diagnostics, capable of testing a variety of photocathodes. In order both to change photocathodes and transfer the photocathodes under UHV conditions, we are designing a metallic photocathode plug. The plug will interface with both the injector and the photocathode deposition system and has strenuous requirements from both. We describe the design of the photocathode plug for CARIE. We will discuss electrical and mechanical compatibility considerations, as well as surface and material properties that could enhance photocathode performance. We will also show preliminary experimental performance of photocathodes grown on these plugs.
A novel 704.4 MHz CH structure is under develop-ment. Due to its relatively small spatial dimensions (22 cm in diameter and 33.7 cm in length), the additive manufacturing (AM) technology is an attractive choice for the construction. For a proof of concept, a simplified model with one stem, one drift tube, and a small part of another stem was printed with copper. This structure was also foreseen for CW operation, so the design of the water-cooling channels inside the drift tubes and stems have been optimized and checked by the Ansys simulation. The progress with the realization of the 704.4 MHz CH structure will be presented.
We have been developing a backside laser-heated thermionic electron gun with a tripolar tube structure for a compact electron accelerator driven neutron source. A lanthanum hexaboride (LaB6) emitter is heated by irradiating a near-infrared laser light transported by an optical fiber to the back of it in this electron gun even though there was no heater wire. The LaB6 electron source with a diameter of 8 mm is heated by irradiating near-infrared light with a wavelength of 980 nm at 127.6 W. As a demonstration of the electron gun, a high voltage of -5 kV was applied to the cathode and a pulsed voltage of 200 V to a grid electrode. As a result, we successfully generated an electron beam up to 6.45 mA. This demonstration was the world’s first operation of a cathode-back laser-heated triode thermal electron gun as far as we can tell. In order to increase the beam current, the electron gun is being upgraded by improving the cathode holding structure and introducing a precise laser alignment system. The latest results of this research will be presented at the conference.
Spin is one of the intrinsic properties of particles. However, there are many incomprehensible problems about it. High energy polarized electron-ion collisions will provide unprecedented conditions for the study of spin physics and lead us to the study on the inner structure of matter and fundamental laws of interactions, and other forefronts of natural science. As the Phase II of the HIAF (High Intensity heavy ion Accelerator Facility) project, Electron-Ion Collider in China (EicC)* is under conceptual design phase. The production, acceleration and collision of polarized ions and electrons are essential for EicC accelerator facility. Therefore, R&D work such as key technologies prototyping has already been initiated. A spin polarized ion source for the production of intense proton and deuterium ion beams with high polarization is under development at the Institute of Modern Physics (IMP). Polarization is one of the key characteristics for polarized ion beams. To make the polarization measurement more precise, faster and more convenient, a polarimeter based on nuclear spin filter (SFP for short) is under design, which measures the polarization directly behind the ion source. Scheme of the SFP will be presented, the measurement process, simulations for crucial physical questions and design of theSFP will be discussed.
Polarized beam is an effective tool in basic research. An Electron-ion collider in China (EicC)*, as a future high energy nuclear physics project, has been proposed. Eicc can provide good research conditions for precision measurements of the partonic structure of nucleon or nuclei and the study on the interactions between nucleons and so on. High quality polarized beam is helpful to the accurate measurement of the relevant experiment date. Polarized proton and deuterium (H&D) beam source is one of the key technologies for EicC. Based on the atomic beam polarized ion source (ABPIS) scheme, a polarized H&D ion source with polarization more than 0.8 and beam current more than 1mA is under construction at the Institute of Modern Physics (IMP), providing theoretical and technical support for the design and construction of Eicc polarized source. In the ABPIS, the separating magnet ensures the electron polarization and the effective transmission of the atomic beam; the radiofrequency transition(RFT) unit ensures that the electronic polarization is converted into deserved nuclear polarization. In order to generate high intensity and high polarization H&D atomic beam, these assemblies need to be precisely designed and optimized. In the paper, an effective method for obtaining the optimal sextupole separating magnet structure will be described in detail; the numerical simulation of the method of adiabatic passage, the design and testing of the RFT units will also be discussed.
Solid-state plasma wakefield acceleration might be an alternative to accelerate particles with ultra-high accelerating gradients, in the order of TV/m.
In addition, due to their thermodynamic properties, 2D carbon-based materials, such as graphene layers and/or carbon nanotubes (CNT) are good candidates to be used as the media to sustain such ultra-high gradients. In particular, due to their cylindrical symmetry, multi-nm-aperture targets, made of CNT bundles or arrays may facilitate particle channelling through the crystalline structure.
In this work, a two-bunch, driver-and-witness configuration is proposed to demonstrate the potential to achieve particle acceleration as the bunches propagate along a CNT-array structure.
Particle-in-cell simulations have been performed using the VSIM code in a 2D Cartesian geometry to study the acceleration of the second (witness) bunch caused by the wakefield driven by the first (driver) bunch.
The effective plasma-density approach was adopted to estimate the wakefield wavelength, which was used to identify the ideal separation between the two bunches, aiming to optimize the witness-bunch acceleration and focusing.
Simulation results show the high acceleration gradient obtained, and the energy transfer from the driver to the witness bunch.
Following the successful Run 1 experiment, AWAKE has developed a program for Run2 that requires designing and implementing a compact electron source (150 MeV, >= 100 pC) for external injection. The baseline design uses a S- and X-band RF photo-injector gun system. The project EARLI investigates the feasibility of an alternative electron source system using a laser wakefield accelerator (LWFA) to produce this electron bunch. Currently, the EARLI project is in the design phase backed by the preparation of experimental demonstrations to prove the feasibility of this accelerator. The main originality of the chosen approach is that the focus is made exclusively on the final beam-targeted characteristics and the reliability and repeatability of the beam quality. EARLI is a stand-alone injector that consists of three main parts: a laser system, a plasma cell and a transfer line, at the end of which the electron beam is injected in a plasma wave driven by a self-modulated proton bunch. Methods from conventional accelerators are applied to LWFA physics. Each part requires specific expertise, that must be investigated in close coupling with the others. A massive campaign of simulations and optimizations with PIC codes is ongoing while the design of the transfer line, the plasma chamber, diagnostics and the laser are carried out in parallel.
High temperature superconductor REBCO has the property of maintain a high critical current density under strong external magnetic field, which makes a promising material for electromagnets in cyclotron and ECR ion source. Therefore, an ECR ion source using iron-less REBCO coils as electromagnet is under development in Research Center for Nuclear Physics (RCNP), Osaka University. A coil system with 3 circular solenoid coils and 6 racetrack sextupole coils was fabricated, and low-temperature performance tests in 77 K were carried out. The test results upon the stability and capability of magnet field inducing will be presented in this work. The design of the ion source will also be discussed. Results yielded in this research will also be made the best use of the development of a skeleton cyclotron, a compact air-core cyclotron being developed in RCNP, which is also planned to use REBCO coils as electromagnets.
Several concepts for future linear colliders are dependent on very high gradient normal conducting RF cavities achieved by operation at cryogenic temperatures in order to reduce breakdown rates (BDR). These maximum fields are intended to be in excess of 200 MV/m. The concepts include the ultra compact Xray free electron laser and the C$^3$ collider. The theory involved with the complex physics of breakdown is a diverse and rich field of study. Most results are empirical so continued understanding of the phenomena becomes necessary. One contributing factor to the reduced BDR is the increased hardness at cryogenic temperatures of the copper. in order to test that assumption we can consider obtaining hardness improvements from the alloying of copper with silver. We will here present a preliminary theory of this alloy based improvement especially with respect to an improved understanding of the surface resistivity using our previously established theory improvements which go beyond the usual Reuter and Sondheimer explanation. We will compare this to quality factors measured in Cband pillbox cavities as a function of temperature.
Plasma accelerators can sustain accelerating gradients of up to ~100 GeV/m.
However, reaching the high energies required for future particle colliders requires the acceleration to be performed in multiple plasma stages.
Solving the challenges posed by multistage acceleration, such a beam quality preservation, requires the capability of simulating large chains of accelerating stages, something that is typically limited by the high cost of full 3D particle-in-cell codes.
Thus, there is a growing need for the development of more efficient models that allow for inexpensive collider studies with reduced physics or dimensionality.
Here, we present the implementation of a novel gridless quasistatic algorithm in the Wake-T code that, coupled with a laser envelope solver, allows for accurate and efficient simulations of multistage laser-plasma accelerators with axial symmetry, a critical step toward their realization.
Laser-generated terahertz frequency pulses have been used to manipulate the phase-space of electron beams at the CLARA test facility.
Acceleration gradients of 20 MeV.m$^{-1}$ were achieved in dielectric lined waveguides with narrow-band 400 GHz sources with MW peak powers, and with bunch charge from 2pC to 100pC.
The high-frequency of the acceleration field provided an extremely fast temporal variation of the acceleration gradient, up to 50 MeV.m$^{-1}$.ps$^{-1}$.
With this temporal gradient we have demonstrated the de-chirping of near-compressed 100fs duration electron bunches, obtaining a seven-fold reduction in energy spread. Similarly, we can impose chirp for THz-driven compression. Staged interactions with independent timing (phase) control of two THz pulses interacting with an single electron beam has been undertaken.
THz phase scans and projected energy spread measurement has provided an energy-time phase-space diagnostic for the electron bunch, while examination of the energy gain as a function of phase and interaction location (timing) within the sub-mm waveguide acts as a diagnostic of the acceleration structure.
Progress towards application of these THz acceleration concepts for THz-driven compression and active synchronisation of higher-energy electron beams, for hybrid THz- and laser-plasma acceleration experiments will be discussed.
Recently, RadiaBeam has designed, manufactured, high power tested and delivered a robust production ready S-Band thermionic RF gun with optimized electromagnetic performance, improved thermal engineering and robust yet precise cathode mounting technique. This gun will facilitate performance improvements of existing and future light sources, industrial accelerators, and electron beam driven terahertz sources. Unlike conventional electrically or side-coupled RF guns, this new gun operates on pi-mode, with a help of magnetic coupling holes. This new iteration of thermionic electron gun was redesigned for cost efficiency without sacrificing performance. Thermal simulations, mechanical engineering, manufacturing and high power testing results will be presented.
EuPRAXIA is the first European project that develops a dedicated particle accelerator research infrastructure based on novel plasma acceleration concepts and laser technology. It focuses on the development of electron accelerators and underlying technologies, their user communities, and the exploitation of existing accelerator infrastructures in Europe. It was accepted onto the ESFRI roadmap for strategically important research infrastructures in June 2021 as a European priority.
To fully exploit the potential of this breakthrough facility, advances are urgently required in plasma and laser R&D, studies into facility design and optimization, along a coordinated push for novel applications. EuPRAXIA-DN is a new MSCA Doctoral Network for a cohort of 12 Fellows between universities, research centers and industry that will carry out an interdisciplinary and cross-sector plasma accelerator research and training program for this new research infrastructure. This contribution gives an overview of this interdisciplinary network and its research.
In the high gradient rf photoinjectors, dark current is the “unwanted beam” not produced by the cathode drive laser. It is a part of field emission from the cavity and photocathode, which is accelerated through the gun. Dark current can cause beam loss, increase the risk of damage to accelerator components, and create additional background for beam users. Furthermore, during operation of the ELBE srf gun, the dark current has been found to correlate with the photocathode QE and life time. Therefore, understanding the sources as well as the dynamics of dark current is crucial to machine safety and gun quality.
In this paper we present our experimental investigations of the dark current at the ELBE SRF gun-II. The beam dynamics of the dark current is studied with the ASTRA code, which helps us to track the field electrons starting from the cathode area and from other sources, so that we can understand their different contributions to the dark current.
D-Pace has a self-heated hot-cathode Penning ion source test stand at their Ion Source Test Facility (ISTF). High-charge state production of boron, arsenic, and phosphorous is interesting to the ion implantation industry, as it allows for higher energy implants of these dopants using the same accelerating gradient in a given accelerator system. We use Neon and Krypton as proxy gases to investigate whether the Penning ion source could be used for high-charge state production in ion implanters. We were able to produce charge states up to Ne$^{3+}$ ($>$ 200 $e \mu$A) and Kr$^{6+}$ ($>$ 7 $e \mu$A). The obstacles in using the current Penning ion source test stand are discussed, with comments on how to potentially increase the current output, stability, and lifetime of this ion source.
The Japan Atomic Energy Agency (JAEA) has been proposing an accelerator-driven system (ADS) as a future nuclear system to efficiently reduce high-level radioactive waste generated in nuclear power plants. As a first step toward the full-scale design of the CW proton linac for the JAEA-ADS, we are now prototyping a low-beta (around 0.2) single-spoke cavity. The actual cavity fabrication started in 2020. Most of the cavity parts were shaped in fiscal year 2020 by press-forming and machining. In 2021, we started welding the shaped cavity parts together. By preliminarily investigating the optimum welding conditions using mock-up test pieces, each cavity part was joined with a smooth welding bead. So far, we have fabricated the body section and the beam port section of the cavity. By measuring the resonant frequency of the temporarily assembled cavity, we have confirmed that there is no significant problem with the cavity fabrication. In this paper, fabrication progress of the prototype spoke cavity is presented.
The 3.2 GeV electron stretcher facility ELSA at the University of Bonn provides electron beams for fundamental research in hadron, detector and medical physics. The beam is extracted from a storage ring, whose injector consists of a 26 MeV linear accelerator and a 1.2 GeV booster synchrotron. The advent of functional plasma-based electron injectors in the MeV energy range raise the opportunity to replace the conventional Linac, which currently delivers electron pulses of up to 16 nC at a repetition rate of 50 Hz.
We conduct a feasibility study of using a plasma based injector for the booster synchrotron. For this, we improve the diagnostic capabilities of the Linac transfer beamline and the injector synchrotron to obtain and verify its acceptance parameters which are to be matched to beam properties from contemporary operated laser plasma accelerator setups. Possible plasma-based facility operating modes are evaluated.
As an option for the proton driver for the next generation spallation neutron source (ISIS-II) at the Rutherford Appleton Laboratory (RAL), a Fixed Field Alternating Gradient Accelerator (FFA) is being considered. A prototype accelerator has been designed, referred to as FETS-FFA, to demonstrate flexible handling of beam repetition for users and high intensity operation with minimum beam loss. FETS-FFA takes the 3 MeV beams from RAL's Front End Test Stand (FETS) linac and accelerates them to 12 MeV. FD spiral optics have been adopted as the basic focusing structure, which allows the operating point to be chosen along the diagonal in tune space. Flexible beam repetition will be demonstrated by RF beam stacking at the extraction energy, which enables users to choose different (lower) repetition rates independent of the acceleration cycle. For high intensity beam study, several schemes of injection painting are being considered. At the injection energy, the space charge tune shift can be easily exceed -0.3. This paper discusses the overall design, while further details of each aspect of the accelerator, including hardware, are presented in separate conference papers.
This article presents a study on the H11(0) end cell of an IH-DTL prototype for accelerating carbon ion beams from 5 to 5.5 MeV/u, which is designed for a hadron therapy linac injector. The voltage across the first and last gap in a drift tube linac tends to drop from a typical uniform voltage distribution along the inner cells. In the case of an IH cavity, the power cost to supply the necessary RF energy in this region is affected by the dimensions of the end cell and gap, as well as the girder undercut. The end cells were modeled in CST Microwave Studio for an appropriate power loss optimization of the most relevant dimensions. The same model also introduced dipole correction based on slanted faces, and transverse fields were analyzed.
The high-intensity, polarized electron source is a critical component for the electron-ion collider which requires a polarized electron gun with higher voltage and higher bunch charge compared to any existing polarized electron source. At Brookhaven National Laboratory, we have built and successfully conditioned the inverted HVDC photoemission gun up to 350 kV. We report on the performance of GaAs photocathode to generate 70 µA average current and up to 16 nC bunch charge with a long lifetime using a circularly polarized laser at 780 nm wavelength. We discuss the Distributed Bragg Reflector GaAs/GaAsP Super Lattice photocathode performance in the DC gun and the anode bias and voltage impact on the lifetime. The gun also integrated a cathode cooling system for potential application on high-current electron sources. The various novel features are implemented and demonstrated in this polarized HVDC.
Novel accelerator concepts such as all-optical terahertz (THz) based compact accelerators demand high-power THz sources that are robust in order to enable reliable testing. THz sources based on the tilted-pulse front scheme have become the method of choice for table-top, high-energy, single-cycle (SC) THz generation due to both their versatility and scalability. However, due to the noncollinear interaction geometry, fine-tuning of the performance and tailoring of the THz beam properties requires a detailed understanding of the dependences on the setup parameters. Here, we present on the use of multi-dimensional parameter scans to systematically map out sensitivities of such THz sources on the primary interaction parameters and show experimental characterization of a robust, high-energy, single-cycle THz source designed and constructed based on these findings. This setup delivers pulses centered at 300 GHz with pulse energies exceeding 400 µJ at 52 Hz repetition rate and a shot-to-shot rms stability < 3.8%. Such robust, high-energy THz sources are crucial for the development of next generation THz-driven particle accelerators and manipulators.
The C-band electron gun is an attractive option for lower emittance with compactness. In this paper, a new C-band photocathode gun has been developed. The electron gun experienced a high-power test and had preliminary reached the designed gradient on the cathode. The high-power test results are the basis of the beam dynamics design and beam testing.
Charged particles moving through a carbon nanotube may be used to excite electromagnetic modes in the electron gas produced in the cylindrical graphene shell that makes up a nanotube wall. This effect has recently been proposed as a potential novel method of short-wavelength-high-gradient particle acceleration. In this contribution, the existing theory based on a linearised hydrodynamic model for a localised point-charge propagating in a single wall nanotube (SWNT) is reviewed. In this model, the electron gas is treated as a plasma with additional contributions to the fluid momentum equation from specific solid-state properties of the gas. The governing set of differential equations is formed by the continuity and momentum equations for the involved species. These equations are then coupled by Maxwell’s equations. The differential equation system is solved applying a modified Fourier-Bessel transform. An analysis has been realised to determine the plasma modes able to excite a longitudinal electrical wakefield component in the SWNT to accelerate test charges. Numerical results are obtained showing the influence of the damping factor, the velocity of the driver, the nanotube radius, and the particle position on the excited wakefields. A discussion is presented on the suitability and possible limitations of using this method for modelling CNT-based particle acceleration.
Insertion devices may be also very detrimental for the dynamic aperture of storage rings, since they introduce linear and higher order perturbations on the optics of synchrotrons. It is essential to study these effects to adjust the lattice to compensate for these terms when possible (high order multipole magnets are present in the lattice of the machine), or optimize the design of the IDs to minimize the higher order effects. We applied our analysis to SLS~2.0, the upgrade of the presently running Swiss Light Source (SLS) facility at Paul Scherrer Institut. In particular, we compared the results using an approach based on the calculation of the multipoles computed on the beam reference trajectory and on the kick map calculation.
Many experiments in biomedicine, security imaging, and condensed matter physics require high brilliance and moderate electron beams. The properties of the photo electron source is defined by the photocathode quality such as low thermal emittance, fast response time, high quantum efficiency (QE) and the photocathodes’ robustness.
Metal cathodes are commonly used in RF Guns because they work robustly and tolerate poor vacuum compared to semiconductor photocathodes. However, metal cathodes only provide low quantum efficiencies in UV range and the most prerequisite for improving the QE is to produce an atomically clean surface. At ELBE, a successfully established process for improving the QE of Mg is laser cleaning [1]. Although this method improves the QE, a non-uniform surface and potential damage of the Mg photocathode arise at the same time. Ideally, an alternative process producing an atomically clean, smooth, and damage-free surface is desired.
In this work, we evaluate and discuss the effect of different surface cleanings, including hydrogen ion cleaning and thermal surface cleaning under UHV conditions, on the QE of Mg photocathodes, with the help of in-situ X-ray photoelectron spectroscopy (XPS).
References
[1] Teichert, J. et al. Successful user operation of the superconducting radio-frequency photo electron gun with Mg cathodes at ELBE. Phys. Rev. Accel. Beams 24, 1–30 (2021).
As the intensity and power quest continue to increase in several physics experiments, collective effects become more limiting, and curing them becomes more involved. Therefore, an accurate description of the machine components is required to investigate such effects. In this work, we present an impedance model for the Fermilab Recycler Ring. We quantify the impedance of several elements in the ring and benchmark our results with experimental data.
MedAustron is a synchrotron-based ion cancer therapy facility located in Austria. Patients are treated with proton and carbon ion beams in an energy range of 62-252 MeV and 120-402 MeV/u, respectively. The facility features three clinical irradiation rooms, among which horizontal and vertical beam lines as well as a proton gantry are available for treatment. A fourth irradiation room is dedicated to non-clinical research. In 2021, a development project started, which aims at commissioning helium ion ($\mathrm{^{4}He^{2+}}$) beam up to the non-clinical irradiation room. A first major milestone was reached by completing the commissioning of helium in the ECR ion source branch, the LEBT and the LINAC section, where the beam is accelerated up to 7 MeV/u. In this work we discuss the challenges and main results achieved during the injector commissioning (i.e. emittance, intensity and transmission efficiency). Furthermore, recent outcomes from the injection of $\mathrm{^{4}He^{2+}}$ beam into the synchrotron as well as acceleration and extraction results are presented.
The High-Luminosity LHC (HL-LHC) project at CERN aims at doubling the beam intensity and the brightness. To achieve this unprecedented performance, the LHC injectors were upgraded during the Long Shutdown 2 (2019-2021) to overcome limitations such as space charge and beam instabilities. Despite these upgrades, the reduction of beam loss on the flat bottom in the Super Proton Synchrotron (SPS) to reach the target beam parameters remains a challenge, avoiding unnecessary activation. Losses are due to several factors: uncaptured beam in the SPS due to the bunch rotation in the Proton Synchrotron (PS) prior to the transfer, large transient beam loading during multiple SPS injections, and transverse tails reaching aperture limitations. Investigations were conducted with HL-LHC beam parameters, aiming at disentangling the different sources of losses and defining specific observables. Finally, refining the optimal beam parameters for improved transfer between PS and SPS is the objective of the study, as well as the possible need for new hardware such as an additional RF system for beam stability and capture or a dedicated collimation system.
The Fermilab 750keV injector sends 25mA H- beam for 30µs at a rep-rate of 15Hz. The beam transmission through the FNAL injector is currently less than 50% from the ion source to the entrance of the drift tube linac. Recently it was uncovered that the primary loss point is within the region prior to the RFQ which houses the solenoid focal elements that match the beam to the RFQ. With recent diagnostic measurements the beam profile was able to be obtained in the LEBT and began to shed light on beam size with the use of a scraper paddle. We will discuss beam emittance measurement in the LEBT and a mitigation plan to improve the transmission efficiency.
The muonium is the bound state of the positive muon and the electron. The muoium can be ionized using a dedicated laser to produce the ultra-slow muon beam. It is one idea that the dense electrons may be used as a substitute of the ionization laser for the muonium. The preliminary study is reported for the ionization of the muonium using the electron.
The IOTA Proton Injector (IPI), currently under installation at the Fermilab Accelerator Science and Technology facility, is a beamline capable of delivering 20-mA pulses of protons at 2.5 MeV to the Integrable Optics Test Accelerator (IOTA) ring. First beam in the IPI beamline is anticipated in 2023, when it will operate alongside the existing electron injector beamline to facilitate further fundamental physics research and continued development of novel accelerator technologies in the IOTA ring. This report details the expected operational profile, known challenges, and the current state of installation.
The ‘Laser-hybrid Accelerator for Radiobiological Applications’, LhARA*, facility is conceived to study the biological response to ionising radiation, specifically focussing upon the co-called ‘FLASH’ (>40 Gy/min) regime. A high repetition laser, directed at a thin target, will generate high intensity, ultra-short, particle bunches, at up to 15 MeV/u (and subsequent acceleration up to 127 MeV/u, as required). These particles will be guided to one of several end-stations, whereby the effects can be studied via in-vitro or in-vivo experiments using newly developed detectors, existing phantoms, and test samples.
The laser driven ion source and capture systems are key technologies for LhARA. We will discuss ongoing R&D into delivery of a laser driven ion source with the required beam parameters, stability and repetition rate. Following the idea originally outlined by Gabor**, the current plan and status of using large volume, high-density, low-temperature, non-neutral plasmas as beam optics within the capture system will also be presented.
Electron Cyclotron Resonance Ion Sources (ECRIS) are commonly used as injectors in many accelerator laboratories and industries and therefore, pushing its limit towards very high charge state and intense ions for nuclear and elementary particle physics and low charge state ions for surface treatments & medical purposes. For these applications, several models of ECRIS were designed and developed by PANTECHNIK.
This article presents a short description of the latest ECR ion source models delivered to the clients along with their typical beam intensities of low and high charge states of various elements.
A focus will be made on our latest Supernanogan source (14.5GHz) which has just been installed at INSP, France. We will present improvements of highly charged ion production as a function of time and the efficiency of the new gas injection design.
A CeB6 thermionic gun is presently operating for the X-ray free-electron laser (XFEL) facility SACLA. The gun emits high-intensity stable electron beams with a low-emittance of 0.6 µm, however, the emission lifetime of CeB6 cathode was unexpectedly limited to only one year or less at the SACLA injector. Recently, it was predicted by a particle tracking simulation and measurements that a cause of the short lifetime was bombardment of high-energy electrons which were accelerated backward at the injector linac. The CeB6 gun tank was modified to detach the horizontal cathode position from the beam axis of injector in order to avoid the back-bombardment. By these attempts, the cathode lifetime was significantly prolonged and the XFEL operation became stable more than ever. In this conference, beam simulation and measurements of the backward-accelerated electrons and apparatus modification to improve the CeB6 cathode lifetime will be presented.
We propose a linear accelerator concept for a Next Generation Nuclear Physics Accelerator Facility - a versatile User Facility with a wide variety and high availability of its instruments and beam time.
The concept is based on the simultaneous acceleration of light and heavy ion primary beams. It improves the utilization of the superconducting driver-accelerator capabilities and allows for the simultaneous and complementary rare isotope production in two different targets, namely a thin target for fragmentation of accelerated heavy ion beams, and a thick spallation target for an isotope separation on-line (ISOL) system driven by light ion beams. This approach supports the multi-user operation of the facility, and enables other research driven by light ion beams.
The concept is presented as an upgrade of the Facility for Rare Isotope Beams (FRIB, MSU) with a 60-MV compact room-temperature continuous-wave light ion injector. The funneling of the light and heavy ion beams as well as their distribution to production targets is discussed.
A facility for the collision of muons offers a unique path to a compact lepton collider with an energy reach in the multi-TeV regime, well beyond the possibilities of conventional electron accelerators. However, due to the short lifetime of muons, the constraints for acceleration and collisions are very different. An extremely fast energy increase in combination with intense and ultra-short bunches is essential for a high muon survival rate and luminosity. A chain of rapid cycling synchrotrons (RCS) for acceleration from around 60 GeV to several TeV is proposed by the International Muon Collider Collaboration. We study the longitudinal beam dynamics and radio-frequency (RF) requirements for these RCSs with respect to induced voltages from intensity effects. A high synchrotron tune due to the large RF voltages is a particular challenge. We present simulation results of the longitudinal bunch distribution to determine the number of RF stations distributed over the RCS to mitigate that large tune. The impact of the induced voltages from short-range wakefields and single- as well as multi-turn beam loading is analyzed, for both fundamental and higher-order modes.
The FAST Injector at Fermilab has been the focus of a number of recent experimental efforts as 1) the driver of a novel FEL experiment, 2) as the injector for IOTA, and 3) as a test-bed for novel machine learning algorithms to reconstruct phase space measurements. Here we present our recent work to simulate the FAST injector and perform realistic comparisons of simulated beam distributions to measured beam distributions using a multi-slit emittance diagnostic. We also present studies on using laser pulse stacking to shape the beam distribution for creating optimal current distributions for FEL experiments.
The high-energy upgrade of the Linac Coherent Light Source II (LCLS-II-HE) will extend the X-ray energy range up to 20 keV. The goal is to produce low emittance (0.1 mm∙mrad) electron bunches (100 pC/bunch) and accelerate 30 μA beams through the superconducting linac to 8 GeV. A low-frequency superconducting radio-frequency photo-injector (SRF-PI) will be a key aspect of the upgrade. An SRF-PI cryomodule with a 185.7 MHz Quarter-Wave Resonator (QWR) for operation at a cath-ode field of 30 MV/m and a cathode system compatible with high quantum efficiency photo-cathodes operating at 55-80 K or 300 K are currently being developed. We report on the design and fabrication status of the SRF-PI cryomodule and cathode system for LCLS-II-HE.
The photon flux resulting from a high energy electron beam's interaction with a target, such as in the upcoming FACET-II experiments at SLAC National Accelerator Laboratory, should yield, through its spectral and angular characteristics, information about the electron beam's underlying dynamics at the interaction point.
This project utilizes data from simulated plasma wakefield acceleration-derived betatron radiation experiments and high-field laser-electron-based radiation production to determine which methods could most reliably reconstruct these key properties. The data from these two cases provide a large range of photon energies; this variation of photon characteristics increases confidence in each analysis method. This work aims to compare several reconstruction methods and determine which best predicts original energy distributions based on simulated spectra.
Fourth generation light sources require high brightness electron beams. To achieve this a cathode with a high quantum efficiency and low intrinsic emittance is required while also being robust with a long lifetime and low dark current. Alkali-metal photocathodes have the potential to fulfil these requirements and, as such, are an important area of research for the accelerator physics community.
A Cs-Te photocathode grown at STFC Daresbury Laboratory is presented. Important photoemissive properties such as quantum efficiency (QE), mean transverse energy (MTE) and lifetime have been investigated using the Transverse Energy Spread Spectrometer (TESS). Elevated MTE beyond the Cs$_2$Te photoemission threshold is reported as well the QE decrease and MTE increase when a Cs-Te photocathode is subject to progressive oxygen degradation.
The photocathodes used as electron sources in high-performance electron accelerators today are largely one of only a handful of materials. While there has been an increased understanding of the properties of the electron beams produced by these cathodes, there has been little change in the overall selection of materials used at accelerator facilities. In fact, nearly all of the photocathodes in use today originated in the photomultiplier tube or night vision goggle industries, where efforts were aimed at discovering new materials by employing trial-and-error based iterative experimental approaches.
Our work in the field of photocathode discovery was initially directed towards improving the brightness of electron beams used in FELs and was the first data-driven approach to screening for high brightness photocathode materials. Through screening over 74,000 semiconducting materials, a list of novel candidate materials was generated. Our current work is focused on two other areas of interest for photocathodes: very high average current photocathodes and spin-polarized electrons. We will apply active learning techniques to reduce the amount of computationally expensive calculations that need to be performed in order to discover more new materials for photocathodes.
Hollow-core dielectric Electromagnetic Band Gap (EBG) microstructures powered by lasers represent a new and promising area of accelerator research since, thanks to the short optical wavelength and to the dielectric's high damage threshold greater accelerating gradients, with respect to the metallic counterparts, can be achieved.
In this paper, we present MeV-scale beam-dynamics simulations and fabrication results relative to a silicon, woodpile-based travelling-wave structure operating at the wavelength 𝜆0 = 5 μm. The simulated CST and HFSS electric field has been evaluated and used as input for a space charge tracking code, in order to perform beam-dynamics evaluations on the beam injection and extraction into the proposed structure as well as the evolution of the main beam parameters.
We also report on the fabrication of first Si prototypes of the woodpile structure that are obtained by the innovative Two Photon Polymerization fabrication process. This technique allows to reach resolutions down to hundreds of nanometers, offering the possibility to print Si-rich structures, or woodpile skeletons to be infiltrated with Si by CVD technique.
The electromagnetic Particle-In-Cell (PIC) code WarpX has been developed by the U.S. Department of Energy’s Exascale Computing Project, in collaboration with international partners, toward the modeling of plasma accelerators on Exascale Supercomputers. We will give an overview of the code and its latest features, such as collision and QED physics modules. We will also report on the latest algorithmic advances that enable full PIC modeling of plasma accelerators with higher efficiency, including a time-averaged pseudo-spectral PIC solver that enables larger timesteps, a hybrid nodal-staggered PIC loop that provides improved stability, an algorithm to handle particles crossing Perfectly Matched Layers, application of mesh refinement to the modeling of ion motion in a plasma accelerator. All presented features are fully CPU and GPU (Nvidia/AMD/Intel) capable and run to full-scale on the world’s largest supercomputers. The status, examples of applications and future developments will be discussed.
High-quality electron beams are critical for generation of
intense X-ray pulses from free electron lasers. It was proposed
that complex thin films and heterostructures with semiconductor
photoemissive layers may be used in photocathodes to produce
electron beams with better quality. New developments in material
science allow designing alkali-antimonide photocathodes with
specific coatings that could significantly increase their
lifetime while not markedly degrading their quantum efficiency
(QE). Moreover, results from recent experiments demonstrated that
QE can be increased by optical interference absorption effects in
layered materials. Modeling of these complex photocathode
material designs is needed to predict and optimize their electron
emission properties. We apply recently developed extended moments
and thin film models to evaluate quantum efficiency and intrinsic
emittance from thin film cesium-telluride and alkali-antimonide
semiconductor photocathodes grown on different substrates. We
will discuss simulation results and suggest possible ways to
optimize electron emission properties from these thin films
photocathodes.
Time-varying fluctuations of the intensity sharing between the islands and the core of the beam extracted via the CERN Proton Synchrotron (PS) Multi-Turn Extraction are the main effects that require manual adjustment for this beam type. To mitigate this, the application of an online controller is explored to further enhance both operational autonomy of the accelerator and physics performance. In this contribution a proof of concept implementation of a multi-objective extremum seeking algorithm is presented. The tuning of the PS parameters, the proper choice of the hyperparameters of the algorithm and the achievements reached during the beam studies are summarised.
Unprecedented electron beam brightness can potentially be achieved by exploiting high gradients in cryo-cooled RF cavities functionalized with high QE semiconductor photocathode materials. However, strong electric fields and thermal stresses from associated emission currents could potentially affect material stability, leading to breakdown events which may shorten device lifetime or degrade performance. To ensure robust performance and long operational lifetimes, the underlying processes leading to microstructural evolution in such semiconductor photocathodes needs to be explored under strong fields. Here, we present a suite of multiscale modeling tools specially tailored to probe the electro-thermo-mechanical behavior of semiconductor photocathodes. We first parameterize a machine learning interatomic potential suitable for classical charge equilibration molecular dynamics (MD) using density functional theory (DFT) calculations of CsTe. DFT and MD informed material properties are further incorporated into a meso-scale finite element (FE) model to predict morphological evolution of cathode surfaces under fields and thermal stresses due to emission currents.
A new, high-efficiency source of a Muonium beam will be useful for fundamental muon measurements, sensitive searches for symmetry violation, and precision tests of theory. In the PIP-II era, Fermilab has the potential to provide the world's highest-intensity Muonium beam, by a considerable margin. Moreover, with the advent of a muon beam at Fermilab's existing 400 MeV linac, the necessary R&D for such a Muonium facility can begin soon, well before PIP-II is operational.
The physics reach of such a facility includes: a) search for Muonium/anti-Muonium conversion (complimenting the Mu2E and MEG experiments); b) precision measurements of the Muonium atomic spectrum (with no hadronic or finite-size effects, and much longer lifetime than positronium); and c) the study of antimatter gravity (>99% of the Muonium mass is in the anti-muon).
State-of-the-art spin-polarized photo-electron sources use GaAs-based photocathodes to provide electron beams with high degrees of spin-polarization. Such photo-guns are required to operate with both quantum efficiency and cathode lifetime as high as possible in order to meet the requirements of high-current applications such as energy-recovery linacs and colliders. Both quantum efficiency and lifetime are determined by the quality of the thin surface layer, typically consisting of Cs in combination with an oxidant, required for GaAs photocathodes to achieve negative electron affinity. This layer is applied during a so-called activation process. It is therefore of great interest to optimize and standardize this procedure in order to provide the best possible conditions for reliable photo-gun operation.
This contribution presents the analysis of bulk-GaAs activations using Cs and O conducted at the Photo-CATCH test stand. The effects of Cs and O partial pressures on final quantum efficiency and lifetime, as well as the duration of the activation process were scrutinized in order to find an optimal partial pressure ratio at a reasonable duration of the procedure.
A new project, NEWGAIN (NEW GAnil Injector), is under development at GANIL, and aims to build a second injector for heavier beams with A/q up to 7, as an extension of the SPIRAL2 accelerator. With this upgrade, SPIRAL2 will provide high intensity beams, from proton to uranium, thus increasing GANIL international competitiveness both in fundamental science and associated applications.
This paper presents the layout and describes the main technical components of the new injector, based on 2 ECR ion sources (one of them existing), two LEBT, one RFQ and a MEBT section to transport the beam into the present MEBT connected to the LINAC.
Electron beams serve many important roles from free electron lasers to medical imaging. Every time beam brightness is improved, a wide variety of fields take another step forward. Nanopatterned field emission cathodes serve as an excellent opportunity to continue to push the envelope on extreme high brightness beams. Their fabrication is thus of crucial importance to this objective. In the past KOH wet etching was performed to create two atomically sharp ridges. This is done by leveraging the selectivity of KOH to etch along a single plane in the silicon crystal. This process is generally used in micro-machining to create a whole array of atomically sharp ridges and cannot be used to produce less than 2. By adopting a different nanofabrication process, a single ridge can be isolated. Additionally, more flexible nanofabrication techniques can be employed to create novel arrangements of blades, such as concentric rings of ridges.
Development of advanced intense and reliable sources of charged particle beams is a direction within accelerator physics on its own right. By changing the temperature of Lithium Tantalate (LiTaO3) single crystal at moderate vacuum conditions leads to generation of strong electric field. The uncompensated polarization during the heating or cooling of the crystal causes the ejection of electrons from the dielectric layer on the surface of the crystal. The electrons ejected either from the crystal or from the target (depending on polarity) are accelerated and gain energy of up to a 100 keV. The energy of these electrons can be determined by measuring the energy spectrum of the X rays that resulted from the electron interactions with the target. The conception of a pyroelectric accelerator enabled us to develop compact (portable) electron source, which does not require an external high-voltage and the use of hazardous materials.
It is experimentally confirmed that a crystal installed in a chamber with a residual gas pressure of about 2 mTorr could be used to generate electrons with energy of up to 35 keV. The correlation between monoenergetic electron production and avalanche discharge is discussed. By using double crystal, the combined fields of two polarized crystals will enable us to double the acceleration potential.
Dielectric-lined waveguides have been extensively studied to potentially support high-gradient acceleration in beam-driven dielectric wakefield acceleration (DWFA) and beam manipulations. In this paper, we investigate the beam dynamics in the alternating-symmetry slab-based dielectric wakefield accelerator proposed and discussed in Ref.[1]. We use the first principle electromagnetic ``macroscopic" solver available in fine-difference time-domain particle-in-cell program WarpX.
This work is focused on the anomalous skin effect in copper and how it affects the efficiency of copper-cavities in the temperature range 40-50 K. The quality factor Q of three coaxial cavities was measured over the temperature range from 10 K to room temperature in the experiment. The three coaxial cavities have the same structure, but different lengths, which correspond to resonant frequencies: around 100 MHz, 220 MHz and 340 MHz. Furthermore, the effects of copper-plating and additional baking in the vacuum oven on the quality factor Q are studied in the experiment.
A “geometric model” based on a spherical Fermi - surface and using the equivalent skin layer model is presented in the paper to calculate the surface resistance which is relevant for the RF power losses in the cavity walls. Finally, Cavity cooling process about the pulsed heat transport from the surface into the bulk copper is simulated.
The motivation is to check the feasibility of an efficient, pulsed, ion linac, operated at cryogenic temperatures.
Protection of free-electron sources has been technically challenging due to lack of materials that transmit electrons while preventing corrosive gas molecules. Two-dimensional (2D) materials uniquely possess both of required properties. Here, we report three orders of magnitude increase in operation pressure and factor of two to four enhancement in the lifetime of high quantum efficiency (QE) bialkali photocathodes (cesium potassium antimonide (CsK2Sb)) by protecting them with graphene. The photoelectrons were extracted through the graphene protection layer in a reflection mode, and we achieved QE of ~0.14 % at ~3.4 eV, 1/e lifetime of 188 hours during operation, and no decrease of QE during operation at pressure of as high as ~1×10-3 Pa. In comparison, the QE decreased drastically at 10-6 Pa for bare, non-protected CsK2Sb photocathodes and their 1/e lifetime during operation was ~48 hours. We attributed the improvements to the gas impermeability and photoelectron transparency of graphene.
This poster will report the progress on optical optimization of Cs2Te photocathodes using simulations and preliminary experimental results. Thin film semiconductor photocathodes are often used in high brightness electron sources. These sources are particularly bright when the cathodes are operated “near threshold”, i.e., with a laser energy close to the sum of the band gap and electron affinity. However, doing so results in very low quantum efficiency, in part due to inefficient light absorption. Most photocathodes that use visible or IR lasers (e.g., alkali antimonides, GaAs, etc.) benefit from optically optimizing the substrate to take advantage of optical interferences. This improves light absorption in the photoemissive thin film to enhance quantum efficiency (QE) and brightness. For example, QE enhancement of over 4x has been shown for Cs3Sb cathodes near threshold. Cs2Te is a commonly used UV photocathode that is more robust than the alkali antimonides and is also a candidate photocathode for the new CARIE injector at LANL. We describe simulations and preliminary experimental data showing optical enhancement of Cs2Te photocathodes. We also describe how the techniques for optically optimizing Cs2Te and other UV photocathodes differs from similar techniques for photocathodes that use visible or IR light, considering, in particular, the lack of reflective materials and the reduced variation in optical constants.
The MYRRHA project (Multi-purpose hYbrid Re-search Reactor for High-tech Applications) is a planned accelerator-driven system (ADS) that will be realised at Mol in Belgium and will demonstrate the feasibility of transmutation of radioactive waste on an industrial scale.
The planned accelerator, which is to provide the 600 MeV proton beam, consists of a normal-conducting 17 MeV injector that supplies a superconducting LINAC. In addition to a 4-rod RFQ and two QWR rebunch-ers, 17 CH structures are planned in the injector, 15 of which will be used for acceleration and 2 as rebunchers. Now that the construction of the first two CH structures has been completed and they have been tested with per-formance, the next cavities are being prepared for con-struction.
Since the next cavities are operated with more power than CH1 and CH2 due to the higher gap voltages re-quired, the cooling of the stems plays a decisive role for reliable operation due to the required cw operation. For this purpose, an insert was developed in several iterative steps that significantly lowers the maximum temperature on the stems.
As part of the EuPRAXIA project[1], the objective of the PALLAS project is to produce an electron beam at 200 MeV, 30 pC with less than 5% energy spread and lower than 2μm normalised emittance using the IJCLAB-LaseriX laser driver at 10 Hz, 1.5 J and 35 fs. Based on available publications[2,3], we propose a two-chamber gas plasma target with a dopant localised in the first chamber. We then perform on-bench calibrated compressible simulations with the code OpenFOAM to predict the density profile. The result is then used as input for two massive random scans and a Bayesian optimisation with SMILEI fast Particle-in-Cell (PIC) simulation varying four input parameters: focal position, laser intensity, dopant concentration and inlet pressure. We further investigate the stability of the optimal working points. The massive amount of PIC results is left as open-source data for further investigation by the scientific community. Such a process can serve as the basis for any input parameters optimisation of a laser-plasma electron source target.
MeV-ultrafast electron diffraction (MeV-UED) has enabled broad scientific opportunities for the studies of structural dynamics, ultrafast chemical processes and coupling of electronic and atomic motions in a variety of gas, liquid and solid state systems. The growing demand of future scientific needs calls for relativistic electron probes with ultra-short bunch length(10 fs) and ultra-low normalized emittance(2 nm). A high brightness, low emittance electron source is required for this purpose. Here, we present optimization studies on a 2.86 GHz S-band RF gun for MeV-UED applications. Gun modeling, beam dynamics simulations and multi-objective genetic algorithm (MOGA) optimizations will be described. Performance with different cell lengths, gun phases and pulse charges will be presented.
Particle-in-cell simulation plays an important role in optimization of today’s plasma-based acceleration research and experiments. Due to many variables involved, the computational cost is usually very high, especially when the experiment includes several different beams, e.g., the AWAKE experiment. AWAKE Run2 uses the proton bunch to drive plasma wakefield and accelerate electron bunch in 10 m plasma. AWAKE50 experiment accelerates electron bunch to about 50 GeV for searching dark photons and other phenomena beyond the standard model. We have successfully applied the forward and inverse neural network models in the simulation of AWAKE Run2 (4 variables and 6 objectives) and AWAKE50 (9 variables and 6 objectives) experiment, which can replace computationally expensive simulation software for the optimization. Our study shows that the forward neural network provides a more efficient way to find optimal solution by Bayesian optimization algorithm. On the other hand, with an inverse neural network, it is possible to find suitable variable settings according to the desired targets. In the models we trained, the coefficients of determination (R2) of both types of models reaches > 0.90 and most of which are > 0.95. In addition, for reducing the computational cost of training dataset, we have successfully trained a forward neural network using the dataset of 10 m to 60 m accelerated distance to predict the parameters of electron bunch at 80 m, the averaged R2 value reaches 0.95.
The problem of standing wave formation by superposing two counter-propagating whistler waves in
an overdense plasma, studied recently by Sano et al (2019 Phys. Rev. E 100, 053 205 and 2020 Phys. Rev.
E 101, 013 206), has been revisited in the relativistic limit. A detailed theory along with simulation has
been performed to study the standing wave formation in the interaction of two counter propagating
relativistically intense whistler waves. The relativistic theory explains such interaction process more
precisely and predicts correct field amplitudes of the standing wave for a much wider range of physical
parameters of the problem as compared to its non-relativistic counterpart. The analytical results are
compared with 1-D Particle-in-Cell (PIC) simulation results, performed using OSIRIS 4.0. The results
are of relevance to ion acceleration to high energy and heating.
2022 has been a performance consolidation year for the Low Energy Ion Ring (LEIR) at CERN that demonstrated its capability of delivering the target beam parameters required for high luminosity production in the LHC in a reproducible and reliable way. The main steps that have led to the high performance reach of this beam, together with the machine stability improvements deployed, are detailed in this paper.
INFN LASA photocathode lab develops and produces films that are used in high brightness photoinjectors. Besides the long-time and still on-going experience on Cs2Te, recently we have restarted an activity on alkali-antimonide films, sensitive to visible light, exploring the possibility of their stable operation in CW machine. We report in this paper the recent results obtained both on the advancements on cesium telluride and on the characterization of alkali antimonide.
As accelerators and electron microscopes become more advancement, high-performance photocathodes are required. In particular, CsK2Sb photocathode is of interest because of its low emittance, excitability in visible light, and high quantum efficiency (QE). On the other hand, it has drawbacks such as weak structure, limited operating vacuum pressure, and short lifetime with time or charge. To resolve these issues, it is necessary to understand the molecular structure of the cathode and its degradation mechanism. In this study, we transported CsK2Sb photocathode to a beamline of synchrotron radiation facility using a vacuum transport system for surface analysis. Specifically, the cathode was deposited at the evaporation system at Nagoya University. We transported it to Aichi Synchrotron Radiation Center (Aichi SR) away from 15 km, and analyzed it in the depth direction by X-ray photoelectron spectroscopy (XPS) at BL7U. Based on the results, we quantitatively evaluated the composition ratios and stoichiometry of the cathode element (Sb, K, Cs). A Cs excess state was observed at the surface, and it is consistent with previous studies. It was observed that K was first desorbed among the three elements of cathode with sputtering. The cause is considered that weakest binding energy of K.
To generate high-current B+ ion beams for ion implantation, a hybrid ion source that combines electron cyclotron resonance and thermal surface ionization, which is called a high-temperature surface microwave source (HSMS), is under development. A high-temperature hot surface (2000℃) and microwave heating are the essential components of an HSMS to produce high-energy electrons for the B+ generation. A helical tungsten filament will be used in the HSMS source to obtain a high temperature and provide an axial configuration with a magnetic field of approximately 875 Gs for the 2.45-GHz electron cyclotron resonance. The mixing ionization of high-temperature surface ionization and ECR ionization is a very complex ionization process. To understand the influence of the two ionization modes on plasma, this paper proposes a plasma model to simulate the mixing processes of the two ionizations. The effects of high-temperature surface ionization and ECR ionization were separately evaluated. The magnetic field configuration, microwave power, and air pressure have been studied through this plasma model.
Particle beams with highly asymmetric emittance ratios are employed at accelerator facilities and are expected at the interaction point of high energy colliders. These asymmetric beams can be used to drive high gradient wakefields in plasmas. In plasma, the high aspect ratio of the drive beam can create a transversely elliptical blowout cavity and the asymmetry in the ion column creates asymmetric focusing in the two transverse planes. The ellipticity of the blowout depends on the ellipticity and normalized charge density of the beam. Simulations are performed to investigate the ellipticity of the wakefield based on the initial driver beam parameters and the corresponding beam transport is discussed.
Plasma-based accelerators enable compact acceleration of beams to high energy and are being explored as a potential technology for future linear colliders. Conventional linear colliders require damping rings to generate the required beam emittance for particle physics applications. We present and discuss a plasma-based linear radiation damping system that allows cooling of ultrashort bunches compatible with plasma-based accelerators. The plasma accelerating gradients enable relatively compact linear damping systems, and there is a trade-off between system length and the achievable emittance reduction. Final asymptotic normalized transverse beam emittance is shown to be independent of beam energy. The impact of coherent radiation emission is considered.
We study ultrafast laser surface nanopatterning as an alternative to improve the photo-emissive properties of metallic photocathodes. By tailoring the physical dimensions of these surface nanostructures, one can localize the optical field intensity and exploit plasmonic effects occurring in such nanostructures. As a result, this surface nanopatterning technique can become a great tool for improving metallic photocathodes photoemission behavior enabling their use for next generation high brightness electron sources. Our goal is to investigate such surface-plasmon assisted photoemission processes with a view on simplifying the photocathode production at CERN while extending the lifetime of existing photoinjectors. The performance of two different femtosecond laser nanopatterned plasmonic photocathodes was analyzed by measuring the quantum yield with a 65kV DC electron gun utilizing 266nm laser excitation generated by a nanosecond laser with 5ns pulse duration and 10Hz repetition rate. By comparing the electron emission of the copper surface nanostructured areas with that of a flat area, our results suggest quantum yield enhancements of up to 5 times.
The new C-Band RF gun, developed in the context of the European I.FAST project has been realized. It is a 2.5 cell standing wave cavity with a four port mode launcher, designed to operate with short rf pulses (300 ns) and cathode peak field larger than 160 MV/m. In the paper we present the realization procedure and the results of the vacuum and low power RF test. The gun is now ready for the high power test that will be performed at PSI, Switzerland.
At its restart after a major shutdown in 2029, the LHC will see its interaction regions upgraded by the installation of the HL-LHC equipment, with new Nb3Sn triplets and cold powering system, crab-cavities for crossing angle compensation and luminosity levelling, an upgraded collimation system, and fully remote alignment for the final focusing region. In the following operational runs, the LHC will aim at a tenfold increase of the integrated luminosity compared to the original design.
The HL-LHC project features a light project management (PM) structure, with strong delegation of PM tasks to the 19 work-packages structuring the project by expertise areas. Unified processes align the community around a common configuration and performance, while shared tools are applied to budget and schedule management . The paper describes committees and processes applied to run this complex project, within the overall organization and planning of CERN. We explain the procedures ruling decisions and change management in configuration, cost and schedule, detail the responsibility share between project and work-packages and explain how quality standards build a common language across the project.
In accordance with the program of NSC KIPT Subcritical Neutron Source physical start up that was approved by State Nuclear Regulator the basic measurement method of reactivity and keff is an area ratio measuring method. In the method, the neutron response of the SCA on the electron beam pulse is measuring. For on-line monitoring of the system reactivity the neutron flux to beam current ratio method was accepted. For brief estimation of the system reactivity and estimation of the critical rate of core loading the one over N method is used.
The neutron flux measurement system of NSC KIPT Subcritical Neutron Source is used CFUF34, CFUF54 detector set (6 over graphite reflector inside ADS tank) and CFUF28 (3 outside the core).
In the paper, the reactivity and keff measuring methodology and measurement results are presented.
The Radio Frequency Quadrupole (RFQ) for the High-Intensity Photon Injector (IPHI) project has been designed and manufactured in the early 2000s. It is now operating at CEA Saclay since 2016 and accelerates a 100-mA continuous beam up to 3 MeV. It is a 6-meter-long, 3 segments vane RFQ, with 352.2 MHz operation frequency and non-constant voltage profile. From this RFQ, a lot of experience has been gained and, based on this feedback, other RFQ were designed at CEA, such as the one for SPIRAL2, LINAC4, or ESS, which are now operating. For maintenance purposes and to simulate the changes before we operate them, a new virtual 3D model has been developed. This model is simplified and may have the same RF performances as the existing one. This paper present this new model.
The recent layout of the Jülich High Brilliance Neutron Source (HBS) driver linac is based on short crossbar H-mode (CH) cavities operated at a fixed synchronous phase. In the last decades the computing power for the development of linacs, available to physicists and engineers, has been increased drastically. This also enabled the accelerator community to finally carry out the required R&D to generate further the idea of drift tube linacs with alternating phase focusing (APF) beam dynamics, originally proposed in the 1950s. This focusing method uses the electric fields in between the drift tubes (i.e., gaps) to provide subsequent transverse and longitudinal focusing to the beam along multiple gaps. The beam focusing properties within each gap are adjusted individually by means of the synchronous phase. As a result of the alternating phase focusing method, these linacs can operate completely without internal magnetic lenses. The R&D-program for the high brilliance neutron source HBS offered the opportunity to investigate the APF concept further in order to open this advanced concept for high duty-factor, high intensity hadron beam acceleration. Besides, a prototype APF-interdigital H-mode (IH)-cavity has been designed and is going to be build and tested in the next future.
Accelerators having large electric field gradients are the need of the hour for building future electron or proton colliders. Plasma wakefield accelerators using short electron or proton bunches can solve the problem of achieving large amplitude plasma wake. In PWFA, we have witnessed that, large amplitude wakefields generated by such mechanisms have both transverse and longitudinal components of wake, where longitudinal component of the wake is used to accelerate the bunch particle whereas the transverse component is used to focus the electron or proton bunch. We investigated the role of twisted and two-color laser pulse using FBPIC code in defocussing and electron or proton injection into the counter-propagating ionization front. It may be noted that there is no significant defocussing observed for longer distances by using a twisted and two-color laser pulse.
IAEC/SNRC (Israel) is constructing an accelerator facility, SARAF, for neutron production. It is based on a linac accelerating 5 mA CW deuteron and proton beam up to 40 MeV. As a first phase, IAEC constructed and operated a linac (SARAF Phase I), from which remains an ECR ion source, a Low-Energy Beam Transport (LEBT) line and a 4-rod RFQ. Since 2015, IAEC and CEA (France) are collaborating in the second phase, consisting in manufacturing of the linac. The injector control-system has been recently updated and the Medium Energy Beam Transport (MEBT) line has been installed and integrated to the infrastructure. It has been fully commissioned during the first semester of 2023 for proton and deuteron beams. This paper presents the results of the integration, tests and commissioning of the injector and MEBT.
A relativistic, charged particle bunch propagating in plasma is subject to various instabilities. When the bunch is much longer than the cold plasma skin depth, it is subject to the self-modulation instability (SMI). This instability is routinely observed in the AWAKE experiment with narrow (200microns), long (7cm) proton bunches. Bunches wider than the skin depth are subject to the current filamentation instability (CFI). The proton bunch can be less focused (500microns). With a discharge source***, the plasma density can be quickly varied to cover a wide range of plasma skin depths, from larger to smaller than the wide bunch radius. The interaction could thus potentially cross the threshold for CFI to occur. At the same time, SMI may not occur with wide bunches in high-density plasmas.
We plan on using both time-integrated and time-resolved images of the bunch after plasmas 3.5, 6.5 and 10m-long, to determine the ranges of occurence of these two instabilities. Time-resolved images could evidence in a single event the evolution of CFI from multiple filaments, to coalescence into a single, broader filament. Varying plasma length, bunch charge and the mass of plasma ions (He, Ar, Kr) could yield information about development, growth rate and saturation of the instabilities. Understanding these instabilities is important for advanced accelerator concepts based on self-modulation, and for the generation of magnetic fields and associated radiation in astrophysics.
Different from the high Q value of ferrite cavity, the Q value of magnetic alloy cavity in CSNS RCS is only about 1.25, the frequency band of impedance is wide, and the beam loading effects is strong. Based on the impedance measurement results, the influence of the beam load effects on the longitudinal distribution of the magnetic alloy cavity in CSNS RCS is studied by simulation, and the induced voltage measured on the machine is consistent with it.
We propose a simulation model of the field enhancement and quantum efficiency (QE) increase of metallic surfaces as a result of a surface nanostructuring. In the framework of photoinjector facilities for electron accelerators at CERN, achieving optimal nanostructuring parameters may become a significant asset. The presence of a well-designed periodic surface topography can give rise to plasmonic resonance and coupling effects within the structures, which yields a local increase in electron density and an electric field enhancement. This model is used to provide a deeper insight into these effects. We investigate the dependency of the electron emission enhancement on the nanopattern geometry and incident wavelength on the plasmonic resonance. We examine, based on former experimental results, the performance of Laser Induced Periodic Surface Structures (LIPSS) and other types of periodic nanoscale features, but we also demonstrate the surprisingly strong contribution of nanoparticles in the global field enhancement of the surface. These particles are a common side effect of ultrafast laser surface processing and themselves exhibit unique plasmonic resonance properties.
One of the key aspects to provide on chip acceleration in Dielectric Laser Accelerators (DLA) from tens of keV up to MeV energies is the phase velocity tapering.
This paper presents the simulated performance of sub-relativistic structures, based on tapered slot waveguides. We engineered channel/defect modification in order to obtain a variable phase velocity matched to the increasing velocity of the accelerated particles. Additionally, we present a hollow-core relativistic electromagnetic band gap (EGB) accelerating waveguide. In DLA structures co-propagating schemes are employed for higher efficiency and smaller footprint compared to the cross-propagating schemes. In this respect, we envisage tapered continuous copropagating structures that simultaneously allow wave launching/coupling, beam acceleration, and transverse focusing. The main figures of merit, such as the accelerating gradient, the total energy gain, and the transverse focusing/defocusing forces, are evaluated and used to guide the optimization of the channel/defect modification.
Index terms: Dielectric Laser Accelerators (DLA), Photonic Crystal, Dielectric Waveguides
Plasma wakefield acceleration (PWFA) is a method for accelerating charged particles using large electric fields sustained by plasma waves (up to hundreds of GV m−1) for the accelerating longitudinal fields. In this project, we will evaluate the impact of perturbations on basic particle motion. These perturbations are affected by any number of terms of the equations of motion. The most important perturbations derive from the fact that the particle beams are not quite monochromatic, the finite spread of energies about the nominal energy. We will discuss the hosing which is a transverse instability due to perturbations. The prototypical parameter set was perturbed in several ways. The main goal of this research is to be able to diagnose the parameters of a beam from the spectral and angular distribution of the betatron radiation which encodes information about the beam-plasma interaction.
The Laser Ion Source (LIS) can easily produce high charge state and high intensity ion beams, especially the refractory metallic ion beams, so it is a promising candidate as an ion source for heavy ion cancer therapy facilities and a future accelerator complex, where a pulsed ultra-intense and high-charged heavy ion beam is required. Due to the capability of LIS to produce high-brightness ion beams, single turn and single-pulse injection mode for a synchrotron could be realized. Experimental research activities on laser ion sources had been carried out in many laboratories around the world. However, there are still many physical mechanisms of LIS that need to be studied by simulation.We have systematically studied the influence of different laser parameters on the LIS with simulation.The distribution of electrons and ions was obtained by simulation. The simulation is in general agreement with the results of experiments. The initial distribution of the laser ablation plasma is obtained, which provides parameters for further research.
A program is under way at the Argonne Wakefield Accelerator (AWA) facility, in collaboration with Euclid Techlabs and Northern Illinois University (NIU) to develop a GV/m-scale photocathode gun, with the goal of producing bright electron bunches. The novel X-band (11.7 GHz) photo-gun (Xgun) is powered by high-power, short rf pulses (9 ns), which are generated by the AWA drive beam in a wakefield structure. In the first series of experiments, the Xgun produced ~400 MV/m peak field on the photocathode surface. The Xgun has also shown exceptional robustness, with no noticeable breakdown observed after being fully conditioned. As a first step towards achieving a complete understanding of the Xgun's performance, we aim to investigate the fundamentals of photoemission in the high-gradient regime. Systematic simulations will be presented for the near-future photocathode thermal emittance measurements.
SIS18 will be used as booster for FAIR’s main synchrotron SIS100. In addition, it provides a wide variety of ions from Protons to Uranium for users directly at GSI and FAIR.
An upgrade program to enhance the overall performance for the booster operation has been carried out.
Part of the upgrade program for booster operation was a complete overhaul of the control system including data supply and timing system. In addition, a new magnetic alloy cavities have been installed for h=2 operation and dual harmonic operation in conjunction with the existing H=4 cavities. The main power supplies have been upgraded to allow reduced cycle times. The vacuum system has been significantly enhanced.
Further upgrades and machine studies have been performed to enhance available beam parameters and provide new features for the users.
We will report about machine studies and recent operation for FAIR Phase0 experiments utilizing various upgrade measures to enhance overall machine performance.
The SPS proton fixed target beams are spilled via a third integer resonant extraction, for which high momentum spread is beneficial. To increase the momentum spread prior to the slow extraction, the bunches are stretched at the unstable phase by inverting the sign of the RF voltage. The RF phase is then flipped back, and the voltage is turned off when the bunch distribution is rotated to the maximum momentum spread. The past production scheme additionally relied on uncontrolled longitudinal blow-up of the unstable beam during the acceleration ramp. After the major upgrade of the main RF system and a successful impedance reduction campaign, the spill quality was significantly compromised. This contribution summarizes the efforts to recover, and improve, the spill quality. The use of the fourth harmonic RF system and controlled longitudinal emittance blow-up are used for beam stabilization along the ramp. Moreover, RF counter phasing is applied during the first part of the de-bunching to profit from the cavity impedance reduction of the feedback systems.
FACET-II is a National User Facility at SLAC National Accelerator Laboratory with the goal to develop advanced acceleration and coherent radiation techniques using a 10 GeV electron beam of unprecedented beam intensity with >100 kA peak current and <10 µm spot size, a 10 TW experimental laser system, and a variety of solid, gas and plasma targets. A diverse experimental program will investigate beam-driven plasma wakefield acceleration (PWFA), injection, and control with the aim of demonstrating efficient multi-GeV/m PWFA while preserving emittance and narrow energy spread – as is required to reach the beam parameters for a future linear collider. Complimentary research programs into the application of machine learning for accelerator diagnostics and control, novel techniques for the generation of intense coherent radiation, and probing strong-field quantum electrodynamics (QED) also make use of the facility’s unique beam intensity and laser capabilities. The first year of beam delivery to experiments has focused on user assisted commissioning of beam delivery and experimental systems, including a novel EOS BPM with 10 fs bunch length and 5 µm transverse resolution. This contribution will describe the status of the facility, experimental systems, and novel diagnostics, in addition to reviewing the first scientific developments from User programs including initial progress towards beam-driven PWFA.
To advance in the characterization of photocathodes for high brightness sources, the measurement of the thermal emittance plays a key role. The TRAnsverse Momentun Measurement device developed at INFN LASA will allow equipping our photocathode laboratory with an advance device able gving in quasi on-line feedback during the photocathode growth process.
This paper reports on the status of the apparatus and its latest achievements.
The European Spallation Source (ESS) aims to build and commission a 2 MW proton linac ready for neutron production in 2025. Commissioning of the normal conducting section of the linac is underway and previous papers have reported the performance of the microwave-discharge ion source, Radio Frequency Quadrupole (RFQ) and first Drift Tube Linac (DTL) tank.
This paper describes the recent assembly, installation, testing and commissioning of an additional threee DTL tanks as well as developments of supporting systems such as RF feedback, control system tools and operating procedures.
Heavy ions have been accelerated for the first time by SPIRAL2 in 2022. A fast method to tune the linac cavities has been used (< 1 hour by now, < 10’ in the future) to obtain a 7 MeV/A 18O6+ beam (50 microA CW). Then an automatic Q/M beam change procedure has been successfully used to directly produce a 18O7+ beam. The goal was to demonstrate the possibility to tune a beam even if its intensity is too low (<10 microA) to be seen by phasemeters (BPM) along the linac. The linac transmission was ~ 100% for both beams and, as expected, the measured output energy was the same. The same oxygen reference beam tuning has been also used to obtain 80 microA of 40Ar14+ at 7 MeV/A. Again, the same method has been used to tune the linac cavities at the RFQ output energy beam (0.73 MeV/A, no acceleration). These different methods and the one used to tune the linac output energy are presented.
A crystal-based hybrid e+ source could be a good alternative to conventional sources based on the e- conversion into e+ in a thick target and is currently under consideration for the FCC-ee [1]. In a hybrid source an e- beam crosses a thin oriented crystal with emission of channeling radiation, featuring enhanced photon flux w.r.t. Bremsstrahlung [2]. It results in an increase in the number of e+ produced at the converter target positioned after the crystal. This allows to reduce the converter thickness and decrease the deposited energy and Peak Energy Deposition Density (PEDD) in it. Here we present the optimization of the hybrid source for the FCC-ee case performed via Geant4; a W crystal was selected as radiator and different configurations were considered; with/without collimators or with/without a sweeping magnet between the crystal radiator and the converter target. In all these cases, a huge reduction of PEDD in the converter was shown. The Geant4 model was benchmarked with experimental tests at DESY TB with 6 GeV electrons [3] and CERN PS&SPS with 6 and 20 GeV e-beams. The tests were performed for either the W crystal and other alternative crystals, e.g., diamond or Ir. The simulation tool is now ready for more sophisticated simulation of the full chain of the injection system.
References
[1] I. Chaikovska et al 2022 JINST 17 P05015
[2] R. Chehab, V. Strakhovenko and A. Variola, NIM B 266 (2008) 3868
[3] L. Bandiera et al., Eur. Phys. J. C 82 (2022) 699
The development of compact accelerator facilities providing high-brightness beams is one of the most challenging tasks in the field of next-generation compact and cost affordable particle accelerators. Recent results obtained at SPARC_LAB show evidence of the FEL laser by a compact (3 cm) particle beam plasma accelerator. This work is carried out in the framework of the SPARC_LAB activities concerning the R&D on particle-driven plasma wakefield accelerators for the realization of new compact plasma based facilities i.e EuPRAXIA@SPARC_LAB. The work here presented is a theoretical study demonstrating a possible scheme concerning the implementation of an innovative array of discharge capillaries, operating as active-plasma lenses, and one collimator to build an unconventional transport line for bunches outgoing from plasma accelerating module. Taking advantage of the symmetric and linear focusing provided by an active-plasma lens, the witness is captured and transported along the array without affecting its quality at the exit of the plasma module. At the same time the driver, being over-focused in the same array, can be removed by means of a collimator.
Plasma wakefield acceleration (PWFA) is a burgeoning field, attracting much attention as an option to extend acceleration gradients from the present 100 MeV/m level to the TeV/m level. The effort will be expended to resolve the question of the long-term behaviour of the disturbances left behind in the plasma and the time it takes to reach equilibrium after the wakefield interaction occurs. The present limitations on gradient arise from material electromagnetic breakdown thresholds.
Methods for exploring the beam's longitudinal and transverse phase space qualities have been developed in the context of an increasing worldwide effort. UCLA LAPD laboratory, with its diagnostics, permits the spatio-temporal resolution of electron density, magnetic field, and electro-magnetic signals in the plasma over long-time scales. We aim to explore intense electron beams for wake excitation available at the LAPD, commissioning the SAMURAI photoinjector and its electron beam production.
Online models are becoming increasingly more important for the tuning of particle accelerators. Photo-injectors are especially notorious due to there sometimes finicky nature and the difficulties involved in developing models that are suitable for online use. Surrogate models using artificial neural networks are increasingly popular for this application due to their ability to model nonlinear behavior and their execution speed. In support of photo-injector commissioning we have developed a neural network surrogate model and an associated GUI to deploy this model during operations. Here we present our results on the simulations, surrogate model development, and GUI deployment.
The Advanced Wakefield Experiment (AWAKE) at CERN relies on the seeded Self-Modulation (SM) of a long relativistic proton bunch in plasma, to accelerate an externally injected MeV witness electron bunch to GeV energies.
During AWAKE Run 1 (2016-2018) and Run 2a (2021-2022), two seeding methods were investigated experimentally: relativistic ionization front seeding and electron bunch seeding.
In the first one, a short laser pulse co-propagates with the proton bunch and ionizes the rubidium vapor, generating the plasma.
In the second, a short electron bunch propagates in plasma and drives the seed wakefields.
Both seeding methods will be further employed during AWAKE Run 2b (2023-2024) to study their effect on the SM evolution in presence of a plasma density step.
In this contribution, we will show the main experimental results and discuss their impact for the future design of the experiment, in particular for Run 2c (starting in 2028), where the plasma will be split in two sections: one dedicated to SM of the proton bunch, and the other to the acceleration process.
X-ray free electron lasers (XFEL) and other x-ray producing light sources are large, costly to maintain, and inaccessible due to minimal supply and high demand. In addition, concepts for future electron colliders benefit from cost reduction size is reduced through normal conducting RF cavities are operated at very high gradients. It is advantageous then to consider miniaturizing electron linacs through a variety of means. We intend to increase beam brightness from the photoinjector via high gradient operation (>120 MV/m) and cryogenic temperature operation at the cathode (<77K). To this end, we have fabricated a new 0.5 cell CrYogenic Brightness-Optimized Radiofrequency Gun (CYBGORG). CYBORG serves three functions: a stepping stone to a higher gradient cryogenic photoinjector for an ultra-compact XFEL (UCXFEL); a prototype for infrastructure development useful for concepts such as the Cool Copper Collider (C^3); and a test bed for cathode studies in a heretofore unexplored regime of cryogenic and very high gradient regime relevant for the National Science Foundation Center for Bright Beams. We present here commissioning status of CYBORG and the associated beamline focusing in particular on C-band RF power development and thermal balancing of the gun in the cryogenic environment.
Mega electron volt (MeV) accelerators used for ultrafast electron diffraction (UED) have provided a unique insight into visualizing elusive ultrafast processes from photochemical reactions and lattice motion, to phase transitions occurring in quantum materials. In this work, we demonstrate recent measurements of strong THz streaking of ultrafast electron bunches generated from an rf photoeinjector using an efficient THz deflector structure. We show that the structure can achieve upward of 1.5 MV/cm of peak THz fields to 3 MeV, 10 fC bunches subsequently improving the timing resolution of single-shot measurements of bunch length and jitter. Such measurements are used to obtain a significant improvement in the MeV-UED timing resolution. With this setup, we have measured coherent charge wave oscillations in photo-excited TaS2 thin film within ~50 fs temporal resolution. These results are essential for the development of a THz timing tool toward new regimes of few femtosecond timing resolution.
Worldwide there is a push for producing medical isotopes using particle accelerators rather than fission reactions. Here we report on the operation of a DC-photogun designed for producing Mo-99 in the Lighthouse facility and commissioned by the Institute for Radio Elements (IRE, Belgium).
The gun is based on the successful CBETA design by Cornell University. It is installed at the RI site in Bergisch Gladbach, Germany. As innovative components it contains a photocathode deposition system allowing an automatic transfer of photocathodes into the gun and it uses Novec 4710, a gas developed by 3M as a sustainable replacement for SF6. The injector was installed at the RI site in Bergisch Gladbach, Germany and has produced first e-beam in April 2022. Currently we are ramping up the e-beam power and optimizing the photocathodes.
The high-voltage has been conditioned up to >400kV and we see no negative impact of the NOVEC gas. The laser produces 40W at 515nm and 1.3GHz repetition rate and adjustable pulse length. It can deliver pulse trains of 100ns up to CW with variable pulse power onto the cathode. In the MBE system we routinely prepare photocathodes with at least 5% quantum efficiency, well sufficient for the design current of 40mA.The beam diagnostics is currently used to optimize the electron beam.
The current focus is on ramping up the power to the design value of 40mA at 350kV.
Electron acceleration in solid-state plasmas is of interest within the Laser Wakefield Acceleration (LWFA) research. Layered nanostructures such as graphene nanoribbons can be used as targets for intense UV lasers to generate and accelerate electron bunches. We present numerical Particle in Cell (PIC) simulations of a novel sub-femtosecond self-injection scheme which relies on edge-plasma oscillations in a layered graphene target. The scheme delivers 0.4 fs-long electron bunches of 2.5 pC total charge with an energy gain rate of 4.8 TeV/m. These parameters are unprecedented and, if confirmed experimentally, may have an impact on fundamental femtosecond research.
The “standard” way of a high energy positron beam in proton accelerator-driven systems includes two stages. Firstly, the proton beam is directed on a target material. The protons produce neutral pions that after a short decay they decay to 2 gamma rays. At the second stage, these gammas are producing electron-positron pairs on a high-Z (typically Pb) converter. Magnets between the target and the converter considerably reduces though does not totally eliminate the hadron contamination. We propose to use a tungsten oriented crystal as the gamma converter. Since an electromagnetic shower in such a crystal is accelerated, one can drastically reduce the thickness of the converter preserving nearly the same positron yield compared with the amorphous Pb converter. This will considerably reduce the level of hadron background at the converter exit. Moreover, by adjusting the crystal thickness, one can increase the positron yield in a certain energy range. We demonstrate the simulation results of the new scheme using as an example the production of positrons in the H4 beam line of CERN SPS North Area external beam line carried out with Geant4 simulation toolkit*.
Particle accelerators demand high particle transmission and reduced longitudinal emittance; hence, effective bunching systems are requested. The concept based on an efficient, compact design called “Double Drift Harmonic Buncher - DDHB” fulfills these two requirements for a c.w. or pulsed beam injection into an RFQ, a DTL, or a cyclotron. The proposal is associated with two buncher cavities separated by a drift space and an additional drift at the end of the system for a longitudinal beam focus at the entrance of the next accelerator unit, whose candidates can be one of those mentioned above. The investigations are focused on exploring accurate acceptance rates. To obtain successful and understandable outputs from the DDHB concept, a new multi-particle tracking beam dynamics code called “Bunch Creation from a DC beam - BCDC” has been developed for detailed investigations of space charge effects. It allows to calculate the transformation of intense dc beams into particle bunches in detail with a selectable degree of space charge compensation at every location. This paper presents the results from various investigations with and without space charge effects.
The Extreme Photonics application Centre (EPAC) is a planned UK national facility. The current intention is for EPAC to use a 1 PW 10Hz laser system to drive laser plasma acceleration with output energies ranging from 100 MeV up to, at least, 5 GeV. The initial design for the electron beam transport of the EPAC facility is presented in this paper. This includes some initial considerations on which type of beam line could be used in order to accommodate as many of the different energies as possible. Subsequently, the 1 GeV option is examined in considerable detail. Field errors as well as misalignments for all magnets in the beam line are examined, both individually and together, as well as multipole errors. Finally, a complete layout of the beam line is produced, this includes all diagnostic locations together with the position of a tape system to remove the laser light post-acceleration.
The EIC requires an electron gun to provide a high current high brightness electron beam for EIC cooler. A 550 kV DC gun using alkali antimonide photocathode was designed to generate a 110 mA electron beam , 1 nC with normalized emittance < 1 mm-mrad. Here, we present the design parameters of this high voltage DC gun. The details of the gun design with electron beam simulation will be described.
Subcritical Assembly Neutron Source facility of the National Science Center “Kharkiv Institute of Physics & Technology” (NSC KIPT), Kharkov, Ukraine is Accelerator Driven System with tungsten or uranium neutron generating target and 100MeV/100kW electron linear accelerator as a driver.
The facility physical start up was started in the middle of 2020 fnd completed in August 2022. The program of the facility physical start-up supposes to operate with tungsten neutron generating target and to carry out stepwise fuel element loadings with neutron multiplication factor and reactivity measurements at the end of each loading step. During the physical start up it was supposed to load 38 fuel elements in several loading steps. 200 W electron beam was used for neutron multiplication factor and reactivity measurements.
After loading of 37 fuel assemblies the measured value of neutron multiplication factor was 0.941. Because of nuclear safety reasons it was decided to complete the facility physical start up and make some clarifying simulation for 38 loaded in the core fuel assemblies taking into account tolerances for fuel mass, geometry and nuclei data uncertainty to be sure that the value of multiplication factor will be not higher than 0.96.
During the the facility start up the results of the reactivity and neutron multiplication factor measurements were in a good agreement with results of Monte-Carlo simulations for NSC KIPT SCA Neutron Source facility.
Electron field emission and the related process of strong laser-field emission are promising mechanisms for the creation of high brightness beams. These processes deviate from the photoelectric effect in that the normal energy – not the total energy – is the predominant factor determining the likelihood for an electron to ionize. In this paper we continue our investigation of the material normal energy distribution (MNED), which is the supply current as a function of the normal energy. We derive analytical expressions for the MNED and mean transverse energy (MTE) for two cases: that of a smooth Fermi surface, and that of a Bragg plane intersecting Fermi surface in a weakly binding potential. We compare these analytical expressions to results calculated using density-functional theory (DFT) for tungsten and copper surfaces. We find explainable discrepancies between our analytical results and the DFT results for the W(100) direction and the Cu(111) direction, associated with the Fermi surface intersecting a Bragg plane, but otherwise find general agreement.
This article presents an IH-DTL prototype, capable of accelerating carbon ion beams from 5 MeV/u to 5.5 MeV/u, for manufacturing and assembling validation in a hadrontherapy linac injector. A multi-physics study is made in CST Studio concerning steady-state thermal, stress and deformation analysis. Convenient water-cooling circuits close to drift tubes are simulated to evaluate field errors and frequency detuning as they can affect directly to beam dynamics.
In this paper, a cooling scheme was designed for the THU VHF gun, and simulations of thermal and structural analyses were conducted. A total of 19 independent cooling channels were designed and distributed on the gun to remove the heat generated. The maximum temperature was 67.8 ℃ with a total flow rate of 3.28 L/s and dissipation power of 92.5 kW. The accelerating gap distance decreased by 124 um when heat and vacuum loads were applied. The tuning efficiency was 2.075 kHz/kN, and the maximum stress was 65.2 MPa. It is safe to conclude that the cooling scheme of the THU VHF gun meets the thermal and structural requirements and shows good properties in the temperature, deformation, and stress distributions. Future publications will thoroughly discuss the recent progress of the THU VHF gun.
Strong laser-field electron emission enhanced by nanostructures is a growing topic of study, owing to its ability to generate high brightness beams. Experiments have shown that the nanoblade structure, a wedge shape, notably outperforms nanotips in the peak fields achieved. These higher fields result in a brighter emission. In this paper we study the thermodynamics of the electron system restricted to a nanostructure. Thermal diffusion of deposited energy near the apex of the structure is dominated by the electronic distribution on the electron-phonon timescale. We show analytically through use of the temperature-squared heat equation that the nanoblade, owing to its larger opening angle and higher dimensionality, thermomechanically outperforms the nanotip.
The LHC Injector Upgrade (LIU) programme forms a cornerstone of the High-Luminosity LHC project. Among its targets, a new Beam Position Monitor (BPM) system has been deployed in the Low Energy Ion Ring (LEIR) to facilitate optics measurements. This paper reports on the commissioning and analysis of turn-by-turn data from the new BPM system. Furthermore, the specific challenges and current limitations in LEIR for achieving long-term coherent excitations with sufficient amplitude for optics measurements are discussed, as well as some of the optics measurements performed so far.
Semiconductor photocathodes, particularly those produced with thin films and heterostructures, are promising candidates of high brightness electron sources. It is also well-known that electron beam brightness increases with the photocathode gun’s operating gradient. Combining both heterostructure semiconductor photocathode and cyro-cooled high-gradient photocathode gun may improve electron sources for many applications. However, effects of the high field gradient on the semiconductor photocathode need to be understood in order to preserve and optimize the quality of the emitted photo-electron beams, which can be done with from detailed simulation study and theoretical analysis. In this work, we apply Monte-Carlo method to study high field transport and emission from semiconductor photocathodes such as Cs2Te. The results will be used to inform a theoretical transport model based on the moments method and the cathode development for the CARIE project at LANL.
The ALTO research platform at the Laboratoire de physique des 2 infinis Irène Joliot Curie (IJCLab) is dedicated to wide-ranging research in nuclear physics, nuclear astrophysics and interdisciplinary activities such as health physics. ALTO-LEB is the low energy beam area of ALTO where neutrons rich exotic nuclei are studied.
A new precision experiment is being installed at the ALTOLEB facility : a double Penning trap mass spectrometer MLLTRAP coupled with a RadioFrequency Quadrupole Cooler and Buncher (RFQCB). This last device requires low energy beams with low emittance, low energy dispersion and with few contaminants. This paper focuses on the beam transport at ALTO-LEB, from the target-ion source vault to the RFQCB. Simulations of the ions extraction from the ion source and beam transport calculations are being presented in this work. Those results are also directly connected to the reliability of ALTO-LEB beam lines initiated at IJCLab in 2018.
Particle accelerators are devices of primary importance in a large range of applications such as fundamental particle physics, nuclear physics, light sources, imaging, neutron sources, and transmutation of nuclear waste. They are also used every day for cargo inspection, medical diagnostics, and radiotherapy worldwide. Electron is the easiest particle to produce and manipulate, resulting in unequaled energy over cost ratio.
However, there is an urgent and growing need to reduce the footprint of accelerators in order to lower their cost and environmental impact, from the future high-energy colliders to the portable relativistic electron source for industrial and societal applications. The radical new vision we propose will revolutionize the use of accelerators in terms of footprint, beam time delivery, and electron beam properties (stability, reproducibility, monochromaticity, femtosecond-scale bunch duration), which is today only a dream for a wide range of users. We propose developing a new structure sustaining the accelerating wave pushing up the particle energy, which will enable democratizing the access to femtosecond-scale electron bunch for ultrafast phenomena studies.
This light and compact accelerator, for which we propose breaking through the current technological barriers, will open the way toward compact accelerators with an energy gain gradient of more than 100 MeV/m and enlarge time access in the medical environment (preclinical and clinical phase studies).
In this proceeding, we demonstrate the synthesis of epitaxial Cs$_3$Sb films with a high degree of crystallinity on silicon carbide substrates. Films less than 10 nm thin are grown in vacuum and exhibit percent level quantum efficiencies at 532 nm. We find a positive correlation between quantum efficiency and improved crystallinity of the photocathode film, particularly in the longer wavelengths of the visible spectrum. We present a model describing the optical interference effects observed in the SiC - Si substrate multilayer that enhance quantum efficiency of the thin film photocathodes by almost a factor of two at particular wavelengths. Additionally, we characterize the surface and bulk crystallinity of epitaxial Cs$_3$Sb films using both X-ray diffraction (XRD) and reflection high energy electron diffraction (RHEED) in an endeavor to identify relationships between crystalline phases and photocathode performance.
High brightness photoinjectors demand low thermal emittance and high electric field to deliver brighter electron beams for modern accelerator-based scientific instruments. High quantum efficiency, low thermal emittance photocathodes, mainly semiconductors, easily degrade in poor vacuum conditions and could not operate with an extended lifetime. Therefore, an ultrahigh vacuum electron gun is necessary to accommodate advanced photocathodes for high performance and reliable operation. In this paper, we report on the development of an ultrahigh vacuum, high gradient S-band gun at Tsinghua University. The gun geometry is redesigned to reach more than one order of magnitude improvement of the vacuum level at the photocathode. Preliminary commissioning results of the new gun will be presented. The new gun and beamline will partially serve as a test facility for advanced semiconductor photocathodes. We will also report on the design and commissioning results of an alkali antimonide photocathode deposition system.
For HL-LHC intensities, transient beam loading after injection between the Super Proton Synchrotron (SPS) and the Large Hadron Collider (LHC) is expected to push the RF power in the LHC to the limit of the installed system. A detailed understanding of this process is necessary to minimize beam losses during LHC injection. Realistic models of the local SPS and LHC cavity control systems were implemented in the Beam Longitudinal Dynamics (BLonD) simulation suite to model bucket-by-bucket and turn-by-turn transient effects. We show the results of studies and detailed benchmarks of key observables such as bunch-by-bunch spacing, RF power at 2023 beam intensity and transfer functions against theory and measurements.
Wakefield acceleration in structured solids (nanotubes and crystals) has a promise of very high accelerating gradients and simultaneous continuous channeling focusing. All that can manifest a new, long thought solution of many challenges faced by advanced acceleration techniques. We outline the concept and present the progress and status of the E336 Experiment at FACET-II.
We have been developing an in-situ work function (WF) measurement system to investigate an unexpectedly short lifetime problem of a CeB6 thermionic cathode at the SACLA electron injector. Photoelectron yield spectroscopy using a nanosecond tunable pulsed laser in the wavelength range from 410 to 709 nm was adopted because this method provides a high S/N ratio in a hot operational condition of the thermionic cathode and makes it possible to perform the measurement during the XFEL operation. As the first step, demonstrative WF measurements using an offline cathode test system have been conducted and the WF of an unused fresh CeB6 cathode was precisely estimated to be a value of 2.44±0.02 eV at a temperature of 836 °C. In this conference, the details of the test system and the first measurement results will be presented.
The FLASH2020+ project will open up new excellent opportunities for science on the highest level. The FLASH facility will not only produce soft x-ray SASE photon beams at full MHz repetition rate in a burst mode in FLASH2, but will also provide in FLASH1 several thousand fully coherent pulses per second using the HGHG and EEHG external seeding schemes. New types of experiments are enabled by major modifications to the linear accelerator and the FLASH1 FEL beamline. Within a 9 month shutdown ended August 2022, a 60 m stretch of the linac has been renewed featuring new acceleration modules adding an additional 100 MeV energy to the electron beam and a significant improvement in RF-stability, fast orbit correctors, a laser heater which allows to smoothen current ripples and variable bunch compression sections. During commissioning first user experiments have demonstrated the increased control, stability, and quality of the FLASH electron beams. The improved beam quality is a prerequisite for the completely new multi bunch externally seeded FEL beamline in 2025. The seeded photon wavelength will span a range of 60 to 4 nm with emerging pulses being uniquely stable and reproducible in phase space. Exploiting the 1 MHz repetition rate available from the accelerator and the seed laser system, an unprecedented average photon flux at full polarization control will be made available to experiments, and will thus attract new high level science groups around the world.
In order to promote the studies of low emittance RF photo cathode and high gradient accelerating structures, a C-band test platform has been initialized since late 2021. In this paper, an overview of the present status and future plans of this platform is given, including a 3.6-cell C-band RF photo cathode and a C-band RF traveling-wave accelerating structure. In addition, other on-going studies on this platform, such as the test of a cryo-copper accelerating structure and the development of short pulse high gradient parallel-coupled structures, are briefly introduced.
Terahertz (THz) radiation sources are increasingly significant for many scientific frontiers, while the generation of THz radiation with high-power at wide-tunable frequencies is still a limitation for most existing methods. In this paper, a compact accelerator-based light source is proposed to produce coherent THz radiation with high pulse energy and tunable frequency from 0.1 THz to 60 THz. By using a frequency beating laser modulated electron beam and undulator taper, intense coherent THz radiation can be generated through undulators. Theoretical analysis and numerical simulations demonstrate that the proposed technique can generate narrow-bandwidth THz radi-ation with a pulse energy up to 6.3 millijoule (mJ) and the three-dimensional effects of beam has limited influence on its performance. The proposed technique will open up new opportunities for THz spectroscopic and time-resolved experiments.
The magnetic and mechanical designs of a force-neutral adjustable phase undulator (FNAPU) are pre-sented. The FNAPU combines two magnetic assemblies with equal periods, one with an undulator magnetic structure and one with a force compensation magnet structure. The latter is used to neutralize the magnetic force affecting the undulator magnetic structure and vice versa in all undulator phases. Assembling in prox-imity a group of different FNAPUs is discussed.
A High Brightness Beams Test Facility has been recently funded at the INFN-LASA laboratory in Segrate (Milan- Italy). The Test Facility will allow to perform developments in ERL construction and design and to carry out experiments with the high current CW electron beam in frontier areas of accelerator physics. The Test Facility setup will comprise a high-performance laser driven DC Gun followed by a normal conducting RF buncher-acceleration section to provide 1 MeV 5 mA CW electron beam. A Superconducting RF booster linac able to increase the electron energies up to 5-10 MeV maintaining beam current up to 2.5 mA is part of the proposal for further funding.
In this paper we report on the status and performance of a newly commissioned high brightness electron beamline at Tsinghua University. The beamline is dedicated to research on the physics and technologies of multi-MeV, low charge, high brightness electron beams, as well as applications including MeV ultrafast electron diffraction and imaging. The layout, simulation and measurement results of the beam parameters and the stability performance of the beamline will be discussed. A liquid-phase UED sample delivery system and experiment methodology have recently been commissioned and established. Near-term upgrade to a variety of key components, including the high power rf source, laser-to-rf timing system, electro-optic lenses, together with the modeled performance improvements will also be presented.
Angular dispersion-induced microbunching (ADM) scheme was proposed to generate high harmonic coherent radiation in the storage ring with weak energy modulation amplitude. However, it is still difficult to convert the external UV seed laser into the sub-nanometer wavelength. In this paper, we proposed a novel scheme based on ADM mechanism. By properly choosing the parameters, theory and one order simulation demonstrate that it is possible to produce ultrahigh harmonic coherent radiation in the storage ring. The high harmonic conversion efficiency of the proposed scheme may open up a new opportunity to produce sub-nanometer X-ray coherent radiation in the storage ring.
X-ray free electron lasers, especially fully coherent femtosecond free-electron laser (FEL) pulses, are widely used in numerous fields. This study aims to propose a new principle for generating fully coherent femtosecond X-ray pulse based on the Shanghai soft X-ray Free Electron Laser User Facility (SXFEL-UF). The principle was based on fresh-slice technique. First of all, the electron beam was kicked transversely to get a time-related transverse tilt. Then, the sub-10-femtosecond bunch was achieved because of the spatiotemporal synchronization effect of the seed laser modulation. The FEL pulse duration was even shorter because of harmonic lasing. In the cascaded HGHG mode, the laser generated by the beam tail modulated the beam head in the second stage to reach higher harmonics, while in the EEHG mode, the same part of the electron beam was modulated twice. The influence of emittance and energy chirp of the electron beam on the scheme was analyzed, and the instability caused by transverse position jitter and energy jitter of the chirped beam was evaluated. The relationship between the pulse duration and the transverse deflection of the beam is verified. The scheme is also explored to generate linearly polarized femtosecond pulse at 6 nm and circularly polarized femtosecond pulse at 3 nm simultaneously by means of the elliptically polarized undulator (EPU) afterburner.
The CERN Linear Electron Accelerator for Research (CLEAR) has been operating since 2017 as a user facility providing beams for various experiments. We created a start-to-end model of the CLEAR setup in RF-Track, aiming to optimise the CLEAR accelerator as a driver for an X-ray source based on inverse-Compton scattering. RF-Track, a CERN-developed particle tracking code, can simulate the generation, acceleration, and tracking of the electron beam from the cathode to the interaction point, across the entire accelerator. Additionally, RF-Track can compute the ICS interaction with an input laser beam, allowing for the first start-to-end optimisation of an ICS source using a single code. The optimisation was aimed to maximise the flux of the outcoming x-rays, while minimising the impact of static and dynamic imperfections. Sensitivity studies were performed, with an estimate of the effect of the jitter on the scattered photon flux.
The superconducting radio-frequency photoelectron injector (SRF photoinjector), now under commissioning at the SEALab accelerator test facility, has the potential to cover a fast area of beam parameters. Electron bunches from fs to ps length, with fC to nC charge can be accelerated to a couple of MeV beam energy. The legacy from the energy-recovery linac (ERL) test facility bERLinPro, the foundation of SEALab, allows us to operate the SRF photoinjector at very high repetition rate, with energy recovery (ERL), in a sustainable way for fundamental accelerator research into novel, energy-efficient electron accelerators. In this paper preparatory work for two applications is detailed. One is the use of the SRF photoinjector as a direct beam source for ultrafast scattering experiments with high 6D coherence, the other are experiments towards an ERL application for high-energy physics at high average current.
The spectro-temporal characteristics of free-electron laser (FEL) radiation emerging from external seeding schemes such as high-gain harmonic generation are shaped by the properties of the initial seed laser. Accurate control of the seed laser envelope and phase is essential to allow for precise manipulation of the FEL output. Based on experimental data obtained at the seeded FEL user facility FERMI, it is shown that detailed bunching spectral analysis enables monitoring of the seed and FEL frequency chirp. The bunching model is extended to be capable of also reproducing the FEL power.
We describe active Q-switched X-ray regenerative amplifier FEL scheme to produce fully-coherent, high-brightness hard X-rays. In this scheme, a moderate energy chirp is introduced to the electron beams to shift the Free Electron Laser (FEL) radiation frequency outside the reflectivity bandwidth of the Bragg crystal. By actively controlling the chirp of the electron beam, the ratio of the out-coupled and recirculated pulse energy can be manipulated flexibly. This allows hard X-ray cavities driven by electron beams with reduced beam repetition rate, relatively low beam energy, and short cavity length. In contrast to typical XRAFEL outcoupling designs involving X-ray optics manipulation, this approach only requires the control of energy chirp of the electron beams, which can be simple and straightforward to implement. We report theoretical and numerical studies as well as error tolerance analysis on this scheme. We further discuss the experimental plans based on self-seeding or cavity-based XFELs on LCLS-II.
In October 2022, the UK XFEL project entered a new phase to explore how best to deliver the advanced XFEL capabilities identified in the project's Science Case. This phase includes developing a conceptual design for a unique new machine to fulfil the required capabilities and more. It also examines the possibility of investment opportunities at existing XFELs to deliver the same aims, and a comparison of the various options will be made. The desired next-generation capabilities include transform limited operation across the entire X-ray range with pulse durations ranging from 100 as to 100 fs; evenly spaced high repetition rate pulses for enhanced data acquisition rates; optimised multi-colour FEL pulse delivery and a full array of synchronised sources (XUV-THz sources, electron beams and high power/high energy lasers). The project also incorporates sustainability as a key criteria. This contribution gives an overview of progress to date and future plans.
The self-seeded free-electron laser (FEL) is developing towards advanced FEL modes such as ultra-short pulse, multi-color and high intensity, and the influence of thermal loading instantaneously loaded on monochromatic elements will not be ignored. Therefore, it is necessary to quantitatively describe the changes in X-ray optical properties of crystals caused by transient thermal loading through an analytical model. In this paper, a method for transient thermal-optical analytical modeling and simulation is introduced. Based on this method, we analyzed the deformation of the monochromator in an ultra-short time scale, and calculated the influence of the FEL pulse on the monochromatic signal generated by forward Bragg diffraction with different pulse duration and two-pulse. This work is significant to the future research of self-seeded FEL in ultrafast and two-color direction.
The development of high-power, attosecond methods at free-electron lasers has led to new possibilities in the probing and control of valence electron dynamics. Beyond simple observation of ultrafast processes, one of the longstanding goals of atomic physics is control of the electronic wavefunction on attosecond timescales. We present a scheme to generate sub-femtosecond pulse pairs from x-ray free-electron lasers with fs-scale separation, few eV energy separation, and a coherent phase relationship. This shaping method can be employed to coherently control ultrafast electronic wavepackets in quantum systems. We study in detail the Auger-Meitner decay process initiated by such a pulse pair and demonstrate that quantum beats of the decaying electronic wavepacket can be shaped by controlling the separation in energy and time of the pulse pair.
A cavity based free-electron laser (CBXFEL) is a next generation X-ray source promising radiation with full three-dimensional coherence, nearly constant pulse to pulse stability and more than an order of magnitude higher spectral flux compared to SASE FELs. In this contribution, an R&D project for installation of a CBXFEL demonstrator experiment at the European XFEL facility is conceptually presented. It is composed of an X-ray cavity design in backscattering geometry of 133 m round trip length with four undulator sections of 20 m total length producing the FEL radiation. It uses cryocooled diamond crystals and employs the concept of retroreflection to reduce the sensitivity to vibrations. Start to end simulations were carried out which account for realistic electron bunch distributions, inter RF-pulse bunch fluctuations, various possible errors of the X-ray optics as well as the impact of heat load on the diamond crystals. The current state of the project shall be presented in this contribution.
X-ray beams with orbital angular momentum (OAM) have emerged as a powerful tool for investigating matter. Traditional optical elements, such as spiral phase plates and zone plates, have been employed to generate OAM light. However, applying these elements in x-ray free-electron lasers (XFELs) remains challenging due to high impinging intensities and efficiency concerns. The self-seeded FEL with OAM (SSOAM) method has been recently proposed to generate intense x-ray vortices, overcoming these limitations. In this study, we focus on optimizing the SSOAM scheme to enhance the production of high-power x-ray vortices. A Bayesian optimization approach is employed to optimize the undulator tapering, ensuring the efficient generation of x-ray OAM pulses in XFELs.
The High Energy Photon Source (HEPS) is a synchrotron radiation source of ultrahigh brightness being built in China. Its accelerator complex is composed of a 6-GeV storage ring, a full energy booster, a 500-MeV Linac, and three transfer lines. The Linac is an S-band normal conducting electron linear accelerator with available bunch charge from 0.5 nC up to about 10 nC. The Linac installation was completed in July 2022 and high-power RF conditioning was finished in September 2022. Physics quantity based high-level applications have been developed for the HEPS Linac using our own platform Pyapas. The beam commissioning of the Linac is scheduled from December 2022 to March 2023. Detailed beam commissioning experiences and results of the HEPS Linac will be presented in this paper.
RUEDI is a proposed relativistic ultrafast electron diffraction and imaging facility for the UK. It will deliver single-shot time-resolved imaging with MeV electrons, as well as ultrafast electron diffraction at 10 fs timescales. The few-MeV-scale imaging and microscopy line aims to deliver high charge (up to 108 electrons), ultra-low emittance electron bunches to a 10µm sample with minimal energy spread and transverse divergence, aiming for imaging resolutions at the 10nm scale. The physical layout of the imaging beamline will be discussed, along with a multi-dimensional study of the beam dynamics of the proposed design. The extreme requirements on the injector specification, and the limitations inherent in such systems, will be investigated, and potential upgrade paths explored in terms of both imaging resolution and technological feasibility.
RUEDI is a proposed relativistic ultrafast electron diffraction and imaging facility. It will have two beamlines: a diffraction beamline and an imaging beamline. This proceeding discusses the beam dynamics design of the diffraction beamline. The diffraction beamline needs to have the best temporal resolution possible which requires short bunch length and minimal time of arrival jitter at the sample. To achieve this a magnetic bunch compressor operated in a jitter cancelling configuration is used. To achieve compression as well as jitter cancellation the beam’s longitudinal space charge forces are used to modify the chirp to compress the beam. The RUEDI diffraction line will operate at 4 MeV meaning that both space charge forces and ballistic effects are significant and need to be accounted for in the design. The diffraction line will be operated in three modes: single-shot, stroboscopic and streaking.
In the framework of a collaboration between Sapienza University of Rome, the Italian Institute for Nuclear Research (INFN) and the Curie Institute, the proposal of a new facility dedicated to the Very High Electron Energy (VHEE) FLASH irradiation is in progress. The aim is to exploit the promising VHEE regime for the translation of electron FLASH radiotherapy into clinical practice in order to treat deep tumors. For the translation to clinical practice, the electron energy should be varied in the 60-160 MeV range. The needed electron peak current is the order of 200 mA, that is 200 nC per 1 $\mu$s pulse. The irradiation system also requires compactness for the installation inside a hospital or treatment facility. In order to satisfy both requirements, i.e. high energy and compact system, we propose a radio-frequency (RF) linear accelerator-based electron-beam source working in C-band at 5.712 GHz. In particular, we present the beam dynamics of the optimized high-gradient C-band linear accelerating system for the transport of high beam current beams for FLASH applications.
A beam dynamics optimization study of an electron injector linear accelerator including an RF photoinjector gun was performed using MOGA (Multi-Objective Genetic Algorithm). To meet the requirements of electron beam characteristics at the linac end, the optimization goal was to minimize transverse beam emittance and energy spread. The transverse and longitudinal beam sizes were constrained to find Pareto fronts effectively. Parameters to be optimized were the input phases of the RF gun cavity and accelerator column cavity as well as the strength and position of the focusing solenoids. In addition to finding physical optimization parameters, we also investigated hyper-parameters in optimization simulations such as population, offsprings, generations, etc. This paper presents the optimization results of the linac design.
The ALBA and BESSY II Linacs consist of a thermionic Pierce-type electron gun that delivers e- at 90 keV in pulses of 1 ns with a maximum charge of 0.25 nC/bunch. The gun is followed by a set of standing wave bunching cavities and traveling wave accelerating structures to further increase the beam energy, up to 50 MeV at BESSY II and up to 100 MeV at ALBA, while keeping the energy spread below 0.5% (rms). In this paper a study of the beam parameters at the exit of the electron gun is presented for different bunch charges, to evaluate the space charge effect. For that, electrostatic field maps have been obtained by means of Superfish, following the technical drawings provided by the manufacturer, Thales. Results from the simulations are compared to the values reported by the supplier at the exit of the gun, and also to real measurements performed at the BESSY II gun test-stand. The implementation of the field-maps of the gun at the Linac model (GPT tracking code) conducts more realistic simulations, improving the understanding of the two Linac beam performances.
We present the conceptual design of a compact light source named BriXSinO. BriXSinO was born as a demonstrator of the Marix project, but contains also a dual high flux radiation source Inverse Compton Source (ICS) of X-ray and a Free-Electron Laser Oscillator of THz spectral range radiation conceived for medica applications and general applied research. The accelerator is a push-pull CW-SC Energy Recovery Linac (ERL) based on the technology of superconducting cavities and allows to sustain MW-class beam power with al-most just one hundred kW active power dissipation/consumption. ICS line produces 33 keV monochromatic X-Rays via Compton scattering of the electron beam with a laser system in Fabry-Pérot cavity at a repetition rate of 100 MHz. The THz FEL oscillator is based on an undulator imbedded in optical cavity and generates THz wavelengths from 15 to 50 micron. The possibility of generating in the FEL cavity also synchronized X radiation is also shown.
In the first prototype of the AXSIS light source, electrons sourced from a 55 keV DC gun are first compressed by a THz-powered buncher, then accelerated in a THz-driven “booster” to 430 keV kinetic energy and finally accelerated to 20 MeV in a THz-powered LINAC. Guided by simulations, a booster prototype was developed employing three layer segmented structures and requires 400-µJ single-cycle THz pulses with center frequency 300 GHz. Since THz-driven accelerators provide electrons over a broad energy range and/or with large momentum spread, a broadband single-shot electron spectrometer with large momentum acceptance and sufficient resolution has been developed for the THz-driven booster accelerator. This energy spectrometer uses a compact in-vacuum tunable dipole magnet, and the special design of the pole shoes is such that electron bunches within 20-430 keV are focused onto a 4cm long image plane where the scintillator is directly mounted to increase energy resolution. We present the design of the magnetic spectrometer, along with the calibrations carried out and expected performance such that the energy distribution of accelerated electrons can be measured.
The PolFEL free electron laser project comprises 185 MeV cw-linac furnished with ASG electron gun and 4 Rossendorf-like cryomodules. The beam diagnostics system, besides bringing the beam to undulators, inverse Compton scattering interaction point, and finally to the dump, system is dedicated to metallic superconducting photocathodes development, in particular to gun performance characterization. Bunch length will be measured in the injector section, behind the bunch compressor, and in each linac branch, behind the wakefield linearizer at the undulator entrance. The bunch length is evaluated from sub-THz coherent Cherenkov radiation spectral distribution. Radiation emitted from a punched radiator will be analyzed with Martin–Puplett interferometer and measured with a broadband detector, both located on the breadboard at linac. A prototype will be preliminary measured with laboratory sub-THz source at IOE-MUT and subsequently at the Solaris linac with 0.5 GeV electrons.
We present our 1.6-cell radiofrequency cavity design for a photoinjector under development for producing intense electron bunches with 250-pC beam charge and normalized emittance below 100 nm rad for cryogenic temperature operation. The cavity cell profile was designed by SLAC and UCLA, optimized for maximal shunt impedance and minimal peak magnitude of the electric and magnetic field. The pi-mode accelerating fields are established in the cells with power coupled into each cell individually through the slot on the sidewall, and the peak electric field magnitude has been tuned to be equal in the two cells. The coupling waveguide network was designed to achieve critical coupling into the port of the input power waveguide and to achieve the desired power distribution. The cavity design has been completed for initial high-gradient test at room temperature.
Laser-wake field accelerators (LWFAs) are potential candidates to produce intense relativistic electron beams to drive compact free electron lasers (FELs) in VUV and X-ray regions. In High-Field Physics and Ultrafast Technology Laboratory at National Central University (NCU), an LWFA is being developed to produce a 250 MeV high-brightness electron beam by their 100-TW laser system. An FEL seeded by a 266-nm UV laser is under design to generate extreme ultraviolet (EUV) radiation. The initial phase of the project is to develop a beam energy modulator through the interaction of the LFWA-produced electron beam with the 266-nm seed laser in a 10-period planar undulator of 35-mm period length. An electron beamline has been designed based on linear optics to deliver the intense electron pulse from LWFA to the undulator and focus properly. However, due to the large energy spread of the beam, chromatic effects on beam transportation may be severe. In this work, we perform a detailed simulation of the LWFA FEL from experimental data of the NCU LWFA electron source. A 6D phase space analysis of multi-particle dynamics using IMPACT code [1] is to determine how significant the effects of beam energy spread on beam properties along the beamline are. The electron beam is then transferred to GENESIS [2] and Puffin [3] to see the laser beam interaction in the undulator. Further study of the HGHG scheme is evaluated using both FEL codes to see the influence of ultra-short electron bunch.
FEL oscillators can produce few-cycle optical pulses with a high-extraction efficiency when the oscillators are operated in the superradiant regime. Such FEL oscillators are unique light sources to explore intense light field science, especially in mid-infrared and longwave infrared where ultrashort pulses are difficult to produce from conventional lasers. Since the laser-matter interaction in the intense field regime is described in terms of the oscillating electric field rather than the instantaneous intensity, the carrier-envelope phase (CEP) must be stabilized in many applications of few-cycle optical pulses to the intense light field science. Stabilization of CEP in FEL oscillators has been proposed with an external seed laser and coherent radiation of electron bunches **. In this paper, we study CEP stabilization in FEL oscillators with numerical simulations and discuss applications of CEP-stable FEL pulses in the intense light field science.
Variable polarization is a required feature of light sources employed to investigate the properties of matter. The possibility to select light polarization is, in particular, attractive for those experiments, which aim at exploring the local symmetry of the sample under scrutiny, e.g., the chirality of a molecule, or the presence of a net atomic magnetic moment. Moreover, several spectroscopic methods rely on the opportunity to choose a well-defined light polarization. Harmonic emission from an undulator can be successfully used to extend the tuning range of a free electron laser (FEL) beyond the fundamental wavelength range supported by the available electron beam energy and undulator parameters. For planar undulators, on-axis harmonic emission is known to be possible for odd harmonics. Instead, for circularly polarized undulators harmonic emission occurs off-axis, preventing to extend the polarization control toward shorter wavelengths. For variable polarization undulators, it has been demonstrated that a special magnetic field configuration can be found, allowing to produce on-axis harmonics with a substantial degree of circular polarization [C. Spezzani et al., PRL107,084801 (2011)]. Recent experiments at the FERMI free-electron laser have shown that such a scheme can be used to reach the Fe L edge photon energy, i.e. 707 eV, with circularly polarized pulses allowing to perform dichroic experiments on magnetic specimens. We report here the obtained results
In the framework of the injector upgrade, which has been completed in 2022 as the first stage of the FLASH2020+ project, a new second bunch compression chicane has been redesigned and installed at the FEL user facility FLASH. The old S-type chicane with a flat vacuum chamber design has been replaced with a movable C-chicane which round vacuum chambers. The inner dipoles and corresponding electron beamline can be moved from straight beam transport to a maximum deflection angle of 6 degrees which offers a wide range of longitudinal dispersion for optimised bunch compression schemes for both SASE and externally seeded FEL operation. The latter is foreseen from 2025 onwards after completion of the second stage of the FLASH2020+ project. In this paper, we report the technical details of the movable chicane as well as its parameter space. First results of beam commissioning are presented.
Dalian Coherent Light Source (DCLS) is an extreme ultraviolet free-electron laser (FEL). The measurement of the longitudinal phase space (LPS) of electron bunch is vital to a FEL facility. In order to measure the LPS, a S-band RF transverse deflecting cavity (TDS) has been installed and commissioned at DCLS facility. This paper will introduce the TDS physical layout and commissioning results with electron bunch.
Phase shifter collocated with undulator is an efficient way to enhance lasing of free-electron laser
(FEL), especially for seeded FEL. Dalian Coherent Light Source (DCLS) is a seeded FEL operating on
high-gain harmonic-generation (HGHG) mode. In order to achieve highly performance of FEL
lasing, five phase shifters are interspersed between six undulators. This paper will present the
commissioning results of the five phase shifters, especially the impact on FEL lasing.
Due to the limitations of Laser Produced Plasma (LPP) Extreme Ultraviolet(EUV) sources, semiconductor industry is seeking the next generation EUV source for sub-nm scale lithography processes. Various accelerator-based light sources have been already proposed as EUV lithography light sources. We investigated the design of a compact high-power EUV light source using laser Compton scattering. The configuration of the linear accelerator and laser system was optimized based on the specifications required for the sub-nm lithography process. Electron beam dynamics and laser electron scattering simulations have also been demonstrated to achieve the required EUV power.
In AXSIS project, we are developing compact, THz-based electron accelerators, which represent a promising technology for the development of next-generation compact electron accelerators that significantly downsize x-ray sources. A key aspect in such a design is transport and focusing of an electron bunch accelerated to 20 MeV kinetic energy to inverse-Compton scattering (ICS) like interaction region with a high energy laser pulse through a dedicated beam transport line. Since ICS performance depends on achieving ultrasmall spot sizes in high current beams, the beam transport system needs shorter focal length electron optics and correction elements such as steering magnets. A permanent magnet quadrupole (PMQ) is one of the candidates for creating such strong focusing systems, because of its compactness without power consumption. A compact electron beam transport system consisting of permanent magnet quadrupoles achieving a gradient greater than 100 T/m based on a Halbach array is reported. The inherent advantages and disadvantages of permanent/electro magnet and hybrid technologies will also be discussed.
The SPES RFQ is designed in order to accelerate beams
in CW with A/q ratios from 3 to 7 from the Charge Breeder
through the MRMS and the selection and injection lines up
to the MEBT (Medium Energy Beam Transport). The RFQ
is composed of 6 modules about 1.2 m long each, made of a Stainless Steel Tank and
four OFE Copper Electrodes. A copper layer is plated on
the tank inner surface and a spring joint between tank and
electrode is used in order to seal the RF. In this article, the main results related to the the module assembly and related RF and mechanical measurements
are shown.
The compact ERL has been built as a test machine of energy recovery linac (ERL) at KEK in 2013. It has been succeeded to operate with 1 mA beam current with energy recovery mode in 2016. Recently, two undulators have been integrated into it to produce an infrared free-electron laser (FEL) light and the light amplification has been successfully observed with a burst mode and without energy recovery mode in 2020.
So far, the beam operation for high beam current at the compact ERL has been performed with machine parameters for a low-charged electron beam. However, to achieve continuous-wave (CW) FEL, it is necessary to have a high-charged beam with high-repetition rate and the energy recovery mode but without beam loss. After the observation of FEL light amplification in 2020, high-charged beam operation has been established with energy recovery mode but still with some losses. In this presentation, the causes of the measured beam losses and the countermeasures will be discussed, as well as prospects for CW-FEL at the compact ERL.
In high-gradient accelerator structures, field emission produces dark current that behaves much differently than the main photobeam current. This dark current can damage accelerator components and increase the radiation dose in the surrounding area. Thus it is important to analyze its behavior when designing a new accelerator or subsystem, such as the superconducting low-emittance injector (LEI) currently under development for the LCLS-II high-energy upgrade (LCLS-II-HE). In principle, the emission of dark current is governed by the Fowler-Nordheim (FN) equation. In practice, variations in surface quality result in localized emission sites at locations that are not predictable a priori. Since the superconducting gun for the LEI does not exist yet, particles must be tracked from a dense array of initial positions and times on all likely emission surfaces and assigned weights according to the FN equation in the early design phases to inform the placement of collimators. We present the results of tracking studies using BMAD* and Python to analyze dark current in the LEI.
An electron beam test stand was designed and constructed at CERN, under the umbrella of the Hi-Lumi project, to tests components for the Hollow Electron Lens (HEL), and in collaboration with the ARIES project for testing the Space Charge Compensation gun. The test facility features normal conductive magnets providing solenoid fields of the order of fractions of Tesla, beam diagnostics including screens (YAG, Cromox and OTR) for the full electron beam characterisation, a Faraday Cup collector to measure the total electron current, and a high voltage power supply up to 40 kV (with the possibility of biasing both gun and collector). It offers the possibility of testing high current and high perveance guns, different beam instrumentation (Beam Position Monitors and Beam Gas Curtain monitors are some examples), electron collectors, and beam pulse modulators. In this paper the facility is described and the first results validating the design of the HEL gun are presented.
The Southern European Thomson back-scattering source for Applied Research (STAR) project, based on a collaboration among University of Calabria (UniCal), CNISM, INFN and Sincrotrone Trieste, has the goal to install and test at UniCal a short linear accelerator for high brightness electron beams that will drive a unique advanced X-ray Thomson source. In 2021 INFN was committed to install, test and commission an upgrade of the STAR Linac (STAR High Energy Linac) aiming to increase the X-ray beams energy from 30 keV up to 140 KeV. The new layout foreseen an increase of the electron beam energy from 65 MeV up to 150 MeV by the installation of two additional C-band acceleration cavities and an additional transfer-line where the high energy beam could be delivered to a second interaction point with the laser.
The whole machine layout foreseen 43 warm electromagnets (solenoids, dipoles, quadrupoles and steerers) powered by 59 DC power supplies that will cover a wide power range from 90W up to 15 kW. In this paper, an overview of the magnet system is given together with the performed tests, the deliveries status and the future steps needed to finalize the complete machine installation.
We report our recent results on the project (XLO) to build, characterize and operate a population inversion x-ray laser at the copper $K{\alpha_1}$ line, using LCLS x-ray pulses as a pump. The results include: gain measurement; design, alignment and focusing elements for the optical bow-tie cavity; copper target measurement of damage caused by the pump pulses; development of a fast system to provide a fresh solid copper target for pump pulses separated in time by 35 ns; development of the generation and control of two electron bunches in LCLS to generate two X-ray pump pulses.
All the results obtained and discussed in this paper support the feasibility of XLO and the unique role it would have for scientific research in atomic and molecular science.
For the Linac travelling wave S-band injector at ELSA a new electron gun is being designed, to enhance the beam parameters of the old gun. Furthermore, a new single bunch injection mode is to be realized alongside the standard long pulse (multi bunch) mode, allowing to use the gun for normal operation for the experimental program as well as enabling single bunch operations for accelerator research and development. For that matter a dual-use design is pursued utilizing a dispenser cathode both as photo- as well as thermionic cathode. First steps including the design of the gun assembly and studies about its usability as a photoemitter are conducted. A preliminary design of the gun assembly and simulation results are presented.
RI Research Instruments (RI) in partnership with The Canadian Light Source (CLS) have designed a new 250 MeV electron linac to inject into the 0.25-2.9 GeV booster synchrotron. The RF frequency is 3000.24 MHz, the sixth harmonic of the 500.04 MHz booster and storage ring RF cavity frequency, and the main accelerating sections consists of three 5 m constant gradient accelerating structures. The 3 GHz bunching sections and the first accelerating structure are fed by a 40 MW klystron, while structures two and three are fed by a single 40 MW klystron with a SLED RF compression scheme. The electron source consists of a 90 keV thermionic cathode with a 500 MHz modulated grid and a 500 MHz sub-harmonic pre-buncher to synchronise with the booster ring cavity frequency. A single-bunch mode can be delivered, as well as a multi-bunch with up to 140 ns bunch trains of up to 5.6 nC of charge per shot, both at a 1 Hz repetition rate to match the booster ramp cycle. The project is scheduled to bring the linac into operation for top-up injection into the CLS storage ring by mid-2024. This paper will present the design with a special focus on the implementation of a SLED to deliver a recovery mode of operation using only a single klystron.
X-band high gradient accelerating technology is a challenging and important technology in advanced electron linear accelerator facilities. The X-band accelerating structure can provide harmonic compensation to eliminate non-linear energy spread and realize linear compression of bunch in linac. In this paper, a special X-band traveling-wave accelerating structure is designed for linearizer, with accelerating gradient of 20 MV/m under the input power below 5 MW according to the requirement of Dalian Coherent Light Source. The fabrication and cold-test of the structure are successfully completed and the transmission efficiency of power is about 0.38.
Ultrafast electron diffraction (UED) is a powerful tool for the direct visualization of structural dynamic process-es in matter on atomic length and time scales. Observa-tions on a femtosecond time scale with atomic resolution spatially have long been a goal in science and are current-ly achieved with large photo injectors developed for FEL frontends. Here we demonstrate a compact 180 keV photocathode S-band electron gun, which employs field-enhancement at a pin-shaped cathode to produce an extraction field strength of 102 MV/m driven by a rack-mountable solid state 10 kW peak power supply. Simula-tions predict that high-brightness electron bunches with RMS duration of 10 fs, a radius of 135 μm, and spatial emittance of 0.1 mm-mrad are possible for a bunch charge of 10 fC. The impact of laser spot size and dura-tion, as well as their spatial distribution, on the temporal bunch length of electrons on the specimen was investigat-ed. Following the successful completion of the condition-ing phase of the RF gun and multipacting suppression, photo-triggered electrons using a UV laser on the photo-cathode were observed.
Non-destructive beam diagnostics as well as experiments and light sources that have a low impact on the beam are important for the operation and applications of an Energy-Recovery LINAC (ERL). Compton backscattering can provide a quasi-monochromatic highly polarized X-ray or gamma-ray beam without strongly affecting the electron beam due to the small cross- section of the Compton scattering. Highest energies of the scattered photons are obtained for photon-scattering angles of 180°, i. e., backscattering. A project at TU Darmstadt foresees to synchronize a highly repetitive high-power laser with the electron beam from the Superconducting DArmstadt electron LINear ACcelerator (S-DALINAC). First, the Laser-Compton Bachscattering (LCB) source will be uses as diagnostic tool for determining the electron beam energy and the energy spread. From the results, optimal design considerations for LCB sources under ERL operations will be deduced. An overview over the design concept and the status of the LCB source at the S-DALINAC will be given.
Short bunch electron beam from linear accelerators can produce broad band and Carrier Envelope Phase fixed coherent radiation in THz spectrum range via various schemes, such as Coherent Synchrotron Radiation and Coherent Transition/Diffraction Radiation. Especially in the high-repetition (or multi-bunch) linac, a CEP-fixed mono-cycle THz pulse train will be available. In order to realize a higher peak intensity and to improve the mode purity at the same time, we consider to convert the multi-pulse into a single pulse by stacking them in an external optical cavity.
We have designed an optical cavity for stacking broad-band THz pulse, and planned a test experiment. We will discuss the principle of the design and present the plan.
A ultra-low emittance electron source utilizing laser-cooled neutral gas as the photo-ionization source has been developed in several laboratories in the accelerator community. We have started the development aiming for using the electron source for the injector of a THz accelerator which has a small aperture and requires a high quality beam.
As the first stage of the development work, we have developed a narrow linewidth laser system and started test experiments of Magneto-Optical Trap of Rb gas.
We will show the present status of the work and discuss the future prospect.
The natural time scale of quantum mechanical motion of electrons in molecules is usually on the order of hundreds of attoseconds. Probing time-dependent dynamics with atomic-site specificity on such timescales requires the generation of soft X-ray attosecond pulses pairs with variable delay and synchronization down to the sub-femtosecond level. We report the generation of GW-level attosecond pump/probe pulse pairs with tunable sub-femtosecond delays at the Linac Coherent Light Source (LCLS). The attosecond 365 eV pump pulse is first generated via the Enhanced Self-Amplified Spontaneous Emission (ESASE) method, then the atto-second 730 eV probe pulse is produced by re-amplifying the electron beam microbunching after the magnetic chicane. Due to the harmonic amplification, the minimal delay between pump-probe pulse pairs (limited by slippage between the light field and the electron bunch) can be shorter than 0.5 femtoseconds. We use the angular streaking technique to measure temporal delays between pump/probe pulse pairs at multiple beamline configurations. When the delay chicane is turned off, the averaged delay is in-creased by ~150 attoseconds by adding one undulator module for probe pulses. Long delays can be set up by turning the delay chicane on. These experimental results agree with start-to-end XFEL simulations. Looking toward future experiments, our sub-femtosecond pump/probe technique can be applied to observe electronic charge dynamics in molecular systems.
Future colliders will require injector linacs to accelerate large electron bunches over a wide range of energies. For example the Electron Ion Collider requires a pre-injector linac from 4 MeV up to 400 MeV over 35 m [1]. Currently this linac is being designed with 3 m long traveling wave structures, which provide a gradient of 16 MV/m. We propose the use of a 1 m distributed coupling design as a potential alternative and future upgrade path to this design. Distributed coupling allows power to be fed into each cavity directly via a waveguide manifold, avoiding on-axis coupling [2]. A distributed coupling structure at S-band was designed to optimize for shunt impedance and large aperture size. This design provides greater efficiency, thereby lowering the number of klystrons required to power the full linac. In addition, particle tracking analysis shows that this linac maintains lower emittance as bunch charge increases to 14 nC and wakefields become more prevalent. We present the design of this distributed coupling structure, as well as cold test data and plans for higher power tests to verify on the structure’s real world performance.
Linear induction accelerators such as the DARHT at Los Alamos National Laboratory are used as sources for flash x-ray diagnosis of dynamic events. The source characteristics of primary interest are the source intensity, the source spot-size, and the illumination uniformity which are determined by the electron beam parameters. We utilize self-developing x-ray film to characterize the x-ray source with a combination of penumbral imaging and spatial dose profile measurements. The penumbral imaging method makes use of a thick, tungsten collimator and Fourier transform methods to reconstruct a source image. Modeling of the bremsstrahlung source profile allows the inference of the beam convergence angle within the x-ray converter target. The two parameters together can be used to estimate the beam emittance. In one example, a self-developing film is exposed with 1300 Roentgen on-axis dose. In one example, a source with Gaussian fall-off of 280$\mu$m is reconstructed from the penumbral image and an inferred convergence angle of about 2.6$^{\circ}$ yields a normalized emittance of approximately 900 mm-mrad.
Background and aim: The potential of a compact, laser-based ion accelerator for radiobiological and medical applications relies heavily on the control of the laser-target source and on the use of custom beam transport and delivery to the final target. Here we show the results of an experimental campaign dedicated to the dosimetry of the beam at the crosswire and the first radiobiological micronuclei (MN) assay study in the regime of ultra-high dose rate at selected proton energies at multi-MeV.
Methods: We have developed a proton beamline based on the so-called Target Normal Sheath Acceleration (TNSA) to deliver a proton beam radiobiological applications. We use TNSA driven by a 200 TW ultra intense laser to accelerate protons with a cut-off energy of up to 10 MeV. We use permanent magnet quadrupoles to select protons at 6 MeV and transport them, in the form of a collimated beam, to the final target position in air.
Results: We measured the spectrum and the deliverable dose of the proton beam at the sample position for each shot. We also evaluated uniformity across the beam and shot by shot fluctuations. We carried out dosimetric measurements that show a ultra-high instantaneous dose rate, with good uniformity over a cm-scale dimension and good shot to shot reproducibility. A preliminary measurement of radiation damage vs dose based on the MN assay was successfully carried out and compared with conventional X-ray source.
In this paper, we present the benchmark results of Bmad space charge tracking on the Electron-Ion Collider cooler injector lattice. Bmad, GPT, and Impact-T are compared in terms of accuracy and performance. We highlight the importance of space charge algorithm and demonstrate that the adaptive step size control improves the performance of Bmad space charge tracking.
The interest in plasma-based accelerators as drivers of user facilities is growing worldwide thanks to their compactness and reduced costs. The EuPRAXIA@SPARC_LAB collaboration is preparing a technical design report for a multi-GeV plasma-based accelerator with outstanding electron beam quality to pilot an X-ray FEL, the most demanding in terms of beam brightness. The beam dynamics has been studied aiming to a reliable operation of the RF injector to generate a so-called comb-beam with 500 MeV energy suitable as driver of the Beam-driven Plasma Wakefield Accelerator. A case of interest is the generation of a trailing bunch with 1 GeV energy, less than 1 mm-mrad transverse emittance and up to 2 kA peak current at the undulator entrance. The comb-beam is generated through the velocity bunching technique, an RF compression tool that enables high brightness beams within relatively compact machine. Since it is based on a rotation of the beam phase space inside the external RF fields, it could be particularly sensitive to amplitude and phase jitters in the RF injector. The electron beam dynamics and the machine sensitivity to the possible jitters are presented in terms of effect on the beam quality so to provide the basis for the alignment procedure and jitter tolerances. Numerical studies have been consolidated with experimental results obtained at SPARC_LAB, a test facility currently oriented to plasma acceleration physics where the velocity bunching scheme is routinely applied.
Ultrafast electron probing techniques offer unique experimental tools for investigating the structural dynamics of ultrafast photo-induced processes in molecular and condensed phase systems. In this work, we propose using the SEALAB Photoinjector's exceptional and versatile electron beam parameters to develop a state-of-the-art facility for ultrafast electron diffraction and imaging (UED and UEI) experiments with high sensitivity in space, energy, and time. We first address the design of an electron lens based on quadrupoles that enables easy switching between diffraction and direct imaging modes with minimal system changes. We compare the performance of the quadrupole-based lens with a simpler solenoid-based lens with similar functionality by calculating their respective aberration coefficients. Furthermore, we introduce the necessary beam-line modifications for enabling dark field imaging in the SEALAB Photoinjector. This development is crucial to achieve high-resolution imaging and enable the study of a wide range of material systems.
An Inverse Compton Scattering (ICS) X-ray source is under development at the ELSA electron RF linac of CEA DIF. The X-rays are emitted by the interaction of a 30-MeV electron bunch with a visible (532nm) or infrared (1064nm) Nd:YAG laser pulse. The radiation spectrum lies in a 10-100 keV range. The electron bunches duration is 30 ps after compression in double-alpha magnets. In such a system, electron trajectories are curved with a short radius, resulting in a noticeable degradation of the beam emittance, that might be a limitation cap to our source yield optimization in our effort to raise the bunch charge from 0.1 to 3 nC.
In the specific case of strongly curved trajectories, the symmetry hypotheses used for space charge calculation in several simulation codes are questionable, especially when calculations are made in the reference particle frame, leading to inaccurate compensation of electric and magnetic components of Lorentz force. We ran simulations of electron beam dynamics within the double-alpha magnets, using codes with different architectures (PIC, PIC Slice, envelope) and space-charge routines such as CST MWS and TraceWin/Partran, that rely on different models and frame references. We compared these results with experiments in order to evaluate the order of magnitude of these errors and to validate the use of a simulation tool to optimize our ICS source.
Blow-out beam generation is an established method to generate uniformly-filled ellipsoidal electron bunches by illuminating the cathode by an ultrashort laser pulse having a parabolic-like transverse profile of laser intensity. A theoretical study of blow-out generation in an APEX-like ultrahigh frequency RF gun revealed emittance oscillations and self-compensation at the gun exit without any additional accelerator components or fields. This regime is observed for a strong space-charge field on the cathode reaching around 30-35% of the accelerating field. The bunch emittance attains its lowest possible value for a given charge. Simulations clearly show an initial growth and a subsequent self-compensation of projected emittance in a divergent electron bunch originating from the effects of: (i) strong space-charge forces of mirror charges on the cathode, (ii) an energy chirp in the bunch and (iii) substantial re-shaping of the electron bunch. The study is in press in New J. Phys., DOI 10.1088/1367-2630/aca5ab.
The high-voltage modulators of the 26 klystrons in the XFEL represent the largest power consumer of the accelerator facility. The beam energy is usually 14 GeV, but a few weeks a year, lower and higher beam energies are also produced. For example, 11.5 and 16.3 GeV. Until mid-2022, the modulator voltages were set so that enough RF power for 16.3 GeV beam energy could be provided at all times. In order to save energy, the modulator voltages will now be lowered to a sufficient level for beam energies of ≤ 14 GeV. In this way, the previous power consumption of the modulators of 5 MW can be reduced up to 1 MW depending on the operation mode. Over the course of a year, this will save several GWh of energy. In the following, the relationship between the output voltage and the power consumption of the modulators is described. Afterwards, it is reported how the power consumption was reduced in various operating conditions in 2022.
Externally seeded free-electron lasers are promising for generating intense, stable, and fully coherent soft X-ray pulses. An earlier study demonstrates that high brightness and coherent soft X-ray radiation can be produced based on coherent harmonic generation and superradiant principles, termed high-brightness high-gain harmonic generation (HB-HGHG). However, due to the limitations of state-of-the-art laser systems, seed lasers in the ultraviolet region cannot induce sufficient energy modulation at high repetition rates. A recently suggested self-modulation scheme shows that the peak power requirement of a seed laser can be reduced by around one order of magnitude in an HGHG setup. In this paper, we present start-to-end simulation results to estimate the feasibility of the self-modulation-enhanced HB-HGHG scheme.
RUEDI (Relativistic Ultrafast Electron Diffraction & Imaging) is a proposed facility which will deliver single-shot, time-resolved, imaging with MeV electrons, and ultrafast electron diffraction down to 10 fs timescales. RUEDI is being designed to enable the following science themes: dynamics of chemical change; materials in ex-treme conditions; quantum materials; energy generation, storage, and conversion; and in vivo biosciences. RUEDI is proposed to be built at STFC’s Daresbury Laboratory in the UK. The Conceptual Design Review and Outline Instrument Design reports were published in November 2022 and summarised in this paper, with a Technical Design Review report to follow in November 2023.
At the University of Melbourne X-LAB we are investigating the use of a low (\beta) acceptance X-band accelerating structure as part of the design of an all X-band RF electron preinjector optimised for the production of low emittance electron bunches for medical physics applications and compact light source development.
In this work we will elaborate on the estimated performance, design issues, and optimisation methodology of the preinjector beamline.
Electron beams with a flat-top transverse distribution are highly desired for uniform dose delivery in irradiation applications, like studies of radiation damage to electronics and radiotherapy, as well as for potential applications in the improvement of light sources. In this work, we report on the optimization of the electron photocathode injector parameters which allow such uniform distributions to be reached. This can be achieved starting from a standard Gaussian transverse distribution of the laser, by tailoring the space charge forces and the magnetic field of the solenoid. We report on the first experimental demonstration of this method at the CLEAR facility at CERN.
Typically, in Self-Amplified Spontaneous Emission Free Electron Laser (SASE FEL) based short-pulse schemes, pulse duration is limited by FEL coherence time. A method, proposed in [1], allows to overcome the coherence time barrier and to get much shorter pulses. When lasing part of an electron bunch is much shorter than coherence time, one can suppress the radiation in the long main undulator while preserving microbunching within that short lasing slice. Then a short radiation pulse is produced in a relatively short afterburner. We performed first experimental tests of this concept at the soft X-ray FEL user facility FLASH. The results are presented and discussed in this contribution.
[1] E. Schneidmiller, Phys. Rev. AB 25, 010701 (2022)
Our laboratory has been studying about polymer electrolyte membrane (PEM) for polymer electrolyte fuel cell (PEFC) by irradiation graft polymerization using electron beam accelerator. Irradiation graft polymerization can reduce the production cost of the PEM compared with the current product, perfluoro-sulfonic acid (PFSA) ionomer such as Nafion®︎ by DuPont. We have two methods to fabricate high-performance PEMs using the accelerator. One is to give the micro-structure of hydrophilic and hydrophobic region to the PEM. The other is to generate the concentration gradient of hydrophilic region inside of the PEM. Both methods were able to generate high power density as much as Nafion®︎. In previous study, we used ion beam to give these characteristics. Ion beam has highly straightness and easy to create micro-structure and the concentration gradient of hydrophilic region inside of the PEM. But, its production equipment costs too much. Therefore, in this study, we use electron beam that production equipment costs less than ion beam and fabricate the PEM which has above both methods for advanced application of the electron beam accelerator.
We study the feasibility for a hard x-ray FEL oscillator (XFELO) at 3 GeV based on harmonic lasing and transverse gradient undulator (TGU) with strong focusing. We carry out optimization of parameters using the formula developed in 2021 [1] for harmonic lasing XFELO with TGU and strong focusing. From previously assumed x-ray cavity loss of 30-20%, we lowered the assumed cavity loss to 5% (which includs an assumed 1% output coupling). This significantly reduced the required single pass gain to 5%, hence the renewed optimization relaxed the very stringent requirment on the electron beam parameters. After the optimization by analytical formula we confirm the single pass gain using simulation by “GENESIS” code.
[1] L.H. Yu, Gain of Hard X-ray FEL at 3 GeV and Required Parameters, in Proc. of IPAC-2021, MOPAB040.
One of the limitations in structure wakefield acceleration is large transverse emittances of high-charge wakefield drivers. The simplest idea to avoid this issue would be to prepare multiple lower-charge drivers and apply RF power from all drivers to a single accelerating tube. However, the method has two significant drawbacks; cost and timing control. We propose a single high-charge beamline that turns a single beam into multiple transverse beamlets to drive wakefield in transverse distributed power extraction tubes. Here, we present the first feasibility study of the concept.
The photon energy in the soft X-ray range corresponds to the fundamental absorption edges of matter. Ultrashort X-ray pulses can be used to observe the breaking of chemical bonds in biochemical reactions and capture the transfer process of electrons in ultrafast physical phenomena, which is of great significance for the research of the next generation of semiconductor materials, such as diamond and graphene. In this paper, the feasibility of ESASE experiments on Shanghai Soft X-ray Free Electron Laser Facility (SXFEL) is theoretically verified. The results show that the ESASE scheme can produce ultrafast light pulses on the order of attosecond, with a peak power of 450 MW. At the same time, the simulation results in this paper verify the feasibility of chirped enhanced SASE schenme based on SXFEL. The results show that compared with the ESASE scheme, the power of the radiation pulse can be greatly improved by this scheme. A relatively low energy electron beam (1.5 GeV) was used to generate about 40 GW of radiation, and the length of the radiation pulse was significantly shortened.
We present an overview of the FERMI seeded free electron laser (FEL) facility located at the Elettra laboratory in Trieste, Italy. FERMI, in operation with both FEL lines FEL-1 and FEL-2 since 2012, covers the spectral range between 100 nm and 4 nm with light characterized by variable polarization, narrow spectral width, stable intensity and central wavelength. A series of infrastructure upgrades have been proposed in recent years to keep the facility in a world-leading position. The upgrade includes profound modifications of the linac and the two FERMI FELs with the ambition to extend the performance of the FEL and the control of the light produced to include the K edges of N and O and the L edges of transition metals. Recently, new accelerating section allowed an increase of the beam energy of about 100 MeV and the configuration of the first FEL-1 has been revamped. The FEL has been changed into an echo-enabled harmonic-generating FEL, and commissioning of this new FEL is underway.
The upgrade of the single cascade FEL-1 of the FERMI free-electron laser, aiming at implementing operation either in Echo Enabled Harmonic Generation (EEHG) or in High Gain Harmonic Generation (HGHG) mode, has started. We have recently modified the layout in order to crate the space required for the installation of the large dispersive section needed for the EEHG scheme. As a result, the radiator has been separated by a 10-meter long drift from the modulator, where the interaction between electron bunch and seed laser takes place. The setup will be completed by the end of the first semester of 2023 and users operations are expected to start shortly afterwards. In this contribution, we present a status report of the FEL-1 upgrade process, focusing in particular on the results obtained during the commissioning.
Within the framework of FLASH2020+, substantial parts of the injector of the FEL user facility FLASH have been upgraded during a nine-month shutdown in 2022 to improve the electron bunch properties in preparation for FEL operation with external seeding starting in 2025. As part of the injector upgrade, a laser heater has been installed upstream of the first bunch compression chicane to control the microbunching instability in the linear accelerator by a defined increase of the uncorrelated energy spread in the electron bunches. In this paper, we present first results of beam heating studies at FLASH. Measurements of the induced energy spread are compared to results obtained by particle tracking simulations.
We report a first observation of terahertz super radiant emission from the Israeli Free Electron Laser. This is the first demonstration of a THz source based on the scheme of coherent spontaneous superradiant emission by an ultra-short e-beam bunch [1].
The FEL is driven by a compact (64 cm long) Hybrid photo-cathode RF gun, emitting a beam of electron with kinetic energy of 3.5 to 8.5 MeV [2]. At 6 MeV, the Undulator emission has a frequency of app 3.5 THz. A chirp-based bunching scheme produces a 100 fs pulse in the center of the undulator, which is less than half a period of the emitted radiation (290 fs). This produces superradiance, a phenomenon where the electrons emit coherently in phase with each other. In this situation the radiation fields emitted by the electrons add up. Thus, the total energy of the radiation is proportional to the square of the electrons number (current) and not proportional to the current as in a conventional spontaneous emitter.
This principle provides a significant advantage over THz FEL schemes based on SASE [3], since the energy is proportional to the number of electrons squared, and thus comparable THz radiation energies (we measured at first attempt ~30 nJ per pulse) can be obtained with a very compact accelerator and a short wiggler.
In the framework of our FEL user center of the Ministry of Science, we aim to apply our special THz source to provide high energy tunable radiation to users in a wide range of disciplines.
X-rays production through betatron radiation emission from electron bunches is a promising resource for several research fields. In the framework of EuPRAXIA project, EuAPS (EuPRAXIA Advanced Photon Sources) project has the purpose to provide a compact, plasma based line designed to exploit internal injection processes occurring in laser-plasma interaction to drive electron betatron oscillations, thanks to plasma-generated fields. The user-oriented character of the project requires advanced diagnostic devices to assure the desired operation conditions. Since emitted radiation spectrum, intensity, coherence and polarization are strongly dependent on the self-injected beam properties, accurate preliminary simulations of the process are mandatory to evaluate the optimal diagnostic devices specs. QUASI-3D cylindrical azimuthal modes decomposition based PIC simulations have been carried on, together with reduced physics beam envelope based models, giving inspection on the accuracy/computational cost ratio. We present simulated betatron radiation spectra and properties for some cases of interest.
The importance of coherent brilliant light sources for research and industry makes free electron laser (FEL) facilities a cornerstone of today’s science. The improvements of such facilities are of great importance. Here I present the first steps to enhance the undulator sections in FEL facilities by adding a plasma inside the undulator [1]. Instead of propagating the electron beam in vacuum inside the undulator, by filling part of the undulator with a low-density plasma one may reduce the transverse divergence of the electron beam during the propagation inside the undulator, thus, keeping or reducing the emittance. In addition, a pre-bunching occurs thanks to the interaction between the beam, plasma and undulator field potentially shortening the necessary undulator length to start FEL generation. The additional focusing could also reduce the needs of magnetic elements between undulator sections. The concept could be considered as a merge between the plasma lens and the undulator. Therefore, is a middle step between the current undulators and the full plasma undulators, i.e., the plasma filled undulator.
A research project was initiated at HZB to develop a new E-Gun control system for the Linac Gun to realize the advanced demands from the BESSY II injection scheme. The Flexi-Gun system will allow significantly higher flexibility in both pulse load and pulse timing structure. The purpose built gun test stand is equipped with a diagnostic beamline. Developed and manufactured in-house, the potential for knowledge transfer has led to a collaboration with ALBA for start-to-end particle tracking simulations. This article presents the motivation and potential of the Flexi-Gun, the development of the driver board and control, and the first measurements of the beam parameters.
With the "Flexi-Gun" project, the upgraded Linac E-Gun becomes the optimal injector for BESSY II.
The lateral position deviation between the electron beam and undulators will lead to an interaction area decrease in practical high-gain free electron laser (FEL) equipment. Corrector magnets can be modified in the FEL control system to regulate the electron beam trajectory and promote laser power. Tuning tasks are time-varying, drifting, and multi-dimensional, and manual tuning by operators takes lots of time and effort. This paper proposes an online optimization algorithm using a twin delayed deep deterministic policy gradient (TD3) to automatically optimize laser energy under ever-changing conditions.
Energy recovery linacs (ERLs) possess bright prospect of the fully coherent x-ray generation. Recently, we designed a 600 MeV energy recovery linac capable of producing high power fully coherent radiation pulses at 13.5 nm with a relatively low-intensity 256.5 nm seed laser profited from the employment of angular-dispersion-induced microbunching (ADM) technology. We also designed a matched multiplexed system that can deflect each radiator by 8 mrad with a carefully choreographed multi-bend achromat (MBA) scheme. As a result of downstream MBA’s dispersion compensation, bunching factors will be enhanced both at fundamental wavelength and high harmonics. The bunching factor of the 19th harmonic increased from 10% to 26%, and that of the 57th harmonic became 7.8%, which is sufficient to generate fully coherent radiation in the soft X-ray range.
Attosecond soft x-ray pulses is of great importance for the study of ultrafast electronic phenomena. In this paper, a feasible scheme is proposed to generate isolated fully coherent attosecond soft x-ray free electron laser via optical frequency beating. Two optical lasers with the opposite chirp are used to induce a gradient frequency energy modulation, which helps to generate a gradually varied spacing electron pulse train. Subsequently, the undulator section with delay lines located between the undulators are used to amplify the target ultrashort radiation. Numerical start-to-end simulations have been performed and the results demonstrate that an isolated fully coherent x-ray free electron laser pulse is achieved with the peak power of 18 GW and pulse length of 650 as by using the proposed scheme.
A periodic system of spirally arranged magnetized annular sectors creates near the axis a helical field, which is close in structure and magnitude to the field in the set of helical magnets. Such a system of relatively few available magnets can be easier to manufacture and assemble than a system containing magnetized helices made from a single piece. In this paper, we theoretically study the dependence of the helical field on the number of sectors per undulator period. Short prototypes consisting of longitudinally and radially magnetized sectors, as well as a hybrid system assembled from longitudinally magnetized NdFeB sectors and preliminarily non-magnetized steel helices, was experimentally studied. The maximum measured value of the field on the axis of an undulator with a period of 2 cm and a relatively large inner diameter of 8 mm is 0.7 T. Such undulators can provide a large oscillatory electron velocity and seem promising for increasing the efficiency of FELs and IFELs in various frequency ranges.
With the best of modern standard lasers, high-energy gamma gamma (gg) colliders from electron beams of E > 250 GeV are only possible at the expense of photon luminosity, i.e. 10 times lower than for photon colliders at c.m. energies below 0.5 TeV. For existing state-of-the art lasers, an optimistic upper energy limit for x=4.8 is an electron beam of less than 250 GeV. We show how a single FEL design can produce a 10 factor gain in the luminosity of gg colliders as second interaction region of e+e- colliders up to at least 1 TeV c.m., thus paving the way for High Energy and High Luminosity gg colliders. The same electron beams and accelerators of the original e+e- collider are used for two identical high gain SASE FELs. At the appropriate energy required by the FEL, i.e. 2.3 GeV, every other bunch from each beam is diverted to each FEL line where a helical undulator produces circularly polarized 0.5 eV light with 0.1-1 Joules per pulse. The remaining bunches continue down the Linac and collide at their nominal energy with geometric luminosity of 1-6 × 10^34 cm2/s. The central FEL wavelength of 2.4 um, obtained with either standard warm magnet or superconducting technology for the undulator, and an x-factor in the range of 2 to 40, maximize the luminosity of the gg collider as second interaction region of a 0.5–10 TeV c.m. electron-positron collider. We therefore recommend that a gg collider be considered a natural part of all e+e- linear collider proposals.
Varex Imaging High Energy Sources Group has developed, built, and tested a Diode Electron Gun (DEG) based 6 MeV Accelerator Beam Centerline ABC-6-S-X-D, which showed excellent performance results, and has been entered into a serial production. The ABC is very similar in performance to its Varian-produced counterpart and may be used as its drop-in replacement in the existing installed Varex linac system base, which exceeds 1000 units. While we intend to utilize a Triode Electron Gun (TEG) based ABC in all new products, this DEG based design can also be used in linac systems for security screening, non-destructive testing, and medical applications. This paper presents high power test results of the developed ABC-6-S-X-D.
A typical commercially available thermionic triode e-gun operates in 10-15 kV range. Certain linac accelerating structures may benefit from higher voltage injection. Based on commercially available low voltage e-guns Varex Imaging High Energy Sources Group has developed an e-gun that could be operated in extended range of voltages of 10-40 kV, provides high adjustability of injecting beam parameters. The new e-gun can be utilized with both triode and diode options
Cavity-based FELs, including x-ray free electron laser oscillators (XFELO) and x-ray regenerative amplifiers (RAFEL), have been proposed to generate fully coherent x-rays at high repetition rates. Among them, the oscillator-amplifier scheme can be used to generate high-brightness x-ray beams. Motivated by this technique, we propose a promising scheme to generate a fully coherent x-ray seed laser for the HGHMG system. In this scheme, an x-ray regenerative amplifier is used to offer a fully coherent x-ray seed laser to modulate the electron beam in a helical undulator. With an energy-chirped electron beam, one part electron beam will not lase in the regenerative amplifier since the FELs resonance relationship is not satisfied. This part of the electron beam will be helically modulated in a helical undulator by the coherent x-ray from the previous regenerative amplifier. With the proposed technique, high power and high repetition rate x-ray with OAM can be produced, which will open routes to scientific research in x-ray science.
Ultrafast science has developed rapidly nowadays thanks to the development of optical and laser technologies, like chirped pulse amplification and high-harmonic generation. In this work, a simulation has been performed to generate high-power femtosecond free-electron laser pulses with chirp pulse amplification in echo-enable harmonic generation. Numerical modeling shows that the peak power reaches tens of gigawatts and pulse duration is about several femtosecond.
The production of soft to hard x-rays (up to 25 keV) at XFEL (x-ray free-electron laser) facilities has enabled new developments in a host of disciplines. However, there is great potential for new scientific discovery at even higher energies (42+ keV), such as those provided by MaRIE (Matter-Radiation Interactions in Extremes) at Los Alamos National Laboratory. These instruments can require a large amount of real estate, which quickly escalates costs: The driver of the FEL is typically an electron beam linear accelerator (LINAC) and the need for higher electron beam energies capable of generating higher energy X-rays can dictate that the LINAC becomes longer. State of art accelerating technology is required to reduce the LINAC length by reducing the size of the cavities, which in turn provides for a high gradient of acceleration. Compact accelerating structures are also high-frequency (S, C, and X-bands). Here, we describe using the Argonne Leadership Computing Facility (ALCF) ), located at Argonne National Laboratory to facilitate our investigations into design concepts for future XFEL high-gradient LINAC's in the C-band (~4-8 GHz). We investigate a Disk Loaded Wave Guide (DLWG) and an elliptical traveling wave (TW) structure modeled for operation at f =5.712 GHz at the ALCF using VSim software. We used an existing account under the ALCF LIGHTCONTROL project.
The oscillator-type mid-infrared free-electron laser (FEL) at Kyoto University named Kyoto University FEL (KU-FEL) has achieved the extraction efficiency of 9.4%. A 1-D simulation predicted that the extraction efficiency can be further increased by reducing the optical cavity loss or increasing FEL gain*. A new photocathode RF gun is installed for increasing the FEL gain by increasing the electron bunch charge. For further increase of the extraction efficiency in addition to the increase of bunch charge, several developments are underway. First one is reduction of the optical cavity loss by changing the out-coupling method from the hole-coupling to the scraper out-coupling. The second one is increase of FEL gain by reducing the minimum gap of the undulator. The third one is optimizing the curvature of optical cavity mirrors. Current status of these activities will be presented in the conference.
Free-electron lasers (FEL) producing ultra-short X-ray pulses with high brightness and continuously tunable wavelength have been playing an indispensable role in the field of materials, energy catalysis, biomedicine, and atomic physics. A core challenge is to maintain and improve the transverse overlap of the electron and laser beams. This requires high-dimensional, high-frequency, closed-loop control with magnetic elements, further complicated by the diverse requirements across a wide range of wavelength configurations. In this work, we introduce a proximal policy optimization architecture for FEL commissioning that autonomously learns to control the set of magnetic elements. We experimentally demonstrated the feasibility of this technique on the alignment of electron beams and laser beams automatically in Shanghai Soft X-Ray Free Electron Laser User Facility, by adjusting groups of corrector magnets to maximize the FEL output power.
Thomson/Compton scattering is a method to produce high energy photons through the collision of low energy photons in a laser pulse onto relativistic electrons. In the linear (incoherent) Thomson/Compton regime, the flux scales linearly with the number of primary particles and the bandwidth of the produced photons depend, amongst other factors, on the energy spread of them. In general, an increase of the primary particles is connected to a larger energy spread (e.g.non-constant acceleration gradients, collective effects, etc). Therefore their number is restricted by the desired bandwidth, and thus limits the flux.
In our previous (theoretical) studies we showed that the ideal Thomson spectrum can be retrieved when an electron bunch with a linear energy correlation of several percent collides with a matched linearly chirped laser pulse. Here we extend the scheme to allow for higher order energy correlations and quantify how the electron distribution influences the bandwidth. Furthermore we discuss the practical viability to maximize the primary particles, with the focus on linear accelerators (LINACS) for the electrons and laser pulses based on the chirped pulse amplification (CPA) scheme. These could potentially provide up to tens of nano-Coulomb electron bunches and tens, or even over a hundred, Joule lasers pulses respectively.
It has been known for decades that the intensity fluctuations of free-electron laser radiation conceal some information about the temporal characteristics of the light. In particular, by measuring the ensemble-averaged spectral intensity correlation function, one can reconstruct the average length of the x-ray pulse [1]. This method in its original form starts to break down once the electron beam has any energy chirp, which is often a feature during practical operating conditions. We recently extended the spectral intensity correlation method to linearly chirped electron beams, however this is still not completely representative of everyday beams [2]. We present here further analysis of nonlinearly chirped electron beams and their spectral statistics, and show that measurement of the spectral intensity correlation function provides non-trivial information about the nonlinear electron beam phase space and therefore the x-ray pulse phase space.
Intra-atomic dynamics are fundamental to organic processes such as photosynthesis. X-Ray spectroscopy, using pulses of tens of femtoseconds durations generated by Free Electron Lasers (FELs), has enabled great progress in understanding this field. Sub-femtosecond pulses would enable new discoveries in the ultrafast timescales of reactions and transitions. In this paper, attosecond pulse generation is investigated for the UK XFEL Conceptual Design project’s short pulse requirements, with a focus on the XLEAP (X-Ray Laser Enhanced Attosecond Pulses) scheme from LCLS. Simulation studies using the code Genesis 1.3 (v4) are used to investigate and optimise the FEL output properties and further explore methods of enhancing the output power. Simulation results indicate that a post saturation magnetic chicane can be used to double the FEL pulse peak power.
Hard X-ray Self-seeding (HXRSS) is a well-know scheme to obtain longitudinally coherent FEL pulses with single SASE mode selected by a crystal. However, multi-modes can also be produced if the electron beam contains lasing parts with different energy chirp slopes (i.e. nonlinear chirp). At the European XFEL we have observed HXRSS with multi-modes and investigated its origin both in simulation and in experiments. In this paper, we present simulations and experimental results and discuss possible ways to suppress this effect.
CLARA at STFC Daresbury Laboratory is a test facility for FEL research and novel accelerator technologies, providing high-quality electron bunches with charges up to 250 pC. Phase two of CLARA, which will bring the accelerator to its design energy (250 MeV) and repetition rate (100 Hz), is expected to begin commissioning in 2024. To maximise exploitation of the upgraded accelerator, a dedicated Full Energy Beam Exploitation (FEBE) beamline is currently being installed, featuring two large chambers where a high-power laser and advanced diagnostics will be available for user experiments that include investigation of novel plasma acceleration methods. Many experiments planned for CLARA-FEBE will require a high level of shot-to-shot beam stability, placing particular importance on the bunch time of arrival (tens of femtoseconds) and peak current (several kiloamperes). Accurate modelling of beam jitter will therefore be critical for the purposes of planning user experiments, and for future work to mitigate the dominant jitter sources in the machine. In this contribution, we investigate the jitter tolerance of CLARA-FEBE using start-to-end simulations of the accelerator complex.
Modern linac-based free electron lasers (FEL) opened a new area of scientific research in physics, chemistry, biology and material sciences. In recent years laser plasma accelerator (LPA) technology has made great progress towards compact electron ‘GeV-energy scale’ accelerators. Combination of compact LPA accelerator with well-established technologies to build dedicated electron beam transport and undulator beam-line opens a possibility to extend ability of existing FEL facilities delivering a photon beam with unique and novel properties for the worldwide photon user community. Development of the laser-plasma accelerator based soft X-ray FEL at ELI-Beamlines (Czech Republic) will extend ERIC-ELI capabilities in multiple science fields such as laser technology, plasma accelerators and photon science technology. In the frame of this report we will present a conceptual solution of the entire setup from the high-power high-repetition rate laser up to the photon beamline aiming to deliver to the user area the coherent photon beam with the wavelength in the soft X-ray range (3÷4.5 nm for the fundamental harmonic) and the peak brilliance, comparable with existing soft X-ray FELs. Challenges, R&D program needed in order to develop such user-oriented setup and connection with the EuPRAXIA (European Plasma Research Accelerator with eXcellence in Applications) project will be discussed.
The PERLE (Powerful Energy Recovery LINAC for Experiment) collaboration is developing a high power energy recuperation linac facility with three acceleration (up to 500 MeV) and three deceleration passes through two cryo-modules at an injection current of 20 mA. Here we present the lattice design of the first stage of this machine with one cryo-module that would demonstrate the six-passes operation with a maximal energy of 250 MeV at a high current. This lattice has a simpler design with less elements therefore it requires lower initial expenses and shorter construction and commissioning times. All the magnets and the cryo-module are chosen to be compatible with both stages to minimise the costs of upgrade to a final one.
Dalian Coherent Light Source (DCLS) is a free-electron laser (FEL) user facility. As a user facility, it is vital to provide the long-term stable FEL light, namely drift suppression. DCLS is a comprehensive integration of various devices, any key part of perturbation will result in drift of FEL lasing. Beam-based feedback (BBF) is an effective method to suppress the drift. This paper will introduce the design and the operational results of beam-based longitudinal feedback system (LBBF) at DCLS, especially its remarkable improvement on the drift suppression of FEL lasing.
Intra-beam scattering and other mechanisms can degrade the beam quality in the EIC Hadron Storage Ring. Strong hadron cooling will maintain the beam brightness and high luminosity during long collision experiments. An Energy Recovery Linac is used to deliver the high-current high-brightness electron beam for cooling. The best cooling rate is realized when the electron beam has low emittance, small energy spread, and uniform longitudinal distribution in the cooling section. Therefore, the initial distribution needs must be optimized to achieve a good cooling distribution. The longitudinal beam distribution at the cathode can be shaped by varying the temporal profile of the laser. The cathode distribution is tracked numerically through the cooler lattice to find the resulting cooling distribution. In this work, we demonstrate the optimization of the cathode longitudinal beam distribution to achieve a uniform longitudinal cooling distribution while maintaining a small emittance. Space charge and cathode image fields are included in the beam tracking.
Cavity-based XFEL, or CBXFEL, is a future highly-coherent photon source under construction at LCLS. In the first phase of the CBXFEL project, we will demonstrate the regenerative amplifier mode of operation with 7 LCLS Hard X-ray Undulators (HXUs). In this paper, we report on the recent measurement of the FEL gain in 7 LCLS HXUs, and hard x-ray self-seeding (HXRSS) under e-beam conditions close to those chosen for the first phase of CBXFEL.
Short bunches, high current and multiple linac pass are all characteristics of Energy Recovery Linacs (ERLs), which may result in collective effects. They in turn, may affect the beam, degrading its quality, or even yield to instabilities causing a beam loss. To study and mitigate these effects one needs a numerical simulation code, that can take into account both the collective effects, as well as, particular ERL features, such as a multi-turn design that does not reach a steady state or the multiple passages of the beam through Radio-Frequency (RF) cavities at different energies. CODAL [1], a code developed by SOLEIL in collaboration with IJCLab, enables such studies. It is a 6 dimensional (6D) tracking code applying 'kicks' based on the integration of the local Hamiltonian for each element of the lattice. It is also capable of simulating space charge, wakefields and coherent synchrotron radiation.
However, to correctly take into account the ERL dynamics, an upgrade had to be made to include the effect of a standing wave RF cavity in 6D. In this paper, we will concentrate on the implementation and benchmarking (with DESY’s tracking code ASTRA [2]) of both the longitudinal and the transverse models (by J.B. Rosenzweig and L. Serafini [3]), which we use to carry out tracking of fully analytical 6D RF cavity.
Modern free-electron laser (FEL) facilities are designed to simultaneously serve multiple undulator lines to pro-vide x-ray pulses with high peak power and tunable wavelengths. To satisfy different scientific demands, it is preferred to make the separate undulator lines work under different FEL schemes, such as the self-amplified sponta-neous emission (SASE) scheme and the echo-enabled harmonic generation (EEHG) scheme. However, different FEL schemes have different requirements on the beam longitudinal distribution. Here, we propose to use multiple bunches to simultaneously serve the undulator lines and put the bunches at different acceleration phase to change the bunch length with two compressor chicanes. The acceleration phase for each bunch is varied by adjusting the time delays of the photocathode drive laser pulses with the accelerator settings unchanged. The start-to-end simulation demonstrates that a fs bunch with high peak current can be produced to serve the SASE line while a bunch with hundred-of-fs length and uniform current distribution can be produced to serve the EEHG line. The FEL performances are simulated and discussed.
We demonstrate a simple method to generate two-color or multi-color soft x-ray FEL pulses. This method mainly uses a chirped electron beam working together with an EEHG alike modulator and chicane setup to produce wide electron beam bunch train. And this bunch train can be used to generate multi-color FEL pulses. By tuning the configurations and parameters of the method, we can easily adjust the property of the multi-color FEL pulse.
The ongoing Plasma-driven Attosecond X-ray source experiment (PAX) at FACET-II aims to produce coherent soft X-ray pulses of attosecond duration using a Plasma Wakefield Accelerator [1]. These kinds of X-ray pulses can be used to study chemical processes where attosecond-scale electron motion is important. For this first stage of the experiment, PAX plans to demonstrate that <100 nm bunch length electron beams can be generated using the 10 GeV beam accelerated in the FACET-II linac and using the plasma cell to give it a percent-per-micron chirp. The strongly chirped beam is then compressed in a weak chicane to sub-100nm length, producing CSR in the final chicane magnet at wavelengths as low as 10s of nm. In this contribution we describe the results expected from this initial setup, as well as future iterations of the experiment in which we plan to use short undulators to drive coherent harmonic generation to produce attosecond, terawatt X-ray pulses down to 1-2 nm.
In addition to PAX, a similar ongoing experiment at the XLEAP beamline at LCLS-II plans to demonstrate GW-scale attosecond pulses at UV wavelengths. We discuss tapering strategies which enable precise tuning of the XUV bandwidth and the generation of few-cycle micron wavelength pulses in this experiment which can be used for time-synchronized attosecond pump-probe experiments.
[1] C. Emma, X.Xu et al APL Photonics 6, 076107 (2021)
Noise and density fluctuations in relativistic electron bunches, accelerated in a linac, are of critical importance to various Coherent Electron Cooling (CEC) concepts as well as to free-electron lasers (FELs). For CEC, the beam noise results in additional diffusion that counteracts cooling. In SASE FELs, a microbunching instability starts from the initial noise in the beam and eventually leads to the degradation of beam energy spread and emittance in the linac. It can also produce nonuniform longitudinal phase-space for seeded FELs and hence affect the seeding efficiency. The development of robust beam-noise diagnostics for the near, mid and far-infrared regimes is essential for mitigating these risks. Here we describe an ongoing experimental program at the Fermilab Accelerator Science and Technology (FAST) facility to measure the level of density fluctuations in intense electron beams using transition radiation. In the initial experiments, we focus on the 0.5 – 2.5 um length scale, which is relevant to CEC concepts.
We have proposed a new method to generate coherent soft X-ray free electron lasers by the reverse-taper enhanced cascade echo-enabled harmonic generation. The method is based on the typical EEHG technique and a latter harmonic undulator section to lase the harmonic of the EEHG output. By using the reverse-tapered undulator at the EEHG undulator, an optimised FEL will be generate at the second stage.
The realization of a plasma based user facility on the model of EuPRAXIA@SPARC_LAB requires to design a working point for the operation that allows to get an high accelerating gradient preserving a low emittance and low energy spread of the accelerated beam. Such beam is supposed to pilot a soft x-ray free electron laser, a device with very challenging requirements in terms of brightness and energy spread. The external injection beam driven scheme by means of an RF photoinjector allows a fine tuning of the working point parameters at the injection, but the high beam current dictates the maximum accelerating gradient that can be obtained while preserving energy spread. These parameters are mostly connected to each other depending on the plasma wavelength and on the separation phase between driver and witness. In this work several simulation scans are presented, varying at the same time the plasma density and driver-witness separation in order to show that, in a realistic working point for EuPRAXIA@SPARC_LAB, it is possible to find an ideal compromise for a witness with a peak current >1kA that allows to preserve the energy spread of the core (80% of the charge) below 0.1%, while maintaining an accelerating gradient of the order of GV/m. The study is completed with a parametric analysis with the aim of establishing the stability requirements of the RF working point and the plasma channel in order to preserve the energy jitter at the same level of the energy spread.
Generation of attosecond XFEL pulses has drawn great attention in a wide range of research fields over the past decade. Adaptation and combination of state-of-the-art FEL techniques have led to advanced working schemes capable of producing the required ultra-short X-ray pulses. At the European XFEL, an R&D project, the AttoSecond Pulses with eSASE and Chirp-Taper schemes (ASPECT), has been launched. A typical scheme employs an external laser to modulate an electron beam and enables efficient lasing only over a short part of the electron bunch. In this paper, numerical simulations are presented, without using an external laser, to explore the capabilities of generating attosecond pulses at the EuXFEL. Obtained results will be shown and relevant discussions are given.
The Mainz Energy-recovering Superconducting Accelerator (MESA), currently under construction at the Johannes Gutenberg University (JGU) in Mainz, will offer two modes of operation, one of which is an energy-recovering (ER) mode in order to deliver electron beams of up to 155 MeV to two experiments. As an ERL, MESA, with it's high brightness electron beam, is a promising accelerator for supplying a Thomson back scattering based Gamma source. Furthermore, at MESA, the polarization of the electron beam can be set by the injector. The aim of this work is to provide a concept and comprehensive analysis of the merit and practical feasibility of a Thomson backscattering source at MESA under consideration of beam polarization and transversal effects. In this paper, the first results of our semi analytical approach to calculate various Thomson back scattering light source scenarios including polarization effects at MESA will be presented.
A THz free electron laser (FEL) prototype has been developed at the Photo Injector Test Facility at DESY in Zeuthen (PITZ) for obtaining high intensity radiation for THz-pump-X-ray-probe experiments at the European XFEL. In this development, a magnetic chicane was recently installed to optimize the THz FEL performance. The aim of this study was to investigate the beam dynamics in the chicane for a trajectory commissioning by tracking the electron beam via ASTRA using a 3-dimensional magnetic field of the chicane simulated with CST-EM Studio. The simulated results indicate the possibility of obtaining on-axis trajectory and zero-momentum dispersion of the compressed beam.
The relativistic interaction of short pulsed lasers or electrons with plasma has recently led to the birth of a new generation of femtosecond X-ray sources. Radiations with properties similar to those that can be observed from a wiggler or undulator, can be generated by the oscillations induced in the exited plasma by electrons (PWFA) or by lasers (LWFA), making plasma an interesting medium both for the acceleration as well as for the radiation source, whit properties of being compact, providing collimated, incoherent, femtosecond radiation, and a lot of effort is being made to understand and improve this new source to make it really competitive. This paper summarizes and shows some theoretical results and numerical simulation of a simplified model called plasma ion column, using as a starting point the parameters expected for EuPRAXIA@SPARC_LAB facility, highlighting strengths, limitations and scaling laws, which allow for a comparison with other types of more consolidated sources of light as Compton, Synchrotron and Free electron lasers.
For storage-ring-based free-electron lasers (FELs), prebunching via echo-enabled harmonic generation (EEHG) is an efficient way to reduce the radiator length and improve the longitudinal coherence as well as output stability. We propose a conceptual design, which uses two straight sections of a synchrotron to seed coherent soft X-ray emission. This scheme requires no change of the storage ring lattice and is fully compatible with other beamlines. To take the large energy spread (of the order of 10-3) of a storage ring electron beam into account, we developed a new modelling tool (EEHG optimizer) and successfully applied it to maximize the prebunching from harmonic 50 to 200 for nearly any synchrotron light source, with significant benefits. We developed a generalized EEHG model based on the critical parameters (momentum compaction, beam emittances, and Twiss functions) determining EEHG performances, which is applicable to nearly any synchrotron light source. We show by numerical simulations that for most of the currently operated and future light sources, the EEHG scheme can produce a significant prebunching up to harmonic 200, and thus generate a few MW scale peak power at 1.25 nm wavelength.
Currently 26 RF stations are in operation at the European X-ray Free Electron Laser (XFEL) and all RF stations can deliver sufficient power to support 600 µs beam pulse with an energy up to 17 GeV. These beam parameters require a power consumption of about 4.9 MW for high-power RF. Of course, the simplest way to save power is to reduce the XFEL repetition rate, but with some additional work and research, and without modifying any hardware, we can save the modulator power, without any impact on the XFEL performance. To reduce the power, we offer two methods that can be used together or separately. The first one is to make full use of the available power of the klys-tron during the rise and fall time of the HV pulse, and partial use of the available power during cavity filling by using phase and amplitude compensation. As a result, we can reduce the length of the HV pulse, because we fill the cavities with energy earlier. The second one is to slowly reduce the klystron HV during flattop. In total we can reduce the power consumption up to 30%, at the cost of making the low-level RF control more complicated as it needs to deal with large phase and amplitude changes. To solve this problem, we propose a new feature, dynamic output vector correction (OVC). In this report we will present some of experimental results from the klystron test stand and from several XFEL RF stations.
In this proceeding, we will examine the designs of cavity-based XFEL (CBXFEL) and X-ray laser oscillator (XLO) currently under construction at SLAC. We will point out the possible improvements in the optical design, and propose new schemes. We especially focus of rectangular and bow-tie geometries.
A THz SASE FEL is currently under operation at the Photo Injector Test facility at DESY in Zeuthen (PITZ) as a prototype THz source for pump-probe experiments at the European XFEL.This prototype should provide tunable (3-5 THz) narrowband THz radiation with THz pulse energies up to several hundred μJ from 17-20MeV electron beams with a beam charge of several nC and a peak current up to 200 A to demonstrate the THz SASE FEL concept. In experiments it has been learned that strong space charge effects, steering effects from quadrupoles and possibly geometrical and conductive wall wakefields should be carefully treated during the beam transport from the photocathode to the undulator. These effects have been reduced by applying a smooth beam transport and improving the beam trajectory in the booster accelerator and the quadrupole magnets. Furthermore, the beam trajectory and matching into the undulator is critical for the THz output energy. This has been optimized by the Bayesian optimization algorithm. In this paper, experimental findings regarding the optimization of electron beams and THz radiations will be reported.
The cryocooled DC electron gun at Arizona State University (ASU) is the first electron gun built to implement single-crystal, ordered surface and epitaxially grown photocathodes to produce cold and dense electron beams at the source. These high brightness electron sources are extremely desirable for ultrafast electron applications such as Xray Free Electron Lasers (XFELs), Ultrafast Electron Diffraction/Microscopy (UED/UEM), and electron-ion colliders. Electron beams are produced from a cryogenically cooled photocathode using a tunable wavelength LASER to emit electrons close to the photoemission threshold. The full four-dimensional transverse phase space of the electron beam can be measured by a single pinhole scan technique, allowing us to directly calculate the transverse emittance in both dimensions. In this contribution we report and discuss the beamline setup and first measurement results.
The ARES linac at DESY (Deutsches Elektronen-Synchrotron) is a dedicated accelerator research and development facility for advanced accelerator technologies and applications, including high gradient accelerating schemes, high-resolution diagnostics and medical applications. It provides ultra-short, high quality electron beams with charges between a few femtocoulombs and a few hundred picocoulombs, with energies up to 155 MeV, characterized by high reproducibility and stability.
The electron bunches are generated in a photoinjector comprising a UV laser and a normal conducting S-band gun with an exchangeable cathode material, enabling the required wide charge range and temporal bunch profile. A set of movable mirrors allows to change the position of the laser spot on the cathode, which in combination with bunch charge diagnostics downstream of the gun can be used for measuring the extracted charge as a function of the laser position. With this method the emission homogeneity and changes of the cathode can be studied and different cathode materials can be compared. We present the first results using this technique at ARES, including charge map and quantum efficiency (QE) measurements.
The photoinjectors of FLASH at DESY (Hamburg, Germany) and the European XFEL are operated by laser driven RF-guns. In both facilities cesium telluride (Cs$_2$Te) photocathodes are successfully used since several years. We present recent data on the lifetime and quantum efficiency (QE) of the current photocathode at FLASH #105.2, operated before and after a long shutdown. In addition, data for the cathodes that recently have been exchanged at the European XFEL will be presented.
Integrating the advances made in photonics with efficient electron emitters can result in the development of next generation photocathodes for various accelerator applications.
In such photonics-integrated photocathodes, light can be directed using waveguides and other photonic components on the substrate underneath a thin (<100 nm) photoemissive film to generate electron emission from specific locations at sub-micron scales and at specific times at 100 femtosecond scales along with triggering novel photoemission mechanisms resulting in brighter electron beams and enabling unprecedented spatio-temporal shaping of the emitted electrons. In this work we have demonstrated photoemission confined in the transverse direction using a nanofabricated Si3N4 waveguide under a ∼20 nm thick cesium antimonide (Cs3Sb) photoemissive film. This work demonstrates a proof of principle feasibility of such photonics-integrated photocathodes and paves the way to integrate the advances in the field of photonics and nanofabrication with photocathodes to develop next-generation high-brightness electron sources for various accelerator applications.
The proposed Shenzhen Superconducting Soft X-Ray Free-electron Laser (S3FEL) aims at generating FEL pulses between 1nm and 30nm. At phase-I, two undulator beamlines work at EEHG principle. The shortest wavelength is about 2.3nm at a harmonic of 104. However, the various three-dimensional effects of beam can smear out the fine structure in the longitudinal phase space for the EEHG, especially at such high harmonic number. To generate intense full coherent FEL radiation at ultra-short wavelength, a novel technique of EEHG cascaded harmonic lasing method is also considered. Physical design and FEL performance are described in this paper.
The proposed Shenzhen Superconducting Soft X-Ray Free-electron Laser (S3FEL) aims at generating FEL pulses whose wavelengths ranges from 1 to 30 nm. As part of the first phase of S3FEL, two undulator beamlines working under SASE operation mode is planned. The two beamlines generate FEL pulses with wavelengths ranging from 1 to 3 nm and 2.3 to 15 nm, respectively. The physical designs and the FEL performances of these beamlines are described and analyzed in this paper.
Shenzhen Superconducting Soft X-Ray Free-electron Laser (S3FEL) is a newly proposed high repetition-rate X-ray FEL facility. It will be located at Guangming Science City in Shenzhen with a total length of 1.7 km. The electron beam is generated from a VHF photocathode gun and accelerated to 2.5 GeV through a superconducting RF linac. At initial phase, it is planned to build four undulator lines with two of them working at the principle of SASE and another two working at EEHG. S3FEL aims at generating X-rays and EUV FELs between 1 and 30 nm at a rate up to 1 MHz to facilitate various scientific applications. This paper describes the physical design of S3FEL.
A 35MeV/2 mA S-band electron linear accelerator used to interact with solid targets to generate neutrons, gamma rays, and X-rays has been proposed to provide a scientific research platform for nuclear energy development, material development, biomedicine, deep space exploration besides other industrial applications. The accelerator has a three-stage accelerating structure, after the first-stage of structure, the beam energy can reach 10MeV, and then completes 270° vertical bend and 45° horizontal bend, respectively, for industrial applications and material irradiation effect research. This paper presents the first-stage acceleration of the linac and its bend branch, including a pre-buncher, an acceleration structure (provides beam energy 10MeV and average current 2mA), 270° and 45° bend magnets, with beam loss rate less than 15%. A detailed physical design and dynamics simulation results are presented and discussed.
In 2021, the Italian Institute for Nuclear Physics (INFN) was awarded the project for installing, testing and commissioning the energy upgrade of the Southern European Thomson back-scattering source for Applied Research (STAR) which is currently installed at the University of Calabria (UniCal). The STAR high-energy Linac, STAR-HEL, consists in a layout comprising RF accelerating structures (linacs), with relative magnetic optics components, in order to boost the electron beam energy from 65 MeV up to 150 MeV. In this paper, we discuss the status of the planning, installation and testing of the RF system (accelerating structures, power, network and LLRF) based on C-band (i.e. 5712 MHz RF frequency) technology. For this purpose, two C-band linacs are installed and are independently powered by two RF power stations, located aside the present S-band RF power station, which will deliver 42 MW (nominal) peak power RF pulses of 1us width and up to 100 Hz repetition rate. Operation in C-band permits acceleration with higher gradients, resulting in a more compact linac footprint.
Betatron radiation produced in the plasma acceleration process could be used as seed for Free Electron Laser (FEL). A broad band radiation in the X-ray spectral region is produced by the strong transverse electron oscillation in the plasma channel driven by particle or laser wake field acceleration. Selecting the betatron radiation wavelength matched with FEL resonance, with proper synchronization of the electron and photon pulses in the undulator, the FEL emission will be stimulated. In this paper the scheme that could be adopted in EuPRAXIA@SPARC-LAB complex together with the betatron and FEL emission simulations are presented.
Cavity based X-ray free-electron lasers (CBXFEL) are next generation X-ray sources promising radiation with full three-dimensional coherence, nearly constant pulse to pulse stability and more than an order of magnitude higher spectral flux compared to SASE FELs. However, especially for the low gain X-ray free-electron laser oscillator (XFELO), the outcoupling of the radiation stored inside the cavity remains an issue, as only small outcoupling coefficients are tolerable.
In this contribution, a scheme is proposed which exploits the polarization dependence of the crystal based X-ray diffraction, which poses the main reflection mechanism for forming the X-ray cavity. Especially for reflections close to a 45° Bragg-angle, as is proposed for the proof of concept experiment at the Linac Coherent Light Source (LCLS) at the Stanford Linear Accelerator (SLAC)"*", the polarization dependence of the reflection coefficient becomes very strong. By properly setting up the polarization of the FEL radiation with respect to the reflection direction, a very simple, yet potent and tunable outcoupling mechanism can be realized.
We are building a new infrared Free Electron Laser (FEL) facility in China that will produce infrared laser covering the spectral range from 2.5 um to 200 um. It is made up of two oscillators generating middle infrared and far infrared laser respectively, which are driven by a single RF linear accelerator (linac) with a tunable beam energy from 12 MeV to 60 MeV. According to the requirement of the FEL physics, the linac is designed with an rms energy spread of less than 0.5%, a transverse rms emittance of less than 40 mm-mrad and a micro bunch length of 4-10 ps with a charge of 1 nC inside. In this manuscript, we present the preliminary design of the accelerator, from the electron gun through the transport line's terminus.
Two-beam acceleration (TBA) in Terahertz (THz) regime is the natural extension of Gigahertz TBA pursued in Structure Wakefield Acceleration Community. Recently proposed CSR-free shaping technique using deflecting cavities showed the feasibility of generating a high-charge (~1 nC per bunch) bunch train compatible with THz frequency. Wakefield from THz structure with such a h high-charge bunch train has potential to reach a few GV/m accelerating gradients or a few GW THz power levels. We present a concept of a compact accelerator using THz-TBA for generating coherent X-ray.
There are two accelerator based infrared light sources in Kyoto University Free-Electron Laser (FEL) facility. One is a mid-infrared FEL covering the wavelength range from 3.4 to 26 micro-m driven by 40-MeV multi-bunch electron beams supplied from an S-band RF gun and an S-band linac. The other is a coherent undulator radiation* covering the wavelength range from 0.1 to 0.6 THz driven by 3.6-MeV electron beam supplied from an S-band RF gun. Present status of those accelerator based infrared light sources will be reported in the conference.
Self-seeding mode is the one of the FEL baselines at the SHINE, which has been used successfully at the LCLS, SACLA, PAL-XFEL and European-XFEL facilities. Both soft and hard X-ray self-seeding are adopted for the wide range of fully coherent X-ray spectrum coverage. Accordingly, the grating monochromator and crystal monochromator are the critical parts of the x-ray self-seeding. At the SHINE project, the scheme design and technological design of the monochromator have been carried out, in which the grating monochromator has been tested online at the SXFEL facility. In this manuscript, we will introduce the progress of the schemes from the basic physical design to the technological design.
Velocity bunching, sometimes called rectilinear rf bunch compression, is a common technique to generate femtosecond MeV electron bunches from a photoinjector system. Such ultrashort beam can be used to generate coherent THz radiations, in particular, coherent undulator radiation (CUR). However, beam properties such as beamsize, transverse emittance, bunch length and energy spread after bunch compression have significant effects on angular and spectral distributions of CUR. In this study, we perform space charge tracking of electron beam in the NSRRC photoinjector when its booster linac being operated near zero crossing phase in rf bunch compression and the resultant electron distribution of the output beam is then used for calculation of incoherent and coherent undulator radiation from a 10-cm period planar undulator by an algorithm based on Lienard-Wiechart potential. We also compared the radiation properties for cases of multiple bunch and single bunch operation with the same total charge.
n recent years the interest in high intensity, short-pulse coherent THz radi-
ation for non-linear experimental research and applications grew with upcoming
high intensity lasers. In contrast to lasers, accelerators provide free electrons
for which emission properties can be tailored to the demand at typically much
higher repetition rates than high-intensity lasers can provide. Efforts are ongo-
ing to augment short-bunch accelerators such as the European XFEL with THz
radiation sources such as undulators.
At the far-infrared linac and test experiment (FLUTE) at KIT, we can facil-
itate experiments to investigate coherent THz radiation from different sources
and provide short electron bunches. As an additional THz source, a supercon-
ducting undulator can be inserted and investigated.
In this contribution, we evaluate the opportunities of this THz undulator at
FLUTE for linear accelerators and FELs in terms of photon science and beam
dynamics.
cERL in KEK is a test accelerator for development works of technologies related to Energy Recovery Linac (ERL) and CW-Superconducting accelerators. It can produce a low emittance and short bunch beam at a high repetition rate. This feature is suitable for producing a high average power terahertz (THz) coherent radiation. We have been developing a THz source based on Coherent Diffraction Radiation (CDR) at the straight section of cERL. In the scheme, a short bunch electron beam passing through a metal target with a small hole emits coherent radiation. We have built a THz transport system from the source to an experiment station at outside of the accelerator shielding.
The unique higher-order mode transverse profile of CDR has been confirmed at the experiment station. We will report the design and tuning procedure of the THz transport optics in beam experiments.
A shared ambition in the R&D of future light sources is designing and constructing an ideal free-electron laser (FEL). Such a machine will produce tunable, multicolor, near transform-limited pulses, with a controlled delay, and fully coherent beams with precisely adjustable phase profiles enabling state-of-the-art measurements and studies of femtosecond dynamic processes with high elemental sensitivity and contrast. For this purpose, a research program towards a fully coherent light source based on generation of higher harmonics at the future superconducting high repetition seeded FEL, FLASH, is ongoing. One of the integral elements of this program is the virtual investigation of characteristics and inherent challenges of external seeding techniques through realistic start-to-end simulations. Some of the highlights of this work will be discussed.
Plasma accelerators are emerging as formidable and innovative technology for the creation of table-top devices thanks to the possibility to sustain several GV/m accelerating gradients at normal conducting temperature. Among others, the particle-driven configuration has been successfully tested at the SPARC_LAB test facility also demonstrating the emission of plasma-based FEL radiation in SASE and seeding operation. Recently we have performed further experimentals devoted to heightening the accelerating gradient in the plasma. The so-called comb beam has been set up with a 500pC driver followed by a 50pC trailing bunch. The maximum measured energy gain in the plasma has been of almost 30 MeV turning in an accelerating gradient of the order of 1.2 GV/m. The result represents a fundamental achievement also looking at the forthcoming EuPRAXIA@SPARC_LAB plasma-based user facility. Further experimental runs are planned for the next year on the measurements of transverse quality of the electron beam and its eventual preservation. The paper reports on the obtained experimental results and on the numerical studies for the next future experiment at the SPARC_LAB test-facility.
Coherent, wide-tunable frequency and high intensity terahertz (THz) source is under preparation at the Shanghai Soft X-ray free-electron laser facility (SXFEL). The strong field THz radiation from 0.1 to 5 THz is generated by coherent transition radiation (CTR) when compressed electron bunches pass through the metal foil. In addition, the electron bunches modulated by frequency beating light can generate coherent, wide-tunable, high intensity THz radiation from 5 to 20 THz through the wiggler. Now the frequency beating optical system has been set at the laser heater of the SXFEL. The electromagnetic wiggler with peak magnetic field up to 2.5 T is adopted and the parameters of the wiggler are optimized to ensure the generation of strong field THz radiation. The simulation results show that the peak power of X-ray can reach the order of GW at 4 nm. The THz pulse energy can still be kept at mJ level under the proposed different parameters of the wiggler. The THz source at the SXFEL will provide an outstanding tool for strong field THz pump-probe experiments in the future.
FLASH, the Free electron LASer in Hamburg is currently undergoing a substantial refurbishment and upgrade project (FLASH2020+). A major stage was the 9 month shutdown in 2021/22. During this shutdown key components of the injector/linac where inserted, moved, rebuild or upgraded to enable the efficient and reliable preparation of electron bunches for HGHG and EEHG seeding in the FLASH1 beamline and simultaneous SASE operation in the FLASH2 beamline. In particular we have, added a new injector laser system, installed a laser heater system, moved the 1st bunch compression chicane downstream to generate space for the laser heater, replaced two old acceleration modules with modern high-gradient modules (thereby gained an additional 100 MeV of energy), replaced the 2nd bunch compression chicane with a more fancy movable one that enables variable longitudinal dispersion while allowing the compensation of bunch tilts, and saves space for an additional matching section section at the entrance to the main linac. Here we describe the more general aspects of the re-commissioning of the machine with beam which started early October 2022.
We review the theory of optical klystrons with SASE FEL applications in mind. Previous theories miss terms in the power gain factor that cannot be neglected, and we illustrate differences between the previously known analytical expressions, new ones discussed here, and numerical calculations. We then consider the use of optical klystrons for electron energy-spread and radiation coherence-time diagnostics purposes.
As Compton X-ray and gamma-ray sources become more prevalent, to understand their performance in a precise way it becomes important to be able to compute the distribution of scattered photons precisely. An ideal model would: (1) include the full Compton effect frequency relations between incident and scattered photons, (2) allow the field strength to be large enough that nonlinear effects are captured, and (3) incoroprate the effects of electron beam emittance. Various authors have considered various pieces of this problem, but until now no analytical or numerical procedure is known to us that captures these three effects simultaneously. Here we present a model for spectrum calculations that does simultaneously cover these aspects. The model is compared to a published full quantum mechanical calculation and found to agree for a case where both full Compton effect and nonlinear field strength are present. We use this model to investigate chirping prescriptions to mitigate ponderomotive broadening.
FLASH, the Free-Electron Laser in Hamburg, houses an experimental beam line for the study of seeding called Xseed. For the upcoming realization of a seeded FEL in the scope of the FLASH2020+ project, these components offer a unique possibility to study hardware, procedures and software for a future seeded operation. In this contribution we give an overview of the FLASH accelerator, the Xseed hardware installation and report recent studies and their results.
Externally seeded free electron lasers (FELs) offer fully coherent and stable FEL radiation in the soft x-ray regime. While electron bunches of superconducting-based FELs are available at MHz repetition rates, seeded radiation is limited by the repetition rate of the seed laser used in the process. Combining standard seeding schemes with an optical klystron is a simple and promising trick to reduce the seed laser power requirements and allow externally seeded radiation at higher repetition rates. To ensure optimum operation, we study the combined effect of a linear and a quadratic electron beam energy chirp on the properties of the output FEL radiation.
With the FERMI2.0 upgrade plan FERMI is planning a major upgrade of the two FEL lines and the linac in order to extend the tuning range toward 2 nm in the fundamental and with full polarization control. The shortest wavelength range will be reach with a two stage FEL relying on a first Echo Enabled Harmonic Generation operating at harmonic close to 30 to convert the UV seed laser wavelength to the EUV. A second stage, operating in High Gain Harmonic Generation, will then generate the final FEL pulses. In this work we report about the sensitivity of the proposed setup to variation of electron beam and seed laser parameters with respect to nominal values.
At Pohang Accelerator Laboratory X-ray Free-Electron Laser (PAL-XFEL), the scheme for generating attosecond XFEL pulse at soft X-ray undulator line is developing. Enhanced Self-Amplified Spontaneous Emission (E-SASE) method with external laser pulse is adopted to induce the current spike in the electron beam and generate attosecond XFEL pulse. E-SASE section consists of the wiggler and the magnetic chicane. When the electron beam passes through the wiggler with the external laser pulse, the energy modulation can be induced in the electron beam. After that, the induced energy modulation can be converted to the density modulation, which is called the current spike, when the electron beam passes through the dispersive section such as magnetic chicane. By using the current spike in the electron beam, attosecond XFEL pulse can be generated at the undulator section. In this presentation, the layout for generating attosecond XFEL pulse at PAL-XFEL will be introduced. Also, the simulation results about generation of current spike and attosecond XFEL pulse will be discussed.
Externally seeded high-gain free electron lasers (FELs) are capable of providing fully coherent radiation with high shot-to-shot stability at wavelengths down to the soft X-ray range.
However, present seed laser sources are not suitable for the generation of short wavelength FEL radiation at high repetition rates. As a result, such setups have been unable to make use of the full repetition rate of superconducting machines.
Cavity-based FELs have been proposed as one possible way to overcome these limitations, allowing to combine short wavelengths and high repetition rates, while preserving the full coherence.
We present simulation studies for such a high-gain FEL oscillator planned for FLASH, which is aimed at the generation of fully coherent radiation at 13.5 nm and the repetition rate of 3 MHz. Achieving bunching on that wavelength would make it possible to generate fully coherent radiation at much shorter wavelengths with the use of harmonic conversion schemes.
In many advanced accelerator facilities such as e+e--linear colliders and high gain free electron lasers, magnetic bunch compressors are often used for enhancement of beam brightness. However, the energy chirp (correlated energy spread) introduced into the beam by the chirper linac remained after bunch compression is undesirable in some applications. In this report, we present our study of a planar dielectric-lined waveguide (DLW) structure that can be used to remove the remaining energy chirp after bunch compression. As revealed from ELEGANT simulation of the high brightness driver linac system, a residual energy chirp of about 42 keV/ m is left after bunch compression. We successfully used a 1-m long corrugated pipe dechirper to remove the residual energy chirp in ELEGANT simulation. However, fabrication of this 1-m long corrugated pipe structure is not an easy task. In order to save space, we consider to use planar DLW structures to remove residual energy chirp after bunch compression instead. Wake potential due to this DLW dechirper has been calculated by CST code. An optimized geometry will be presented in this report. Wake potential as calculated form CST code is de-convoluted to obtain a wake function. The effect of the dechirper on beam distribution can be studied by particle tracking using this wake function in ELEGANT. We expect the performance of the DLW dechirper will be equivalent to the 1-m long corrugated pipe dechirper but with a much more compact size.
In this study we investigate simulation results for a virtual diagnostics concept that is planned for the SASE1 beamline at the European XFEL. These virtual diagnostics will be used to predict photon beam properties like pointing and divergence. We first use the GENESIS simulation framework to compute different lasing conditions in the undulator beamline, and then use Artificial Neural Networks (ANN) to predict the pulse properties. The final model will be able to estimate X-ray pulse characteristics based on properties like electron beam trajectories inside the undulator sections along with other diagnostics data. This study will provide insight towards the development of online virtual diagnostics in the real machine.
SOLARIS injector LINAC is designed to efficiently fill the electron storage ring. The injection currently takes place at 540 MeV, two times per day. After the accumulation of electron current, the energy is ramped up inside the ring to 1.5 GeV via two active RF cavities.
Top-up injection would be of extreme benefits for user operation, therefore here we present a simulation study for the design of a new injector that would make this possible in the future.
The major constraint for the simulation campaigns has been the space available in the existing LINAC tunnel. The idea is to replace the current machine (or modifying it) without infrastructural interventions in terms of tunnel expansion.
Performed studies demonstrate that the best solution is provided by a Hybrid S-band/C-band LINAC. Simulations have been performed using different codes and results are shown here.
Finally, a new machine working at 1.5 GeV would also pave the way to further diagnostic and/or experimental beamlines for particles and radiation solely based on the LINAC. In particular, one of the main goals is to achieve bunch compression below the picosecond level and low-emittance beams for a future short-pulse facility or a Free Electron Laser.
Developments of new research areas and breakthroughs in science are often linked to the progress in new instrumentation. Here we briefly summarize the scientific opportunities and the proposed layout of an X-ray Compton source based on superconducting accelerator technology. The X-ray source is envisioned to provide scientists at Uppsala University and collaborating research groups with 100 kHz femtosecond flashes of X-ray radiation for discovering novel materials systems, investigating biological structures, and characterizing catalysts and nanostructures. The X-ray source is envisioned to consist of a normal conducting ultrahigh frequency electron injector, a 1.3 GHz superconducting linear accelerator, a 5 kW IR laser based on thin-disk technology, and two X-ray beamlines. X-ray pulses in a range 2-8 keV with a duration of 400 fs FWHM and a source size of 3 microns, containing 10^6 photons per shot into 1% BW are demonstrated through start-to-end numerical simulations. The X-ray source combined with a momentum microscope for performing time-resolved ARPES is considered to be a powerful tool for studying quantum materials for new sustainable technologies.
Optimising the slice energy spread in X-ray free electron lasers (XFELs) is key to their effective operation, and must be considered from the photoinjector at the very beginning of the machine. The standard approach, in which the measured beam size is entirely attributed to the product of the dispersion and the energy spread, has only a resolution on the order of several keV, meaning that a precise measurement in photoinjectors where the energy spread is predicted to be on the order of a few keV is challenging. However, recent techniques developed at SwissFEL, the Photo Injector Test Facility (PITZ) and at the European XFEL (EuXFEL) enable the slice energy spread to be determined with sub-keV precision. In this paper recent slice energy spread measurements at the EuXFEL are presented and contrasted with previous results. Furthermore its dependence on beamline parameters is explored. Finally, recent developments in the automation and simplification of the measurement procedure at the EuXFEL that allow for a broader investigation of the slice energy spread and its dependence on the beamline configuration are stated.
At Eindhoven University of Technology a lab-based tabletop Inverse Compton Scattering (ICS) source is being commissioned. This compact and affordable X-ray source will bridge the gap between conventional lab X-ray sources and synchrotrons.
A 100 kV DC photo electron gun is used in combination with a bunching cavity to produce electron bunches that are injected in a X-band accelerator. The high gradient X-band accelerator is adapted from an original design for the Compact Linear Collider (CLIC). The accelerated electron bunches are focused and collide with a focused 12 mJ/pulse 800 nm laser beam thereby producing X-ray photons with energies between 10 and 40 keV. The physical basis behind the production of the X-rays is the ICS process in which photons from the laser pulse are bounced off a relativistic electron bunch, turning them into X-ray photons through the relativistic Doppler effect.
An overview of the design and results of the commissioning will be given.
Inverse Compton Scattering (ICS) sources are becoming more popular as the future of lab-based x-ray sources. Smart*Light is one such facility, under commissioning at Eindhoven University of Technology (TU/e). This compact X-ray source aims at bridging the gap between conventional lab X-ray sources and synchrotrons.
Electron bunches are produced by a 100 kV DC photo electron gun in combination with a bunching cavity. The electron bunches are injected in a high gradient X-band accelerator that is driven by a 24 MW 200 ns RF pulse coming from a klystron/pulse compressor combination. After being focused with a solenoid magnet, the electron bunches collide with focused 800 nm laser pulses resulting in X-ray photons with energies between 10 and 40 keV.
This work introduces the design of the low- and high power RF system, gives an overview of measurements of the electron bunch quality, and shows the results of the conditioning of the high gradient accelerator.
Seeding of free-electron lasers (FELs) is based on a periodic modulation of the electron energy by an external radiation pulse converted to a density modulation in a dispersive section. In complex configurations such as cascaded high-gain harmonic generation (HGHG) or echo-enabled harmonic generation (EEHG), the density-modulated electron beam may need to be propagated through drift spaces or detuned undulators before starting the lasing process in the FEL undulator (the “radiator”). In such a case, space charge tends to smear out the maxima of the electron density but also reduces the energy spread of the electrons between them. Studies on the evolution of the density-modulated beam in drift spaces and detuned undulators were carried out in different configurations of the FEL-1 beamline of FERMI, the FEL user facility at Elettra Sincrotrone Trieste in Italy. The paper compares the experimental findings on FEL emission after propagating the electron bunches with and without density modulation with simulation predictions and analytical estimates.
Shanghai HIgh repetitioN rate XFEL and Extreme light facility (SHINE) is an x-ray FEL facility based on an 8 GeV CW superconducting linac and 3 FEL undulator lines, with the capability that delivering wide spectral range coherent radiation to multi end stations.
In this paper, we present the detailed dynamics design strategy based on global optimization with start-to-end simulations from the photocathode to the end of the accelerator. In addition, we discuss the impact of Coherent Synchrotron Radiation (CSR) diminishing the peak current of the beam in the second bunch compressors. Through the optimization study, we showed that a 100 pC beam with sub-μm projected emittance and over kilo-Ampere final core current can be attained using a VHF gun and 1.3GHz Tesla cryomodules.
Southern Advanced Photon Source (SAPS) is a 3.5 GeV diffraction limited storage ring, being planned to be built near the site of the China Spallation Neutron Source (CSNS). Full energy Linac injector reserves the possibility of using the Linac for free electron laser application in a future upgrade. In this paper, the start-to-end simulation of the full energy Linac working on the ring injection mode are given.
FLUTE (Ferninfrarot Linac- Und Test-Experiment) at KIT has a compact versatile linear accelerator. One of FLUTE's main goals is to serve as a platform for a variety of accelerator studies as well as for the generation of high intensity, ultra-short THz pulses for photon science experiments. The linear accelerator is envisioned as an injector for a Very Large Acceptance compact Storage Ring (VLA-cSR), which is designed at KIT in the framework of the project cSTART (compact STorage Ring for Accelerator Research and Technology). It is necessary to provide stable RF power to achieve acceleration of electrons in the RF photo-injector and linac with high stability. For this goal, an upgrade of the existing RF system is currently being implemented. In this contribution, an updated RF system design and the status of the RF photo-injector commissioning will be reported.
The free-electron laser user facility at DESY – FLASH – is operating two undulator beamlines simultaneously and delivers XUV and soft X-ray radiation for photon experiments. It is driven by a superconducting linear accelerator. In a shutdown from November 2021 to August 2022 FLASH underwent a comprehensive refurbishment and a substantial upgrade (FLASH2020+). In this paper we summarize the recommissioning of FLASH and its upgraded injector as well as the restart of user operation in 2022. The year 2023 focuses on user operation in order to establish as much as possible beamtime before the next shutdown in 2024.
In the framework of the FLASH2020+ project, the FLASH1 beamline will be upgraded to deliver seeded FEL pulses for users. This upgrade will be achieved by combining high gain harmonic generation and echo-enabled harmonic generation with a wide-range wavelength-tunable seed laser, to efficiently cover the 60-4 nm wavelength range. The undulator chain will also be refurbished entirely using new radiators based on the APPLE- III design, allowing for polarization control of the generated light beams. With the superconducting linac of FLASH delivering electron beams at MHz repetition rate in burst mode, laser systems are being developed to seed at full repetition rates. In the contribution, we will report about the progress of the project.
European XFEL is a x-ray free-electron laser (FEL) user facility covering a nominal photon energy range from 250eV to 25keV. At the soft x-ray undulator beamline SASE3 and the two hard x-ray undulator beamlines SASE1 and SASE2, identical permanent magnet phase shifters are installed. In standard operation of the hard x-ray undulator beamlines these phase shifters introduce only small delays between electron and photon beam. When operated with significantly higher delays, these devices can be used as dispersive sections in a so-called distributed optical klystron, resulting in faster generation of microbunching. In this contribution we give an overview of experimental studies of distributed optical klystron.
The electron accelerator S-DALINAC at TU Darmstadt was successfully operated in single and double-turn energy-recovery mode. The latter was realized using a shared beam-transport where two beams are superimposed in the first recirculation beamline. Due to its current design, the S-DALINAC can be upgraded with reasonable effort to be operated in triple-turn energy-recovery mode with shared beam-transport. Here, two beams are superimposed in both, the first and the second recirculation beamline. This mode is particularly challenging due to a reduced number of degrees of freedom compared to an individual beam-transport. Therefore, the triple-turn energy-recovery mode requires precise determination of the accelerator setup obtained from beam-dynamics simulations prior to beam-tuning. The results of the necessary beam-dynamics simulations for this mode are presented.
An energy-recovery-linac (ERL)-based X-ray free-electron laser (FEL) is proposed considering its three main advantages: i) shortening the linac by recirculating the electron beam by high-gradient SRF cavities, ii) saving the klystron power and reducing the beam dump power through the energy recovery in the SRFs, iii) producing a high average photon brightness with high average beam current. Such a concept has the capability of optimized high-brightness CW X-ray FEL performance at different energies with simultaneous multipole sources. In this paper, we will present the preliminary results on the optics design, parameter optimization, beam dynamics study and identification of potential R&D aspects.
Fermilab pre accelerator (Preacc) and Linac send H- beam at 15Hz to the Booster which is a resonant circuit synchrotron. The beam is accelerated from 35 keV to 750 keV with RFQ in the Preacc, and then accelerated to 400 MeV in the Linac. There are 17 cavities in the Preacc and Linac, however a few of the cavity phases are adjusted for a daily tuning. The phase and amplitude have not been optimized for many years. We revisited the beam emittance and RF parameters with beam measurements and compared with simulation from low energy beam transport (LEBT) in the Preacc to the 400 MeV beam transfer line between Linac and Booster. In this work we are going to discuss our study result and future plan.
Cryo-cooled C-band (5.7 GHz) copper distributed-coupling cavities are a new approach to the structure-based accelerators for the future multi-TeV energy range linear collider. It provides numerous degrees of freedom to optimize the cavity geometry to achieve high gradient and high-power in the linear collider. In this study, we analyze the dipole modes of C-band 20-cells cavity and calculate the wall loss Q-factors, shunt impedance, and the impact of transverse wakefields in the frequency range up to 40 GHz by using ACE3P code (Omega3P and ACD tools). Next, we equip each cavity with four waveguide manifolds with damping loads to suppress undesirable higher-order-modes (HOM). The results of ACE3P simulations are compared with the CST microwave studio simulations.
Nanostructured electron sources exhibiting simultaneous spatio-temporal confinement to nanometer and femtosecond level along with a low emittance can be used for developing future ordered electron sources to generate unprecedented electron beam brightness and can revolutionize stroboscopic ultrafast electron scattering and steady-state electron microscopy applications. In addition, high current density electron beams generated from nanostructured electron sources can be used for applications that include nanoelectronics and dielectric laser accelerators. In this work, we report our efforts to develop and characterize two kinds of nanostructured electron sources: (i) nitrogen incorporated ultrananocrystalline diamond [(N)UNCD] tips and (ii) plasmonic
Archimedean spiral focusing lens. We demonstrate the ability to fabricate these cathodes and characterize them using a photoemission electron microscope under femtosecond laser illumination thereby demonstrating the ability of these structures to be used for next generation electron sources.
Terahertz radiation plays an important role in cutting-edge scientific research. Terahertz radiation source based on relativistic electron beam can provide excellent terahertz radiation source. The performance of such radiation is closely related to the distribution of the electron beam. Therein, the laser modulation technology based on the undulator is widely used to manipulate the distribution of the electron beam, thereby manipulating the radiation characteristics, such as improving coherence, tuning spectrum and controlling pulse width. In this paper, we analytically discuss the effects of various non-ideal factors during the process of dual-laser difference frequency modulation, such as finite laser pulse width, laser frequency chirp, and electron beam phase space distribution distortion. This will help to further understand the laser modulation technology of relativistic electron beams in the terahertz band, thus promoting the development of terahertz photonic science.
High-Brightness SASE (HB-SASE) is a proposed method for greatly improving the temporal coherence of SASE FEL pulses using magnetic delay chicanes along the undulator beamline. Isochronous chicanes, which include high-strength quadrupoles, promise to deliver the greatest improvement in temporal coherence but it is more convenient if the delay chicanes are composed only of dipoles. In this paper we present a simulation study of a FEL operating at 25keV, driven by a low charge electron bunch, in which HB-SASE is implemented with dipole-only chicanes to generate fully temporally coherent FEL pulses. Post-saturation tapering is then employed to further amplify the FEL pulse while maintaining its temporal coherence. The scheme is predicted to produce fully coherent, mJ pulse energy FEL pulses with few-femtosecond duration and excellent shot-to-shot stability of wavelength, pulse energy and pulse profile – as such it is a candidate for implementation on a future UK-XFEL.
Corrugated structure modules are being proposed for installation after the end of the linac and before the undulator regions of SHINE facility, where it has been used for energy chirp control and as a fast kicker for two color operation of the FEL.When ultra-relativistic bunch of electrons passing through corrugated structure will generate strong wakefield, we find most of the wake power lost by the beam is radiated out to the sides of the corrugated structure in the form of THz waves, and the remaining part casue Joule heating load on the corrugated structure wall. In this paper, we estimate the Terahertz radiation power and Joule power loss of the corrugated structure in SHINE facility.
The terawatt-scale free electron lasers (FELs) are of great interest for the possibility to allow X-ray single molecular imaging experiments and nonlinear x-ray science. At Pohang Accelerator Laboratory X-ray Free Electron Laser (PAL-XFEL), for the second hard undulator plan (HX2) the enhanced Self-Amplified Spontaneous Emission (E-SASE) scheme with an external laser pulse will be installed to generate a single high peak current spike which can be used to generate the terawatt-scale XFEL or attosecond XFEL. The current profile of the single spike is manipulated by controlling the external laser wavelength and the modulator, and the bending angle in the magnetic chicane. At the entrance of the undulator, the e-beam has a peak current of a few tens of KA and a pulse duration of less than 10 fs. The self-seeded FEL scheme is utilized to effectively enhance XFEL energy using the undulator tapering method. In this presentation, we will introduce the terawatt-scale XFEL using ESASE and the self-seeded FEL scheme.
In this work, we develop a concept of an accelerator arranged as follows: electrons are accelerated by an electromagnetic field in a waveguide immersed in a longitudinal uniform axial magnetic field and a transverse spatially periodical undulator magnetic field. There are several types of resonances in such a system. Namely, cyclotron, undulator, and combined resonances. Herewith, these resonances are of the same type and are realized at different energy values. Thus, by consistently achieving these resonances, electrons can accelerate to sufficiently high energies with a relatively small amplitude of the accelerating field.
The acceleration process is investigated analytically and numerically. According to calculations, with all other conditions being equal, the proposed method turns out to be 4 - 6 times more efficient than cyclotron acceleration. One must note a disadvantage of the discussed method. In comparison with cyclotron acceleration, all particles are accelerated equally, in the system under consideration, particles can "get stuck" at intermediate resonances. This problem is partially solved by optimizing the system parameters.
Cavity-based X-ray free-electron laser (XFEL) is promising to produce fully coherent pulses with the bandwidth of a few meV and very stable intensity, while the currently existing self-amplified spontaneous emission (SASE) XFEL is capable of generating ultra-short pulses with chaotic spectra. In general, cavity-based XFEL can provide spectral brightness three orders of magnitude higher than that of the SASE mode, thereby opening a new door for cutting-edge scientific research. With the development of superconducting MHz repetition rate XFEL facilities such as FLASH, European-XFEL, LCLS-II and SHINE, the cavity-based XFEL operation becomes more and more achievable. In this paper, Megahertz cavIty eNhanced x-ray Generation (MING) is proposed, on the basis of China’s first hard XFEL facility SHINE, i.e., MING@SHINE.
The minimum achievable particle beam emittance in an electron accelerator depends strongly on the intrinsic emittance of the photocathode electron source. Reducing the electron beam emittance in an accelerator which drives a FEL delivers a significant reduction in the saturation length for an X-ray FEL, thus reducing the machine’s construction footprint and operating costs whilst increasing X-ray beam brightness. The intrinsic emittance is correlated to the mean transverse energy (MTE), therefore measuring the MTE is a notable figure of merit for photocathodes used as electron sources. This work presents the Transverse Energy and Momentum Analyser (TEMA), a system which will measure the MTE of different cathodes, such as Cs_2Te currently used at FLASH and European XFEL.
We study THz radiation generation from a few-periods magnetic device for THz pump – x-ray probe experiments at the European XFEL, or at other facilities like the LCLS-II. We compute THz radiation accounting for the boundary conditions imposed by a vacuum pipe. Calculations were performed for a single-period magnetic device as well as for a nine-period one. We address the problem of modes matching when entering the iris line and the final radiation distribution at the sample. With the help of wavefront propagation techniques, we simulate the propagation of THz radiation in an overmoded iris line downstream to the users’ sample.
We are developing an ultrafast and ultracold electron source (UCES), based on near-threshold femtosecond photoionization of a laser-cooled cloud of rubidium gas, stored in a Magneto Optical Trap (MOT). The UCES is characterized by electron temperatures as low as ~ 10 K, enabling a unique combination of ultra-low emittance ~ 1 nm rad and relatively high bunch charges. Recently we have demonstrated the generation of sub-ps electron bunches, whose bunch length is fundamentally limited by the duration of the ionization process.
The UCES may find application in single-shot, ultrafast electron crystallography of proteins, but also as an injector for dielectric laser acceleration, and as an injector for highly coherent inverse Compton scattering X-ray sources. All three applications require electron energies of ~100 keV. The present UCES, however, is based on DC acceleration in relatively low electric field strengths ~ 1 MV/m, allowing electron bunch energies of maximally ~10 keV. Recently, we have shown that the electron energy can be boosted by a separate 3 GHz TM-010 RF cavity to 30 keV with conservation of beam quality. A dedicated DC-RF UCES is under construction which will produce ultracold and ultrafast bunches at 100 keV and 1 kHz rep rate.
Progress, both in source development and towards first applications, will be reported.
This talk will report on the status C-band high gradient research program at Los Alamos National Laboratory (LANL). The program is being built around two test facilities: C-band Engineering Research Facility in New Mexico (CERF-NM), and Cathodes And Radio-frequency Interactions in Extremes (CARIE). Modern applications require accelerators with optimized cost of construction and operation, naturally calling for high-gradient acceleration. At LANL we commissioned a high gradient test stand powered by a 50 MW, 5.712 GHz Canon klystron. The test stand is capable of conditioning accelerating cavities for operation at surface electric fields higher than 300 MV/m. CERF-NM is the first high gradient C-band test facility in the US. CERF-NM was fully commissioned in 2021. In the last several years, multiple C-band high gradient cavities and components were tested at CERF-NM. Currently we work to implement several updates to the test stand including the ability to autonomously operate at high gradient for the round-the-clock high gradient conditioning. Adding capability to operate at cryogenic temperatures is considered. The construction of CARIE began in October of 2022. CARIE will house a cryo-cooled copper RF photoinjector with a high quantum-efficiency cathode and produce an ultra-bright 250 pC electron beam accelerated to the energy of 10 MeV. The status of the facility, the designs of the photoinjector and the beamline, and plans for photocathode testing will be presented.
The Large Hadron electron Collider (LHeC) is proposed as a future particle physics project colliding 60 GeV electrons from a six-pass recirculating energy-recovery linac (ERL) with 7 TeV protons stored in the LHC. The ERL technology allows for much higher beam current and, therefore, higher luminosity than a traditional Linac. The high-current, high-energy electron beam can also be used to drive a free electron laser (FEL). In this presentation, we examine how the LHeC ERL can serve as a source of high-energy photons for studies in nuclear physics, high energy physics, axion detection, dark energy and protein crystallography. In the first section, we discuss the performance of an LHeC-based FEL, operated in the SASE mode for generating pulses of X- and gamma rays at wavelengths ranging from 5 Å to 3 pm [1]. In the second section, we investigate photon production via inverse Compton scattering (ICS).
[1] Physical Review Accelerators and Beams 24, 10 (2021)
The Shanghai high-repetition-rate XFEL and extreme light facility (SHINE) is designed to be one of the most advanced free electron laser user facilities around the word. The repetition is aiming at 1 MHz and the high-repetition-rate electron beams are delivered into three undulator lines through the beam delivery section. The main functional elements are kickers. The vacuum chamber in the kicker is a dielectric pipe made of ceram. The wakefield of a dielectric pipe is much stronger than that of a metal pipe and the accumulation of static charges in the ceramic wall is undesired. Thus a metal layer should be applied to the inside of the chamber wall. In order to limit eddy currents which could lead to losses of the applied magnetic filed when penetrating through the chamber, the layer should be as thin as possible. On the other hand, the thickness of the layer should not be smaller than the skin depth in order to avoid new problems. We simulate the motion of electrons in a metal layer to find the “effective skin depth” and calculate the wakefield of our kicker. Based on the results, we give suggestions to the design scheme of kickers.
The energy loss of the electron beam due to synchrotron radiation and wakefields determines an undulator tapering in order to keep the resonance condition along the undulator. The contribution of synchrotron radiation to energy loss can be calculated analytically, whereas the calculation of wakefield energy loss requires knowledge of the beam current profile and the wakefield function at the undulator section. We present an experimental method for accurate measurement of the energy loss due to wakefields in the undulator section for the European XFEL. We compare the results of the measurements with earlier developed analytical model of the wakefunction.
FEL oscillator is the main working mode to produce infrared and THz radiation. However, in the long wavelength range, the waveguide is essential to suppress the diffraction losses. We have developed a method to study this effect by wGenesis that is modified with Genesis in combination with OPC code. However, this method is limited by the optical elements given in OPC. In this paper, we tried to give a more general optical element case based on the ABCD matrix. Then the simulation based on FELiChEM parameter is done to reduce the truncation loss at the waveguide port by choosing proper toroidal curvature radius. The results show that output power can be increased about 6.4 times than spherical mirror.
In our recent work [1], we proposed a plasma-driven light source that can generate coherent tunable XUV pulses with TW peak power and pulse durations of 40 attoseconds (or longer) in a m-length undulator. The pulses synthesized in this approach carry particular merit for tracking chemical dynamics and enabling measurements that extend beyond the range of conventional HHG and XFEL sources.
In this presentation, we share early commissioning results from preliminary experiments undertaken at the FACET-II facility at SLAC National Accelerator Laboratory, making use of the GeV-energy nC-charge beam available to users. We show measurements of the radiated UV/Vis spectrum and spatial mode of coherent synchrotron radiation generated by the uncompressed drive beam, which will be used in future plasma chirping and compression experiments. These early results provide a roadmap for successful commissioning of the weak 4-dipole chicane that will later be installed to compress the beam before injection into a m-length undulator.
J-PARC has three accelerators, 400MeV linear accelerator (LINAC), 3GeV rapid cycling synchrotron (RCS), and 50GeV (currently 30GeV) main ring (MR), which are connected by beam transport lines. The proton beam is delivered from the RCS to muon and neutron targets in the materials and life science experimental facility (MLF) via a beam transport line called 3NBT. A pulsed bending magnet in the 3NBT, which is also the first magnet of another beam transport line called 3-50BT, provides 8 bunches of proton beams to the MR. A power supply excites the pulsed bending magnet according to the cycle of MR to deliver the proton beam at the injection timing of MR. In near future, the repetition rate of MR will be higher to increase the output beam power. However, the current power supply of the pulsed bending magnet does not support higher repetitive operation, so we planned to manufacture a new power supply that supports 1 Hz operation. In this proceeding, the specifications of the new power supply, and the measured results of operating tests using dummy loads and the pulsed bending magnet will be reported.
In order for the new ATLAS Materials Irradiation Station (AMIS) to take advantage of the future multi-user capabilities at ATLAS, a pulsed kicker is needed to switch 1 MeV/u heavy-ion beams. At this energy and due to space limitations, a pulsed electric kicker is very challenging due to very high voltage requirement, and a magnetic kicker is also very challenging due to the high magnetic field and fast switching requirements. A solution that satisfies the beam switching requirements is a pulsed Wien filter that combines a DC magnetic field with a pulsed electric field, where each provide only half of the kick angle. During the kicked beam pulse, the two fields combine to provide the full kick angle, while the electric field switches sign to cancel the magnetic field during the un-kicked beam pulse. The electromagnetic and beam design for this novel device will be presented and discussed. The device is now under construction and will be tested in the coming year, first offline then online with beam.
The China Spallation Neutron Source (CSNS) is a large scientific facility for frontier research by using the medium energy protons bombardment of tungsten target to produce a large number of scattered neutrons. The rapid cycling synchrotron (RCS) adopts the single-turn fast extraction scheme to extract the proton beam with the energy of 1.6GeV, and the extraction repetition frequency is 25Hz. In order to optimize the painting distribution and reduce the beam loss in the beam commissioning, it is necessary to measure the transverse beam distribution during the injection and acceleration processes. In this paper, a scheme to extract the beam in advance is proposed which is performed by adjusting the extraction timing and extraction mode. By using this extraction mode, the beam can be extracted at different time and the transverse beam distribution can be measured by a multi-wire scanner located on the beam transport line from the RCS to the target (RTBT). Then, the beam distribution at the desired position on the RCS can be deduced by using the beam transfer matrix.
Adiabatic capture of a coasting beam can be used to minimise the emittance of the resulting bunched beam – for example to capture the injected beam at the start of the acceleration cycle. In some cases, the voltage follows the so-called iso-adiabatic voltage law in order maintain the same adiabaticity throughout capture. Here we show that a linear evolution can result in a smaller final emittance than an iso-adiabatic scheme. This is shown by tracking a distribution through various capture schemes, taking as our example capture at injection in the FETS-FFA proton ring. We include preliminary results on the effects of longitudinal space charge which can be significant in this ring.
The synchrotron SIS18 at GSI uses resonant extraction for slow beam extraction. Recently it was discovered that about 50% of the anode wires of the electrostatic extraction septum were broken during beam operation. In this paper, we present the analysis of the possible loss scenario that led to the anode wire damage and suggest machine protection measures to prevent future damage. The investigations revealed the importance of having access to stored data representing machine parameter settings and their changes as well as signals from devices and beam instrumentation to be able to analyse the events leading to losses. Relevant signals include beam current, beam loss monitor signals, and vacuum pressure. Systems for logging and archiving such data are under development for FAIR, but are not yet routinely available.
For the high power spallation neutron sources,
The RAON accelerator has been constructed for various fields of science programs since 2011. The installation of the low-energy superconducting accelerator section (SCL3) had finished at the end of 2021, and the cooling of the cryogenics system started in early 2022. Prior to the SCL3, the beam commissioning has been carried out at the injector section of the RAON accelerator since 2020, and the beam was successfully accelerated with five quarter-wave resonator (QWR) cavities at the front of the SCL3 in October 2022. For successful and efficient beam commissioning, various beam physics studies have been conducted for several years, and physics applications have been also developed. Here we will introduce various physics applications used for beam commissioning and show the results of these beam tests.
The new generation BNCT facilities require the management of high intensity proton beams (tens of mA). As a matter of fact, the total beam power can easily overcome hundreds of kW. Consequently, it is not only important to keep under control the losses but also to manipulate the beam distribution to decrease the power deposited along the accelerator and on the target. In this paper we will present the strategies implemented and the design studies to achieve this result.
HPSim, the GPU-powered multi-particle simulation code developed for LANSCE, can provide critical 6-D beam distributions in near real-time to LANSCE user facilities. We will present the benchmarking results for HPSim to the LANSCE linac and our effort to provide a real-time distribution to the Isotope Production Facility.
Resonant slow extraction is a beam extraction method which provides a continuous spill over a longer duration than can be achieved with fast single-turn or non-resonant multi-turn extraction. By using transverse excitation to drive the circulating particles onto the resonance, a beam can be delivered to stationary target experiments which require low intensity, long-duration beams.
In order to accurately and efficiently simulate the extraction process over a wide range of timescales, new modelling tools and computing platforms must be explored. By utilising optimised computational hardware - such as General Purpose Graphics Processing Units (GPGPUs), and next-generation simulation software (such as Xsuite), computation times for simulations can be reduced by several orders of magnitude.
This contribution presents recent developments of resonant slow extraction modelling and benchmarking with a comparison to measurements made at CERN’s Proton Synchrotron (PS), with a particular focus on understanding the dynamics of transverse RF excitation and effect on spill quality.
The heavy ion synchrotron SIS100 is the flagship accelerator of the Facility for Antiproton and Ion Research (FAIR) currently under construction at GSI, Darmstadt. It will provide high intensity beams of particles ranging from protons to uranium ions at beam rigidities up to 100 Tm. Part of the machine protection system is an emergency beam dump that is partly inside the vacuum system and partly outside. Due to the beam dump’s tight integration with the beam extraction system, there is little flexibility for design of the dump or beam optics defining the shape of the impacting beam. High energy deposition densities and the wide range of accelerated ions pose unique challenges to the survival of the dump. In this paper we identify the most demanding beam impact scenarios for the different dump components that will consequently guide choices for materials and design.
Xi’an 200 MeV proton application facility (XiPAF) upgrading project is now in the design phase. For the synchrotron of the project, the influence of the dipole and quadrupole errors on the closed-orbit distortion(COD) is a matter we must pay attention to. However, Before the synchrotron assembly is complete, we do not know the actual errors of magnets. So we set certain distribution for different types of magnet errors according to the previous engineering experience and then investigate the COD caused by it, and finally we use the principle of statistics to find the relationship between them.
This work was carried out with MADX program. Results show that for almost all types of magnet error, the rms value of COD is in direct proportion to the rms value of magnet error, except the rotation error around the y-axis for dipoles, in which case the COD is in direct proportion to the square of the rms value of the error. In addition, the proportionality coefficient between COD and different types of magnet error varies a lot. This can guide us to restraint the error type with high coefficient strictly for better synchrotron performance and relax the requirements slightly of the error type with low coefficient for a more economic cost.
During the third operational run of the Large Hadron Collider at CERN, starting in 2022, the beam energy was increased to 6.8 TeV and the bunch population is planned to be pushed to unprecedented levels. Already in the first year of operation, beam stored energies up to 400 MJ were achieved. An improvement in cleaning performance of the LHC collimation system is hence required. In this paper we review the collimation system performance during 2022, and compare it to previous years. Particular attention is put on the performance during $\beta^*$-levelling, which is part of the nominal cycle in Run 3. The performance of the automatic alignment tools is also discussed. Finally, we review the stability of the collimation system, which was monitored regularly during the run for all machine configurations to ensure the continued adequate functionality of the system.
A 70 MeV H- cyclotron system has been installed at the Institute for Basic Science (IBS) from Nov. 2021 as a driver for ISOL system. Internal beam was first accelerated in May 2022 and utilized to highly isochronize the magnetic field using Smith-Garren method. In June, a beam of 70 MeV was extracted to two beam lines and beam emittance was measured by variations of quadrupole strengths and using a beam profile monitor. Site acceptance tests were carried out with a temporary beam line installed to measure beam profiles at the location of ISOL target employing a wobbling magnet to shape beam current distributions. A beam position monitor built in-house was also used to measure beam off-centers and currents. Commissioning was completed in Nov. and now we are planning to utilize this newly established facility for the productions of neutrons and medical isotopes. As spare spaces are available for both applications, we will present a design of full utilization along with beam commissioning results.
The Frankfurt Neutron Source FRANZ will be a compact accelerator driven neutron source utilizing the 7Li(p,n)^7Be reaction with a 2 MeV proton beam. Recent comissioning efforts showed succesful proton beam operation at the targeted RFQ injection energy of 60 keV up until the point of RFQ injection. The RFQ was retrofitted with new electrodes for the injection energy of 60 keV. We report on the status of comissioning of the beamline and RFQ.
The Rare isotope Accelerator Complex for ON-line experiments (RAON) has been proposed as a multi-purpose accelerator facility for providing beams of exotic rare isotopes of various energies. It can deliver ions from hydrogen (proton) to uranium. Protons and uranium ions are accelerated up to 600 MeV and 200 MeV/u respectively. It can provide various rare isotope beams which are produced by isotope separator on-line system. The RAON injector was successfully commissioned in 2022 to study the beam parameters from the main technical systems, such as the ECR ion source and RFQ, and to find the optimized LEBT and MEBT setpoints and matching conditions. In addition, the low-energy superconducting linac (SCL3) is under commissioning. In this paper, we present the current beam commissioning status of the RAON injector and superconducting accelerator.
The beam optics in the SNS normal conducting linac is analyzed for the 1.4 MW beam-on-target operation settings. The first section is a room temperature copper linac which include Medium Energy Beam Transport (MEBT) section with four re-bunching radio-frequency (RF) cavities, Drift Tube Linac (DTL), and Coupled Cavity Linac (CCL). The Radio Frequency (RF) cavities in this section accelerate H- beam to 185.5 MeV. For production runs the parameters of RF cavities in this section are chosen by using combination of models and empirical tuning providing low beam loss and low rate of discharge events inside the cavities. For some cavities the set parameters are significantly different form the design values. The paper discusses accuracy of these settings and discrepancies between design and real-life high-power production settings in the warm linac section of SNS.
The IFMIF-DONES facility (International Fusion Materials Irradiation Facility – DEMO Oriented Neutron Source) is currently under design and being prepared for the construction phase within the framework of a EUROfusion Consortium work package. Its location will be in Escúzar, Granada and it will be the largest science and technology infrastructure project developed in Spain. Its objective is the study and certification of irradiated fusion materials by the generation of a neutron flux with a broad energy distribution covering the typical neutron spectrum of a (D-T) fusion reactor. For this purpose, a facility which accommodates a 40 MeV at 125mA deuteron Linac, a liquid lithium target and test module are being undertaken. Building and conventional plant systems are also designed to house, serve and allow main systems correct operation. Due to the complexity and high number of collaborators involved, it is of utmost importance to properly manage design and configuration integration activities.
This paper describes current CAD management approaches and methodology followed in the project to coherently arrange Structures, Systems and Components (SSCs) throughout the facility’s lifecycle, easing identification of potential design inconsistencies and interferences as early as possible to actively resolve them and speed-up development of the project towards a ready-to-construct status, minimizing future construction, commissioning and operation issues and associated cost-overruns.
The demand for muon facilities has been continuously increasing since surface muons play a significant role in particle and solid-state physics. The installation of a refurbished muon target station and two new High-Intensity Muon Beam lines (HIMB) in the framework of the Isotope and Muon Production using Advanced Cyclotron and Target technology project (IMPACT) at PSI will pave the way to unprecedented muon intensities allowing, among others, next generation lepton flavor violation experiments.
In this context, a new collimation system composed of three collimators made of oxygen free copper has been designed in order to reduce the divergence of the proton beam due to multiple scattering in the new target. The thermomechanical integrity of each collimator has to be investigated also in the prospect of an increased proton beam current up to 3 mA. The cooling of the collimator system is provided by water flowing in a system of eight helicoidal stainless steel pipes brazed to the main copper bodies. Steady-state computational fluid dynamics simulations and tailored semi-analytical models in the ANSYS software package have been used to provide the optimal design of the collimator system.
The Isotope and Muon Production using Advanced Cyclotron and Target technology (IMPACT) project at the Paul Scherrer Institut aims to produce and fully exploit unprecedented quantities of muons and radionuclides for further progress in particle physics, material science and life science. The proposed Targeted Alpha Tumor Therapy and Other Oncological Solutions (TATTOOS) facility will provide, for research purposes, medically relevant radionuclides, especially α-emitters, via proton-induced spallation. This new 100 μA / 590 MeV proton beamline will deliver up to 40 kW to an oxygen-free copper beam dump.
A hybrid analytical / numerical cooling model was developed to reduce the simulation time and the total amount of CFD simulations. This model consists of analytical surface temperatures applied as boundary conditions to an ANSYS thermal model. It was validated using CFD simulations and then used in the design process of the beam dump.
Since the copper blocks are brazed together at temperatures beyond the recrystallization point, a temperature dependent multilinear isotropic hardening model was used to simulate the behavior of soft-ductile annealed copper. Irradiation induced hardening was also taken into account to ensure that no exhaustion of ductility would occur in the beam dump.
The energy contained in the LHC's two beams must be safely absorbed in external beam dumps (TDE). High Luminosity (HL) is a future upgrade which will increase this stored energy to 700 MJ, compared to 150 MJ in Run 1. The TDE design has changed little since Run 1; it is a cylindrical stainless-steel vessel with a core made of graphite. During long shutdown 2 (LS2), upgrades were made to the TDEs to address issues found during Run 2 and to prepare for the higher intensity of Run 3. Further upgrades will be needed for HL, due to three key challenges, i.e., a) increased vessel vibration will lead to higher stresses; b) graphitic materials able to withstand energy densities up to 5.7 kJ/g (as determined by FLUKA Monte Carlo simulations) are required; c) a new TDE cooling system is necessary, so that temperature build up following consecutive dumps will not affect the LHC’s availability. This paper describes work completed to develop a conceptual design of the HL TDE and the planned future work. Results of Finite Element (FE) simulations of the TDE’s response to the beam energy deposition and Computational Fluid Dynamics (CFD) simulations of the cooling system will be presented.
The quarter wave resonator (QWR, a.k.a. λ/4 resonator) for the new ISIS MEBT is a bunching cavity that longitudinally compresses the H- beam into smaller bunches. It has 2 gaps with a distance of βλ/2 between mid-gaps, and works in π mode at the resonant frequency of 202.5 MHz, with a phase angle of -90 degrees. The maximum voltage per gap (E0L) is set to 55 kV. A detailed RF model has been developed to tune the main dimensions to the required frequency and to estimate the Kilpatrick ratio and the RF power dissipation. The cavity is designed to be made of copper plated stainless steel, which has a considerable effect on the design of the cooling system; the thermal calculations include a thermo-mechanical analysis to estimate the dynamic tuning requirements. The cavity has two tuners to allow for a fine and a coarse tuning of the resonant frequency. The manual tuner coarsely adjusts the frequency to cope with the manufacturing tolerances. The automatic tuner finely tunes the frequency within a range of working temperatures. The tuners are heavily coupled both in terms of frequency resolution and tuning range, which presents some challenges to the design. The design of the power coupler was adapted to the QWR from another project and the coupling coefficient was adjusted to the new cavity. A sensitivity analysis for the critical dimensions was also developed, but is not presented here.
The electrostatic chopper for the new ISIS medium-energy beam transport (MEBT) is a fast deflecting device to create gaps in the beam coming out of the RFQ, which will improve the trapping efficiency when injecting the beam into the ISIS synchrotron. Due to the stabilization time required by the ion source, it is expected that the first 100 μs of the 400 μs pulse need to be removed in order to deliver a clean flat top pulse to the synchrotron. The 300 μs pulse will then be burst-chopped into shorter pulses to reduce the losses at higher energies during the injection into the synchrotron at 50 Hz. The chopper must remove a maximum of 40% of the 300 μs pulse at the initial synchrotron frequency of 1.3 MHz. The deflected beam will be dumped into a beam dump inside the chopper device, while the remaining beam continues into the ISIS DTL. The chopper electrode dimensions were initially estimated from analytical calculations and from the beam dynamics simulations of the MEBT beamline. Electromagnetic (EM) simulations were developed to accurately estimate the field shape, the peak electric fields and the transient response of the chopper. Thermal calculations and a dimensional sensitivity study were also developed, but they are not presented here.
Proton FLASH, which combines the advantages of a better spatial dose distribution of protons with the unique temporal effect of FLASH radiotherapy, is currently a hot topic of international research. Proton FLASH radiotherapy is technically demanding and currently lacks equipment support. There are only a few devices that have been modified to achieve small target section, fixed-energy penetrating irradiation by proton radiotherapy equipment, which cannot give full play to the advantages of proton spatial dose distribution. In this study, a series of innovative methods are proposed to manipulate the beam from the longitudinal dynamics level and to extract particles from the synchrotron, thus meeting the dose rate requirements for proton FLASH radiotherapy in a 1L volume in the target area. In combination with the splitting of small beam clusters, a synchrotron scheme for point scanning of proton FLASH radiotherapy is proposed for the first time. The synchrotron is used to control the number of particles required for a single scan point and to rapidly change energy, which solves the problems of long intervals between different energies and scan points of conventional point scanning and increases the dose rate in the target area. It provides a possible technical route to support the development of proton FLASH radiotherapy and enriches the application scenario of synchrotron.
The matter-antimatter asymmetry might be understood by investigating the EDM (Electric Dipole Moment) of elementary charged particles. A permanent EDM of a subatomic particle violates time reversal and parity symmetry at the same time and would be, with the currently achievable experimental accuracy, an indication for further CP violation than established in the Standard Model.
The JEDI-Collaboration (Juelich Electric Dipole moment Investigations) in Juelich has performed a direct EDM measurement for deuterons with the so called precurser experiments at the storage ring COSY (COoler SYnchrotron) by measuring the invariant spin axis.
In order to interpret the measured data and to disentangle a potential EDM signal from systematic effects in the radial part of the invariant spin axis, spin tracking simulations in an accurate simulation model of COSY are needed. Therefore a model of COSY has been implemented using the software library Bmad. Systematic effects were considered by including element misalignments, effective dipole shortening, longitudinal fields and steerer kicks. These effects rotate the invariant spin axis in addition to the EDM and have to be analyzed and understood. The most recent spin tracking results as well as the methods to find the invariant spin axis will be presented.
Two new eddy-current-type septum magnets were installed at the fast extraction section of J-PARC main ring in April 2022. Eddy septum magnets (EDDYs) are energized pulse currents; thus, it is necessary to consider the possibility of misfires. Based on simulation results, if one of the EDDY misfires, the extraction beam will be irradiated to the ducts of the superconducting magnets (SCs) on the beamline to the neutrino facility. If this occurs, then the SC can be quenched owing to heating. Therefore, we built a safety device to prevent beam failure by monitoring the output pulse currents of the EDDYs. If a pulse-current anomaly is detected, the beam is kicked to the abort line using kicker magnets. This process must be completed within 390 µs, known as the pulse rise time period. The parameters used to determine the pulse-current waveform anomalies were determined from the beam optics simulation. This pulse-monitoring device has an added functionality to stop and protect the power supplies of the EDDYs when the pulse current waveform is abnormal. We consider that by 2023, it will be remotely controlled by the accelerator control system.
An ultrahigh dose rate (UHDR) MV-level X-ray radiation platform for FLASH radiotherapy (RT) research based on a normal conducting linear accelerator is presented in this work. A S-band backward traveling-wave linear accelerator powered by a commercial klystron produces electron beams with 11 MeV energy, 300 mA pulse current, and 2.6 mA mean current at 0.88% beam duty ratio. The radiation platform generates X-ray by bremsstrahlung. Flattening filters and collimators are included to produce a 4 cm × 3 cm field with flatted profile dose distribution. The measured dose rate was 129 Gy/s and the flatness was 14% after flattening. The UHDR X-ray platform now is used for FLASH preclinical animal research.
Tokyo Institute of Technology is planning a linac facility to produce 211 astatine, an isotope for αemitter cancer therapy. To produce astatine, we aim to bombard a bismuth target with helium ion beam of sufficient intensity at 28 MeV. Unlike a cyclotron, this facility will be able to accelerate a milliampere class high intensity helium ion beam. In addition, the subsequent accelerator system can be made compact by providing fully stripped helium ions. For this purpose, the ECR ion source is best suited. The multiply charged ions are generated by resonant absorption of microwaves by electrons orbiting in a magnetic field and are capable of supplying high-intensity beams. The ECR ion source will use an RF frequency of 10 GHz, and a suitable magnetic field distribution will be designed to confine the plasma by a composite magnetic field consisting of a mirror field using two solenoid coils and a magnetic field generated by a sextupole magnet to increase the charge states of the ions in the chamber. The final goal is to extract He2+ at 15 mA. In this presentation, the design and magnetic field distribution are reported, including experimental results.
The proposed Targeted Alpha Tumor Therapy and Other Oncological Solutions (TATTOOS) facility at the Paul Scherrer Institute aims to produce radionuclides, especially alpha-emitters, via proton-induced spallation for potential clinical studies of advanced cancer treatments. This new 100 microA / 590 MeV proton beamline delivers in the best-case scenario 26 kW to the target.
In this study, a numerical CFD model for the TATTOOS target was developed. The boundary condition to this model is the energy deposition calculated with the particle transport Monte Carlo method.
Since the operation temperature of the target is up to 2900 degree Celsius, close to the melting point of Ta, to enable the diffusion of the radionuclides, the temperature distribution of the target has to be well predicted. As it is not possible to cool the target directly, the main cooling is by radiation. For this reason, it is important to optimize the geometry of the target by maximizing the surface area.
The incoming Gaussian beam will induce an inhomogeneous temperature distribution on the spallation target, consisting of stacked discs. To ensure that the temperature of the target is within the acceptable limits, a twofold optimization strategy was selected. Firstly, the inner geometry of the target was optimized using a genetic algorithm, to ensure uniform power deposition. Secondly, a more spread “wobbled” beam and a large outer surface area will be used.
Beam uniformity is an important factor that must be considered in slow extraction optimization, and the tune ripple caused by the power supply ripple is an important factor
that causes beam uniformity to deteriorate. In this study, based on the beam excitation concept for two regions (extraction and diffusion regions), a differential equation of
beam spill under the influence of a mono frequency tune ripple was established. By solving and analysing the differential equation, several conclusions were obtained and verified by simulation.
Vertical orbit excursion Fixed Field Accelerators (vFFAs) feature highly non-linear magnetic fields and strong transverse motion coupling. The detailed study of their Dynamic Aperture (DA) requires computation codes allowing long-term tracking and advanced analysis tools to take the transverse motion linear and non-linear coupling into account. This coupling completely transforms the beam dynamics compared to a linear uncoupled motion, and an explicit definition of the DA is needed to characterize the performance and limitations of these lattices. A complete study of the DA in the 4D phase space in highly non-linear and strongly coupled machines must give a measure of the stability domain but also means to assess the operating performance in the physical coupled space. This work presents a complete set of methods to perform such detailed analysis. These methods were explored and compared to compute and characterize the DA of an example vFFA lattice. The whole procedure can be further applied to evaluate DA using realistic models of the magnetic fields, including fringe fields and errors.
The 800-MeV proton linac at the Los Alamos Neutron Science Center (LANSCE) includes a drift-tube linac, which brings the beam to 100 MeV, followed by a coupled-cavity linac (CCL) consisting of 44 modules. Each CCL module contains multiple tanks, and it is fed by a single 805-MHz klystron. CCL tanks are multi-cell blocks of identical re-entrant side-coupled cavities, which are followed by drifts with magnetic quadrupole doublets. Bridge couplers – special cavities displaced from the beam axis – electromagnetically couple CCL tanks over such drifts. We have developed 3D CST models of CCL tanks. The RF fields in the tanks are calculated with MicroWave Studio, and magnetic fields of quadrupole doublets are found with ElectroMagnetic Studio. Beam dynamics is modeled with Particle Studio for bunch trains with realistic beam distributions using the CST calculated fields to determine the output beam parameters. Beam dynamics results are compared with other multi-particle codes and provide data for training physics-based surrogate models.
The J-PARC Main Ring (MR) delivers high-intensity proton beams for
the neutrino experiment.
The beam intensity delivered to the neutrino experiment reached 520kW with a cycle time of 2.48 seconds in 2021.
We chose to shorten the MR cycle time to 1.36 seconds to achieve higher beam intensity.
An anode power supply feeds a high-voltage DC current to the tetrode vacuum tubes, which drive the RF cavity.
Beam acceleration in a shorter MR cycle requires a higher RF voltage to keep the RF bucket large enough and a larger anode power supply current for the beam loading compensation.
We plan to add RF systems to achieve higher RF voltage and to manage the output current of each anode power supply under limitations.
To estimate the anode power supply current with a shorter MR cycle,
we derived the beam loading compensation contribution in the power supply current using the data recorded during the operation with a cycle time of 2.48 seconds.
We present the estimated anode power supply current for various combinations of RF voltage and the number of RF cavities.
At iThemba Laboratory for Accelerator Based Sciences (LABS), particle beams are pre-accelerated in a K8 injector cyclotron and further accelerated in a K200 Separated Sector Cyclotron. The accelerated beams are transported to various target stations, including targets stations used for radionuclide production and fundamental subatomic physics research. All along the trajectory of the beam path, from the ion source to the target station, the beam is prone to various instabilities. Finding the root cause of such instabilities can be an arduous task. With the rapid progress in Machine Learning (ML) algorithms new possibilities exist to narrow down and even identify the sources of such beam instabilities. During this presentation some preliminary results will be presented on using the signals from non-destructive diagnostics and ML to locate the sources of beam instabilities.
The future Accelerator Facility for Antiproton and Ion Research (FAIR) belongs to the category of international mega-projects and is under construction in Darmstadt, Germany. The FAIR project includes the construction of 24 accelerator and experimental buildings with a total area of about 150,000 m2, as well as 12 sub-projects in the areas of accelerators (pLINAC, SIS100, SuperFRS, p-bar, CR, HESR), experiments (CBM, APPA, NUSTAR, PANDA), installation and commissioning. The management and control of such a project in a very rapidly changing world is a very challenging responsibility and requires specific skills and competences of the project management. In order to steer the FAIR project, a Project Management Office (PMO) was established. This contribution gives short overview of FAIR PMO organization, objectives and describes transition process from classic simple PMO controlling type to highly modern hybrid form of PMO with focus of strategies, expediting and support.
A fast neutron facility, called NDPS (Nuclear Data Production System), has been constructed for nuclear science and applications at RAON (Rare Isotope Accelerator complex for ON-line experiments) in Korea. The installation of NDPS and transport beamline from SuperConducting LINAC 3 (SCL3) to NDPS was finished in 2022. The NDPS is designed to provide both white and mono-energetic neutrons, using 98 MeV deuteron and 20 – 83 MeV proton beams with a thick graphite and thin lithium targets, respectively. The energy of the neutron is determined by employing the time-of-flight (TOF) technique, along with a pulsed deuteron (or proton) beam with a repetition rate of less than 200 kHz. Fast neutrons are produced in the target room and are guided to the TOF room through a 4 m long neutron collimator consisting of iron and 5 % borated polyethylene. In the TOF room, a gas-filled Parallel Plate Avalanche Counter (PPAC) will measure the neutron arrival time and position as it has a neutron converter of a thin $^{\mathrm{232}}$Th layer. Additionally, EJ-301 liquid scintillation detectors will be used for the measurement of neutron flux with pulse shape discrimination capability. The beam commissioning for NDPS is scheduled for 2024 with a proton beam. The present status of NDPS will be reported, together with our future plan.
Fixed field Alternating gradient (FFA) accelerator is an option as a proton driver for the next generation spallation neutron source (ISIS-II). To demonstrate FFA suitability for high intensity operation, a 3 to 12 MeV proton prototype ring is planned at RAL, called FETS-FFA. The main magnets are a critical part of the machine, and several characteristics of these magnets require development. First the doublet spiral structure has never been designed before, and the essential feature of operational flexibility in terms of machine optics requires a wide range of changes for the field gradient. Finally, control of the fringe field is a challenge both mechanically and from the nonlinear optics point of view. This paper will discuss the design of the prototype magnet for FETS-FFA ring.
The cyclotron C70XP of the Interest Public Group ARRONAX is regularly producing radio-isotopes for medical and research purposes. To support these productions an internal data network based on EPICS has been deployed, extending the collection of data on the accelerator components and, beam and technical diagnostics. With the accumulation of the new data, a study program is being addressed focusing on the application of data mining and Machine Learning (ML). ML Algorithm, e.g. clusterisation such as density-based spatial clustering of applications with noise or isolation forest, are used to explore the capacity to highlight anomalies for long runs with two extreme temporal cases. First explored approaches and results are presented in this paper as well as the robustness of the algorithms, which are investigated using dedicated methods (indices or iterations).
A Gabor-lens is an ion optical device using the electric self-field of a stable confined electron column providing the focusing strength. This lens type was investigated in detail and it was shown that it is possible to use it in a LEBT for intense heavy ion beams. The homogeneous electron density results in linear focusing forces and provides space charge compensation of the beam. On the other hand it is not clear, how the charge state changes when a highly charged ion beam passes the pure electron plasma confined in a Gabor-lens. Therefore, an experiment was designed, which enables the possibility to transport an 15keV Ar8+-beam through a Gabor-lens and estimate the collisional three-body (e – e – ion) recombination to lower charge states. A variation of the relative velocity of the beam with respect to the electron plasma was performed and it was possible to measure the electron density at the same time. Experimental results are presented and future strategies for the transport of highly charged intense ion beams are discussed.
A compression of the ESS proton pulse from the present 2.86 milliseconds to a few tens microseconds which is better matched to the moderator time constant of thermal neutrons would considerably boost the performance for many instruments at ESS. Generating such a proton pulse with preserved instantaneous beam power requires a storage ring to be added to the ESS accelerator. Such a ring has been studied within the ESSnuSB neutrino super-beam study. The proton pulse length extracted in single turn extraction from this ring would be 1.2 microseconds long which could be destructive for the present ESS target and is very short compared to the moderator time constant. The more desirable medium length pulse could possibly be generated by multi-turn extraction. Another way to generate the longer pulses is to extract a bunch train using fast strip line kickers but this would require a larger storage ring. Using a “bunch train” has been successfully applied at the CERN ISOLDE facility to avoid destruction of sensitive liquid metal targets used for Nuclear Physics experiments. Other challenges are linked to the injection into the storage rings and the understanding of the target, moderator and neutron extraction systems with short and medium pulse length. We will in this presentation review the technical challenges linked to a future medium pulse length ESS facility and the ways proposed to address them for the accelerator and target.
The Los Alamos Neutron Science Center (LANSCE) is a MW-class H-/H+ 800-MeV proton linear accelerator and storage ring that serves five distinct user facilities in support of LANL’s national security mission and DOE’s Office of Science medical isotope program. We will describe future directions of LANSCE over the next two decades, which includes revitalization and modernization of existing subsystems and upgrades with significantly increased operational capabilities. We will also be describing ongoing and future R&D activities will enable these enhancements. Some of this R&D is truly cross-cutting, leading to foundational technologies that broadly support multiple LANSCE directions, such as high-gradient normal-conducting RF, artificial intelligence/machine learning, and high-brightness, robust cathodes. Other R&D is more specific to particular applications, and include such topics as narrow bandwidth inverse-Compton scattering, short-range wakefield studies, and novel X-ray free-electron laser architectures.
The 3-GeV RCS at J-PARC at present operates at a relatively high intensity beam of nearly 1 MW for the spallation neutron source. The beam loss and the corresponding residual radiation, which is the key limitation against beam intensity ramp up, has been well mitigated to a minimum level in a recent series of beam studies and feedback from realistic numerical simulations. The residual beam loss even at the designed 1 MW beam power is now mostly due to the foil scattering of the circulating beam during multi-turn injection, while other beam loss sources have been well optimized to minimize the beam loss for achieving a stable operation presently at 800 kW.
A unique feature of the current LANSCE accelerator facility is acceleration of four H- beams (differing in time structure) and one H+ beam. This is achieved by utilization of an injector system based on two ion sources (H+/H-), and a combination of chopper and RF bunchers in the Low Energy Beam Transports. Since the end of 1990’s, the large LANSCE experimental, Area-A, has been largely unused. In order to restore usage of Area-A, we have been exploring the possibilities of bringing low-intensity power beams into Area-A*. The proposal is based on partial stripping of the 800 MeV H- beam that is transported to the Weapons Neutron Research Facility, and to deliver the resulting 10 – 100 nA proton beam to Area-A. The appropriate place for generating proton beam was found to be the beginning of Line D after LANSCE Switchyard by first neutralizing the beam from H- to neutral hydrogen beam ahead of the bending magnet using a laser, and then by fully stripping the neutral hydrogen beam to protons utilizing a stripper foil. The paper discusses design details of the proposed high-energy beamline and beam parameters.
Increasing energy of proton beam at the Los Alamos Neutron Science Center (LANSCE) from 800 MeV to 3 GeV will improve radiography resolution ten-fold. This energy boost can be achieved with a compact cost-effective linac based on normal conducting high-gradient (HG) RF accelerating structures. Such an unusual booster is feasible for proton radiography (pRad), which operates with short beam pulses at very low duty. The pRad booster starts with a short L-band section to capture and compress the 800-MeV proton beam from the existing linac. The main HG linac is based on S- and C-band cavities. An L-band de-buncher at the booster end reduces the beam energy spread at 3 GeV three times below that at the exit of the existing 800-MeV linac. We continue developing proton HG standing-wave structures with distributed RF coupling for the booster. Results of measurements for a two-cell test cavity at the LANL C-band RF Test Stand and a comparison with conventional traveling-wave structures are presented.
Within the EU-funded activity IFAST, the task REX (Resonance Extraction Improvement) was launched in 2021 as WP 5.3. The IFAST-REX consortium comprises European hadron synchrotron facilities CERN and GSI, the hadron therapy centres CNAO, HIT, MedAustron, MIT and SEEIIST, as well as the companies Barthel HF-Technik and Bergoz Instrumentation. It deals with the crucial challenge of slow extraction in mitigating the current fluctuation on the time scale of typically 0.01 to 10 ms, primarily caused by magnet power supplier ripples. Higher frequency ripples due to the properties of beam excitation methods are also considered. IFAST-REX is organized into four modules: Two modules execute the realization of a high dynamic range low-frequency current transformer and tailored high power amplifiers for beam excitation. The other two modules focus on developing simulation tools for accurate long-term slow extraction and developing diagnostics related to extracted particle detection and analysis. This contribution summarizes the current status of the consortium efforts by indicating to selected results.
J-PARC Main Ring delivers 65 kW (7x10^13 ppp) slow-extracted beam over 2 sec. at 30GeV to the hadron experimental hall to drive various nuclear and particle physics (hadron) experiments. Unexpected behavior of the high-intensity beam caused by the accelerator trip could cause serious machine damage. In March 2021, the first electrostatic septum (ESS1) was broken by a bump orbit distortion caused by the quadrupole field decrease by the trip of a vacuum circuit breaker for the quadrupole power supplies in the straight section. The slow extraction operation was resumed after replacing the ESS with a spare one and shortening the decreasing time of the slow bump power supplies triggered by the trip signal. In the long shutdown after the run, the power supplies for the main magnets have been upgraded for a higher cycle operation for the neutrino oscillation and the hadron hall experiments. The impact of the slow-extracted beam by the new main power supply trip has been investigated by the beam simulation. The simulation showed that each trip of defocusing quadrupole and bending families could deliver a short-pulsed beam and break a gold production target in the hadron hall. The mechanism forming the short-pulsed beam and the countermeasure will be also reported in this paper.
Acceleration grids of the Neutral Beam Injector in nuclear fusion reactors must be extremely accurate and satisfy specific geometrical requirements to work properly. The implementation of the additive manufacturing technology was proposed since 2017 starting the characterization of pure copper up to the recent excellent results in terms of density, process reliability and repeatability. To assure the required performance and maximize the beam optics and the overall system efficiency, an intense study of the geometry of these components was performed, adopting a spherical aspect of planes. The material selection was also an important step of the work. An integrated cooling system, peculiar of the AM technology, was optimized, ensuring a relevant reduction of temperature peaks. Pure copper and CuCrZr alloy were investigated for reaching the best material properties: parameters optimization was executed using different machines and laser beams, and several post processes were assessed, such as surface treatments to smooth the cooling ducts. After the material characterization, which was focused on the evaluation of density, thermal conductivity and mechanical strength of the AMed parts. Lastly, several prototypes were produced and power tests were carried out.
Requirement of availability of CiADS (China Initiative Accelerator Driven System) is greater than 0.8. As a part of CiADS, high power RF system, including SSA (solid-state amplifier), high power transmission line, which availability should greater than 0.999. And hot-plug technology is a significant way to improve availability of SSA. But in the process of hot-plug, there will exist high power standing wave in the hot-plug port of power combiner. And reduce the combining power severely. Although, we can optimize the length of input arm of power combiner to a wavelength or closely to zero to avoid high power standing wave.
Antiprotons are generated at CERN by extracting a high-intensity proton beam
from the Proton Synchrotron (PS) onto a target. The resulting antiprotons are
captured in the Antiproton Decelerator (AD) ring. As the AD is about three
times shorter than the PS, the entire primary proton beam must be compressed
to less than one third of the PS circumference. The previous batch compression
brought four bunches injected from the PS Booster (PSB) into consecutive RF
buckets at a harmonic number of 20. An improved injection and compression
scheme has been developed and commissioned to deliver five bunches to the
AD. It became feasible thanks to the upgrades of the injector complex for the
High-Luminosity LHC (HL-LHC). One of the four PSB rings delivers twice
higher intensity in two bunches, and an optimized sequence of nine different RF
harmonics has been set up to obtain five bunches within one quarter of the PS
circumference. The contribution summarizes the main changes to the antiproton
production beam, as well as the experience of the first year of operation. Results
of beam tests with increased total intensity are presented.
Transfer lines provide the beam transport from accelerators to experimental areas. In the study presented in this paper, commonly used beam optics are supplemented by Gabor-lenses (GL) to investigate their effect on the luminosity for fixed-target experiments.
With GLs it is possible to confine a pure electron plasma with densities up to 10E15 m-3. The self-field of the homogeneous electron density provides a focal strength, whereas the space charge forces of the beam are fully compensated. The performance of GLs was numerically investigated in the GeV range (p, $\pi$+, K+) in the past. The weak but continuous radial focusing improved the acceptance of the whole transfer line.
The preparation of the experiments is planned in two steps. First, a GL (GL2000) which provides a 2m long electron column was commissioned successfully at the Van-de-Graaf beam line at Institute of Nuclear Physics of Goethe-University. Beam transport measurements to investigate the stability of the confined electron column were performed using He+, Ar+ and Xe+ beams in an energy range of 0.5-2MeV. In a second step the implementation of several GLs in an existing transfer line at GSI Darmstadt was investigated numerically. The beam transport simulations using TraceWin shall take into account, that existing focusing devices and beam instrumentation should not be affected by the implementation. This enables the possibility to provide and compare the beam transport with and without electron atmosphere.
The minimum emittance of ion beams achieved using electron cooling is limited by the heating processes of Intra Beam Scattering and diffusion driven by resonance crossing of particles due to space-charge. We describe a new experiment to explore the intense space-charge regime with a transverse tune shift approaching -0.5 using 2.5 MeV protons at the Integrable Optics Test Accelerator (IOTA) at Fermilab. We also report on the results from PyORBIT simulations incorporating transverse space-charge and electron cooling with emphasis on the incoherent dynamics of the particles.
MedAustron is an ion therapy facility for protons and carbon ions located in Wiener Neustadt, Austria. The beam is presently extracted for clinical operation from the synchrotron with third-order resonant slow extraction via acceleration with a betatron core. However, due to the flexibility of the synchrotron operation for Non Clinical Research (NCR) purposes, other extraction methods can be investigated for potential improvement of the machine performance as presented in this work.
Radio-Frequency Knock Out (RFKO) extraction was investigated by applying an RF signal voltage across the horizontal Schottky plates in the synchrotron. Different excitation signals were evaluated with the required transverse excitation frequency band applied.
Investigation of the synchronous ramping of all synchrotron magnets for extraction via Constant Optics Slow Extraction operation (COSE) was undertaken for a bunched beam in order to extend the implementation of COSE with possible Multi Energy Extraction (MEE).
The last extraction method presented here is via longitudinal RF manipulation in order to extract the beam by sweeping a properly configured empty bucket through the beam stack. This method is known as Phase Displacement Extraction (PDE).
Extraction rates with these methods were observed which meet the clinical requirements and might also be considered compatible with FLASH.
Radio Frequency Knock Out (RF KO) extraction is used to extract stored particle beams from synchrotrons through transverse excitation, delivering spills of particles for experiments and medical therapy. Minimizing the fluctuations of spill intensity is vital to prevent detector pile-up and interlocks while making most efficient use of the extracted beam. To improve the spill quality, different excitation signals with characteristic frequency spectra are explored. Results of experimental studies at the Heidelberg Ion Beam Therapy Center (HIT) are presented. These demonstrate the possible improvements by tuning multi-band spectra at different harmonics. Particle tracking simulations of the slow extraction process at HIT are used to understand how different excitation signals influence the spill quality.
The future AMBER experiment aims to measure the inner structure and the excitation spectra of kaons with a high intensity kaon beam at the CERN secondary beam line M2. One way to identify the small fraction of kaons in the available beam is tagging with the help of differential Cherenkov detectors (CEDARs), whose detection efficiency depends critically on the beam parallelism. In the framework of the Conventional Beams Working Group of the Physics Beyond Colliders Initiative at CERN, several possible improvements of the conventional beam optics have been studied, trying to achieve a better parallelism, investigating especially the reduction of multiple scattering. Additionally, with the aim of increasing the Kaon purity of the beam, a Radio-Frequency separation technique has been also studied. This method exploits the differences in velocity due to the particle mass in the beam, kicking out unwanted particles with the help of two RF cavities. The limitations posed by the beam line for intensity and purity will be presented along with preliminary results of the potential purity and intensity reach of the RF-separated beam. Finally, the RF-separated beam is compared with the conventional hadron beam in terms of potential physics reach.
JSPEC (JLab Simulation Package on Electron Cooling) is an open-source C++ program developed at Jefferson Lab, which simulates the evolution of the ion beam under the influence of both IBS and electron cooling effects. In this paper, we will report the latest updates to JSPEC. Firstly, we have added theoretical and numerical models that simulate the effect of the electron beam dispersion on non-magnetized cooling. Secondly, the cooler can now be treated as an element with length, rather than a thin lens. This change will impact the modeling of the ions and the electrons in the cooling rate calculation for both magnetized and non-magnetized cooling. Numerical results will be provided to demonstrate the performance of the new models.
In the next heavy ion runs at the LHC, the cleaning of the beam halo will rely on crystal collimation. A test system installed in the collimation cleaning insertion is being upgraded for the operational challenges of the ion runs. Therefore, it is crucial to experimentally test the performance of the newly installed crystal primary collimators. During a dedicated short Pb ion beam test in 2022, crystal collimation was tested for the first time with 6.8 Z TeV Pb beams. These results provide very important input for the configuration of
the Pb ion run at the LHC in 2023. In this paper, the results and analysis of the crystal measurements in the 2022 ion test are presented.
The ever-enriching beam application scenarios have put forward more demands on accelerators. With the research and application of multiple energy extraction technology in synchrotrons, how to extract multiple energy bunches in a shorter time has become the next problem to be solved, and it is expected to be applied in tumor radiotherapy. This paper provides three methods for generating short bunches in synchrotron. By adjusting the pulse parameters of the potential well in the induction synchrotron, the short bunches can be easily generated. The short bunches can be kicked out of the beam reference orbit by special equipment such as kicker. When the processes are repeated for many times, and the energy-changing process is added to the time gap during which the short bunches are continuously generated, the short bunches of multiple energy can be extracted in one working cycle. Combined with the analysis of longitudinal dynamics, the number of particles in the short bunches can be better controlled, making an important contribution to further enriching the application scenarios of synchrotron beams.
The vast majority of nuclear physics simulations are dependent on the National Nuclear Database, maintained at Brookhaven National Lab, and these in turn are all based on published experimental measurements. Even today, there are gaps in this database in low energy ranges, which can be filled even by older machines. In addition to the scientific output, these measurements provide a unique educational opportunity. The cyclotron at the Crocker Nuclear Laboratory at UC Davis is a capable of accelerating protons, deuterons, or alpha particles to variable energies up to a maximum of 67 MeV for protons. We have developed a facility to perform ``stack foil" cross section measurements, in which stacks of target foils sandwiched with degraders are exposed to proton or deuteron beams, thus allowing us to exploit the energy loss through the stack to measure energy dependent cross sections in a single exposure. Daughter nuclei are assayed using a high purity germanium (HPGe) detector.
This poster will describe the facility, including the range of available beam parameters and energy and current calibration, as well as presenting some representative cross section measurements. Future plans will also be discussed.
A new secondary beamline was recently installed in the MeV Test Area (MTA) with the objective of enhancing mu+/mu- production by factors of 3/8 by using a tungsten target versus the conventional graphite production target using the 400 MeV Fermilab proton Linac beam. Ultra-low energy muon beams can support world-class physics experiments for fundamental muon measurements, sensitive searches for symmetry violation, and precision tests of theory. The beamline was designed to transport up to 100 MeV/c decay-in-flight pi- for mu- and down to a few MeV for mu+ surface muons. Mu- will be applied to a muon-catalyzed fusion experiment, which requires a large momentum acceptance within a small transverse acceptance. Studies are also underway towards a high-efficiency source of muonium by stopping the mu+ beam in superfluid helium. Muon production and transport scenarios have been simulated and optimized using the particle tracking code, G4Beamline. The results of these G4Beamline studies and target optimization will be presented here. Plans for experimental measurements to benchmark simulations and future applications using this multi-user, low-energy muon MTA facility will also be discussed.
The China Spallation Neutron Source (CSNS) has been operated with 100kW beam power on target since 2020. The Linac consists of an H- ion source, a low-energy beam transport line (LEBT), a 3 MeV Radio Frequency Quadrupole (RFQ), a Medium Energy Beam Transport line (MEBT) and a Drift Tube Linear (DTL) accelerator to boost the beam energy to 80 MeV with a beam intensity of 10 mA. A power upgrade project (CSNS-II) has been approved in 2021 to increase the beam power to 500 kW, for which the Linac energy will reach 300 MeV and the beam intensity is expected to be 50 mA. Now we are gradually increasing the beam intensity of the CSNS Linac to fully explorer its capability and furtherly deepen our understanding of the properties of high intensity beam. In this study, we show the beam measurement results given by the wire scanners and the emittance monitor at various current intensities, and the numerical modeling and fitting methods to obtain the evolution of the beam envelope and emittance along the CSNS MEBT.
Resistive oven technique is used to inject vapours of metallic species in plasma traps, where plasma sustained by the electron cyclotron resonance (ECR) mechanism provides step-wise ionisation of neutral metals, producing charged ion beams for accelerators. We present a numerical survey of metallic species suitable for oven injection in ECR ion sources to explore neutrals diffusion and deposition, under molecular flow regime. These aspects depend on geometry of the evaporation inlet, thermodynamics, and on plasma parameters, which strongly impact on ionisation and charge-exchange rate, thus on the fraction of reacting neutrals. We considered diffusion of metals with and without plasma, and the impact of a liner for re-emitting deposited species. Numerical predictions might be relevant to reduce the metal consumption and to increase the overall efficiency. As test beams, we simulated most relevant ones for modern nuclear physics field, such as 48Ca and rare earths species.
XiPAF (Xi'an 200MeV proton application Facility) synchrotron is using H^- stripping injection and phase space painting scheme. With the demand of more particle species for single event effect study, XiPAF synchrotron has been upgraded to multiturn injection from stripping injection, the injection system must be redesigned. This paper report XiPAF synchrotron multiturn injection scheme, a simulation results by PyOrbit show that the injection efficiency is ~80% for proton and ~70% for heavy ions. The influence of space charge and magnet errors on accumulated particle number has been studied by simulation.
The K12 beam line and NA62 experiment in the North Area at CERN in beam dump mode exploits the interactions of 400 GeV protons with a movable dump-collimator, the so-called XTAX. Such interactions are theorised to generate potential light dark matter candidates such as the axion. Any rare process search requires precise knowledge and experimental reduction of the predominant muon background. A previous examination has been performed successfully, involving tuning the magnetic fields of the first achromat in K12. This contribution aims to explore further improvements using similar methods on the second achromat in the same K12 beam line, using BDSIM simulation software.
Gabor-lens 2000 (GL2000) is an hadron optic device which confines a 2m long electron cloud. This opens up new possibilities in research with very long confined static electron ensembles. Due to the optimization of technical design it was possible to successfully complete the conditioning process creating a stable confinement of electrons. Also, the diagnostic tools were extended and the control and measurements was automated. This made it possible to scan a large parameter space with varying the external confinement parameters magnetic field, potential and residual gas pressure. In addition, numerical models of GL2000 confinement parameters were simulated to derive the operation function for different production and loss mechanisms at different potential and magnetic field settings. This should make it possible to adjust the particle ensemble within the Gabor-lens (GL) in a way, that the plasma state is defined. For applications of GLs in transport channels, particle accelerators or final focus sections it is than possible to create a perfect linear mapping of the beam and therefore a smooth focusing with space charge compensation. Using the TraceWin tool, simulations were made for beam transport through high energy beam transport lines. In addition, GL2000 was implemented to the Van-de-Graaf beamline at IKF*, to be able to investigate beam-cloud interactions and perform first transport measurements.
Recent studies by Dejan Trbojevic have confirmed that Non-Scaling Fixed Field Accelerators (NS-FFAs) can have their tune dependence on momentum flattened by adding non-linear components to the magnet fields, although not necessarily for an unlimited momentum range. This paper presents such a cell suitable for the proposed 3-12MeV FETS-FFA proton R&D ring at RAL.
The nonlinear magnetic field components are found automatically using an optimiser and settings covering a ring tune range of one unit in both planes independently are attainable. A fully configurable magnet with multiple windings across its horizontal aperture has been designed in 2D using Poisson, which can produce the required nonlinear fields without exceeding 5A/mm^2 current density.
The LANSCE accelerator facility has been in operation for 50 years performing important scientific support for national security. The unique feature of the LANSCE accelerator facility is multi-beam operation, delivering beams to five experimental areas. To reduce long-term operational risks and to realize future beam performance goals in support of the laboratory missions, we develop a novel high-brightness Front End injector. Proposed injector includes two independent low-energy transports for H+ and H- ions merging beams at the entrance of a single RFQ. These beamlines also perform preliminary beam bunching before RFQ. The challenge of the present project is associated with simultaneous acceleration of protons and H- ions with multiple beam flavors in a single RFQ, which has never been done before. Proposed injector must provide better than existing beam parameters while beam intensity is supposed to be increased by a factor of two and injection energy is reduced from 750 keV to 100 keV. The paper discusses details of beam physics design and presents injector parameters.
In the J-PARC Main Ring, a project to upgrade the beam power to 1.3 MW is currently underway. The most important issues in realizing such a high-power beam operation are controlling and minimizing beam loss, which are essential for sustainable beam operation allowing hands-on maintenance. In this paper, we report on our recent efforts to understand the mechanism of beam loss and to reduce it.
CRYRING@ESR is a low-energy heavy-ion storage ring recently recommissioned at GSI, Darmstadt, as part of the FAIR project. With its standard working point lying on the lowest-order difference resonance, the ring contains a compensation solenoid to counter coupling of betatron motion introduced by the electron cooler magnetic field. That solenoid largely occupies one of the drift sections of CRYRING, which would otherwise be available for additional experimental inserts. We performed a series of machine experiments to gain better understanding of the performance of the compensation solenoid and its importance for successful operation of the ring, especially with regard to damping rates and final emittances reached by electron cooling. Our measurements show that omission of the compensation solenoid does not lead to a notable deterioration of beam intensity, lifetime or quality. However, we could clearly observe the resulting betatron coupling in the cooled ion beam and its predicted impact on the tunes of the ring, effects that are cancelled surprisingly well with the compensation solenoid enabled, and that may be of importance for some experimental schemes. Our results can serve as basis for a discussion about a possible future removal of the compensation solenoid.
The Los Alamos Neutron Science Center (LANSCE) is a very flexible H-/H+ 800-MeV proton linear accelerator and storage ring that serves five distinct user facilities in support of LANL’s national security mission and commercial applications. It is unique because of the intensity and energy spectrum of the neutrons produced. The Isotope Production Facility (IPF) operates using an H+ beam line at 100-MeV. The Proton Radiography Facility uses the 800-MeV H- beam stripped to protons. The Ultra-Cold Neutron (UCN) Facility, the Lujan Center, and the Weapons Neutron Research (WNR) Center all use spallation neutrons from tungsten targets with water and liquid hydrogen moderators for Lujan, a solid deuterium moderator for UCN, and no moderation at WNR. These spallation targets all receive 800-MeV beam each with a unique beam pulse structure specific to that target. LANSCE celebrated its 50-year anniversary of 800-MeV beam during the summer of 2022. We will summarize operational experiences and challenges at a half-century old accelerator facility, including recent improvements and current upgrade plans.
Xi'an Proton Application Facility (XiPAF) synchrotron provides 10~200MeV proton beam for the experimental simulation of the space radiation environment. Due to the space charge effect, the slow extraction of 10 MeV proton beam is a work full of challenges. In a past experiment, the total extraction efficiency was over 65% with 4.5 ~ 6.5×1010 protons stored before extraction but decreased to 52% with 9×1010 protons stored. In order to study the beam loss caused by a strong space charge effect, based on experimental parameters, the beam loss fractions at different positions of XiPAF synchrotron are obtained through the simulation. According to the beam loss analysis, optimized parameters are found for reference in subsequent experiments. It is also noted that negative beam average momentum spread before extraction is beneficial to the improvement of extraction efficiency
The JEDI experiment is dedicated to the search for the electric dipole moment (EDM) of charged particles using storage rings, which can be a very sensitive probe of physics beyond the Standard Model. In order to reach the highest possible sensitivity, a fundamental parameter to be optimized is the Spin Coherence Time (SCT), i.e., the time interval within which the particles of the stored beam maintain a net polarization greater than 1/e. To identify the working conditions that maximize SCT, accurate spin-dynamics simulations with the code BMAD have been performed on the lattice of a "prototype" storage ring which uses a combination of electric and magnetic fields for bending. This contribution presents an analysis of the mechanisms behind the decoherence, and a technique to maximize SCT through the optimization of second-order optical parameters.
Cooling of secondary beams is often critical to accelerator based nuclear and sub-nuclear physics, with beams ranging from positrons e+ to muons μ+/- to hadrons (for the respective collider facilities) to exotic nuclei ions (like 132Sn1+) as in the SPES (Selective Production of Exotic Species) project at LNL. A prototype of a radiofrequency quadrupole (RFQ) cooler (RFQC) was developed at LNL and is under test in the Eltrap facility at Milan University; Eltrap provides a solenoidal magnetic field. Typical limits of RFQC and high resolution mass spectrometer (HRMS) performances are discussed, and relevant formulas are implemented in easy reference tools; HRMS requires less than 1 eV energy spread. The necessary collisional data are reviewed, in particular for Cs+ against He gas, whose pressure ranges from 2 to 9 Pa; status of Milan test bench is updated, with radiofrequency multiplexer and matching box details; the energy analyzer concepts are discussed. Practical consideration on gas pumping are also included.
This paper proposes a new coupling slots design for the Pi-Mode structure high-frequency cavity in the China Spallation Neutron Source (CSNS) Phase II. Through simulation calculations and experimental verification, it was found that the new coupling slots design significantly improves the Q value and transmission efficiency of the high-frequency cavity. This study is of great significance for improving the performance of the high-frequency cavity in CSNS II, and thus improving the accuracy and efficiency of neutron scattering experiments.
The {2, 2} Danilov distribution is self-consistent — it is a Vlasov equilibrium distribution that produces linear space charge forces. Additionally, the distribution has zero (four-dimensional) transverse emittance. Thus the Danilov distribution may be of use for overcoming space charge limitations at high intensities, increasing collider luminosity, or pushing the limits of transverse bunch compression using round-to-flat transformers. When such a distribution is matched to one of the eigenmodes of a ring it is possible to use phase space painting to build the distribution over many turns, maintaining self-consistency throughout. This provides a way to create high-intensity beams with unique properties that could increase accelerator performance, with direct implication for experiments. Here we report on the results of a proof-of-principle experiment using the flexible transverse phase space painting system at the Spallation Neutron Source to demonstrate the creation of an approximate Danilov distribution, including the effect of recently installed solenoid magnets.
The CERN-wide coordination of the programmed stops requires a tool to centralize and collect all the activities at a macroscopic scale. It includes the activities foreseen during Long Shutdowns (LS) and Year End Technical Stops (YETS).
The CERN tool named PLAN centralises all the activities foreseen by the Groups, to have a global strategic view, assessing priorities across CERN. Thanks to the tool, arbitration processes are possible with Programmed Stops coordination, Groups and Departments. The LS2 (2018-2022) experience and the similarity of needs made the PLAN tool the obvious choice to fulfill this function for the period following the LS2.
However, this tool needs some significant changes to be adapted to the constraints defined by the Run3 (2022-2025) programmed stops and previous Shutdown completion (LS2). The paper will describe the methodology to define the changes, the improvements implemented, and future developments, to support more effectively the CERN-wide coordination.
The RAON ultra-low energy experiment team decided that the first experiment was to accelerate the proton 70 MeV using a cyclotron and collide with the SiC target to generate a radioactive isotope beam. Before this experiment, a preliminary experiment was conducted to confirm the exact location and shape of the proton beam before directly colliding with the target to generate a lot of radiation or prevent the loss of the target. The pre-experiment was done to understand the characteristics of the proton beam at the target position by configuring the faraday cup, wire grid, collimator, and slit inside the proton module. The beam current was from 1~1.5 μA, and the beam size was confirmed under the slit size 2˟2 cm2.
A high-power proton linac at KOMAC uses a drift tube linac structure to accelerate protons up to 100 MeV. Currently, a total of 148 drift tubes with electromagnetic quadrupoles are used in DTL sections for accelerating protons from 3 MeV to 20 MeV. A drift tube based on a permanent magnet quadrupole has been designed and prototyped to replace the EMQ-based drift tube to enhance the DTL reliability. A designed PMQ with an integrated field gradient of 1.6 T is assembled from 16 segments, which are made of Sm2Co17 magnetic material for its radiation hardness. Details of the prototyping study on the PMQ including design, fabrication, and test along with the beam dynamics effects are given in this presentation.
The Electron-Ion Collider (EIC) incorporates beam crabbing to recover geometric luminosity loss from the nonzero crossing angle at the interaction point (IP). It is well-known that crab cavity imperfections can cause growth of colliding beam emittances, thus degrading collider performance. Here we report a particle tracking study to quantify parts of these effects.
The 3 GeV rapid cycling synchrotron (RCS) at the Japan Proton Accelerator Research Complex (J-PARC) provides more than 800 kW beams to the Material and Life Science Facility (MLF) and Main Ring (MR). We have been continuing a beam study to achieve 1-MW, design power operation. In addition, we have also improved and maintained the accelerator components to establish a stable operation. This paper reports the status of the J-PARC RCS in recent years.
Future proton superconducting RF (SRF) linacs used as accelerator driven systems (ADS) must achieve high reliability and availability to meet the challenging parameters for applications in medical treatment, nuclear waste reduction, and nuclear power generation. What SRF innovations and advanced concepts are needed? To answer this question, a case study of the past, current, and possible future downtime sources is carried out for the Spallation Neutron Source (SNS) SRF linac systems. SNS is an accelerator-driven neutron source facility routinely operated at a 1.4 MW beam power with a 99% availability in its SRF systems and is currently undergoing an upgrade to a new level capable of a 2.8 MW beam power. The preliminary outcome of this study is to be presented. We will discuss its implications to the needed development of the next generation SRF systems and related systems towards 10-20 MW proton SRF linacs required for future ADS facilities.
Xi 'an 200 MeV Proton Application Facility (XiPAF) will be upgraded to proton and heavy ion synchrotron recent-ly. In order to ensure the enough life of heavy ion beam, the synchrotron requires ultra-high vacuum, and the de-signed static vacuum is better than 5×10-10 Pa. In order to place enough vacuum pumps in the synchrotron, the circumference of the synchrotron was increased from 30.9m to 39.96 m. The cyclotron frequency range of heavy ions is 0.49~1.03 MHz. In order to reduce the en-gineering difficulty and improve the lower limit of fre-quency bandwidth requirement of the RF system, the harmonic of h=2 is used to capture and accelerate the heavy ions, and the frequency bandwidth range of the RF system is adjusted from 1~6 MHz to 0.8~5.0 MHz. In this paper, the longitudinal dynamics parameters of the upgraded synchrotron are designed, and the simulation calculation is carried out. Finally, the parameter require-ments of the RF system are proposed.
The Linear IFMIF Prototype Accelerator (LIPAc) is designed to accelerate 125mA of deuteron beam to 9MeV in continuous wave (CW). The superconductive RF Linac has not yet been installed and the final accelerating stage now under commissioning is the RFQ. This system has been designed and developed by INFN (Italy) before installation in QST (Japan). The RFQ is the longest in the World with its 9.8m and requires RF power injection from 8 independent and synchronized coupler ports. LIPAc demonstrated the acceleration of 125mA deuteron beam at 5MeV for 1ms with a 1s repetition period in 2019. A fundamental milestone to extend beam operations to CW is the completion of the RFQ cavity RF conditioning up to CW. This work presents the strategy followed to successfully reach CW RF injection at 80% of the nominal 132kV vane voltage. The field distribution correction scheme (acting on cooling system at various power level) was successfully verified. We discuss as well the main challenges encountered on the way, which include updates of the RF system, failure of a circulator (by arcs) and the damages occurred on some of the RF couplers. Finally, the recent status and outlook will be provided.
The Cyrcé facility of IPHC in Strasbourg operates a TR24 cyclotron to produce medical isotopes, lead radiobiology programs and test detectors.
A RF kicker has been developed in order to discard one beam bunch over two to get a rate close to 40MHz. An RF voltage at a quarter of the cyclotron frequency applied to a deflector in the injection line allows to reach that goal. The 30keV DC beam from the ion source is discarded except at the zero crossing of the RF. With a proper phase difference between the two RF, only one accelerating phase of the cyclotron over two is populated resulting in a bunch rate of 42.5MHz.
A second need for radiobiology is to switch the beam on and off with the highest raise and fall times. This is done by adjusting the phase of the kicker to block the beam.
The kicker is made of a collimator (diam. 8 mm), followed by 2 deflectors ( 55 mm long, 50 mm wide) spaced by 40 mm and a second collimators (diam. 6mm) at 160 mm downstream the deflectors, also used as a beam dump for the deflected ions.
The high voltage is achieved by a resonant circuit consisting of a coil and the deflector, excited by a second coil. A second variable capacitor is added for tuning. The excitation coil position allows to adjust the matching. Scintillators associated with fast electronics has shown that the bunche rate was half the cyclotron frequency as expected. The beam rejection was measured to values up to 10-5.
The raising and falling times of the beam was measured to 10µs.
Flat beams are preferred at high energies due to their ability to achieve high intensity and luminosity, as one of the transverse emittances is smaller. However, at low energies, collective effect such as space charge becomes dominant in the smaller dimension. Intra-beam scattering(IBS) effect is dominant when local beam density is high, from medium to high energies. Circular mode beams, which have equal beam sizes in both planes and are intrinsically flat, can help mitigate these effects while maintaining intrinsic flatness. Circular mode beams can be transformed from and to flat beams, enabling the beam to bypass collective effects while maintaining the intrinsic flat beam state. Angular momentum conservation is crucial for maintaining the circular mode, and we will present rotation-invariant systems that can conserve angular momentum. Additionally, we will investigate the effects of IBS on circular modes and different beams.
The Scheduling Tool Project (ST Project) is in charge of ensuring the scheduling and coordination of CERN accelerator programmed stops and facilities installation managed within the Accelerator Coordination and Engineering (ACE) Group, inside the Engineering Department (EN) at CERN, since 2019. The scheduling tools should consider all the activities, that take place in large facilities, composed of complex and interdependent systems, ensuring the safety rules and quality standards. The current goal of the ST Project is to consolidate the scheduling tools that are used, and to homogenize them through the different facilities, merging the user needs with the developer solutions. This will lead to be ready for the Long Shutdown 3 (LS3) which will start in 2026. This paper describes the tools used to manage CERN programmed stops to build a coherent schedule, follow up, and report progress. It gives the details of the requirements, code design and future works to create a linear view on a web interface and the first results. It also describes the specifications needed to implement a report indicator in this linear view (i.e., broken line curve).
ECR ion sources produce ion beams with an intensity proportional to the heating frequency. SEISM (Sixty gigahErtz Ion Source using Megawatt magnets) is a unique source operating at the record frequency of $60~GHz$ thanks to a gyrotron producing high intensity HF pulse (up to $300~kW$). The prototype is based on a simple magnetic geometry, the cusp, using polyhelix coils (developed with the LNCMI, Grenoble) to generate a closed ECR surface at $2.1~T$.
Since 2019, several experimental campaigns were carried out with helium and argon beams and production of ion current densities of $1~A/cm^2$) were achieved. The transport of high intensity beam is studied thanks to the dedicated transmission line and qualified with emittance measurements using a pepperpot device. Using several support gases, plasma studies are also carried out as function of source parameters such as extraction high voltage, gas pressure, bias disc potential. The dynamic of the afterglow pics is also investigated.
Recent experimental results, short- and long-term research plans as well as technological choices (metal 3D printing) will be presented to transform this high current density into a high intensity ion beam that can be used for the accelerators of the future.
Extraction by third order resonance in low-energy stage will suffer from strong space charge effect, high beam emittance, high power ripple and so on. Low-energy slow extraction at 10 MeV has been explored theoretically and experimentally at synchrotron of Xi'an Proton Application Facility (XiPAF), which is a compact synchrotron with injection energy of 7 MeV and extraction energy up to 230 MeV. In this paper, simulation and experiment results of slow extraction of 10 MeV intense beam are presented. By using high-order harmonic excitation, the RF-KO slow extraction scheme below resonance is the best choice for slow extraction in low-energy stage with strong space charge effect. Slow extraction experiment is carried out when the maximum incoherent tune shift of space charge reaches -0.06, during which, quasi-uniform extracted beam and extraction rate around 65% are achieved.
J-PARC Main Ring (MR) delivers slow extracted 30 GeV proton beam to the Hadron Experimenal Facility using third-order resonance.
Various particle and nuclear physics experiments are being conducted there, and one of the important properties required for the proton beam is the flatness of the time structure of the extracted beam (spill structure).
At J-PARC MR, the large current ripples in the main magnet power supplies caused the fluctuation of the betatron tune, resulting in a large spill structure.
But the main magnet power supples were upgraded from 2021 to 2022, and the adjustments of the power supply controls are currently underway. Improvement of the current ripples of the power supplies is expected and the first beam test for the slow extraction with new power supplies is planned in early 2023.
Thus we performed a simple beam simulation of the MR slow beam extraction to investigate the effect of the current ripples of the main magnet power supplies on the beam spill structure.
In addition, we investigated in the simulation the effects of the feedback control system using fast Q magnets and the transverse RF system aiming to improve the spill structure by kicking the beam in the horizontal direction by adding white noise to the stripline kickers. We tried to optimize thier parameters with the improved current ripples of the new main magnet power supplies. This study reports those results.
The matter-antimatter asymmetry may be explained through CP-violation by observing a permanent electric dipole moment (EDM) of subatomic particles. An advanced approach to measure the EDM of charged particles is to apply a unique method of "Frozen spin" on a polarized beam in a storage ring. To increase the experimental precision step by step and to study systematic effects, the EDM experiment will be performed within three stages: the magnetic ring COSY*, a prototype EDM ring, and finally all electric EDM ring. The intermediate ring will be a mock-up of the final ring, which will be used to study a variety of systematic effects and to implement the basic principle of the final ring. The simulations of beam dynamics of the prototype EDM ring with different lattices are carried out to optimize the beam lifetime and minimize the systematic effects. The preliminary design of the prototype EDM ring helped to estimate the beam losses by using analytical formulas. Beam-target effects with more detailed simulations are being studied for beam losses and the application of stochastic cooling to control beam emittance growth is also being studied by using a simulation program. Further investigations to reduce systematic effects are also in progress.
After more than 40 years of operation in different machines, the Antiproton Decelerator (AD) electron cooler (e-cooler) is expected to be replaced by a new one designed at CERN. This new design is primarily driven by the necessity to ensure the reliable operation of the CERN antimatter facility for the next decade and beyond. This will also be the occasion to overcome the known limitations of the present e-cooler, as well as to integrate the most promising recent technologies. In this paper, we review the present AD e-cooling performance and discuss the main effects that have an impact on that performance. We then outline the chosen parameters and the design choices based on studies and experience. Finally, a preliminary analysis of the expected performance of AD with the new e-cooler is presented.
The 70MeV cyclotron at Laboratori Nazionali di Legnaro was installed and commissioned in 2017 and the accelerator was operational until March 2021. The shut down was foreseen in order to permit the completion of the SPES facility, while the resume of activities is expected on 2023. The status of the cyclotron and related high intensity beamlines will be presented as well as the last performance achieved in terms of accelerated current up to 1 MeV. Moreover the program of upgrade of the ancillary systems shall be discussed.
The synchrotron SIS100 at FAIR, currently under construction in Darmstadt, Germany, will deliver slow extracted proton and ion beams up to 100 Tm employing resonant extraction. Its compact super-ferric dipole and quadrupole magnets allow fast ramping of magnetic field up to 4 T/s and 57 (T/m)/s, respectively. Recently, field errors has been measured for the dipole magnets and the first batch of quadrupole magnets. Higher order multipoles may interfere with resonant extraction, changing the geometry of the separatrix and conditions for resonant particles. The latter are affected most during their last turns and in the extraction channel owing to their large amplitudes, which amplify the effect of higher order multipoles. SIS100 comprises a set of corrector magnets up to octupole order, which can be used to compensate the impact of magnetic field errors. In this contribution, we report on the status of the slow extraction simulation studies including field errors. Furthermore, we present alternative working points for slow extraction, which are necessary to avoid the transition energy for some of beams required by the FAIR experiments.
A beam cooler device has been constructed by the Laboratories de physique corpusculaire (LPC) of Caen (France) in collaboration with Laboratori Nazionali di Legnaro (INFN) for the SPES project. The design phase started in 2018 and the construction was carried out in 2021. In 2022 the functionality test have been done at LPC and the beam commissioning started. The Beam Cooler is capable to improve the quality of ion beams at low energy in terms of reduction of the transversal emittance and decreasing the energy spread. The description of the device will be done and the result of beam test done at LPC will be reported.
A prototype electron lens for space charge compensation in the synchrotron SIS18 that could pave the way for pushing the space charge limit of hadron synchrotrons is currently under development at GSI. Accompanied by beam transport simulations, a 3D construction model is being worked out as well as the integration into the existing accelerator facility. The electron gun and collector conceptual design studies are completed and their technical design is ongoing.
In a continuing collaboration with GSI, an electron lens test stand was designed and constructed at Goethe-University Frankfurt in order to commission major parts of the electron lens e.g. electron gun, collector and diagnostics. The demonstration of beam extraction from a tungsten cathode heated by an arc discharge, technically realized in the IRME-gun that was developed within the ARIES collaboration*, is under preparation and first results of this new heating concept look very promising.
In this contribution, the conceptual layout of the electron lens and its major components will be outlined as well as its preliminary technical layout. Furthermore, first measurements of the electron beam extracted from the IRME-Gun will be presented.
The H– linac pre-injector used at the ISIS spallation neutron and muon source is being upgraded to include a medium energy beam transport (MEBT) line after the radio frequency quadrupole (RFQ). The improved beam transport allows the use of a more modern and reliable RF-driven H– ion source. To test the new ion source and MEBT for long-term end-to-end reliability, an entire pre-injector test stand (PITS) is being assembled offline. All beamline components are installed on the PITS and electrical services are nearing completion. The latest performance of the ion source will be presented, including beam current measurements and emittance scans.
The laser manipulations of H- ion beam by single or double neutralization is a very promising technique and highly essential to utilized in accelerator processes such as stripping, pulse chopping, collimation, extraction, and beam diagnostics for the present and future high-intensity proton accelerators. At J-PARC, we are preparing for a POP (Proof-of-Principle) demonstration 400 MeV H- stripping by using only lasers. A prototype YAG laser system and a laser cavity system to reduce the laser power are being developed through 3 MeV H- neutralization studies. Fermilab utilizes H- neutralization at 0.75 MeV by establishing a laser Notcher system for a gap in the H- pulse needed for a clean beam extraction from the ring. To minimize the laser power and maximize the interaction efficiency are common issue at both laboratories. Under the US-Japan collaboration for high-intensity neutrino beam, we are closely working to establish recycling/reusing of seed laser pulses to reduce a size of the laser system. In parallel, we have also developed non-destructive beam diagnostic systems at lower H- energy of 3 MeV, which will be implemented to the 400 MeV as well as easily applicable to the Fermilab linac including PIP-II linac. Installation of the laser system at J-PARC linac for 400 MeV H- stripping is ongoing to start the POP experimental study in 2023.
The heavy ion synchrotron SIS100 is the flagship accelerator of the Facility for Antiproton and Ion Research (FAIR) currently under construction at GSI, Darmstadt. It will provide high intensity beams of particles ranging from protons to uranium ions at beam rigidities up to 100 Tm. Part of the machine protection system is an emergency beam dump that is partly inside the vacuum system and partly outside. The wide range of particles means that all components of the dump system are potentially exposed to high energy deposition densities at short time scales. The resulting shock waves are challenging for the mechanical stability of the components, including the vacuum window between inner and outer part of the dump. In this paper we present the status of thermomechanical simulations regarding the response of dump components to the most challenging beam impact scenarios. A first adaption to the vacuum window is assessed regarding it’s potential to mitigate risks of failure.
For the China Spallation Neutron Source (CSNS), during the injection process, there are some stripped electrons. Because of their low energy, small number of particles, and wide distribution, we had not used an electron catcher to collect the stripped electrons for CSNS-I. However, for CSNS-II, the number of stripped electrons becomes large and the energy increases. Then, an electron catcher will be needed to collect the stripped electrons. In this paper, we will conduct an in-depth study of the stripped electrons and propose a stripped electron collection scheme.
The SPIRAL2 installation at GANIL, Caen France is al-ready in operation since 2019 and produce a large num-ber of new radioactive ion beams at high intensities. In 2027, the DESIR facility will receive beams from the upgraded SPIRAL1 facility of GANIL (stable beam and target fragmentation) and from the S3 Low Energy Branch (fusion-evaporation and deep-inelastic reactions). The construction of the DESIR building will start in 2023. Many parts of the process is already build and stored on site at GANIL. The DESIR facility require some long transfer beam lines and distribution lines up to ex-perimental set-ups. These lines must be very robust and will transport mono-charged radioactive ion beams up to 60keV. All along the design of the beam lines since 2012, various electrostatic systems have been design and care-fully reviewed like quadrupoles, steerers and deflectors. This paper will focus on the design of different deflector developped for the DESIR project.
The search for the Electric Dipole Moments (EDM) of charged particles in storage rings necessitates polarized beams with long Spin Coherence Time (SCT) of the circulating beam. The SCT is the time during which the RMS spread of the orientation of spins of all particles in the bunch reaches one radian. A long SCT is needed to observe the coherent effect of a polarization build-up induced by the EDM. For deuterons a SCT of 1000 s has been achieved at the COoler SYnchrotron COSY (Jülich, Germany). Accomplishing such long SCT for protons is far more challenging due to their higher anomalous magnetic moment, but essential for the planned EDM experiments. It has been shown that for protons, the SCT is strongly influenced by nearby intrinsic and integer spin resonances. The strengths of the latter have been calculated for a typical optics setting of COSY and the overall influence on the SCT was predicted. In addition, the efficiency of proton spin flipping with an RF-solenoid from initially vertical direction into the ring plane is also investigated.
CSNSII is an upgrade project of China Spallation Neutron Source (CSNS), which needs to increase the beam power from 100kW to 500kW. In order to find a suitable working point area in advance and evaluate the influence of space charge effect on CSNSII, the measurements of beam loss with different tunes on CSNS was carried out and beam loss simulation in transverse tune space on CSNSII has been performed using PyORBIT code. We gave the relationship between the beam survival rate and the working point, compared four groups of candidate working points and confirmed the influence of the fourth-order resonance on the beam through the single particle model.
Extraction of beam from the Fermilab Delivery Ring for the Mu2e Experiment is hindered by large radiative losses initiated within the electrostatic septum (ESS) components of the resonant extraction system (RES). Of particular concern are beam losses causing potential damages to the support components of the RES, diminished intensity for experimental statistics, and high radiation levels in the area of the RES. Here we present the detailed study of beam energy deposition and radiation levels of components and surrounding regions of the ESS in the RES at Fermilab using the MARS Monte Carlo code system.
Slowly extracted beams from a synchrotron have temporal fluctuations, the so-called spill micro structure. The reason is related to power supply ripples that act on the quadrupole magnets, leading to unintended tune fluctuations during extraction. Related simulations regarding the dependency of spill quality on the power supply ripples are executed with varying excitation levels of the sinusoidal ripples and bandwidth-limited white noise. In addition, transit time spread is simulated, a few simulation approaches are proposed, and related data analysis procedures and preliminary results are described.
The Los Alamos Neutron Science Center (LANSCE) is a highly versatile H-/H+ 800-MeV linear accelerator that serves five distinct user facilities. Currently, H+ is accelerated through the drift tube linac down a stub line for the Isotope Production Facility at 100 MeV. The other four user facilities at LANSCE use the H- beam accelerated to 800 MeV. The H+ beam had historically been accelerated to 800 MeV for Area A operations but has not done so for over two decades. There are potential benefits to accelerating the H+ beam to 800 MeV to serve the Proton Radiography and Ultra-cold Neutron facilities in terms of potentially higher peak currents, improved emittance, higher ion source reliability, etc. A study was commissioned this year to conduct a cost/schedule/benefit analysis of converting from H- operations to H+ operations for these two facilities. The status of that study will be discussed.
A key aspect of the LHC Injectors Upgrade project is the connection of the PSB to the newly built Linac4 and the related installation of a new 160\,MeV charge-exchange injection system. The new injection system was commissioned in winter 2020/21 and is now used operationally to tailor the transverse characteristics for the various beam types at CERN, such as high-intensity fixed target beams, LHC single bunch beams, and high-brightness beams for LHC.
This contribution outlines the different injection strategies for producing the various beam types and discusses the application of numerical optimization algorithms to adjust injection settings in operation efficiently.
A new tool is under development aimed at complementing the hadronic physics of GEANT4.
The tool interfaces most of the standalone nuclear interaction models and the pre-equilibrium and evaporation models to Geant4.
The tool can generate primary hadronic interactions between particles, ions, and matter.
The tool has been designed to optimize the design of targets for the next generation of high-intensity facilities.
In this talk, the physics of the interaction of proton beams on different target materials will be presented, and the results from different nuclear interaction models will be compared.
We present the latest developments of the test facility for LANSCE Front-End Upgrade. The upgrade will significantly improve the operations and reliability of LANSCE, with upgrade options for future capability. This effort includes a highly diagnosed ion injector, low-energy beam characterizations, and RFQ analysis. Comparisons between beamline measurements and simulations are presented.
The C70XP is a cyclotron operated for production of radionuclides in nuclear medicine, for research in physics, radio-chemistry and biology. It aims at providing high intensity beams to the various experiment for long or very short time runs. The beam transverse distribution, e,g. homogeneity and emittance, has a great impact on the experiments. The ion source and subsequently the injection line, which can hold 4 types of particles (HH+, D-,He2+ and H-), being the first stage of the accelerator defining the beam, are therefore of particular focus for the beam studies.
Thus, a first study of the transverse beam distribution in the injection line has been measured with an Allison-type emittance-meter. Additionally, various simple shape collimators have been used and their impact has been measured in the extraction beam line. These studies have also been combined with multiple magnets tuning simulating various operating mode.
A model of the injection line based on G4Beamline has been performed. The experimental and simulation results are given in this paper as well as the on-going studies for a potential future collimator.
Accelerator facilities are among the most complex projects, integrating advanced engineering systems and components. At the ESS, the need to visualise the intricate integration activities has led to the development of Aggregation Diagrams (ADs). The diagrams follow the facility breakdown structure with sections and system diagrams showing their integration of the devices with enabling and interfacing systems such as the vacuum, cooling, power suppliers and control systems. Commissioning diagrams have also been developed and are used to visualise the main steps and events in the commissioning of the accelerator. The main advantage of using ADs is to help in the activities planning, provide easy access to high-level plans and develop a standard tool that could be used among the different work packages. In this paper, we present the workflow on the development of ADs giving some examples of their use in the activities planning at the ESS.
As part of the goal of increasing the beam power of the Main Ring for Fast eXtraction (FX) in J-PARC to 750 kW, the two low-field septa and three high-field septa for FX were installed into MR in 2022. The most significant goals regarding the magnets are achieving an extremely low leakage field in the circulating line. To reduce the leakage field in
the circulating line, the new pure iron duct-type magnetic shields were produced for all the septa in 2021, and mounted in the circulating line in 2022. We verified that the leakage field in the circulating line of a low-field septum and high-field septa were greatly reduced. We also confirmed that the impact of the leakage field of all of the septa for FX on the 3-GeV circulating beam was below 1/10 of that of the previous septa for FX in beam test in July 2022. We also measured the leakage field in the circulating line of the new high field septum magnets. We verified that the field integral was about 1/10 lower than previous septa. The quadrupole component was about 1/100 lower than previous septa. Consequently, the leakage field of high field septa could be reduced extremely.
A new proton beam-delivery line for the TOP-IMPLART linac is under assembly and testing at the ENEA Frascati Research Center. TOP-IMPLART is an RF pulsed linear accelerator developed for medical applications, consisting of a 425 MHz, 7 MeV injector, followed by eight accelerating SCDTL modules operating at 3 GHz, driven by two 10 MW peak power klystrons. Proton beam can be accelerated at 63 MeV or 71 MeV (other energy values can be achieved by suitable degraders) in 3µs pulses with a typical repetition rate of 25 Hz. Following the experience gathered in multi-year irradiation campaigns based on the use of a passive spreading in air of the beam, the new line employs a magnetic scanning system and has been designed to accommodate the requirements of different targets, for multipurpose applications ranging from radiobiology experiments, test of innovative dosimeters, up to qualification of components in the field of aerospace. The paper describes the setup, the monitors of the parameters of interest (dose, fluence, flux) integrated in the line, the control system and the first characterization measurements of the main elements.
SNRC and CEA collaborate to the upgrade of the SARAF accelerator to 5 mA CW 40 MeV deuteron and proton beams (Phase 2). CEA is in charge of the design, construction and commissioning of the linac downstream the existing RFQ (SARAF-LINAC Project).
The MEBT is now installed at SNRC and has been commissionined with beam. Transverse and longitudinal emittances have been measured and beam transport has been compared with TraceWin simulations.
The low-beta HWR and superconducting solenoids have all achieved their design performances on Saclay test-stand.
First cryomodule has been assembled and tested at Saclay and is being installed at SNRC.
This paper presents the results of the MEBT commissioning, the qualification of the HWR and the solenoids and the test results of the first cryomodule.
A 1 MeV/n Radio-Frequency Quadrupole (RFQ) has been developed and commissioned at Korea Multipurpose Accelerator Complex (KOMAC). The RFQ is designed to accelerate ions with mass to charge ratio up to 2.5. The designed peak current is 10 mA with 10 % duty factor. Currently we are utilizing the RFQ as a test bench for the reliable operation of the 100 MeV proton linac operational at KOMAC since 2013. The test bench has two beamlines installed with beam transport optics, diagnostics and irradiation chambers. We performed a quad scan experiment using a wire scanner installed in the beamline to obtain beam emittance and Twiss parameters at the entrance of the scanning quadrupole magnet. From these value, we calculated the beam emittance and Twiss parameters at the exit of the RFQ. In this paper, we report the current status of the RFQ test bench, the quad scan result and the characterization results of the 1 MeV/n RFQ output beam at KOMAC.
The design betatron tune of the rapid cycling syn-chrotron (RCS) of China Spallation Neutron Source (CSNS) is (4.86, 4.78), which enables incoherent tune shifts to avoid serious systematic betatron resonances. Serious beam instability was observed when the opera-tional bare tune was set to (4.86, 4.78). The tunes dur-ing the beam acceleration were optimized based on the space charge tune shift and beam instability. Waveform compensation on CSNS RCS quadrupole magnets was performed to accurately control and optimize the tune variation during the beam acceleration process. After the tune optimization, the beam loss induced by space charge and beam instability was well controlled. The beam power of CSNS achieved the design value 100 kW with small uncontrolled beam loss.
LNL heavy ion accelerator complex is based on three main accelerators: Tandem, ALPI and PIAVE. The Tandem XTU is a Van de Graaff accelerator normally operated at terminal voltages of up to about 14 MV. It can be operated in stand–alone mode or as an injector for the linac booster ALPI. The linear accelerator ALPI is built of superconducting resonant cavities and consists of a low–beta branch, particularly important for the acceleration of the heavier mass ions, a medium–beta branch, and a high–beta branch. ALPI can be operated also with the PIAVE injector that consists of a superconducting RFQ and an ECR source. In the last two years, accelerator complex underwent special maintenance to improve its availability and reliability in view of the operation with both Uranium and radioactive beams. In this framework, the main improvements that will be presented will concern Tandem injector and laddertron system, PIAVE ECR source, cryogenic control system and SRFQ tuning system, ALPI low and medium beta design, vacuum control system and new techniques for beam dynamic simulation and commissioning.
A 350 MHz, 3 MeV radio frequency quadrupole (RFQ) has been operating since 2005 at Korea Multi-purpose Accelerator Complex (KOMAC) as a low energy part of the 100 MeV proton linac. Recently, it was considered to upgrade the existing RFQ because of its low beam transmission rate and vane erosion. Several options were compared to upgrade the RFQ considering a number of sections, coupling plate and shaper energy. In this paper, the status of the existing RFQ was summarized and an upgrade plan is discussed.
Tetrode vacuum tubes are used under the positive grid region
to accelerate a high intensity beam in the RCS.
A tube amplifier is operated in push-pull mode and two tubes are installed in the amplifier. Although each control grid should be driven in counterphase for the push-pull operation, the waveform becomes asymmetric by the positive grid biasing. The vacuum tube operation analysis should include such an effect caused by the positive grid biasing. The analysis becomes complicated because the anode current and
the control grid voltage waveforms interact each other under the heavy
beam loading. The effects caused by the positive grid voltage are analyzed with the self-consistency. We will describe the analysis result under the positive grid biasing.
Experiments at CRYRING using beams accelerated and decelerated in the accelerator chain SIS18 - ESR - CRYRING at GSI are considered as the first real FAIR experiments. For these experiments, CRYRING receives fast extracted beams from the ESR, which are cooled and decelerated down to about 10 MeV/u in the ESR. The beam transport from ESR to CRYRING is difficult, since part of the beamline has been reused and was not designed for such low-energy beams. Furthermore, developments inside the ESR are on-going and - especially after switching to the new control system - one could not expect that beam parameters and optics functions at the extraction point are necessarily the same as in the past. Therefore, a measurement campaign has been carried out to verify the optics model for the ESR-CRYRING beamline. The initial values for the optics functions at the ESR extraction point and the transverse emittance have been also measured. The results are discussed in this paper.
Electron beam irradiation is a method that has shown a good potential to reduce several pollutants in wastewater. One of the main challenges towards wider adoption of this method is the need for compact, reliable, cost-effective, high-power accelerators. Jefferson Lab is working on the design and prototyping of accelerator components, based on superconducting radio-frequency (SRF) technology, aiming at accelerators for industrial applications. The project aimed at designing, procuring, installing, and commissioning a beamline at the Upgraded Injector Test Facility (UITF) accelerator to allow electron-beam irradiation studies of different materials, beginning with wastewater. After successful commissioning, the beamline was used to irradiate wastewater samples with different concentrations of 1,4-dioxane.
Multi-bend achromat (MBA) lattices have initiated a fourth generation for storage-ring light sources with orders of magnitude increase in brightness and transverse coherence. A few MBA rings have been built, and many others are in design or construction worldwide, including upgrades of APS and ALS in the US. The Hybrid MBA (HMBA), developed for the successful ESRF–EBS MBA upgrade has proven to be very effective in addressing the nonlinear dynamics challenges associated with pushing the emittance toward the diffraction limit.
The I.FAST CBI is an immersive challenge-based innovation program funded by the H2020 I.FAST project. The 10-day face-to-face challenge brings together students of different disciplines from all over Europe to work together on innovative projects using accelerator technology applied to environmental challenges. We report on the first edition of the I.FAST CBI, the proposed projects and feedback from the students.
In this contribution we report on the commissioning of the ELIMAIA beamline laser-plasma Ion Accelerator carried out with the high repetition-rate, high peak-power L3-HAPLS (>10J in 30 fs) laser available at the ELI Beamlines user facility. The optimization process to achieve a stable energy cutoff exceeding 30MeV with high proton fluxes will be described providing an overview of the available technology for user experiments. These results demonstrate the robustness of the developed technology available for users at the ELIMAIA beamline, thus paving the way towards the future use of the ELIMED beamline for the application of controlled and stable high dose rate ion beams in a wide range of research, in particular biomedical ones. We will present some beam optics and Monte Carlo simulation results obtained using the experimental evidence of the accelerated ion beam characterization and showing the capability of the ELIMED beamline.
To ensure physical start up of NSC KIPT SCA Neutron Source, 100 MeV/ 100 kW electron linear accelerator should provide stable operation mode with 100 MeV electron beam energy, 20 Hz repetition rate, 35-40 mA pulse beam current, ± 3 beam energy spread and about ± 3 mm beam sizes. During preparations to the facility start up the required beam parameters were adjusted and secured during the SCA facility start up. The accelerator showed stable operation performance.
The procedure of the accelerator stable operation mode tuning, adjustment secure during the whole period of the facility physical start up are described in the paper.
ALBA is working on the upgrade project that shall transform the actual storage ring, in operation since 2012, into a 4th generation light source, in which the soft X-rays part of the spectrum shall be diffraction limited. The project was launched in 2021 with an R&D budget to build prototypes of the more critical components. The storage ring upgrade is based on a 6BA lattice which has to comply with several constraints imposed by the decision of maintaining the same circumference (269m), the same number of cells (16), the same beam energy (3GeV), and as many of the source points as possible unperturbed. At present, the lattice optimization, iterating with the technical constrains of space and performance, is ongoing. This paper presents the status of the project, with the present proposed lattice, first magnet’s designs, the vacuum chamber initial considerations, the girder concept, the proposed RF system with fundamental and harmonics cavities, and the general context of the upgrade.
SIRIUS is a green-field 4th generation Synchrotron Light Source Facility based on a 3 GeV electron storage ring with 518 m circumference and 250 pm.rad emittance. It was de- signed, built, and is operated by the Brazilian Synchrotron Light Laboratory (LNLS/CNPEM). After completion of Phase-0 commissioning of the accelerators and first beam- lines, SIRIUS is now open for external users, with 6 fully operational beamlines, 4 close to start scientific commis- sioning, and 4 in different stages of installation. We report on the status of SIRIUS operation with users in the recently implemented top-up mode, with important upgrades in the orbit feedback systems and in the reduction of transient perturbations to the stored beam during injection process.
In recent years, even accelerators, which are fundamental tools for advanced researches, should be green regarding energy/resource consumption and operation efficiency. How to improve the performance of accelerators in such an environment will be a major challenge for the field of accelerator science and technology. Against this backdrop, we have developed a long-term plan to promote the green-oriented upgrade of accelerator complex at the SPring-8 campus. We have started to integrate and rationalize the two independent accelerator systems, SPring-8 and SACLA, achieving a 20 % energy saving in a synchrotron radiation facility. We will then, as a next step, renovate the current SPring-8 storage ring by incorporating cutting-edge technologies not only to improve its performance but also to significantly reduce energy consumption by half. Upgrade of current SACLA will follow the SPring-8 upgrade. This presentation will describe our strategic accelerator upgrade plan, its progress and achievements, and future developments.
Measurements of the small beam sizes in current and future low-emittance light sources represent a serious challenge to the accelerator community due to the diffraction effects, and X-ray inteferometric techniques offer an interesting method to overcome this challenge. Here we report on 2D beam size measurements with a novel interferometric technique named Heterodyne Near Field Speckles (HNFS). It relies on the interference between the weak spherical waves scattered by nanospheres suspended in water and the intense transilluminating X-ray beam. Fourier analysis of the resulting speckles enables full 2D coherence mapping of the incoming radiation, from which the beam sizes along the two orthogonal directions are retrieved. We show experimental results obtained with 12.4 keV X-rays at the NCD-SWEET undulator beamline at ALBA, where the vertical beam size has been changed between 5 and 15 micrometers by varying the beam coupling. The results agree well with the estimated beam sizes from the pinhole calculations, proving that the HNFS method can resolve few-micrometer beam sizes.
IFMIF-DONES (International Fusion Materials Irradiation Facility, DEMO-Oriented Neutron Early Source) – a powerful neutron irradiation facility for irradiation of materials to be used in fusion reactors – is planned as part of the European roadmap to fusion electricity. Its main goal will be to characterize and qualify materials under a neutron field similar to the one faced in a fusion reactor, developing a material database for the future fusion nuclear reactors.
The facility is based on an intense neutron source produced by a high current deuteron beam impinging on a liquid lithium curtain, aiming to generate by stripping reactions neutrons with an energy spectrum and flux similar to those expected to be seen by the first wall of a fusion reactor.
The IFMIF-DONES facility has accomplished the preliminary design phase and currently in its detailed design phase. The next phase will be the preparation for the construction of the facility. This contribution presents the status of IFMIF-DONES design developed in the framework of the EUROfusion work programme, integrating the lesson learnt from the IFMIF/EVEDA Project (International Fusion Materials Irradiation Facility/ Engineering Validation and Engineering Design Activities - Broader Approach (BA) Agreement signed between EURATOM and Japanese Government), through a common program which includes the different commonalties and interfaces of the two projects.
An overview of the present design status of the facility will be provided putting emphasis on the design status of the high current superconducting LINAC, responsible for delivering the 5 MW D+ beam at 40 MeV with very high inherent availability, focusing on the main challenges and the related R&D programme. The prospects for the construction and the commissioning of the facility in Granada (Spain) will be also reviewed.
FLASH (Free Electron Laser in Hamburg) is the first FEL in the world to deliver ultrashort radiation pulses in extreme ultraviolet and soft X-ray ranges, currently being upgraded at DESY within the FLASH2020+ plan. The upgrade covers implementing new tunable undulators, improving the beam energy to 1.35 GeV, and a complete redesign of the FLASH RF Reference Generation System. That system generates and distributes ultralow phase noise reference signals at several frequencies, all synchronized to the main 1.3 GHz signal. Lower frequency signals are created using a new version of a frequency divider module, originally developed for European-XFEL. The upgraded module is equipped with an input signal detection circuit that disables RF outputs when no input signal is provided. The new divider is significantly smaller and designed to be as universal as possible, therefore it is possible to use it in other systems and applications. This contribution presents the new frequency divider module, its performance, and its target application in the new FLASH RF Reference Generation System.
The complete knowledge of electron bunch properties is of great interest to understand and optimize the performance of accelerators and their applications. A new tomographic beam diagnostics method to reconstruct the full 5-dimensional phase space (x, x', y, y', t) of bunches has recently been proposed. This method combines a quadrupole-based transverse phase-space tomography with the variable streaking angle of a polarizable X-band transverse deflection structure (PolariX TDS).
In this contribution, we show preliminary data of the first experimental demonstration of the method including the reconstruction of the full 5-dimensional phase space distribution of an electron bunch at FLASHForward.
Commercial electron microscopes with a few hundred keV energies are fundamental tools for understanding the micro- to nano-scale world. One of the frontiers in electron microscopy development is to push the beam energy to MeV range to achieve improved lateral resolution for thick samples. Here we show the theoretical and preliminary experimental analysis of the electron beam quality required in the imaging and diffraction processes with different beam energy. By correlating the diffraction and imaging modalities, we use the focused beam scheme to characterize the beam emittance of a 200 keV TEM and a MeV UED. The quantitative correlation between the measured emittance and the obtained image resolution are established. This work demonstrates a characterization technique for electron microscopy and provides a guidance for designing a MeV electron diffraction and imaging beamline.
The European Spallation Source is a spallation neutron source driven by a superconducting proton linac and currently under construction in Lund, Sweden. The proton linac of a 5 MW design power, with a 62.5 mA peak current, 2.86 ms pulse length, and 14 Hz repetition rate, is undergoing staged beam commissioning towards the initial user operation planned in 2026 at a reduced power of 2 MW. In 2022, beam was accelerated up to 21 MeV with the first tank of a drift-tube linac (DTL), consisting of five tanks. Following the commissioning step this year (2023) up to the fourth DTL tank and 74 MeV, low power beam commissioning through superconducting structures is planned for the next year (2024), up to 570 MeV and against a beam dump. The last beam commissioning step prior to the initial user operation, when the beam is sent to the spallation target, is planned for 2026. This paper provides a summary of the past beam commissioning activities and presents the current strategy for the upcoming beam commissioning steps, including machine configuration at each step.
To develop the next generation of safe and cleaner nuclear energy, the accelerator-driven subcritical(ADS) system emerges as one of the most attractive technologies. The Chinese ADS proofing project(CAFe) was launched in 2011 under the management of the Chinese Academy of Sciences to demonstrate the key technologies including superconducting proton linac, heavy metal target and subcritical nuclear reactor. A 25 MeV superconducting proton linac is developed by the cooperation between Institute of Modern Physics and Institute of High Energy Physics. Recently a 10mA, 100kW CW proton beam has been accelerated successfully, which reaches a new world record in the CW proton linac field. In this paper, the beam commissioning activities and issues are reported.
The MYRRHA design for an accelerator driven system (ADS) is based on a 4mA, 600 MeV CW superconducting proton linac. The first stage towards its realization is called MINERVA and was approved in 2018 to be constructed by SCK CEN in Belgium. This consist of a 4mA 100MeV superconducting linac as well as two independent target stations, one for radio-isotope research and production of radio-isotopes for medical purposes, the other one for fusion materials research.
This contribution presents the main design choices and current status of the overall project parts (civil engineering, particle accelerator and target facilities).
Firstly introduced in 2010 at the MIT Francis Bitter Magnet Laboratory, the so-called “no-Insulation (NI)” winding technique has been regarded as a “game changer” in high temperature superconductor (HTS) magnet technology, as it enables an NI HTS magnet to be highly compact and affordable, yet reliable to a level that has never been achieved with conventional systems. Significant progress in the NI-HTS technology has transformed future dream of HTS machines into reality, i.e., meet rigorous HTS system specifications that were infeasible mainly due to old technical challenges and high cost of HTS machines. The recent achievement of the record high direct-current magnetic field of 45.5 T by use of an NI HTS insert coil is an example, which was recognized as a “top 10 breakthrough for 2019” by Physics World of the Institute of Physics. Some industrial partners initiated innovative research programs, with over 2 billion US dollars of investment from private sectors, to develop a compact fusion system based on the NI HTS magnet technology, which was recognized as a “top 10 breakthrough technology in 2019” by the Bill Gates foundation. We are now at the threshold of a new era in which HTS will play an increasingly indispensable role in a number of applications that include biochemistry, high energy physics, medical diagnostics, fusion, electric propulsion and more. Not to mention, the “particle accelerator” is one of the key applications, where the compact and high field HTS magnet technology is expected to play a key role. This paper resents an overview of the recent progress in the NI HTS magnet technology with focus on the next-generation particle accelerators.
In the past five years, seven short models of the inner triplet quadrupole for the High Luminosity LHC, based on Nb3Sn conductor, have been built and tested, reaching conductor peak fields above 13 T. In this talk we will review the main features of this program, outlining the scope of the program, the different variants manufactured, and the test results. Special emphasis will be given to test to assess the performance versus the preload strategy. The potential of this technology, together with the challenges and the possible outlook for other accelerator magnets based on the same technology will be presented.
The Electron Ion Collider is preparing now the design for the project baseline, to provide the high luminosity, polarization and flexibility for the EIC. This talk outlines the accelerator physics challenges including complex interaction region, flat hadron beams, beam cooling, high beam currents leading possibly to electron clouds and instabilities, and high beam polarization.
A lepton-collider Higgs factory, to precisely measure the couplings of the Higgs boson to other particles, followed by a higher energy run to measure the Higgs self-coupling, is widely recognized as a primary focus of modern particle physics. In the talk a description of the new technology based on cool copper that can lead to compact and affordable machine will be described as well as the issues and challenges of this type of technology.
In laser-plasma accelerators (LPA), due to extremely high accelerating gradients, electron bunches are accelerated to high energies in only a few millimeters to centimeters of acceleration length. To efficiently capture and transport the LPA-generated bunches in a compact transport line, beam line designs employing high-strength combined-function magnets based on high-temperature superconductor technology have been studied. Moreover, to overcome coil winding challenges in fabricating miniature HTS magnets, novel periodic magnets have been designed, which can collimate and guide the electron beams in a well-controlled short-length transport line. In this contribution, we present the beam dynamics calculations as well as the magnet designs for a 1.4 m transport line matching the LPA-generated electron beams to a transverse-gradient undulator.
Novel iron lamination with additional interlaminar insulation has been successfully developed for magnet cores of fast kicker magnets in particle accelerators. By minimizing the eddy current induced between core laminas, a pulse profile of the excited magnetic field has been significantly improved up to a few MHz range. The magnet core is formed by alternately stacking thin steel and insulation sheets to avoid electrical contact between the steel sheets on the cutting edge. A pair of test magnets with the new iron lamination was assembled to evaluate magnet performances focusing on applications to matched kickers in the accelerators. The magnetic field pulse profiles of the two magnets have successfully proved to match below 0.1% over the entire pulse duration, which is significantly better than those with conventional iron lamination. The developed fast kicker magnets are promising for the beam injection kickers in the coming next-generation light sources and future colliders, where suppression of the transient stored-beam oscillation during beam injection is crucial.
Coupled-bunch instability arising from impedances of higher-order modes (HOMs) in RF cavities is a problem to be suppressed in high-current, low-emittance electron storage rings. As a countermeasure against the problem, we have developed a compactly HOM-damped cavity resonating in the TM020-mode at a frequency of 509 MHz. The damping structure compromises circumferential and shallow slots in the cavity inner-wall and ferrites inside the slots. Since the slots are along the magnetic nodes of the TM020 mode, the ferrites absorb only RF powers of the HOMs. The cavity has a shunt impedance of 6.8 MΩ and generates an accelerating voltage of 825 kV at a 100 kW input. The cavity has a slot-type input coupler with a variable-length stub to match its coupling degree with change in beam loading during the operation. The prototype cavity demonstrated satisfactory performance in high-power operation up to 120 kW. Therefore, this innovative cavity is about to be utilized for beam acceleration in the new 3 GeV synchrotron radiation facility, NanoTerasu. We report on the performance of four fabricated cavities, problems and countermeasures experienced in their high-power tests.
Based on current efforts in the U.S. on the novel concept of parallel-feed RF accelerator structures, and in the U.S. and abroad in producing Nb3Sn films on either Cu or bronze, we rec-ommend that the Particle Physics community foster R&D in Superconducting Nb3Sn coated Cu RF Cavities instead of costly bulk Nb. The paper includes methods to process the coated cavi-ties at temperatures consistent with Cu retaining its shape. A devoted global effort in develop-ing Cu cavity structures coated with Nb3Sn would make the ILC or Higgs factories more afforda-ble and more likely to be built. Not only do parallel-feed RF structures enable both higher ac-celerating gradients and higher efficiencies, but they would be applicable to both Cu and Nb3Sn coated Cu cells. Increased effort on these two techniques would synergize expenditures to-wards progress, which will converge on the choice of technology for the RF of an ILC or any fu-ture accelerator. The current methods of Nb3Sn coatings on Cu or bronze can be geared also towards standard cavity cells. In conclusion, the use of distributed coupling structure topology within improved performance parameters together with Nb3Sn coating technology can lead to a paradigm shift for superconducting linacs, with higher gradient, higher temperature of opera-tion, and reduced overall costs for any future collider.
In a linear collider, the colliding beam has to be flat in the transverse plane to suppress energy spread by Beamstrahlung and to maximize the luminosity, simultaneously. In the current design of ILC, the flat beam is realized by the asymmetric emittance generated by the radiation-damping effect. We propose to generate the equivalent beam directly in the injector linac employing the emittance repartitioning. As an experimental demonstration, a beam experiment was carried out at KEK-STF. We present the experimental results.
The development of ERLs has been recognized as one of the five main pillars of accelerators R&D in support of the European Strategy for Particle Physics (ESPP). The international panel in charge of the ERL Roadmap definition recognized PERLE project as “a central part of the roadmap for the development of energy-recovery linacs”, with milestones to be achieved by the next ESPP in 2026.
PERLE project is aiming at the construction of a novel ERL facility for the development and application of the energy recovery technique in multi-turn configuration, high current and large energy regime. It will operate in a 3-turns mode, first at 250 MeV, then upgraded to 500 MeV with 20mA beam current. Such challenging parameters make PERLE a unique multi-turn ERL facility operating at an unexplored operational power regime (10MW), studying and validating a broad range of accelerator phenomena, paving the way for the future larger scale ERLs.
PERLE will be the necessary demonstrator for the future HEP machine (LHeC / FCC-eh), with which it shares the same technological choices and beam parameters. Furthermore, PERLE opens a new frontier for the physics of “the electromagnetic probe”. It will be the first ERL dedicated to Nuclear Physics for studying the eN interaction with radioactive nuclei.
Here we will report on the project status, introduce the main ongoing achievements and describe the staged strategy we will adopt toward the construction of PERLE machine at its nominal performances.
The fourth-generation synchrotron light sources aim to achieve ultralow emittances and have very small dynamic aperture, which are expected to adopt on-axis injection schemes. Lower frequency rf systems are required for a large separation between RF buckets due to the limitations of kicker. We designed a 166.6 MHz normal conducting cavity with HOM damped used for the main cavity of storage ring. In this paper, we present the simulation studies of cavity including electromagnetic, HOMs, mechanical, and thermal calculations. A compact beam line absorber, which is uncommon in the copper cavities, is adopted to damp the harmful HOMs. The simulation results show that it can deeply damp the HOMs, but has no effect on the accelerating performance.
The control of beam emittance growth in high-current Radio Frequency Quadrupole (RFQ) accelerator is fairly challenging because of the strong space charge effect. The transverse beam emittance growth in the RFQ is well controlled in many international high power accelerator projects, while the longitudinal beam emittance growth is really significant which affects the beam transmission in the later accelerating structure especially in the super-conducting section. In this study, the beam dynamics design studies performed with respect to a 100 mA, continuous-wave proton RFQ linac are presented. The reasons for emittance growth have been analyzed, and great attention has been paid to both transverse and longitudinal beam dynamics to control the beam emittance growth. The beam dynamics has been simulated with the codes TranceWin and TOUTATIS. And the beam losses and field errors of the RFQ have been analyzed.
Additive manufacturing is a promising approach to reduce production costs for high-frequency cavities while increasing design freedom. This potential will be evaluated through studies on several cavity prototypes and their performance. Especially for the evaluation of the field distribution in cm-sized S-band cavities and thus the shunt impedance, the development of a measurement setup for qualitative and fast measurements is useful. Therefore, we present a perturbation measurement (bead-pulling) test stand that allows a standardized and efficient measurement of the field distribution in cavities. It consists of a motorized linear translation stage, a microcontroller, and a vector network analyzer, all controlled via LabVIEW. The perturbation constant $\alpha$ ($\mathrm{Al_2O_3}$) was determined using a drift tube cavity previously characterized with a 16 MeV tandem Van de Graaff proton beam. In addition, the measurement accuracy with different step sizes and speeds of the linear translations stage was tested on this cavity. Subsequently, the first measurements on an additively manufactured 5-cell drift tube cavity were performed to determine its shunt impedance.
Due to a recent interest in scanning thinner containers such as cars or aviation unit load devices (ULDs), lower energy linac solutions are required in order to obtain sufficient image contrast. In this work, we present the complete design of a C-band, bi-periodic, 2 MeV electron linac to fulfil this need. Multi-objective optimisation techniques are employed to optimise the RF cavities for maximum shunt impedance and to optimise the cell lengths/amplitudes of the bunching cavities to achieve a 90% capture efficiency. A full thermal analysis of the system, including the X-ray target, has been performed to explore the thermal management of the system, including a CFD analysis to estimate the effectiveness of typical thermal approximations made during the design process. Finally, a novel RF system for connecting and firing multiple linacs sequentially to generate quasi-3D images is described.
Fringe fields at the entrance and exit of multipole magnets can adversely affect the dynamics of particles in the beam, but there is also the possibility that fringe fields of the right form could be used to enhance the accelerator performance. Accelerator design work could benefit from efficient and realistic models of multipole fringe fields at an early stage in the design process. We explore novel techniques based upon analytical solutions of multipole fringe fields to produce magnets that satisfy specific requirements for the beam dynamics. Machine learning techniques are used in the design process currently being developed, to link properties of the beam dynamics to the magnet geometry in an efficient way.
Due to the beam in the storage ring has a very low vertical emittance. The angular dispersion induced microbunching (ADM) scheme is used to generate high brightness coherent synchrotron radiation. To apply a similar scheme in a linear accelerator, it is necessary to reduce the vertical emittance of the beam in the linear accelerator. Generally, angular-momentum-dominated round beams can be generated by immersing the cathode into the axial solenoid magnetic field, the angular momentum is then removed by skew quadrupoles downstream of the solenoid, resulting in a flat beam with low vertical emittance. In this paper, on the basis of the existing basic structure, considering the chromatic effects in the round-to-flat beam transformation, we propose an achromatic scheme that uses chicane to generate dispersion segment, inserts skew quadrupoles in the dispersion segment for matching, and uses sextupole to correct chromatic aberration. The numerical simulation results of ASTRA and ELEGANT show that the transverse emittance ratio of the beam has been further improved.
The Dynamic Aperture (DA) is an important concept for the study of non-linear beam dynamics in a circular accelerator. The DA is defined as the extent of the phase-space region in which the particle's motion remains bounded over a finite number of turns. Such a region is shaped by the imperfections in the magnetic fields, beam-beam effects, electron lens, electron clouds, and other nonlinear effects. The study of the DA provides insight into the mechanisms driving the time evolution of beam losses, which is essential for the operation of existing circular accelerators, such as the CERN Large Hadron Collider (LHC), as well as for the design of future ones.
The standard approach for the numerical evaluation of the DA relies on the ability to accurately track initial conditions, distributed in phase space, for a realistic time scale, and this is computationally demanding.
In order to accelerate the DA calculation, we propose the use of a Machine Learning (ML) technique for the DA regression based on simulated HL-LHC data. We demonstrate the implementation of a Deep Neural Network (DNN) model by measuring the time and assessing the performance of the DA regressor, as well as carrying out studies with various hardware architectures including CPU, GPU, and TPU.
Vertical Fixed-Field Alternating Gradient (vFFA) accelerators exhibit particle orbits which move vertically during acceleration. This recently rediscovered circular accelerator type has several advantages over conventional ring accelerators, such as zero momentum compaction factor. At the same time, inherently non-planar orbits and a unique transverse coupling make controlling the beam dynamics a complex task. In general, betatron tune adjustment is crucial to avoid resonances, particularly when space charge effects are present. Due to highly nonlinear magnetic fields in the vFFA, it remains a challenging task to determine an optimal lattice design in terms of maximising the dynamic aperture.
This contribution describes a deep learning based algorithm which strongly improves on regular grid scans and random search to find an optimal lattice: a surrogate model is built iteratively from simulations with varying lattice parameters to predict the dynamic aperture. The training of the model follows an active learning paradigm, which thus considerably reduces the number of samples needed from the computationally expensive simulations.
For an integral part of electron-ion collider (EIC) de-sign, the crab crossing scheme provides a head-on collision for beams with a nonzero crossing angle. Recently we provided a framework for accurate numerical simulations of beam-beam effects with crabbing crossing dynamics. The framework was implemented in a simulation code package named “CASA BeamBeam”. We offer com-prehensive formulas for calculation of collider luminosity for various cases in the code package. The luminosity calculation module of CASA Beam-Beam now includes the hourglass effect, the beam-tilt effects and the beam offset effect. The benchmarking results show good agreement between the numerical calculation and analyt-ic solution.
Transverse wigglers and wakefield structures are promising candidates for imparting arbitrary correlation on transverse and longitudinal phase spaces respectively. They provide sinusoidal electromagnetic fields that become building blocks for Fourier synthesis. We present the progress of arbitrary correlation generation using transverse wiggler and wakefield structures.
In ultralow-emittance synchrotron light sources, harmonic RF cavities are very useful to lengthen the beam bunches by which the adverse effects due to intrabeam scattering can be mitigated. We are developing a 1.5-GHz TM020-type normal-conducting harmonic cavity which is to be used for the KEK future light source project. The harmonic cavity using the TM020 resonant mode has distinct advantages such as: 1) small RF-voltage fluctuation under the transient beam loading, and 2) sophisticated parasitic-mode damping structure which locates at the node of the accelerating field. In our design, we optimized* the inner shape of the cavity so that the coupling impedances due to parasitic modes were minimized. To minimize the losses of accelerating field in the parasitic-mode damping structure, we arranged three frequency-tuners symmetrically and devised an optimum loop of an input coupler, by which an axial symmetry of the cavity was almost maintained. Based on these concepts, we conducted a basic design of high-power cavity including thermal-structural analysis, which will be presented in this paper.
Beam Delivery Simulation (BDSIM) is a program based on Geant4 that creates 3D radiation transport models of accelerators from a simple optical description in a vastly reduced time with great flexibility. It also uses ROOT and CLHEP to create a single simulation model that can accurately track all particles species in an accelerator to predict and understand beam losses, secondary radiation, dosimetric quantities and their origins. We present a broad overview of new features added to BDSIM in version 1.7. In particular, the ability to transform and reflect field maps as well as visualise the fields in Geant4 are presented. A new “CT” object is introduced to allow DICOM images to be used for simulations of Phantoms in proximity to a beamline. For experiments such as FASER, SHADOWS and NA62, a muon production biasing scheme has been added and is presented.
At EuPRAXIA@SPARC_LAB an X-ray FEL user facility is driven by a plasma accelerator in the particle-driven configuration where an ultra-relativistic beam, the driver, through a plasma generates a wake of charge density useful for accelerate a witness beam. The electron bunches are generated through the so-called comb technique in an RF injector that consist of a 1.6 cell S-band gun followed by four S-band TW accelerating structures. The main working point foresees a 30pC witness and a 200pC driver longitudinally compressed in the first accelerating structure operated in the velocity-bunching regime, that allows to accelerate and manipulate the beam to reach proper transverse and longitudinal parameters. The optimization of the witness emittance is performed with additional magnetic field around the gun and the S-band structures and by shaping the laser pulse at the cathode. The paper reports on beam dynamics studies performed also for beams with higher charges to maximize the transformer ratio in the plasma and the beam brightness. In addition, the insertion of an X-band RF cavity after the gun is proposed aiming to shape the beam current distribution as needed and stabilize it with respect to RF jitters.
The upgrade of the European XFEL to support a future high duty cycle (HDC) operation mode requires new design concepts for the photoinjector. In particular, the electron gun is crucial for achieving high quality beams at high peak currents. Among other variants, a 1.6-cell TESLA-type RF-gun is the preferable solution for the HDC EuXFEL. The SRF gun design, however, requires the application of unconventional emittance compensation schemes. One alternative is embedded RF focusing by means of a retracted cathode. Such a scheme has been previously successfully tested, e.g., at the ELBE accelerator of the HZDR. However, the beam dynamics characterization and parameter optimization for this design remains a challenge. This is primarily due to the 3D geometry of the cathode region, which cannot be easily handled by available tracking codes. In this work, we present a simulation and optimization study of the EuXFEL injector line including the geometrical and space charge effects related to a retracted-cathode SRF gun design.
At KEK a design of the compact 10 MeV, 50 mA accelerator for irradiation purpose was proposed. Current design includes a 100 kV thermionic DC electron gun with an RF grid, 1-cell normal-conducting buncher cavity, and Nb3Sn superconducting cavities to accelerate the beam to the final energy of 10 MeV. The goal of the present beam dynamics study is the beam loss suppression (to the ppm level), since it results in a thermal load on the cavity. Then the beam performance at the accelerator exit should be confirmed. The main issue was to transport the beam without loss, since the initial electron energy (100 keV) is low, and the beam parameters are intricately correlated. In addition, the space charge effect is considerable. For this reason, simultaneous optimization of multiple parameters was necessary. Here we report optimization results and their effect on the design of the machine.
Beam-beam effects are known to undermine the performance of the LHC during proton-proton collisions. In order to enhance the luminosity production and increase the tolerance of the working point of the machine after the High Luminosity upgrade of the LHC, it is relevant to study the possibility of using current-carrying wires to compensate long-range beam-beam effects. Following proof of principle studies in LHC Run 2, beam-beam wire compensators embedded in the collimators of the LHC are used in standard operation since the start of Run 3. In this paper, a figure of merit quantifying the efficiency of luminosity production is introduced and measurements from LHC Run 3 are presented. Bunch-by-bunch data is used to demonstrate the successful compensation of beam-beam effects in the LHC.
Beam-ion instabilities belong to a broader class of two-beam instabilities caused by the interaction of a primary beam (electron or hadron bunches) with a secondary beam (ion or electron cloud). The transverse oscillations of these beams can couple with each other. Their amplitude will grow, leading to beam losses. These instabilities can limit the operation of fourth-generation light sources with low emittances and high intensity. Many existing light sources, including synchrotron SOLEIL, are conducting upgrade studies towards fourth-generation light source parameters. This contribution investigates beam-ion instability and potential mitigation measures in SOLEIL II. The instability threshold is determined with analytical estimations and particle tracking results. The trapping of ions in the primary electron beam is discussed for the current lattice design. Differences between different numerical models of this beam-ion interaction are briefly discussed.
The advanced storage ring light source needs to realize ultra-low emissivity beam operation, and improving the Touschek lifetime puts forward higher requirements for the performance of RF cavity. In this paper, a novel bimodal normal conducting RF cavity is proposed. In one cavity, two power sources will be connected at the same time to realize the simultaneous operation of the two frequencies. The TM010 mode with the frequency of 500MHz is used for acceleration, and the TM020 mode with the frequency of 1.5GHz is used as the third harmonic to improve the height of the RF bucket and achieve the purpose of lengthening the beam bunch. Two couplers are designed to adapt to the working characteristics of bimodal RF cavity.
Linear coupling in storage rings mixes horizontal and vertical beam motion. This is similar to the mixing of states in an atomic two-level system by a resonant laser interaction or the mixing of the two states of any spin-½ particle in static and dynamic external magnetic fields like, for example, in nuclear magnetic resonance, NMR, measurements. These coupled two-level systems are usually described by the Bloch equation [1] which is a set of coupled, first-order differential equations connecting the population of the states with some other parameters which contain in addition to the strength of the coupling and the detuning, some sort of phase information of the involved states. In linearly coupled storage rings horizontal and vertical emittance can be viewed as the population of ground and excited level and it will be shown that the Bloch equations can also model the time-dependent evolution of the transverse emittances of an ensemble of circulating particles. This is especially useful in cases where the emittance is exchanged by crossing the coupling resonance or where the coupling strength itself is a function of time.
[1] F. Bloch, “Nuclear induction,” Physical Review, vol. 70, no.
7-8, pp. 460–474, 1946.
The description of coupling phenomena in electron storage rings is extended beyond the very common formula based on the coupled Hamiltonian [1] into the region where the small coupling is in competition with damping and diffusion from synchrotron radiation. In the derivation, the moment mapping approach is used in combination with the simplified simulation of radiation effects introduced by Hirata and Ruggiero [2]. The results of this theoretical approach are compared to the predictions of well-established theories dealing with coupling in electron storage rings: The envelope mapping approach from Ohmi, et al. [3], and Chao’s SLIM approach [4].
[1] G. Guignard, “Betatron coupling and related impact of radiation”, Phys. Rev. E 51, 6104, June 1995, or his contributions to CERN Accelerator Schools
[2] K. Hirata, F. Ruggiero in “Treatment of Radiation for Multiparticle Tracking in Electron Storage Rings”, Part. Acc. Vol. 28, pp. 137-142 (1990)
[3] K. Ohmi, et al., in “From the Beam-Envelope Matrix to Synchrotron-Radiation Integrals”, Phys. Rev. E, Vol. 49, p. 751
[4] A. Chao, in ”Evaluation of Beam Distribution Parameters in an Electron Storage Ring”, J. Appl. Phys. 50, 595 (1979) or SLAC-PUB-2143, June 1978
Over recent years four dedicated facilities have been built at Daresbury Laboratory by a team working on thin film SRF cavities. Firstly, a conventional DC resistance facility allows measurements of critical temperature and residual resistance ratio. In addition, three other facilities were designed in house to address superconducting thin film (STF) characterisation specific to cavities. In a magnetic field penetration facility, a DC parallel magnetic field is applied locally from one side of the sample similar to the field within an RF cavity. The STF behaviour under RF conditions is tested with planar samples using a 7.8 GHz choke cavity with the main advantage of a quick turnaround. The final facility uses a novel idea of split single cell 6 GHz cavities. Such a cavity can be deposited with both planar and cylindrical magnetrons allowing for both deposition techniques to be tested in the same cavity. Also, the results can be compared to choke cavity measurements for planar samples. They can also be inspected easily both visually and with surface analysis instrumentation. All facilities are based on liquid helium free cryocoolers to simplify operation, safety and maintenance.
Measurement of hadron beam emittances with very high dynamic range, one part-per-million and above, become available recently. This level of dynamic range is required for studying the origin and evolution of the halo in high intensity hadron linacs. There are no established or commonly known metrics to describe such distributions. Using data from the emittance measurements of 2.5Mev H- beam at the SNS Beam Test Facility we demonstrate that most common emittance metrics the RMS emittance and the Halo parameter H are totally insensitive to low level features of the distribution. We also suggest a new metric, which is unambiguously computable, invariant of linear simplectic transformations, and capturing features important for low loss beam transport.
HZB has completed the commissioning of SupraLab, a complete cavity processing and testing facility. It has been used to recover several superconducting cavities for different accelerators. This article describes all the tested and validated steps from cavity processing to cold rf test and module assembly. They include approved filed-emission free cleanroom work, on-site chemical processing, high-pressure rinsing with a standard or a specially designed nozzle (e.g. for gun-cavities), low- and mid-temperature baking, cold rf test in helium bath or horizontal test with an FPC and a cavity tuner, additional diagnostics (second-sound quench detection, thermal mapping, magnetic field mapping, tests with variable antenna) and cryogenic tests of a cold-string.
Minimizing projected emittance of high brightness electron beam is important for efficient overlap between electron beam and radiation pulse in an FEL facility. Coherent synchrotron radiation (CSR) emission in a single bending section in the beam transport system usually introduces different slice energy modulation hence different slice transverse kicks in the designed dispersion-free lattice, causing projected emittance growth. Here we present theoretical and simulation study of CSR effect on the projected emittance growth in the beam switchyard arc before SASE2 undulator beamline at the European XFEL. We analyze arc optics impact on CSR effect, as well as emittance degradation compensation by controlling beam properties upstream of the arc. With the projected emittance optimized, the overall FEL radiation pulse energy can be improved.
As various experimental reactors in Europe are already
or will be decommissioned over the next years, new neutron
sources will be necessary to meet the demand for neutrons
in research and development. The High Brilliance Neutron
Source is an accelerator driven neutron source planned at the
Forschungszentrum Jülich. The accelerator will accelerate
a proton beam up to an end energy of 70 MeV,
using normal conducting CH-type cavities. Because of the high
beam current of 100 mA, the beam dynamics concept requires special
care. In this paper, the current status of the beam dynamics
for the drift tube linac is dicsussed.
Particle accelerators and light sources are some of the largest, most data intensive, and most complex scientific systems. The connections and relations between machine subsystems are complicated and often nonlinear with system dynamics involving large parameter spaces that evolve over multiple relevant time scales and accelerator systems.
Data Intensive Science offers exciting prospects for accelerator design and operation. This includes the optimization of machine design and the reconstruction of transverse beam distributions using machine learning, as well as data analysis in high data rate monitors. This contribution presents the new Liverpool Center for Doctoral Training for Innovation in Data Intensive Science (LIV.INNO) and its exciting research and training program.
In Particle accelerators, commissioning of a complex beam line requires extensive use of computer models. When the as-built beam line cannot be exactly modeled by the simulation (due for example to mechanical errors or to the extensive usage of the non-linear focusing forces), the solution found in the simulations needs to be adjusted. Thus, it is often required to modify the settings by exploring different parameters ranges on the real accelerator. Given the high parameter space, this is a demanding task both in term of beam time and in term of required expertise. Furthermore, there is no guarantee to reach the optimal solution. This paper proposes a Reinforcement Learning approach to develop a model able to efficiently explore the parameter space of a beam line and iteratively move towards the optimal solution. The approach is first applied for the ADIGE Medium Resolution Mass Separator (MRMS) at INFN Legnaro National Laboratories (LNL), where the potentials of an electrostatic multipole must be correctly tuned to minimize the output beam emittance after the separation stage.
We describe an experiment to demonstrate Derbenev’s flat-to-round (FTR) and round-to-flat (RTF) optical transformations, designed to match electron beams from a high-energy storage ring into and out of a solenoidal cooling channel. We are using a linear transport system with a design optimized by a computationally-efficient adjoint moment equation technique developed by our group for general application to beam optical systems*. We will explore cases on FTR/FTR, first with low space charge, followed by further examples with significant space charge, comparing simulations to beam measurements and reoptimizing the design as needed to test alternative experimental configurations. Our goal is to experimentally and computationally test the Derbenev scheme, which has not been done in its entirety, and to carry out a rigorous, experimental validation of the adjoint moment equation techniques.
Cornell is designing a standalone superconducting radio-frequency (SRF) accelerating cryomodule which utilizes a conduction cooling scheme in place of liquid helium. A key component of this system is a new single-cell 1.3 GHz Nb$_3$Sn-coated SRF cavity. This cavity was designed based on Cornell’s ERL injector cavities in order to replicate their RF properties, such as being able to operate at high current (> 100 mA) and high average power (> 100 kW). Thermal modelling of the cavity was then used in order to optimize the design and placement of heat intercept rings to enable the use of conduction cooling. The cavity has since been fabricated and welded, and is currently undergoing chemical treatment before baseline RF tests are performed.
In 2018, an Advanced Electron Test Facility, named Dalian Advanced Light Source (Pre-research) was proposed and approved, which consists of an electron source, two cryomodules based on superconducting technology, a Transverse Deflecting Structure (TDS) system, and beam dumps. As an eminently practical instrument, TDSs are used for longitudinal and transverse phase-space analysis in Free Electron Laser facilities like EXFEL, SXFEL, LCLS and DCLS. Four TDSs (three for phase-I) operating at the frequency of 2997.222 MHz are expected to be used for the two beam-lines of DALS-pre, including both X-direction and Y-direction. A set of klystron-based pulsed microwave power source consist of a klystron, a modulator, a high-voltage power supply, will be used to provide high RF power in S-band. To transmit the RF power from power source to TDSs, a group of waveguides are designed, including variable power splitter, phase shifter, E-bends, H-bends, waveguide switches, ceramic windows, waveguide absorbing loads, directional couplers, vacuum pumping waveguides and straight waveguides. In this manuscript, the design of TDS system and layout of waveguide system will be presented in detail.
Transverse deflecting cavity (TDC) providing time-dependent kick with fixed polarization is an important tool for beam diagnostics and manipulation. Recently, several types of novel TDC with variable polarization have been developed to fulfill the requirements of multi-dimensional phase space measurement of high-quality electron beam as well as fast scanning in proton therapy. Based on the parallel feeding technology, we propose a new design with alternating racetrack cells where the two chains are fed by waveguide networks independently. Each chain provides fixed polarization in either horizontal or vertical plane and variable polarization can be achieved by adjusting the amplitude and phase of the input power to the networks. The structure has several advantages, such as compactness, tunability, high shunt impedance, etc. In this manuscript, physical and mechanical design of this TDC will be presented in detail.
The investigation of the processes, materials, technology and welding procedures used to manufacture accelerating components for maximum accelerating gradient (>100 MV/m) and minimum RF breakdown probability has led us to the proposal of hard-copper structures in Ka-Band made of multiple parts.
In this paper, we illustrate the TIG welding tests, including visual inspection and temperature monitoring, of Ka-band metallic RF cavities for the cases of two-half and four-quadrant models.
The RF cavities made of multiple parts operate at ultra-high accelerating gradients (well above >100 MV/m). Therefore, the following aspects of the welding procedure were used as references for the positive outcome of the process: 1) Successful execution of each weld bead/seam in order to assure vacuum tightness of the cavity. 2) The cleanliness of the inside surfaces of the cavities: visual inspection for absence of oxidation after cutting the cavity samples; 3) The temperature of the cavity surfaces always below the annealing one (mechanical properties significantly change after heating above 590 ◦C), in order to keep the hardness of the copper.
We image the five-dimensional phase space distribution of a hadron beam in unprecedented detail. The resolution and dynamic range of the measurement are sufficient to resolve sharp, high-dimensional features in low-density regions of phase space. We develop several visualization techniques, including non-planar slicing, to facilitate the identification and analysis of such features. We use these techniques to examine the transverse dependence of longitudinal hollowing and the longitudinal dependence of transverse hollowing in the distribution. Our results strengthen the claim that low-dimensional projections do not adequately characterize high-dimensional phase space distributions.
The Future Circular Collider (FCC) study develops the technologies for next generation high performance particle colliders and accelerating structures. It places high requirements on the performance of Superconducting Radio Frequency (SRF) cavities used to accelerate the particle beam. While niobium-coated copper cavities are being considered for FCC-ee, alternative superconducting materials are investigated in view of reducing considerably the energy consumption of such a large machine.
Nb3Sn, an A-15 intermetallic type II superconductor, is one of those potential candidates. However, due to its brittle nature, the only way to produce an Nb3Sn SRF cavity consists of elaborating it as a thin film using, for example, magnetron sputtering to coat copper-based cavities.
The latest developments at CERN on Nb3Sn films production by DC-Magnetron Sputtering (DC-MS) and bipolar High Power Impulse Magnetron Sputtering (HiPIMS) are presented, together with a comprehensive microstructural and mechanical characterisation of the films. Special attention is paid to the role of interlayers to avoid Cu diffusion during the high temperature reaction and to the influence of the deposition method and parameters on the film superconducting performance.
The injector of Hefei Advanced Light source Facility (HALF) will choose the full energy injection method with beam energy up to 2.2 GeV by a LINAC, which will contain 40 S-band normal conducting traveling wave tubes. Quasi-symmetric single-feed racetrack couplers were used in design of TW tube utilized for reduction the field asymmetry inside the coupler cavity. The design and test result of prototype tube are discribed in this paper.
An RF Fundamental Power Coupler(FPC) designed to operate under 7 kW CW for 325 MHz superconducting(SC) single spoke resonator(SSR) in the high energy SC Linac of the RAON. A prototype FPC has a coaxial shape with an impedance of 98 ohm and an outer radius of 36 mm. It is checked that the MP exists within the SSR operating range. Reduction or elimination of the MP is estimated applying DC voltage at the center conductor of the FPC. Detailed test setup and test results are presented.
Coherent Synchrotron Radiation (CSR) is regarded as one of the most important reasons that limits beam brightness in modern accelerators. Current numerical packages containing CSR wake fields generally use 1D models, which can become invalid in extreme compression regime. On the other hand, the existing 2D or 3D codes are often slow. Here we report a novel particle tracking codes --- DFCSR --- which can simulate 2D/3D CSR and space charge wakes in relativistic electron beams 2 or 3 order of magnitude faster than conventional models like CSRtrack. We performed benchmark simulations based on FACET-II beams, where electron beams are compressed to reach 300kA peak current. The tracking code is written in Python and C programming languages with human-friendly input styles and is open-sourced on Github. It can serve as a powerful simulation tool for the design of next-generation accelerators.
Dielectric Assist Accelerating (DAA) structures based on ultralow-loss ceramic are being studied as an alternative to conventional disk-loaded copper cavities. This accelerating structure consists of dielectric disks with irises arranged periodically in metallic structures working under the TM02-π mode.
Here, the numerical design of an S-band DAA structure for low beta particles, such as protons or carbon ions used for hadrontherapy treatments, is shown. Three dielectrics with different permittivity and loss tangent are studied as well as different particle velocities depending on the energy range.
Through optimization, most of the RF power is stored in the vacuum space near the beam axis, leading to a significant reduction of power loss on the metallic walls. This allows to realize cavities with extremely high quality factor over 100 000 and shunt impedance over 300 MΩ/m at room temperature.
The design optimization has been improved to reduce the peak electric field in certain locations of the cavity. In addition, first multipactor simulations are being carried out, using several coatings to reduce SEY, which has also been taken into account in the electromagnetic result.
The design and tuning of accelerators are both complicated processes involving many physical effects. Of these, the modeling of coherent synchrotron radiation has long been one of the most complicated and time consuming. This is especially true when modeling two and three-dimensional CSR, which is often neglected in state-of-the-art accelerator modeling due to its time consuming nature. We present a neural network designed to model 2D CSR, demonstrating both faithful accuracy to the physics and a dramatic speedup over even the fastest existing codes. We study its performance in the context of the last bunch compressor of the FACET-II facility, where the intense short pulse demands at least a 2D treatment, and find that we can reproduce the results of more standard tracking codes in a fraction of the time.
The electrodeposition of copper onto niobium using commercial acidic and alkaline electrolytes was tested. The continuous dense polycrystalline copper films were successfully obtained in aqueous alkaline-type bath containing copper sulphate, sodium hydroxide and sodium gluconate. The effect of benzotriazole and sodi-um lauryl sulphate additives on the morphology and crystal structure of the deposited copper was investigat-ed by optical and scanning electron microscopy, and X-ray diffraction. No copper oxides were found in the grown films. Copper films had moderate adhesion properties that would be insufficient for cryocooler application. We are currently exploring different com-positions of electrolyte baths for obtaining the coatings on niobium with improved adhesion.
X-ray flash radiography is a powerful diagnostic used worldwide for investigating the structural response of matter under impulsive loading during hydrodynamic experiments. These experiments require a specific X-Ray source generated by a Linear Induction Accelerator (LIA). LIAs produce an intense electron pulsed beam, with a high-energy and providing a high dose at 1 m. Therefore, comprehension and prediction of the electron beam dynamic are essential to guarantee correct realization of the hydrodynamic experiments. At CEA DAM, X-Ray flash radiography experiments are performed on the UK/FR joint facility EPURE, a unique triple-axis radiographic facility with two LIAs and one Inductive Voltage Adder “MERLIN”.
In this study, envelope and particle-in-cell codes simulate the electron beam transport from the production of the beam in the injector to its transport along the accelerator. Thanks to the developed models, parametric studies are made about the influence of beam parameters, as the initial emittance, on the transport. Moreover, the developed codes take into account some beam instabilities, as the beam breakup instability or corkscrew motion. Studies show that the initial beam centroid offset has a significant impact on the beam instabilities during the transport. In addition, simulation results are compared with experimental data acquired on the EPURE facility, notably comparisons about our method to center the beam for limiting beam instabilities.
The Future Circular Collider (FCC) study is developing designs for a new research infrastructure to host the next generation of higher performance particle colliders to extend the research currently being conducted at CERN. In particular, FCC-ee is an electron-positron collider, which is the first stage towards a 100 TeV proton-proton collider FCC-hh.
FCC-ee may be affected by electron cloud (e-cloud) and the strongest effects are foreseen for the Z configuration, due to the highest number of bunches, which corresponds to the smallest bunch spacing. The presence of a large electron density in the beam pipe can limit the achievable performance of the accelerator through different effects like transverse instabilities, transverse emittance growth, particle losses, vacuum degradation and additional heat loads of the inner surface of the vacuum chambers. In the design phase, the goal is to suppress the e-cloud effects in FCC-ee and, therefore, a preliminary study to identify the parameters, which play a significant role in the e-cloud formation has been performed.
In this paper, an extensive e-cloud simulation study is presented. In particular, the impact of the e-cloud is studied for different configurations, for example: for the electron and the positron beam; in the different elements of the particle accelerator; changing the beam chamber geometry; for different values of the Secondary Emission Yield (SEY); and for different beam parameters.
Fermilab Booster synchrotron requires an intensity upgrade from 4.5×1012 to 6.5×1012 protons per pulse as a part of Fermilab’s Proton Improvement Plan-II (PIP-II). One of the factors which may limit the high-intensity performance is the fast transverse instabilities caused by electron cloud effects. According to the experience in the Recycler, the electron cloud gradually builds up over multiple turns inside the combined function magnets and can reach final intensities orders of magnitude greater than in a pure dipole. Since the Booster synchrotron also incorporates combined function magnets, it is important to measure the presence of electron cloud. The effect of the electron cloud was investigated using two different methods: measuring bunch-by-bunch tune shift by changing the bunch train structure at different intensities and propagating a microwave carrier signal through the beampipe and analyzing the phase modulation of the signal. This paper presents the results of the two methods and corresponding simulation results conducted using PyECLOUD software.
When operated with the nominal bunch spacing of 25 ns, the Large Hadron Collider (LHC) suffers from significant electron cloud effects. During the second operational run (Run 2) of the LHC, beam-induced conditioning allowed a satisfactory exploitation of 25 ns beams for luminosity production but could not fully suppress electron cloud formation. It has since been understood that this limitation was due to a degradation of some of the beam screen surfaces that occurred with beam operation after air exposure during the first long shutdown period. In the LHC Run 3, several electron cloud effects are expected to become even more important due to the increase in bunch intensity foreseen during the run. In addition, the beam screens have again been exposed to air during the preceding shutdown period, leading to a reset of most of the conditioning acquired in Run 2 and opening the possibility for further degradation. In this contribution, we describe the experimental observations of electron cloud effects during operation with beam after the start of Run 3 in 2022 and discuss their implications for future operation and mitigation strategies for the remainder of the run.
Optical Stochastic Cooling (OSC) is a feedback beam cooling technique that uses radiation produced by a beam to correct particles' own momentum deviation. This system is made up of two undulator magnets, the pickup and kicker, separated by a bypass chicane that introduces a momentum-dependent path length. The beam produces radiation in the pickup and arrives in the kicker with a delay relative to its momentum, where it is coupled with the undulator radiation, receiving a corrective kick. The undulator radiation can be amplified to increase the strength of the corrective kick; this is done using an optical amplifier. The optical amplifier is driven by a pump laser which can be used to selectively amplify temporal slices of the undulator radiation. In this paper, we propose a method to use the amplified-OSC mechanism to create micro-bunches within the beam and study the performance of this multi-bunch-formation mechanism by considering diffusive effects and gain of the amplifier.
A simple acceleration of a high charge, needle-shaped electron bunch from a cathode is affected by strong correlated emittance growth due to current-dependent transverse space-charge forces. It was shown that such emittance growth could be reversed by focusing the bunch soon after it emerges from the cathode, and that one can expect to retrieve the emittance the beam was born with – the intrinsic emittance. We present a space charge emittance compensation study for a 250 pC radiofrequency photoinjector based on a 100 pC design developed by the UCLA team. We expect that a bright electron beam with an order of magnitude improvement over currently operating photoinjectors can be achieved with 250 pC electron bunches that maintain their emittance below 100 nm-rad.
The exchange of transverse and longitudinal emittances is a unique feature of emittance exchange (EEX) beamline, but it is also a limitation of it at the same time. Most of the modern high-brightness injectors provide much smaller emittance in the transverse plane than the longitudinal plane. Thus, a beam passing through a single EEX beamline ends up with a large transverse emittance, which significantly limits EEX beamline’s use for its various applications. Here, we present a preliminary study for avoiding this issue by optimizing the beamline for longitudinal emittance, correcting nonlinearities, and cutting the periphery of the phase space.
We describe here field emission measurements set-up, diagnostics tools used, analysis and results developed for ESS medium and high beta cryomodules tests . For high gradient, in particular, field emission can be the mechanism which limits cavities performances. A particualar focus will be given to analysis tools developed to tack potential materials activation, due to high energy photons emitted during cavities power ramp up.
Measurements at ESS test stand in Lund (and data collection plus analysis developed) are a joint effort between ESS and in-kinds at CEA (Saclay): details, description and outcome is here described.
Upcoming projects requiring ~650 MHz medium-to-high-beta elliptical cavities such as Michigan State University’s Facility for Rare Isotope Beams’ energy upgrade and Fermilab’s Proton Improvement Project-II drive a need to understand magnetic RF loss mechanisms in greater detail. It remains to be seen whether flux trapping mitigation techniques used in 1.3 GHz cavities are as effective at ~650 MHz, given differences in cavity geometry, material of manufacture vendor, and frequency-dependent superconducting RF dynamics. We explore the fast-cooldown method, and high-temperature annealing (900°C), which promote flux-expulsion efficiency, but are more difficult to implement in ~650 MHz cavities. In high-power RF testing, we measure the cool-down temperature gradient vs flux expulsion efficiency, the cavity’s residual resistance sensitivity to trapped flux as a function of cavity treatment. We further used the Physical Property Measurement System available at Fermilab to directly measure the flux pinning force in bulk niobium samples, and correlate changes in the flux pinning force with different niobium vendors, heat treatments, and cavity flux expulsion performance.
A higher-order-mode-damped 166.6 MHz beta=1 quarter-wave superconducting cavity is being developed for the High Energy Photon Source. The frequency variation of the cavity in all the processes comprising of manufacturing, post-processing and cooldown to 4.2 K, should be strictly controlled due to the relatively small coarse tuning range. The step-by-step evolution of the cavity frequency was determined and the target frequency after fabrication was given. The pre-tuning scheme during fabrication was made in which the length of the inner conductor and the outer conductors are the free parameters for frequency pre-tuning while the cavity length is kept constant. The environment of the cavity in the cryomodule was considered in the analysis. Three bare cavities and one jacketed cavity were fabricated, post-processed and vertical tested with careful frequency monitoring. The measured frequencies were consistent with the predictions in each process.
Field emission (FE) is one of the main reasons for the degradation of superconducting cavity quality factor. Its presence can limit the ultimate performances of superconducting RF (SRF) cavities and hence the cryomodule in which they are assembled.
For these reasons, it is essential to better understand how this phenomenon is generated and evolves from the SRF cavity preparation, in the clean room, through their assembly in the cryomodule until their final test and operation on the machine.
The effort to develop diagnostics required to check for occurrence of FE, its characterization and its consequences in terms of radiation has been limited.
Due to the shielding environment in the cryomodule, the more faint radiation occurring at the FE onset remains undetected. Pulsed operation is also a cause of misreading of the dose rate with general-purpose radiation monitors. More precise diagnostic and analysis tools are required to gain more information.
We present the development of dedicated time-resolved detectors for the FE radiation which aim at improving its coverage in terms of solid angle and lower energy threshold sensitivity. We approach this topic through detailed simulation based on GEANT4 toolkit in order to analyze the interaction of FE radiation with the cavity environment and optimize the detectors with respect to their application in cryomodule or vertical test stands. We illustrate by analyzing recent cryomodule experimental test data.
Accurate and efficient particle tracking through Siberian Snakes is crucial to building comprehensive accelerator simulation model. At the Alternating Gradient Synchrotron (AGS) and Relativistic Heavy Ion Collider (RHIC), Siberian Snakes are traditionally modeled in MAD-X by Taylor map matrices generated at specific current and energy configurations. This method falls short during ramping due to the nonphysical jumps between matrices. Another common method is to use grid field maps for the Snakes, but field map files are usually very large and thus cumbersome to use. In this work, we apply a new method called the Generalized Gradient (GG) map formalism to model complex fields in Siberian Snakes. GG formalism provides an analytic function in x and y for which automatic differentiation, i.e. Differential Algebra or Truncated Power Series Algebra can find accurate high order maps. We present simulation results of the Siberian Snakes in both the AGS and RHIC using the Bmad toolkit for accelerator simulation, demonstrating that GG formalism provides accurate particle tracking results.
In the radio-frequency system of synchrotron light sources, it is necessary to lengthen the bunches by creating harmonic cavities to improve the beam lifetime. In this paper, we propose three harmonic cavity designs: TM010 mode cavity, TM020 mode cavity, and dual mode cavity, with the Wuhan Advanced Light Source (WALS) as the background. By comparing the beam quality, beam lifetime, and radio-frequency system conditions, a more suitable harmonic cavity system is proposed for the fourth generation synchrotron light source.
The industrial, medical and homeland security markets for low-to-moderate energy electron linacs are growing rapidly, often requiring beam currents that strongly load the accelerating fields. The two-beam accelerator (TBA) is one concept for the structure wakefield acceleration approach to an electron-positron collider. Transient beam loading effects are a significant challenge for the drive beam in a TBA structure, where energy droop in high-charge bunch trains must be understood and compensated. The Hellweg code accurately models steady state beam loading for traveling wave RF structures with a fast reduced model. The Hellweg equations of motion have recently been generalized to include arbitrary charge-to-mass ratio and to use momentum as the dynamical variable. These and other recent developments are discussed, including a new browser-based GUI. Proposed future developments include support of standing wave RF structures and transient beam loading effects.
The MAX IV 100 MHz RF cavities are the main contributors for the 3 GeV storage ring longitudinal coupled bunch instabilities. With the knowledge of strong higher order modes (HOMs) since the design stage of the cavities, extra ports are present for the future HOM dampers. This contribution presents the electromagnetic and mechanical designs and the thermal simulation for the HOM damper prototypes. They are planned to be installed during the summer 2023 shutdown in one of the 6 cavities of the 3 GeV ring.
Two types of crab cavities, one at 197 MHz and the other at 394 MHz, are designed to compensate the loss of luminosity due to a 25 mrad crossing angle at the interaction point (IR) in the Electron Ion Collider (EIC). The Higher Order Mode (HOM) damper designs of the EIC differs from the LHC designs since in the EIC the impedance budget is tighter, especially longitudinally, and in the EIC the HOM power is much higher due to the short and high intensity electron and ion beam. In this paper, HOM power in these two cavities are evaluated and optimized.
The modeling of current and next-generation particle accelerators is a complex endeavour, ranging from the simulation-guided exploration of advanced lattice elements, over design, to commissioning and operations.
This paper explores hybrid beamline modeling, towards coupling s-based particle-in-cell beam dynamics with machine-learning (ML) surrogate models.
As a first example, we train a surrogate model of an advanced accelerator element, a laser-wakefield accelerator stage, via the time-based particle-in-cell code WarpX [1].
A second example trains trains a model for the IOTA nonlinear lens via the s-based code ImpactX [2].
The LHC particle-physics program requires that the delivered luminosity be measured to an absolute accuracy in the 1% range. To this effect, the absolute luminosity scale at each interaction point (IP) is calibrated by scanning the beams across each other according to the van der Meer method. During such scans, the orbit and the shape of the colliding bunches are significantly distorted by their mutual electromagnetic interaction; the resulting biases, if left uncorrected, would absorb a major fraction of the systematic-uncertainty budget on the luminosity calibration. The present report summarizes recent studies of such biases in the single-IP configuration, and generalizes it to the more typical case where bunches collide not only at the scanning IP, but also experience additional head-on encounters at up to 3 locations around the ring. Simulations carried out with the COherent-Multibunch Beam-beam Interaction multiparticle code (COMBI) are used to characterize the dependence of beam--beam-induced luminosity-calibration biases on the phase advance between IPs, and to derive scaling laws that relate the multi-IP case to the simpler and better understood single-IP configuration.
This proceeding addresses the effect of the neutral molecules trapped by the beam. It is in particular discussed the effect of a non-uniform neutral molecule distribution on the beam profile and the resulting beam lifetime. According to the trapping temperature it is discussed in a general framework how the beam profile is modified. and the consequent beam loss.
Barrier-Bucket (BB) systems provide a method to apply a short gap to a coasting beam. This is utilized for different applications, like ion cleaning, or to compensate the medium energy loss caused by internal experiments. BB-cavities are broadband cavities, and the applied signal is commonly a short sine burst, followed by a flat section at zero voltage. Since the transfer function of the BB-system is usually neither flat nor linear, it is common to predistort the signal to obtain the desired shape at the rf gap. Nevertheless, the resulting waveform still has a ripple in the flat section. This is due to the lowpass characteristic of the amplifier and the sharp edges at the ends of the sine, which lead to an infinite number of harmonics. This paper provides better suited BB-waveforms, which are designed with a finite number of harmonics from the beginning. It is shown that a much better flatness can be achieved than for a conventional BB-waveform, without sacrificing any performance. These advanced waveforms are currently used at the hadron synchrotron COSY at Forschungszentrum Jülich, leading to improved BB-bunch shapes, in particular for electron-cooled beams.
RF pulse compressors are used for higher acceleration gradient in the KEK electron positron injector linac. S-band spherical-cavity type pulse compressors (SCPC) with a high quality factor Q of 100,000 have been newly developed, and one of them was installed in the linac. The performance of the compressor is characterized by its cavity parameters such as resonant frequency and Q-value. Although these parameters are usually measured at low power, analyzing them during high-power operation is difficult. In addition, the ohmic heating modulates them. Therefore, obtaining cavity parameters in-situ is important especially in the developing stage of the new compressors. We developed an evaluation method to determine the cavity parameters by analyzing pulse-to-pulse output waveforms from the compressor based on its equivalent circuit model. The method gives resonant frequency with an accuracy of less than 0.4 kHz, which corresponds to the frequency shift caused by the bulk temperature change of 0.01°C. The method also gives Q-value with a relative accuracy of less than 3%, the effect of which is smaller than energy multiplication factor changes of 0.3%.
As the series production of PIP-II 650 MHz low beta cavities approaches, INFN-LASA R&D activities on cavity prototypes are ongoing. Different surface treatments have been exploited in a joint effort between INFN and FNAL, to establish the series cavity recipe. Meanwhile, the vertical test facility has been upgraded for the test of high-Q cavities, by increasing its capability to reduce the trapped magnetic flux and by developing of a magnetic mapping system suitable in the cryostat environment. Here, we report the latest experimental results.
It is crucial to have a particle beam with high intensity and small emittance in a timely manner. The main challenges restraining the availability of the beam to the user and limiting the beam intensity in storage rings are a lengthy optimization process, and the injection losses. The setup of the Injection Beam Line (IBL) depends on a large number of configurations in a complex, non-linear, and time-dependent way. Reinforcement Learning (RL) methods have shown great potential in optimizing various complex systems. However, unlike other optimization methods, RL agents are sample inefficient and have to be to be trained in simulation before running them on the real IBL. In this research, we train RL agents to learn the optimal injection strategy of the IBL for the Cooler Synchrotron (COSY) at Forschungszentrum Jülich. We address the challenge of sim-to-real transfer, where the RL agent trained in simulation does not perform well in the real world, by incorporating domain randomization. The goal is to increase the beam intensity inside COSY while decreasing the setup time required. This method has the potential to be applied in future accelerators like the FAIR facility.
Octupole magnets are a central mitigation method against the transverse collective instabilities expected for the high-intensity operation of the SIS18 and SIS100 synchrotrons in the FAIR project. For these beam parameters, the self-field space-charge effect dominates the betatron footprint, and strongly modifies the instability drive and the Landau damping properties. The space-charge tune shifts are related to all three incoherent amplitudes, and is an intrinsic interaction. We consider all these effects and study Landau damping of head-tail modes due to the combination of octupoles and space-charge. Using the data from experimental instability observations, and particle tracking simulations, we provide estimations for the expected high-intensity operation of the SIS synchrotrons.
The 3rd harmonic cavity is a key component for the 4th generation storage ring. A bunch lengthening by the harmonic cavity increases the Touschek lifetime, which can reduce the emittance in the storage ring. The resonant frequency is selected as 1500 MHz due to the resonant frequency of the main RF cavities being 500 MHz. The prototype cavity is an elliptical double-cell geometry to reduce power losses. Based on this design, three niobium cavities are fabricated. Deep drowned half-cells are welded by the electron beam welding machine after trimming at the edge of the equator and iris. The surface treatments are performed to increase the quality factor such as buffered chemical polishing, high-pressure rinsing, and annealing. In this paper, we presented the fabrication method of the 3rd harmonic superconducting cavity from niobium sheets to an elliptical double-cell cavity.
Magnetic alloy cavities have been used in many accelerators. We have irradiated small magnetic alloy rings in J-PARC to evaluate radiation effects on magnetic properties. Complex permeabilities and hysteresis curves were measured before and after the irradiation. No significant variation was observed by the total ionization dose of 18 kGy and neutron flux of 2.3$\times10^{14}$ n/cm$^2$. The doses were measured by RadMON ver.6 developed by CERN. The test will be continued to higher dose. High neutron irradiation caused radio activities and radioactive nuclei in the cores were identified in this work. We also tried to use RadMON with low gain mode. It suggested that RadMON can be used beyond 16 kGy. Gallium nitride devices were also tested for future applications in accelerator tunnels. They showed excellent radiation hardness.
A pulsed electron lens produces a betatron tune shift
along a hadron bunch as a function of the longitudinal coordinates, which is a longitudinal detuning. An example of transverse detuning is the tune shifts due to octupole magnets. This paper considers a pulsed electron lens as a measure to mitigate the head-tail instabilities. A detailed analytical description within a Vlasov formalism presents the coherent properties of the longitudinal and transverse detuning.
The analytical predictions are compared with the results of the particle tracking simulations. A pulsed electron lens is demonstrated to be a source of tune spread with two components: a static one, leading to Landau damping; and a dynamic one, leading to an effective impedance modification, which we demonstrate analytically and in our particle tracking simulations. The effective impedance modification can be important for beam stability due to devices causing longitudinal detuning, especially for nonzero head-tail modes. The Vlasov formalism is extended to include the combination of longitudinal and
transverse detuning. As a possible application at the SIS100 heavy-ion synchrotron (FAIR at GSI Darmstadt, Germany), a combination of a pulsed electron lens with octupole magnets is considered.
A new accelerator simulation code named Advanced Virtual Accelerator Software (AVAS) was developed by the Institute of Modern Physics, Chinese Academy of Science. Although the code is proposed to simulate the particle transport in the linac of the China Initiative Accelerator Driven System (CiADS), it can be also used for common linacs. The code is based on particle-in-cell (PIC) algorithm and implemented in the C++ language. All accelerator elements as well as algorithms are packaged into an executable program, which can be run after installation on the windows operating system. Due to a variety of optimization and parallel schemes, AVAS greatly reduces the time required for linac simulations. Next, more usable elements and graphical interfaces will be added.
Landau damping plays a crucial role in preserving single-bunch stability. In view of delivering the beam to the High-luminosity LHC (HL-LHC), the Super Proton Synchrotron (SPS) must double the intensity per bunch. In this intensity range, the loss of Landau damping (LLD) in the longitudinal plane can pose an important performance limitation. Observation of the beam response to a rigid-bunch dipole perturbation is a common technique to study the LLD. This contribution presents measurements for a single bunch at 200 GeV in a double-harmonic RF system with a higher harmonic voltage at four times the fundamental RF frequency are presented, showing the impact on Landau damping. Beyond the analytical estimates, the observations are moreover compared to the results from novel stability criteria implemented in the semi-analytical code MELODY, as well as with macroparticle simulation in BLonD.
Longitudinal microwave instabilities are driven by beam coupling impedance sources which have a very short wavelength compared to the bunch length. These instabilities can be a significant limitation to performance on an accelerator. In the CERN Proton Synchrotron (PS), microwave instability is mostly observed at transition crossing for ion and proton beams, when bunches are shortest. Vacuum equipment such as pumping manifolds and sector valves are suspected as a driving impedance. The method used to study the instability relies on measuring the longitudinal profile modulation of long bunches with a minimal momentum spread while debunching in the PS, with RF off and only induced voltage acting upon the beam. The low momentum spread minimises the variation in particle drift speeds and increases the duration in which the modulations are visible. The spectral analysis of the modulated beam, combined with modelling of long bunch instability growth aims to fully characterise this instability and its origin. The objective being to mitigate the instability and improve the performance and versatility of the PS beam production schemes.
In the next-generation light sources, the bunch lengthening using the combination of the fundamental and harmonic cavities is a key technology to generate ultra-low emittance beam. Since the performance of the above bunch lengthening is limited by the transient beam loading (TBL) effect on the cavities, we proposed a TBL compensation technique using a wide-band longitudinal kicker cavity [1]. Then, we considered the kicker design based on the KEK-LS storage ring as an example of the next-generation light sources [2]. We employed a frequency of 1.5 GHz (third-harmonic) and the single mode (SM) cavity concept where harmful HOMs are damped by rf absorbers on the beam pipes. The SM-type concept has two advantages. One is its simple structure where it has no HOM dumper on the cavity and another is its low R/Q which reduces the TBL effect in the kicker itself significantly. The RF power is supplied with two large coupling holes whose total external Q is 300. The small external Q is essential to provide a voltage of 50 kV with a -3dB bandwidth (BW) of about 5 MHz which is needed to compensate for the TBL effects sufficiently. To verify the small external Q and damping of HOMs, we fabricated the low-power model of the kicker and measured its performance. In this presentation, we introduced the kicker's design and the performance tests' results.
The electron injection chain of the DELTA accelerator facility starts with a 90 keV electron gun, followed by a linear accelerator (70 MeV), a first transfer line (T1) between linac and booster, a booster synchrotron (70 MeV to 1.5 GeV) and a second the transfer line (T2) connecting the booster and the storage ring (1.5 GeV). Since DELTA does not use a fast topping-up injection mode, each software-driven injection ramp cycle takes about 7 seconds. Depending on the injection efficiency, 250 to 400 ramp cycles are required to reach the maximum beam current of 130 mA in the storage ring. Therefore, for fast post-injection a high electron transfer rate is crucial. During the injection, a large number of parameters (e.g., magnet settings, timings of pulsed elements) have to be adjusted manually. The injection efficiency depends mainly on the settings of the booster extraction elements, the transfer line magnets, and the storage ring injection components. In order to automate the injection procedure and to improve the electron transfer efficiency, the application of innovative machine learning concepts (e.g., neural networks, Gaussian processes and decision trees) was studied.
Traditionally PIC solver compute electric field created by the beam as a mean field. The effect of particle collisions is normally neglected by the algorithm. In this proceeding we address how to include the collisions between the macro particles, and discuss the computational challenges and strategies to include the collisionallity in PIC solvers as particle-particle interaction. We present simulations that benchmark our understanding and analyse potential artifacts as energy conservation or other effects.
In this report, we present our recent progress in the de-sign and high-power testing of the 2nd harmonic cavity for the China Spallation Neutron Source upgrade project. To achieve optimal performance, high-performance mag-netic alloy (MA) cores with dimensions of Ф850mm × Ф316mm × 25mm were meticulously developed and fabricated to serve as the load material for the radio-frequency (RF) cavity. Through rigorous testing, we were able to achieve a remarkable cavity accelerating gradient of over 40 kV/m under 15% duty cycle. To ensure opti-mal cooling efficiency, we conducted a comprehensive fluid dynamics simulation analysis and verified our re-sults through experiments. Finally, to assess the long-term stability and performance of the cavity, we conduct-ed a series of extended operation tests. These experiments successfully confirmed the high-performance capabilities and exceptional stability of the 2nd harmonic cavity.
Work at the SNS beam test facility has focused on high dimensional and high dynamic range measurements of the medium energy (2.5 Mev) beam distribution. This is motivated by the need to understand and predict beam losses down to one-part-per-million. The initial demonstration of full-and-direct 6D phase space measurement was done at a current of 40 mA transported through the RFQ. Since that demonstration, more detailed studies have been performed at lower transported currents (in the range 30 mA and below). This is due to a hardware change - recent runs utilize the original SNS RFQ, which after a decade of service in the SNS achieves transmission significantly below design (50-60%, vs >80%). A short run in 2023 with a newly-commissioned RFQ enables maximum transmission. Preliminary results from beam distribution measurements during this run are discussed.
Landau damping represents the most efficient stabilization mechanism in hadron synchrotron accelerators to mitigate coherent beam instabilities. Recent studies allowed expanding the novel analytical criteria of loss of Landau damping (LLD) to the double harmonic RF system case above transition energy, providing an analytical estimate of the longitudinal stability. The threshold has a strong dependence on the voltage ratio between the harmonic and the main RF systems. Based on that, measurements of single bunch oscillations after a rigid-dipole perturbation have been performed in the CERN Proton Synchrotron (PS). Several configurations have been tested thanks to the multi-harmonic RF systems available in the PS. Higher-harmonic RF systems at 20 MHz and 40 MHz, both in phase (bunch shortening mode) and in counter-phase (bunch lengthening mode) with respect to the principal one at 10 MHz, have been measured.
Nb3Sn superconducting radiofrequency (SRF) cavities have been an ongoing research topic for many years motivated by the potential for higher accelerating gradients and quality factors compared to niobium SRF cavities. The highest performing Nb3Sn cavities are manufactured using tin vapor-diffusion coating, which creates a Nb3Sn film with a surface roughness of around 100-200 nm. This is thought to be one of the limiting factors for the accelerating gradient of Nb3Sn cavities due to enhancement of magnetic field near sharp surface features. To smooth Nb3Sn SRF cavities, we have developed a mechanical polishing procedure which uses centrifugal barrel polishing to smooth the surface followed by a secondary tin coating step to repair the surface. We show that the accelerating field of a Nb3Sn SRF cavity is improved by applying this procedure. We also investigate the quench mechanism of the polished cavity by utilizing temperature mapping to measure which regions of the cavity experience heating during RF operation. We then cut samples from these regions and analyze the film microstructure and chemical composition in 3D using EDS and EBSD measurements together with a focused ion-beam (FIB) tomography technique.
The planned Electron Ion Collider (EIC) has an Energy Recovery Linac (ERL) which provides Strong Hadron Cooling (SHC) in order to control the beam quality of the hadrons. This requires that the electron beam delivered to the cooling section be minimally perturbed by the preceding bunch stretcher necessary in the 100 GeV configuration. This paper evaluates different stretcher designs for the SHC ERL, based on current design requirements.
A system is being developed for the maintenance of a space-charge neutralising plasma from the residual gas within the LEBT of the Front End Test Stand (FETS) at UKRI-STFC Rutherford Appleton Laboratory. Space-charge neutralisation will occur when an ion beam is allowed to collide with and ionise a background gas with pressure greater than 10-4 Torr in the presence of a solenoid fringe field, neutralisation can mitigate excess beam loss and reduce the need for beam chopping. To maintain a low density plasma between pulses, S-Band (3.4 GHz) microwaves will be injected into a LEBT cavity situated between solenoids. In order to provide sufficient microwave power to the cavity a two stage amplification system will be employed, with each stage providing a gain of 10 dB. A novel high-speed, low light-level optical diagnostics system based on Silicon Photomultiplier MPPC’s will be used in combination with a directional coupler for forward and reverse RF power measurement to provide feedback about the state of the plasma within the cavity. An overview of the design of this system will be presented along with preliminary test results.
In CLS, Deep Learning was applied to make a dynamic model for the Orbit Correction System (OCS). The OCS consists of 48 sets of BPMs BERGOZ (96 data sheets with 900 Hz recording) that measure the beam position and use the SVD matrix to calculate the strength of the orbit correctors (48 sets of Orbit Correctors 'OC'). The Neural Network was built, trained, and tested using 96 BPM signals. Five layers of the network (Input Layer, Three Hidden Layers, and Output Layer) provide the time evolution of OC's signals (18 Hz), which can be achieved with high accuracy (Mean Square Error = 10e-7). The results are based on data collected during all challenging situations of the CLS storage ring’s current beam position. An Arduino Board was used to test this methodology in real-time, and the time of operation was within the range of system timing (30 - 40 microseconds).
Optical Stochastic Cooling (OSC), a beam cooling technique based on Stochastic Cooling, is in the early stages of experimental development. It uses radiation produced by the beam in an undulator magnet (the pickup) to correct the momentum deviation of particles downstream in another undulator (the kicker). The OSC mechanism was recently demonstrated at Fermilab’s IOTA ring using a passive configuration. However, the cooling rate of OSC can be dramatically increased by first amplifying the undulator radiation before applying the corrective kick. In collaboration with the IOTA experiment, we developed a computational model of the OSC mechanism. This paper presents beam-dynamics simulations of the amplified-OSC configuration. We implement a model of intrabeam scattering and study the effects on beam equilibrium and diffusion rate as a function of bunch charge. Finally, we investigate the phase-space dynamics with various coupling configurations between the transverse and longitudinal planes.
Current-carrying wires have long been proposed as measures to mitigate beam-beam effects. Dedicated hardware has been installed at CERN Large Hadron Collider (LHC) and experimental sessions have been organised to study the beam dynamics in the presence of the wire compensators. In this paper, a diffusive model is presented to model the collected experimental data and its performance is discussed in detail.
Exploring the fundamental properties of materials, including niobium or Nb3Sn, in high-precision surface resistance measurements is relevant to superconducting radio-frequency (RF) technology. For the precise determination of the RF properties of such materials, the calorimetric measurement is carried out with a quadrupole resonator (QPR). Mathematically, a QPR model is governed by a set of electromagnetic-stress-heat (EM-S-T) equations in the time domain under geometric and material uncertainties. It allows for profound insight into the QPR physics phenomena, such as dynamic Lorentz force detuning and microphonics, potentially resulting in measurement bias observed for the third operating mode of the given HZB-QPR (1.3 GHz). On top of the coupled EM-S-T problem, due to manufacturing imperfections, the stochasticity of input parameters substantially affects the performance of QPRs. Thus, uncertainty quantification (UQ) becomes necessary to provide reliable and predictable simulations of QPRs. The generalized polynomial chaos (gPC) expansion technique with the stochastic collocation method is proposed to find the UQ propagation by the QPR model. This methodology offers a more realistic mathematical model of the QPR, providing statistical moments, local and variance-based sensitivity, and cumulative/probabilistic density functions. Based on that information, a physically-based approach can be proposed to re-design the QPR and improve the measurement accuracy.
An ongoing study at the Spallation Neutron Source (SNS) seeks to better understand and address potential multipacting issues associated with the Drift Tube Linac (DTL) RF vacuum windows. An analysis of several failed operational windows showed indications of excessive RF heating on the TiN-coated alumina ceramics. Coupled with vacuum bursts and arcing during conditioning and/or operational periods, these problems have been attributed to electron activity likely caused by multipacting. The status of the study, 3-D electromagnetic simulation results, mitigating techniques and a future experimental plan for studying multipacting in the SNS DTL vacuum windows are presented.
The Future Circular Collider (FCC) is a project of high performance particle collider. Several accelerating cavity technologies may equip it and are currently under study. One of them is the Slotted Waveguide ELLiptical (SWELL) superconducting (SC) cavity. It is a good candidate for nearly all the range of electron-positron interaction energies. It is made up of four independent quadrants clamped together, allowing for a seamless and very stiff structure. One of the important issues that remain to be addressed is the position of the multipactor barriers. In this study, we focus on the SWELL 1.3 GHz mono-cell prototype, which is very close to the well-known TESLA cavity. We calculated the position of its multipactor barriers using the simulation tools CST Microwave Studio and SPARK3D. These calculations were backed by electron emission measurements led on a Nb sample representative of the cavity’s coating. These are focused on the impact energy range between 0 and 80 eV. As a matter of a fact, we found it to be very important for the multipactor apparition while often being overlooked.
SRF photoguns become a promising candidate to produce highly stable electrons for UEM/UED applications because of the ultrahigh shot-to-shot stability compared to room temperature RF photoguns. SRF technology was prohibitively expensive for industrial use until two recent advancements: Nb3Sn and conduction cooling. SRF gun can provide a CW operation capability while consuming only 2W of RF power which eliminates the need of an expensive high power RF system and saves a facility footprint.
Euclid is developing a continuous wave (CW), 1.5-cell, MeV-scale SRF conduction cooled photogun operating at 1.3 GHz. In this paper, we present the current status of the project.
Nb3Sn on Nb thin films cavities by Tin Vapor Diffusion already show performance at 4.2 K comparable to Nb bulk cavities at 2 K, but a real breakthrough would be the use of copper (instead of Nb) as substrate, to enhance the thermal conductivity, opening up the possibility to cool down the cavity using cryocoolers instead of the more expensive helium bath.
Magnetron sputtering is the most studied technology for this purpose, however coating substrates with complex geometry (such as elliptical cavities) may require targets with non-planar shape, difficult to achieve with classic powder sintering techniques due to the brittleness of Nb3Sn.
In this work, carried out within the iFAST collaboration, the possibility of using the Liquid Tin Diffusion (LTD) technique to produce sputtering targets for 6 GHz elliptical cavities is explored. The LTD technique is a wire fabrication technology, already developed in the past at LNL for SRF applications, that allows the deposition of very thick and uniform coating on Nb substrates even with complex geometry. Improvements in LTD process, proof of concept of a single use LTD target production, and characterization of the Nb3Sn film coated by DC magnetron sputtering with these innovative targets are reported in this work.
In recent years, the use of machine learning methods has proved to be capable of considerably speeding up both fundamental and applied research. Accelerator physics applications have also profited from the power of these tools. This includes a wide spectrum of applications from beam measurements to machine performance optimisation.
PETRA III is one of the world's brightest storage-ring-based X-ray radiation sources. The beamlines are supplied with light from various undulators tailored to the specific needs of the experiments. In the ideal case, a perfectly tuned undulator always has a first and second field integrals equal to zero. But, in practice, field integral changes during gap movements can never be avoided for real-life devices.
Deep Neural Networks can be used to predict the distortion in the closed orbit induced by the undulator gap variations on the circulating electron beam. In this contribution a few current state-of-the-art deep learning algorithms were trained on measurements from PETRA III. The different architecture performances are then compared to identify the best model for the gap-induced distortion compensation.
Crab cavities are fundamental components of the LHC upgrade in the framework of the HL-LHC project. These Radio Frequency cavities, operated at the appropriate frequency, ‘tilt’ the proton bunches to increase the luminosity at the collision points IP1 (ATLAS) and IP5 (CMS). During operation, the walls of the cavities are deformed due to the loading conditions. This deformation changes the electro-magnetic field inside the cavity and thus its RF frequency. Two different superconducting crab cavities have been developed: RF Dipole (RFD) and Double Quarter Wave (DQW). In the present study, the numerical evaluation of the Lorentz Force Detuning (LFD) and the Pressure Sensitivity (PS) of the DQW cavity, using COMSOL Multiphysics, is presented. The LFD analyses the change in fundamental frequency of the cavity due to the electro-magnetic forces acting on its walls, while the PS investigates the frequency shift when the cavity is subjected to pressure fluctuations of the Helium bath. Finally, a comparison is presented with the results measured during the cold test of the manufactured cavities.
In recent years the generation of high power millimeter wave and Terahertz radiation has progressed substantially, enabling electron beam manipulation and acceleration in structures with a footprint of several centimeters. However, in many experiments the external driving pulse is coupled collinearly into the waveguide structure which increases the coupling footprint relative to the wavelength tremendously (≈30 𝜆 or more) in comparison to conventional structures (≈1 𝜆 or less). Here, the design of a double-bend mode converter for 300 GHz is presented which converts the fundamental TE11 mode quasi-instantaneously to the TM01 mode for the accelerating structure. In comparison to an s-shaped converter, the present design makes an additional waveguide bend obsolete. The structure length along the beam axis is only 4 mm (4 𝜆), showing a major advance in compactness. Combined with a horn antenna for free-space to waveguide coupling, the maximum power coupled into the structure reaches 83%, while the collinear scheme does not exceed 74%.
An accelerating charged particle emits electromagnetic radiation. The motion of the particle is further damped via self-interaction with its own radiation. For relativistic particles, the subsequent motion is described via a correction to the Lorentz force, known as the Lorentz-Abraham-Dirac force.
The aim of this research is to use the Lorentz-Abraham-Dirac force to computationally simulate the radiation damping that occurs during nonlinear inverse Compton scattering. We build on our previous work and the code which simulates single-emission inverse Compton scattering to incorporate the effect of multiple emissions, thereby modeling the radiation reaction.
OPAL (Object Oriented Parallel Accelerator Library) is a C++ based massively parallel open-source program for tracking charged particles
in large scale accelerator structures and beam lines, including 3D space charge, collisions, particle-matter-gas interaction, and 3D undulator radiation.
The meticulous parallel architecture allows large and difficult problems, including one-to-one simulations with high resolution and no macro
particles, to be tackled in a reasonable amount of time. The current code state as well as the most recent physics advancements and
upgrades are discussed, including the unique feature of a sampler for creating massive, labeled data sets with tens of thousands of cores
for machine learning. We also demonstrate scalability of our core algorithms up to 4600 GPUs and 32'000 CPUs, as part of our effort to make OPAL exascale ready.
Electropolishing (EP) and buffered chemical polishing (BCP) are conventional surface preparation techniques for superconducting radiofrequency (SRF) cavities that remove damaged material from the cavity surface. One main issue with EP and BCP treated SRF cavities is high field Q-slope (HFQS), a drop in quality factor at high gradients that limits quench field. High gradient performance in EP cavities can be improved by applying a low temperature bake (LTB), but LTB does not consistently remove HFQS in BCP cavities. There is no consensus as to the why LTB is not effective on BCP prepared cavities, and the cause of HFQS in BCP cavities is not well understood. We examine the origins of quench in EP, BCP, EP+LTB, and BCP+LTB treated SRF cavities. We also show the effect of these treatments on the onset of HFQS, heating within the cavity up to quench, concentration of free hydrogen, and surface roughness.
In view of the High-Luminosity (HL-LHC) upgrade of the LHC collimation system, different materials were investigated to determine how the jaws of the new collimators could be manufactured to meet the demanding requirements of HL-LHC, such as thermomechanical robustness and stability, RF impedance, UHV, etc. During the Long-Shutdown 2 (LS2), five primary and 10 secondary low-impedance collimators were already produced using novel material. For LS3, in addition to more secondary collimators, the production and installation of other types of collimators, including tertiaries and physics debris units, is planned. This paper details the final material choices and rationale for each collimator family.
At TTX, we try to use machine learning to give the virtual detection of the beam spot. The prediction of beam spot is difficult when the dimension becomes larger. We try to use PCA to make it smaller and use Neural networks to predict it. However, the weight of different dimension varies widely. We predict them parallel and get good results with easy neural networks.
We present a physics-constrained neural network (PCNN) approach to calculating the electromagnetic fields of intense relativistic charged particle beams via 3D convolutional neural networks. Unlike the popular physics-informed neural networks (PINNs) approach, in which soft physics constraints are added as part of the network training cost function, our PCNNs respect hard physics constraints, such as ∇⋅B=0, by construction. Our 3D convolutional PCNNs map entire large (256×256×256 pixel) 3D volumes of time-varying current and charge densities to their associated electromagnetic fields. We demonstrate the method on space charge dominated, relativistic (5 MeV), short (hundreds of fs), high charge (2 nC) electron beams, such as those in the injector sections of modern free electron laser and plasma wakefield accelerators. We show that the method is accurate, respects physics constraints, and that the trained 3D convolutional PCNNs perform electromagnetic calculations orders of magnitude faster than traditional solvers which require a O(N2) process for calculating the space charge fields of intense charged particle beams.
We present the latest updates to the PLACET3 tracking package which focus on the impact of both transverse and longitudinal wakefields on a beam travelling through accelerating and decelerating structures. The main focus of this update was the first implementation of 6D tracking through Power Extraction and Transfer Structures (PETS) for the Compact Linear Collider (CLIC) which is described through short and long-range longitudinal wakefields. Additionally, we present the impact of different numerical schemes on the computation of wakefields in accelerating structures.
Plasma processing can be used to mitigate hydrocarbon-related field emission in SRF cavities in situ in cryomodules. At Fermilab we developed plasma cleaning for LCLS-II 1.3GHz N-doped cavities and we successfully applied to the LCLS-II High Energy verification cryomodule (vCM). This test demonstrated that plasma processing can be a valuable tool to mitigate both field emission and multipacting in situ in cryomodules. This would result in a significant decrease of the CM testing time, of the linac commissioning time and cost, and in an increase in the accelerator reliability.
Building upon this successful experience, we are now working on developing plasma processing for different cavity geometries, focusing both on the ignition method and on the gas mixture recipe.
As a part of the effort to expand the capabilities of CE-BAF 12 GeV (Continuous Electron Beam Accelerator Facility) at Jefferson Lab, the addition of a polarized positron source is considered. This capability would provide acceleration of high duty-cycle polarized posi-trons, with spin >60% polarization, through the same main CEBAF accelerator machine with appropriate mag-net field reversals and linac phasing to the four CEBAF experimental halls. To produce this positron beam, a high average current (3-10 mA) highly polarized electron beam with energy of 100 – 150 MeV is required at the positron source target. The focus of this paper is the de-sign of that polarized electron beam injector. We will describe the production and delivery of a >3 mA highly polarized electron beam. We will discuss different aspects of the design, the photocathode gun, beam dynamics simulation results, spin manipulation, bunching and accelerating process and final electron beam parameters.
Superconducting magnet technology is one of the foundations of large particle accelerator facilities. A challenge with operating these systems is the possibility for the magnets to quench. The ability to predict quenches and take precautionary action in advance would reduce the likelihood of a catastrophic failure and increase the lifetime operability of particle accelerators. We are developing a machine learning workflow for prediction and detection of superconducting magnet quenches. In collaboration with Brookhaven National Laboratory (BNL), our methods for algorithm development will utilize magnet data from test stands and the Relativistic Heavy Ion Collider ring magnets to allow for a robust identification of magnet quenches. Our methods divide the problem into two different aspects. First, we are developing machine learning algorithms for binary and multi-classification of the various types of quench events. Second, our prototype machine learning model will be used to predict a quench event using precursor identification. We plan to integrate and test our monitoring system at the BNL facility to perform quench identification and prediction.
Research Instruments (RI) and Thales have been producing the first two prototype 1.5 GHz fundamental power couplers for the VSR (Variable pulse length Storage Ring) DEMO since early 2021 and delivered these prototypes in late March 2023. These couplers are designed to provide up to 16 kW power to two 1.5 GHz superconducting cavities of the VSR DEMO module and provide variable coupling with a Qext range from 6x10^6 to 6x10^7. The paper describes the challenges in fabricating a scaled coupler and provides details on the modifications to the design as a result of these challenges. The impact of the late-stage design modification is discussed along with how this affects future conditioning plans.
The EIC to be built at BNL is a unique high-energy, high-luminosity, polarized electron-proton/ion collider. The EIC accelerator complex consists about 10 new RF and SRF systems operating with frequencies spanning 24 MHz to 1,773 MHz, requiring at least 60 new high power fundamental power couplers (FPCs). These couplers will operate in either pulsed mode or CW modes with peak traveling wave power ranging from tens to 380 kW. A 1 MW broadband RF window suitable for all the EIC RF and SRF systems up to 591 MHz was designed and under prototyping. This paper will present the status on FPC window development, FPC airside and vacuum side components for 591 MHz test, 591 MHz high power conditioning box, and FPC testing plan.
PyTao is a Python interface to the Bmad based Tao program for accelerator design and simulation. This enables advanced design and optimization beyond the normal capabilities of Tao as well as simplifying the use of Tao as an online model for an operating accelerator. Here we will describe this interface and some of its applications, including online models for the the LCLS and LCLS-II at SLAC National Accelerator Laboratory.
Superconducting materials such as niobium have been extremely useful for rf accelerator technology but require low temperatures for operation ~2-4 K. The development of high temperature superconductors (HTS) is promising due to their transition temperature in excess of 80 K. In this work we are exploring the high-power RF performance of such materials at X-band (11.424 GHz). We are testing two kinds of REBCO coatings, deposition and tapes, on a copper substrate. Testing was done in a hemispherical cavity with a TE mode due to its ability to maximize the magnetic field on the sample and minimize electric field. We will report on the performance in terms of conductivity vs temperature at low and high power. These measurements will then be compared to the design performance of a full 3D cavity that is coated with REBCO. This cavity will utilize the TM010 mode, and we are targeting a Q of ~1 10^6 at 80 K. Such a cavity could be useful for high power rf accelerator applications. In one example, a cryogenic copper linac operating at liquid nitrogen temperature (77 K) could utilize such a high-Q cavity in its superconducting state for pulse compression.
Controlling beam losses is of paramount importance in superconducting particle accelerators, mainly for ensuring optimal machine performance and an efficient operation. Models based on global diffusion processes, in which the form of the diffusion coefficient is the stability-time estimate of the Nekhoroshev theorem, have been studied and proposed to investigate the beam-halo dynamics. Recent measurements with collimator scans were carried out at the CERN Large Hadron Collider (LHC) with the aim of reconstructing the form of the diffusion coefficient. The results of the analyses performed are presented and discussed in detail.
As a scientific system with many subsystems, particle accelerator system is getting more complex， due to rising demands on accelerator performance. Meanwhile, it is increasingly difficult to study such complex systems using traditional research methods based on physical models. At present, machine learning (ML) is mature enough to be applied in accelerator science such as beam diagnostics and equipment control. Compared with traditional research methods, machine learning has strong generality and high computational efficiency. However, problems such as incomplete database or insufficient test time often hinder the application of ML in accelerator operation control and optimization.
To further explore the application of ML in accelerator science, in this paper, we demonstrate the feasibility of reinforcement learning in accelerator control using: 1) replacement model of linear accelerator components based on neural network; and 2) reinforcement control and fast matching of the LEBT and RFQ of the linear accelerator, which is based on reinforcement learning. These methods will be experimentally verified on a linear accelerator.
The compact 166 MHz HOM-damped quarter-wave superconducting cavities for HEPS have complex geometries, resulting in streak defects on the inner surface of the cavity after BCP etching. Surface areas with low flow velocity from fluid dynamics simulations coincide with defects observed on the cavity inner surface. Based on the 166 MHz cavity structure, an improved BCP setup with holes and discs was designed. The flow velocity at the defect locations was greatly increased, and defects did not reappear. An excellent cryogenic performance has been achieved in the subsequent vertical tests, indicating that the post processing of the cavity was successful. This paper presents the analysis, solution, and final results of BCP etching defects in the chemical processing of the 166.6 MHz srf cavity.
The cryomodule qualification test stand (TS2) at Lund has been commissioned fully in 2021 and is delivering the components for the installation in the linac, which started in Q1 2023 after the end of the cryogenic distribution system commissioning.
All the available medium beta cryomodules have been tested and the facility is now delivering the high beta cryomodules for the full scope of the linac.
Statistics of the tests and operational experience of the facility is reported here.
Recent efforts have shown that the SRF technology developed for accelerators can be successfully applied to new applications, including quantum computing, dark matter searches and beyond the standard model physics. The ultra-high quality factor of SRF cavities can allow to achieve unprecedented sensitivity in fields outside of the usual accelerator applications, for examples in dark photon and axion searches (both as dark matter candidates and lab-produced particles), to study the superconductor nonlinear behavior and could also allow to set a limit on photon-photon scattering. Applications of SRF cavities for gravitational waves searches are also being investigated. In this work we propose an overview of the applications of SRF technology originally developed for accelerators to new frontiers. The SQMS Physics and Sensing thrust is working on this effort as it strives to combine SRF cavities with the quantum technology, with a focus on new particle and BSM physics.
Future high duty cycle (HDC) operating modes are under development for the
European XFEL. A L-band superconducting RF (SRF) gun is foreseen as the
injector operating continuous wave (CW). To preserve the small beam
emittance distracting effects like RF kicks from the power coupler,
trapped higher order modes (HOMs) in the cavity end group and RF field
asymmetries need to be considered and countermeasures to be taken. Apart
from the beam dynamics, the feasibility and effort of the manufacturing
and surface treatment, the later assembly and operation needs likewise
consideration. In our contribution we present the outcome of our studies
and the cavity end group which will be realized at our next prototype
cavities.
We present here the RF test program of the ESS TS2. Several tools have been prepared at TS2 for the later stages of the technical commissioning in the linac. Automated tools for tuning the cavities to resonance using spectral analysis or cavity gradient calibration have been deployed and tested to assist the later stages of facility commissioning.
In this paper, the design of a compact C-band SLED RF Pulse Compressor for a Very High Electron Energy (VHEE) FLASH machine is presented. A spherical cavity RF pulse compressor - selected because of its compactness and relative ease of fabrication - is adopted to compress the 50 MW 3 µs RF pulse, down to 1 µs obtaining a peak power gain greater than 3. The main parameters – operating resonant mode, unloaded quality factor, coupling factor, peak power gain, geometry, peak surface fields - and S-parameters of the full RF design (spherical storage cavity + mode converter/polarizer) are computed and analyzed.
Moreover, the pulse-compression effect on the acceleration performances is analyzed through the evaluation of the main figures of merit (charge per pulse, energy gain, accelerating gradient and efficiency)
A pulse compression system based on double-height waveguides was designed for the Klystron-based CLIC main linac. The optimized power gain of the system is 3.81 with the particular pulse shape required for the CLIC-K accelerating structure. This pulse compression system consists of a main Barrel Open Cavity (BOC)-type pulse compressor and 4 novel correction cavities. The BOC pulse compressor has the Q0 of 2.36e5 with working mode TM1,1,32 and the β of 6.6. A novel coupling waveguide network which can ease the machining procedure was designed for the BOC pulse compressor. For the correction cavities, a new method based on a single cylinder cavity and a 3-dB hybrid was studied. Each of the correction cavities has the Q0 of 5e4 and the β of about 1.3.
A new RF Module was designed for the Klystron-based CLIC main linac. The new module deploys two X-band klystrons to feed eight CLIC-K accelerating structures giving a beam energy increase of 156 MeV. This module will use a double-height waveguide distribution network which can reduce the RF power loss in the network by about 37%. All the RF components were redesigned to match the double-height requirement, mainly including the 3 dB hybrid, the RF vacuum flange, the bending waveguide, correction cavies and the BOC pulse compressor. A CLIC-K accelerating structure with bended damping waveguides was designed for the new module. The result of RF design work for the klystron based CLIC module is summarized.
The brightness can be increased by minimizing the emittance in the light source, but the reduced emittance also increases the number of collisions of electrons in the beam bunch. Therefore, the bunch lengthening by using the 3rd harmonic cavity reduces the collisions of electrons and increases the Touschek lifetime. Since the resonant frequency of the main RF cavity is 500 MHz, the resonant frequency of 3rd harmonic cavity is selected as 1500 MHz. The prototype cavity is a passive type in which a power coupler is not used, and power is supplied from the beam. The operating temperature is 4.5 K, which is a superconducting cavity. The elliptical double-cell geometry was selected to increase the accelerating voltage of the cavity and reduce power losses. Based on this design, three niobium cavities are fabricated and tested. In this paper, we presented the results of the RF measurement at room temperature to cryogenic temperature.
QWR cavities are prepared for beam commissioning. RF conditioning is performed for each QWR cavity. The total heat load including static and dynamic heat loads are measured for each cavity. The helium pressure fluctuation is reduced by changing the flow rate, supply pressure, return pressure, liquid helium level in reservoir, cryogenic valve control, etc. The cavity pressure is monitored during RF preparation. The amplitude and phase of the QWR cavity are stably controlled for beam commissioning.
What happens when the temperature reaches absolute zero? Physical phenomena at the zero-temperature limit are studied in accelerator physics. The background temperature of the universe goes down as long as expansion goes on. The BCS resistance of a superconducting cavity is shown as a function of temperature at different frequencies. The surface resistance of the Nb superconducting cavity is reduced to residual resistance and flux-trapped resistance at 0 K. Blackbody radiation is stopped by heat radiation at 0 K. Thermal expansion and thermal diffu-sion become zero at 0 K. Black holes evaporate at 0 K.
Tuning becomes essential at the end of manufacturing an RFQ to acquire the operating frequency and achieve the required RF field profile along the length of the structure. During commissioning, unexpected detuning events may also necessitate tuning to obtain the original design field profile. Proper separation of quadrupole and dipole modes is needed to maintain the desired field distribution in the RFQ. We use transmission-line theory to model the field distribution as a weighted summation of quadrupole and dipole modes. Applying perturbative fields, we evaluate the effect of slug tuners on the same field. Using the measured field profile along the length of the RFQ obtained from the bead-pulling technique, the new tuner depths that can deliver the desired field profile are calculated. The RFQ tuning code takes the field profile as input and provides delta change in tuner depths as output. Iterations of the above steps are needed to accurately obtain the desired field profile. This paper presents an RFQ tuning procedure with a tuning example. We discuss the advantages and pitfalls of this method.
In this paper, we present a study of the transformation of a magnetized electron beam from round to flat and back to round using a skew quadrupole triplet. Electron cooling of hadron beams requires a magnetized electron beam, which can be generated from an RF photoinjector. However, such a beam is coupled in four-dimensional phase space, making it difficult to transport through beamlines. To address this challenge, we use a skew quadrupole triplet to remove the coupling and form a flat beam with different emittance in the horizontal and vertical planes and a high aspect ratio. Likewise, we use an additional skew quadrupole triplet to restore the correlation to the beam. We use particle tracking simulations to identify the optimal positions and strengths of the skew quadrupole magnets for the beam transformation. Finally, we present experimental demonstrations of the beam transformation at the Argonne Wakefield Accelerator Facility.
In the injector section of electron linacs, both internal space charge forces and wakefield effects influence the beam dynamics. To account for both effects, full electromagnetic PIC simulations are usually required. Unfortunately, PIC solvers require large computational resources. On the other hand, particle-tracking codes in the bunch reference frame describe the beam dynamics under space-charge fields. These codes, however, often fail to include the effect of geometric wakefields especially for low energy beams.
As an alternative modeling approach, we propose to decouple the wakefield scattered by the geometry from the space-charge field. Then, we use for each of the contributions the simulation approach that is more appropriate for the respective interaction. We decompose the total electromagnetic field into an incident and a scattered part. The incident field is computed by a space-charge solver in the rest frame of the bunch assuming that particles are in free space. Since this field does not fulfill the boundary conditions at the chamber walls, it acts as an excitation for the scattered part. The latter can be efficiently computed using a particle-free wakefield code. In the full paper, we will present beam dynamics simulations for the injector section of the European XFEL. The aim of these simulations is the quantification of the uncorrelated energy spread induced by geometric wakefields at low energies, which so far is not considered in existing wakefield models.
This work investigates the behavior of a free-electron laser (FEL) system composed of a slowly modulated wiggler field, constant laser field amplitude, and self-consistent fields due to the charged particles. The dynamics of each particle of the beam is studied through a Hamiltonian formalism, from which a ponderomotive approach represents its mean motion. The purpose of the present analysis is precisely to add collective effects into the description of electron acceleration in the inverse free-electron laser device described previously. The transverse self-consistent beam dynamics has been largely analyzed and understood when beams are transported at constant axial speeds, in the absence of accelerating fields. However, when accelerating fields are turned on, and the beam velocity is no longer constant, the system's behavior changes significantly.
The electron ion collider, the next generation nuclear physics collider is being actively studied. In order to achieve the designed luminosity 10^34/cm^2/s with a reasonable lifetime, an efficient coherent electron cooling scheme was proposed to reduce the hadron beam emittance and counter intrabeam scattering. Such a cooling scheme requires a good electron beam quality with a small energy spread. However, the shot noise in the electron beam through the accelerator might be amplified due to the microbunching instability and might degrade the electron beam quality in the modulator section of the strong hadron cooling channel and correspondingly cooling rate. In this study, we reported on a self-consistent simulation study of these effects using the real number of electrons. This captures the details of shot noise.
The effect of radiation reaction is often negligible in inverse Compton scattering. However, in the nonlinear Compton regime, at high laser fields and high electron beam energies where electron recoil must be properly accounted for, there is experimental data which demonstrates the onset of radiation reaction * . We model the radiation reaction as a series of emissions from individual electrons with decreasing energy. This allows us to use the code we previously developed for simulating single-emission inverse Compton scattering events ** . We use the new code to simulate the experiment reported in Cole et al. 2018, and to compare it to other models of radiation reaction.
The half-integer resonance is considered to be one of the strongest effects limiting the intensity of the FAIR SIS100 heavy-ion synchrotron which is currently under construction at GSI. Results of simulations under realistic synchrotron-operation conditions show that for bunched beams, a relatively small gradient error can result in a large half-integer stop-band width significantly reducing the maximum achievable bunch intensity. In addition to the results of simulations in SIS100, we characterize the half-integer stop band in SIS18 using experimental data.
Many current accelerators use cavities that are manufactured as two half cells that are electron beam welded together, across the peak surface current of the cavity. This weld can limit the performance of Thin Film (TF) coated cavities by causing an increase in the surface resistance. Many problems with the coating process for TF Superconducting Radio Frequency (SRF) cavities are also due to this weld. TF SRF cavities can perform as well as bulk niobium cavities if the cavity is manufactured seamlessly, without any weld, however, they are much more difficult and expensive to manufacture. A cavity with a split parallel to the direction of the electric field, would not need to be welded. These cavities are easier to manufacture and coat. Thus, different coating techniques may be used leading to new materials and multilayer coating options which may allow SRF cavities to operate at better parameters than current state of the art cavities.
TF SRF cavities have been developed for use in particle accelerators, as they have many advantages over normal conducting and bulk niobium cavities. One such advantage is that SRF TF cavities have a lower surface resistance, below the critical temperature, than NC cavities and a higher thermal conductivity than bulk niobium cavities leading to a more uniform temperature of the superconductor.
This work discusses development and testing of longitudinally split seamless TF SRF cavities at Daresbury Laboratory
The question we try to answer in this paper is: what is the standard error of using particle tracking result to represent the real beam parameters? Or how much confidence do we have when we say that the tracking gives the correct theoretical prediction? Particle tracking or numerical simulation in general is used by accelerator physicists every day and we believe this question needs a definite answer.
Longitudinal beam manipulation have been widely employed for various scientific and industrial applications in many hadron (heavy ion or proton) synchrotrons. One of the most important manipulations is the longitudinal bunch merging based on the dual rf system. For high-intensity hadron beams, longitudinal space-charge matching and cavity beam loading matching and compensation are of practical concern to minimize the emittance blow-up for merging of high-intensity beams. For rapid cycling synchrotrons, a trade off should be made between the limited bunch merging time and the high-intensity effects. This paper discusses the schemes for high-intensity hadron bunch merging and proposes a fast bunch merging scheme for rapid cycling synchrotrons. Some experimental preparations for the bunch merging in the CSNS/RCS are also introduced.
Modelling electron cloud driven instabilities using a Vlasov approach enables studying the beam stability on time scales not accessible to conventional Particle In Cell simulation methods. A linear description of electron cloud forces, including the betatron tune modulation along the bunch, is used in the Vlasov approach. This method is benchmarked against macroparticle simulations based on the same linear description of electron cloud forces. Applying high chromaticity settings is the main mitigation strategy for these instabilities. The effect of chromaticity can be taken into account using the Vlasov method. The Vlasov approach agrees with macroparticle simulations for strong electron clouds, and a stabilizing effect from positive chromaticity can be seen in both approaches. For positive chromaticity, the Vlasov approach shows the existence of weak instabilities which are not observed in the macroparticle simulations. This feature suggests the existence of damping mechanisms that are not captured by the linearized Vlasov equation.
Al2O3 is one of the potential insulator materials in the superconductor-insulator-superconductor (SIS) multilayer coatings of superconducting radio-frequency (SRF) cavities for pushing their performance limits.
We report on the successful coating of two 1.3 GHz Tesla- shaped SRF cavities with 18 nm and 36 nm layers of Al2O3 deposited by thermal atomic layer deposition (ALD). The coating recipe was developed by thermal atomic layer deposition (ALD). The coating recipe was optimized with respect to different the applied process parameters such as exposure and purge times, substrate temperature and flow rates. After a proof-of-principle Al2O3 coating of a cavity, second the cavity maintained its maximum achievable accelerating field of more than 40 MV/m and no deterioration was observed [1]. On the contrary, an improvement of the surface resistance above 10 MV/m has been observed, which is now further under investigation.
The microbunching instability (MBI) driven by beam collective effects can cause significant electron beam quality degradation in advanced x-ray free electron lasers. Typically, multiple stage magnetic bunch compressors used to generate high peak current electron beam will dramatically amplify the microbunching instability. In this paper, by redesigning the solenoid elaborately and adopting a dual-mode buncher cavity with the third harmonic mode used to correct the RF curvature, it is potential for the electron beam to be further compressed in VB process. Therefore, a VB plus one bunch compressor could be a promising alternative scheme to achieve moderate peak current beam for high-repetition-rate X-ray FELs to suppress the additional MBI gain due to multi-stage magnetic bunch compressors.
Annealing of niobium (Nb) cavities in UHV is crucial for the performance in the later cryogenic tests and operation. Recently, a so-called “mid-T bake” treatment has exhibited very high-quality factors for Nb cavities. In this way, the first set of mid-T treated samples were produced with cavities at Zanon Research & Innovation Srl. The cavity performances have been improved with lower BCS and residual resistances, however the residual resistances were varied very different between 3-12 nΩ and didn’t achieve the low values as we expected. Thus, the characterization of these samples is discussed, and the source of residual resistance mitigation has been studied here in detail. We present our investigation on potential origins. For this, we used XPS, MOKE and Auger measurements to study the surface magnetic domains and stoichiometry of structures.
The performance of superconducting cavities depends extremely on the material and surface properties. In the last decades processes have been developed for the successful series production of accelerating cavities needed for large scale facilities like the European XFEL. A main feature of these cavities are relatively large beam ports on both sides which can be used for the surface treatment processes. In contrast, superconducting gun cavities have only one beam port and a half-cell with a back-wall acting as mirror plate with some small space for the cathode in the center. Being apparently only a small feature, this fact tuns out requiring special attention for the surface treatment. This is in particular the case, if the target are similar high gradients like in the accelerating cavities. In our contribution we present the experience made within the last years and how we finally achieved high gradients.
The self-consistent nonlinear dynamics of a relativistic charged particle beam interacting with its complete self-fields is a fundamental problem underpinning many of the accelerator design issues in high brightness beam applications, as well as the development of advanced accelerators. A novel self-consistent code is developed based on a Lagrangian method for the calculation of the particles’ radiation near-fields using wavefront/wavelet meshes via the Green’s function of the Maxwell equations. These fields are then interpolated onto a moving mesh for dynamic update of the beam. This method allows radiation co-propagation and self-consistent interaction with the beam in 2D/3D simulations at greatly reduced numerical errors. Multiple levels of parallelisms are inherent in this method and implemented in our code CoSyR [1] to enable at-scale simulations of nonlinear beam dynamics on modern computing platforms using MPI, multi-threading, and GPUs. Our simulations reveal the slice emittance growth in a bend and the interplay between the longitudinal and transverse dynamics that occurs in a complex manner not captured in the 1D longitudinal static-state coherent synchrotron radiation model. Finally, we show that surrogate models with symplectic neural networks can be trained from simulations with significant time-savings for the modeling of nonlinear beam dynamics effects.
Radio-frequency (RF) modulations can influence the microbunching instability dynamics and serve to eventually control them with reinforcement learning (RL) methods. Implementing such a feedback system at the Karlsruhe Research Accelerator (KARA) will require that the action decided by the RL agent, in this case an RF modulation, is applied effectively to the electron beam. Such a modulation can be carried out at KARA by two different devices: the kicker cavity of the bunch-by-bunch feedback system and the accelerating cavities of the main RF system. The Low-Level RF (LLRF) feedback system would require hardware and firmware modifications to accept the continuous action signal given by the RL agent, so systematic measurements were performed to decide which system should be used in the future. Modulations around different harmonics of the synchrotron frequency were applied and the coherent synchrotron light emitted due to the microbunching dynamics analyzed. These measurements were also performed at negative momentum compaction optics, a regime in which the control of the microbunching instability could yield especially intense light.
A major part of the 520 MeV Cyclotron's RF system is the high-power RF amplifier. The amplifier is based on eight 4CW250,000B tetrodes. A new high-power tetrode or a high-power tetrode that underwent refurbishing could trip the RF system through inner sparks. The likelihood of those sparks should be reduced prior to applying nominal power to the new and refurbished tetrodes. This could be achieved by RF conditioning of these tetrodes on a test stand. The test stand represents a 150 kW RF amplifier loaded by a dummy load. The amplifier is built using common grid schematics. The test stand's output stage incorporates the 4CW250,000B tetrode that is under test. This paper describes the mechanical and electrical designs of the test stand, procedures of testing and conditioning for 4CW250,000B tetrodes, and the results of test stand's commissioning.
The superconducting radio-frequency (SRF) community has shown that introducing certain impurities into high-purity niobium can improve quality factors and accelerating gradients. We question why some impurities improve RF performance while others hinder it. The purpose of this study is to characterize the impurity profile of niobium with a low residual resistance ratio (RRR) and correlate these impurities with the RF performance of low RRR cavities so that the mechanism of impurity-based improvements can be better understood and improved upon. The combination of RF testing and material analysis reveals a microscopic picture of why low RRR cavities experience low temperature-dependent BCS resistance behavior more prominently than their high RRR counterparts. We performed surface treatments, low temperature baking and nitrogen-doping, on low RRR cavities to evaluate how the intentional addition of oxygen and nitrogen to the RF layer further improves performance through changes in the mean free path and impurity profile. The results of this study have the potential to unlock a new understanding on SRF materials and enable the next generation of SRF surface treatments.
A uniform distribution of nucleation tin sites is essential to the growth of high quality Nb3Sn thin film by vapor diffusion method. The less-nuclear zones were commonly observed in previous nucleation experiments. However, a fully understanding of the occurrence of less-nuclear zones has not yet been achieved. Here, the adsorption energy of nuclear agent SnCl2 on different crystal planes of niobium (Nb) including Nb (110), Nb (100), Nb (211) are studied through density functional theory (DFT) calculations and several types of adsorption configurations are optimized. The large differences of calculated adsorption energy of SnCl2 on three different crystal planes reveal strong crystal direction selectivity during nucleation stage. In addition, the phenomenon of nucleation experiment on large grain samples further consolidates the accuracy of the calculation results. The calculation results explain the presence of less-nuclear zones during nucleation process and provide guidance for the subsequent suppression of these regions.
Optical Stochastic Cooling (OSC) was recently demonstrated at Fermilab’s Integrable Optics Test Accelerator (IOTA) storage ring. This demonstration marked the first realization of the stochastic cooling (SC) principle in the optical regime and achieved a system bandwidth of approximately 20 THz, more than three orders of magnitude greater than state-of-the-art SC systems. The initial experiments, which used 100-MeV electrons and a radiation wavelength of 950 nm, included comprehensive measurements with both beams and individual electrons in one, two and three-dimensional configurations. Here we describe the results of these experiments, which did not include optical amplification, as well as our current development efforts at the Fermilab Accelerator Science and Technology (FAST) facility towards a high-gain, amplified-OSC demonstration in the near future.
Nb3Sn thin films are mainly used on superconducting radio frequency (SRF) cavities, single-photon detectors and RF logic circuits. Copper-based Nb3Sn thin-film SRF (TFSRF) cavities are promising for particle accelerators because they may combine the advantages of high thermal conductivity and high gradient. In this paper, a bronze method, including multi-layer deposition and heat treatment, was used to generate Nb3Sn thin film on copper substrates. We first made a precursor by sputtering a niobium layer on the copper substrate and then electroplating a thicker bronze layer. Then we annealed the precursor in a vacuum tube furnace to synthesize Nb3Sn film. Considering the morphology and superconductivity of the Nb3Sn films, we compared the effects of various annealing temperatures and optimized the preparing conditions. The samples characterization of the morphology and superconductivity showed that high-quality Nb3Sn thin films had been successfully deposited on copper substrates. The superconducting transition temperature Tc can reach higher than 17.0 K. This synthesis route provides a new approach towards high-stability Nb3Sn TFSRF copper cavities.
The Mainz Energy-Recovering Superconducting Accelerator (MESA), an energy-recovering (ER) LINAC, is currently under construction at the Institute for Nuclear physics at the Johannes Gutenberg-Universität Mainz, Germany. In the ER mode continues wave (CW) beam is accelerated from 5 MeV up to 105 MeV. The energy gain of the beam is provided through 2 enhanced ELBE-type cryomodules containing two 1.3 GHz 9-cell TESLA cavities each. By pushing the limits of the beam current up to 10 mA, a quench can occur at the HOM Antennas. This is caused by an extensive power deposition within the antenna. Calculations have shown that a power transfer of 1 W must be assumed. However, tests of the 1.5 GHz version of the TESLA HOM coupler have shown a quench limit of 43 mW in CW. To prevent a quench of the HOM antennas by high beam currents without mayor modification of the design of the HOM antenna and F-part it is necessary to find suitable materials. Nb3Sn and NbTiN can be applied as a coating to the HOM antennas and have higher critical parameters than pure Nb which will lead to a higher power limit. As a further approach to improve the power transfer the material for the HOM antenna will be changed to oxygen-free high thermal conductive (OFHC) Copper. The antennas with a Cu core will be coated first with Nb. The limit of the coated antennas will be tested with the cavities of a cryomodule from the decommissioned ALICE accelerator from STFC Daresbury.
The study and understanding of collective effects plays a vital role for fourth-generation light sources. These effects mostly need to be mitigated and controlled to achieve the design operational parameters. However, they can also be utilized to gain insights into the properties of the machine.
While the 3 GeV storage ring at the MAX IV light source is running in multi-bunch mode during user operation. Single-bunch operation is available in dedicated machine study shifts, providing the possibility to study collective effects at higher bunch currents. In such a current range an instability has been observed in the longitudinal plane. Above the threshold current of the instability a dynamic deformation of the bunch profile and a strong increase in energy spread occurs.
Dedicated measurements were conducted with multiple diagnostic tools such as time-resolved bunch profile measurements. First simulations of the observed effects were performed with a Vlasov-Fokker-Planck solver.
This contribution presents measurement results and draws a comparison to the simulations.
The existing code for particle scattering and tracking in collimation systems integrated in SixTrack, called K2, was migrated from the current software in FORTRAN, to a new Python/C interface integrated in the Xsuite tracking code that is being developed at CERN. This is an essential step towards a full integration of collimation studies using Xtrack, and will allow profiting from GPU computing advances and the BOINC volunteer computing network. Furthermore, several improvements to the functionality of the code were introduced, for example aperture interpolation for more precise longitudinal location of particle losses in a collimator. A thorough testing of the new implementation was performed, using as case studies various collimation layout configurations for the LHC Run 3 and HL-LHC. In this paper, the challenges are outlined and the first results are presented, including simulated loss maps which are compared to the reference results generated by SixTrack.
Optimization and design of particle accelerators is challenging due to the large number of free parameters and the corresponding lack of gradient information available to the optimizer. Thus, full optimization of large beamlines becomes infeasible due to the exponential growth of free parameter space the optimization algorithm must navigate. Providing exact or approximate gradient information to the optimizer can significantly improve convergence speed, enabling practical optimization of high-dimensional problems. To achieve this, we have leveraged state-of-the-art automatic differentiation techniques developed by the machine learning community to enable end-to-end differentiable particle tracking simulations. We demonstrate that even a simple tracking simulation with gradient information can be used to significantly improve beamline design optimization. Furthermore, we show the flexibility of our implementation with various applications that make use of different kinds of derivative information.
An upgrade project is ongoing at Elettra Sincrotrone Trieste for a 4th-generation storage ring light source called Elettra 2.0. The new machine poses new challenges in terms of performance of the accelerator and sub-systems. One concern, currently under investigation, is about the effects of the passive superconducting third harmonic cavity on the stored beam due to the presence of a dark gap in the beam filling pattern. A simulator based on an analytical frequency-domain model was developed to evaluate the variation of the synchronous phase and synchrotron frequency along the bunch train, as well as the distortion of the bunch profile. Experiments have been carried out in the present Elettra storage ring to characterize the harmonic cavity and to measure the ef-fect of transient beam loading by using the longitudinal multi-bunch feedback system. An ongoing benchmarking of the model and experimental results is reported.
The Karlsruhe Research Accelerator (KARA), the storage ring at KIT, allows short electron bunch operation with positive as well as negative momentum compaction factor. For both cases, the beam dynamics are studied. Using a line array camera KALYPSO (KArlsruhe Linear arraY detector for MHz rePetition rate SpectrOscopy), based on TI-LGAD, the horizontal intensity distribution of the emitted visible part of the synchrotron radiation is measured at a 5-degree port of a bending magnet on a turn-by-turn time scale. As the measurement is located at a dispersive section, the dynamics of the energy spread can be studied by measuring the horizontal bunch profile. The MHz acquisition rate and the low-light sensitivity of the line camera allow measurements at low bunch currents and the investigation of the microbunching instability. This contribution presents the results of the bunch profile measurements performed at positive and negative momentum compaction factor.
Coherent Synchrotron Radiation (CSR) occurs when electron beams traverse a curved trajectory. In novel accelerators, CSR poses a potential limit for electron beams to reach high brightness. While the longitudinal CSR wake has been well studied in one-dimensional theory and implemented in several simulation codes, transverse wakefields have received less attention. Following the recently developed two-dimensional CSR theory, we developed software packages in Julia to simulate the 2D transient CSR effects. To speed up computation for CSR wakes, the packages have GPU compatibility. We applied these codes to simulate the 2D CSR effects in the LCLS-II and FACET-II particle accelerators at the SLAC National Accelerator Laboratory.
A high-density temperature and X-ray mapping system has been developed.
The X-ray mapping system, which uses strips with 32 channels of X-ray sensors, is now ready for use. The current sensor chip was selected about 10 years ago for Nb cavities operating at 2K, but recent advances in SRF cavities have required detection at higher temperatures, such as 20K for Nb3Sn materials. The current sensor chip was selected about 10 years ago for Nb cavities operating at 2K, but recent advances in SRF cavities have required detection at higher temperatures, such as 20K for Nb3Sn materials. Therefore, we are searching for a new temperature sensing element. These are reported.
New S-band disk-loaded TM01-2pi/3-travelling-wave structures and pulse compressors have been developed for upgrades of the injector linac for SuperKEKB and Photon-factory storage rings in KEK. The structures 2-m long have ingenious disk irises with oval fillets reducing discharge in high-power operation and modulations in radius suppressing beam break-up instabilities arising from HEM11 wakefields. The pulse compressors are of compact spherical-cavity-type resonating at the degenerate TE112 dipole modes with a high Q-value of 98,000 and yield a peak power gain of 6.2. The structures generate an acceleration gradient of 25.9 MV/m in power operation of 40 MW by using the pulse compressor and stably accelerate a two-bunch beam with a bunch charge of 4 nC.
The relatively high transition temperature of A15 superconducting materials makes them a potential alternative to Nb for radio-frequency applications. We present PVD deposition of one A15 material, V$_3$Si, on Cu and sapphire substrates. The surface structure and composition of the films were characterised via SEM and EDX. The superconducting properties were investigated using a field penetration facilty, four point probe and SQUID magnetrometry. Analysis showed that the composition was slightly Si rich by a few percent with a granular suface structure. Despite this superconductivity was observed on both Cu and sapphire substrates with critical temperatures of 12.8\,K and 14\,K. Field penetration measurements were conducted through two different facilities.
The storage ring of the High Energy Photon Source will be driven by five higher-order-mode-damped 166.6 MHz beta=1 quarter-wave superconducting cavities operating at 4 K. Three prototype cavities were manufactured in Beijing and the surface preparations were conducted in Ningxia and Beijing. The cavities were subsequently vertical tested at PAPS in Huairou (Beijing). The cavity Q0 at design voltage of 1.5 MV reached 3.8×109 at 4 K, exceeding the design goal of 1×109. One cavity was subsequently welded with a helium jacket and vertical tested at 2 K achieving an RF performance comparable to the undressed cavities. No chemical polishing was conducted for the jacketed cavity.
Superconducting radio-frequency cavities made out of niobium form the fundamental block of modern particle accelerators. A model proposed by Gurevich [1] suggests the use of a superconductor-insulator-superconductor (SIS) structure to achieve higher accelerating fields and a reduced surface resistance beyond the thermodynamic limits of Nb. As a first step to pursue this approach, a single-cell cavity was coated with a thin Al2O3 film via atomic layer deposition (ALD) to create an insulating layer [2] and baked for 3h at 300°C (mid-T heat treatment) [3]. In parallel, a mechanically polished two-grain-Nb sample was treated and coated analogically to the cavity. To further understand the RF performance of the coated and annealed cavity, an XRR analysis of the sample was carried out at each processing step to follow the changes in the niobium native oxides at process conditions (120°C) and throughout the chemical deposition and show that the coating technique and the resulting structure form a viable way for a further tailoring of cavity properties.
An important problem in present accelerators is the determination of the electromagnetic (EM) wakefields and their effect in the machine performance. These wakefields are generated inside the accelerator vacuum chamber due to the interaction of the particle beam with the surrounding structure. Among the properties that characterize their impact on the machine are the beam coupling Impedance in frequency domain, and the wake potential in time domain. An accurate evaluation of these properties is crucial to effectively predict dissipated power and beam stability. This paper presents an open-source tool that integrates the EM wakefields for general 3D structures and computes the wake potential and impedance for longitudinal and transverse planes. Its usefulness is verified with the open-source EM-solver WarpX and benchmarked with the commercial software CST Studio.
Thanks to recent evolutions of electromagnetic computer-aided engineering tools, nowadays the simulation of complex particle accelerator components is feasible by commercial software packages. A practical limitation of these tools is strictly related to the solver ability to discretize real devices’ material and geometry into a numerical model, which, in some particular situations, could lead to ambiguous results. To address this issue, this paper presents the realization of a microwave test bench for the electromagnetic characterization of the prototypes of some components and devices designed for Elettra 2.0, which is exploited to experimentally check the results provided by the simulation platforms.
The tracking code PLACET is widely used in the linear collider community to simulate the beam dynamics. It is a powerful tool for analyzing the static and dynamic imperfections in the lattice and has many built-in correction techniques. The original PLACET code was written in C with a TCL interface. Detailed data analysis including plotting is often performed with other programming languages, primarily Python. This paper describes the project of the Python application programming interface (API) for PLACET.
Space charge forces represent main induced effects in an RF-injector that degrade the beam quality. In this scenario the laser distribution sent on the photocathode acquires an
important role in the emittance compensation process, as the slice analysis shows. A novel model of space charge forces is proposed for bunch with arbitrary charge distribution to derive expressions of self-induced forces. As the performance of the fields near the cathode is under present analysis, we can investigate use of this model in low charge regime. Further, the model has been benchmarked with the behavior of the distributions present in the literature and studied for new ones. It has also been applied for the study of the optimization of a C-band hybrid photoinjector now being commissioned, thus explaining the factor two reduction of the emittance observed at the exit of the gun by changing the initial distribution at the cathode.
Thus ends 63 years without a theory of longitudinal capture able to predict the final beam distribution and optimize the voltage law. We show the relationship between average values of the initial and final Hamiltonian is a universal function independent of voltage law, provided the adiabaticity parameter is small. The deviations from average are also given. This means the bunch profile and energy spectrum are predictable, without particle tracking. Beam measurements at the BNL AGS Booster and MedAustron are also reported.
Design of circular lattices involves optimizing figures of merit (FoMs) characterizing the beam properties subject to the constraint that the beam distribution function be approximately periodic in trips around the lattice. We have developed an algorithm that accomplishes this with minimal computational effort. The algorithm takes advantage of recent developments in adjoint techniques * that allow the derivatives of the FoM with respect to the many parameters describing the lattice to be evaluated. The present description of the accelerator is based on the 10 second moments of the beam distribution function in the transverse phase space. However, extensions to kinetic descriptions will be discussed. Our algorithm, works as three separate minimizations run concurrently. These three working together force the beam into a periodic state, while varying parameters to minimize an FoM. An examples of a 10 - period FODO lattice will be presented.
High brightness electron beams enable a wide spectrum of applications ranging from short wavelength radiation sources to high gradient wakefield acceleration. The rich dynamics that are intrinsic in charged particles accelerated in complex systems require a careful description in the analysis and design of a given machine, particularly regarding its stability. Numerous computer codes are in use by the accelerator community for such purposes. In particular, MILES is a simple tracking code we have developed that allows fast evaluations of collective effects in RF linacs. In this paper we extend the simple models previously developed to describe specific, diverse applications that can benefit from the fast simulation tools developed in MILES. Examples of this kind include particle driven acceleration schemes in a plasma where driver and witness beams propagate in the ``comb" pulse-train configuration. Specifically, we investigate the self-induced fields excited within both the rf-linac stage and the capillary. Further, we discuss additional advanced topics such as wakefield effects in planar FEL undulators and the emission of coherent synchrotron radiation in a magnetic chicane.
The microbunching instability is one of the most significant effects,
which can lead to a severe degradation of the beam quality in the linac
section of free-electron lasers.
Direct analytical treatment of the microbunching instability is however
challenging.
In particular when multiple bunch compression stages are considered,
an exact closed-form expression for the charge density of the electron bunch
typically cannot be derived.
As a remedy, perturbative methods might be considered.
Here, the instability is investigated by analyzing the propagation of
small perturbations to an otherwise stable phase-space density.
One such approach is based on the expansion of the collective
Perron-Frobenius operator of the collective system into a Frechet-Taylor
series.
Applying the expanded Perron-Frobenius operator to a slightly perturbed
phase-space density allows to derive closed-form expressions for the
propagated perturbation term, potentially to arbitrary order.
In this contribution new advances in a perturbation theory based on the
Frechet-Taylor expansion of collective Perron-Frobenius operators are
presented.
The ALBA synchotron operates in a Touschek dominated lifetime regime, which depends mainly on the momentum acceptance and the transverse beam size along the machine. Although in the current ALBA machine the RF dominates the momentum acceptance, this will not be the case for the foreseen upgrade of the machine ALBA-II. For this reason, we have developed an algorithm to optimize the beam lifetime by varying the sextupole magnets. This algorithm is based on the Powell optimization of the Robust Conjugate Direct Search (RCDS) method, and several tests have been performed at the present ALBA machine. In this case the sextupole settings are first modified so that the RF is no longer the only limiting factor in the momentum acceptance. The algorithm optimizes the ALBA beam lifetime by varying the sextupoles to follow a constant chromaticity, while the skew magnets are tweaked to keep the beam sizes constant during the optimization. This paper shows the experimental results using this algorithm, and discusses its application to the ALBA-II case.
While the design of the ALBA-II is in progress, it is required to assess the consequences of realistic imperfections such as alignment tolerances and magnetic errors. Compensation of insertion device induced optics variation has been studied, as well as the small impact on the emittance due the introduction of 3 T superbends. We demonstrate that non-linear optics is rather robust in the presence of realistic imperfections, rendering a ±6 mm dynamic aperture sufficient for off-axis injection and a large momentum acceptance that supplies more than 5 hour lifetime including errors. Moreover, studies in preceding low emittance light sources required simulating the full accelerator tuning, starting from the commissioning phase. To this end, the Simulated Commissioning (SC) toolbox has been used intensively. Specific set of tests have been developed to complement the SC simulations including lifetime and dynamical aperture calculations assuming a possible operation in full coupling.
KIT operates the storage ring KARA (Karlsruhe Research Accelerator) as an accelerator test facility, which serves as a testbed for different electron beam-based experiments. Thus, it motivates to study the beam conditions extensively.
To extend the existing characterisation of non-linear parameters, the amplitude dependent tune shift (ADTS) was measured. ADTS is typically controlled by octupole magnets in a storage ring, which are not available at KARA, but the installed insertion devices exert a certain octupole component on the beam resulting in a change of the ADTS.
This contribution presents measurements of the amplitude dependent tune shift for different combinations of active insertion devices.
Many high intensity proton or ion accelerators employ sources with solenoidal magnetic fields that produce beams carrying a large amount of angular momentum. To simulate such beams, one has to generate a 4D transverse phase space distribution with the right amount of angular momentum as initial conditions. In this paper, we first show that such distributions can be obtained through different methods such as linear transformation or the addition of azimuthal impulses. Next, we discuss how the resulting distributions differ, whether such differences affect beam transport, and which method tends to produce more realistic distributions. We hope that these studies will help clarify simulations in high intensity ion and proton accelerators, particularly in the front ends.
A new method is introduced to process the closed orbit modulation by two corrector magnets modulated with sinusoidal waveforms. The new method can extract linear optics information from tens of thousands of orbits and represent such information with only a few parameters per beam position monitor. The concise form makes it easy to fit for linear lattice errors. The method has been demonstrated for linear optics correction on SPEAR3 and NSLS-II storage rings. One iteration of optics correction, including data taking and lattice fitting, takes only tens of seconds.
Beam splitting can be performed by adiabatic crossing of a given one-dimensional non-linear resonance. This process is routinely used at the CERN PS to deliver the proton beam to the SPS fixed-target physics. To improve the efficiency of the intensity sharing between the various beamlets, a dipole kicker can be used to excite the beam during the resonance crossing process. This entails a double-resonance crossing phenomenon that will be described and discussed in detail in this paper.
We explore the physics of high-current electron beam propagation through the accelerating cells of linear induction accelerators (LIAs), using a field-adapted coordinate transformation that extends the usual rotating Larmor frame analysis to account for simultaneous acceleration. This is useful for LIAs, since the focusing solenoids must be integrated into the accelerating cells to transport the high-current beam, and therefore the axial electric and magnetic fields overlap significantly. Existing LIA analysis methods rely heavily on numerical envelope equations solvers and particle-in-cell (PIC) simulations to track the beam through these fields. While these tools are essential for validating a design or a proposed tune, further insight into the development of such designs or tunes could be gained by developing an improved analytical model of the beam’s propagation through these overlapping fields. By analyzing the beam in a rotating frame with a complex Larmor phase, we seek to develop electric and magnetic field profiles that minimize effects that would increase the beam emittance, such as spherical aberration and parametric amplification of envelope oscillations.
Single-bunch instabilities are among the major effects limiting beam intensity in synchrotrons. In the case of a light source with ultra-low emittances, this might be a critical issue causing poor performance of the synchrotron. This study elaborates on the case of the Diamond-II storage ring showing the results of particle simulations for different configurations of the updated lattice and the impedance model. Alongside with the results of simulations, we present an updated database of the Diamond-II impedance. The resulting impedance-induced betatron tune shifts, bunch lengthening, and synchrotron phase shifts obtained in simulations agree with analytical predictions. We obtain optimal parameters for horizontal and vertical chromaticities for all possible lattice and impedance configurations considering chromaticity variation as one of the measures to mitigate single-bunch instabilities.
As part of the Diamond-II upgrade project, the booster synchrotron is due to be replaced with a low-emittance solution that enables efficient injection into the Diamond-II storage ring. The new booster lattice uses cells of combined-function gradient bends that integrate dipole, quadrupole and sextupole components into single magnets, alternating between focussing and defocussing bends. Accurate modelling of these magnets in particle tracking codes is vital to ensure the beam dynamics is accurately simulated during the entire ramp. In this paper we report on the methods used to correctly model the Booster-II dipole magnets and summarise the impact on lattice performance.
Formulae to compute the footprint (amplitude-dependent detunings) and Resonance driving terms RDT, generated by long-range beam-beam collisions and wire correctors have been implemented in a Python code. The paper briefly outlines the method and code and provides several examples of its usage. The maximum extent of the footprint (in geometric sense) can be efficiently computed.
We adopt the standard field matching technique to solve the general electromagnetic problem consisting of two parallel layers with arbitrary complex relative permittivity and permeability. Analytical formulae for the longitudinal impedance are discussed in the general case, and in the specific case of a two-layer system consisting of a metal-coated ceramic chamber. The solution of the electromagnetic problem allows also for the calculation of the power density deposited on the metal coating, thus permitting to address the important issue of the ceramic chamber beam-induced heating. The analysis is discussed with the parameters of the NSLS-II storage ring.
The potential in the Radio Frequency Quadrupole (RFQ) can be expressed as a sum of a transverse multipolar expansion: $\sum_{m=1}^\infty{A_{0m}}\left(\frac{r}{r_0}\right)^{2m}\cos(2m\theta)$, and a longitudinal term expressed as sum of Bessel functions: $\sum_{m=0}^\infty\sum_{n=1}^\infty A_{nm}I_{2m}(nkr)\cos(2m\theta)\cos(nkz)$. Since the paper of Kapchinskii and Teplyakov \cite{osti_4032849} this potential is used considering only the first term in transversal and longitudinal components, unfortunately such approximation does not reproduce properly a realistic RFQ as the one installed at the European Spallation Source (ESS). In this paper we evaluate the potential when more terms are considered and we compare it with the field map obtained from a numerical Poisson solver used at ESS.
Minimizing resonance driving terms (RDTs) is a traditional approach to enlarge the dynamic aperture (DA) of a storage ring. However, small RDTs can not guarantee a large DA. In this paper, the fluctuation of RDTs along the ring is taken into consideration. A large number of nonlinear lattice solutions based on one double-bend achromat lattice are analyzed. The results show that minimizing the RDT fluctuations can more effectively enlarge the DA area than minimizing the commonly used one-turn RDTs. Also, reducing the third-order RDT fluctuations is beneficial for controlling the fourth-order RDTs and ADTS terms. Then we use it as an objective to optimize the nonlinear dynamics and good results are obtained.
The CERN Linear Electron Accelerator for Research (CLEAR) has been operating since 2017 as a user facility providing beams for a large variety of experiments. Its RF photocathode-based linear accelerator can accelerate electrons up to 220 MeV with a bunch charge of 0.1-1.5nC with single or up to 150 bunches per train. The flexibility of providing various beam parameters following user demands brights drawbacks and complexity in operating the accelerator. Standard beam steering based on the sequential variation of quadrupole and corrector magnets, performed by an operator manually, results in a very time-consuming process. This paper presents a tool we developed for automatic and global Beam-Based Alignment (BBA) for CLEAR based on dispersion-free steering and one-to-one corrections to transport beams with various charges and time structures.
High luminosity electron-positron linear colliders constitute a fundamental instrument in the field of elementary particle physics. The ``Cool copper collider", or C3, is a proposal for a 250 COM GeV Higgs factory, with possible extension to the TeV-scale, and it represents a promising candidate for the near future high energy physics. The C3 infrastructure is conceived as a modular facility utilizing cryogenic, distributed coupling standing wave accelerating sections. Interestingly, the independent feeding scheme allows for arbitrary phase advance among consecutive linac cells. The latter becomes part of the parameter space affecting the optimal acceleration and, thus, configurations alternative to the standard standing wave pi-mode can be investigated. Here we use the tracking code MILES to study both short and long-range beam breakup effects in various phase advance scenarios. The analyses include the intermediate stages of the facility starting from a simple 3 GeV demonstrator as well as the 250 and 550 GeV working points. Further, possible mitigation techniques are aimed at establishing the tolerance for the alignment of the accelerating structures.
The accurate analysis of any possible source of beam instability is mandatory for the design of a new particle accelerator, especially for high current and ultra low emittance synchrotrons. In the specific case of instabilities driven by the coupling between the charged particle beam and the electromagnetic field excited by the beam itself, the corresponding effect is estimated through the beam coupling impedance. The modeling of this effect is fundamental to perform a rigorous evaluation of the coupling impedance budget able to account for all devices present in the entire machine. To deal with this problem, this paper focuses on the estimation of the contribution of the joints lying between the different vacuum chamber sections, by performing a comparative numerical analysis that takes into account for different aperture gaps between the flanges. The results point out the criticality of many small-impedance contributions that, added together, must be lower than a predefined impedance threshold.
The NEWGAIN (NEW GAnil INjector) project aims at supplying higher mass-to-charge ratio ions (from A/Q=3 to 7) with an energy of 590 keV/A to the present SC-Linac of SPIRAL2. It comprises a new SC source, a dogleg LEBT, an 88 MHz RFQ, and a MEBT, optimized for a current of up to 350 uA of uranium. Additionally, an extension of the present LEBT is considered to merge into the new one. This paper presents the last layout and beam dynamics results for these new lines, including the mass resolution, chopping, admittance slit and tuning scheme as the Design Study Phase ends.
Accelerating technology is evolving towards compactness and high intensity. In such a scenario, beam loading effects result in significant energy losses for long trains of bunches. To address these effects, we generalised the Beam Loading module of the tracking code RF-Track to allow the study of beam loading independently of the particle type and velocity or the accelerating cavity design. This paper describes the implementation of this effect in standing wave (SW) structures. Particular attention has been devoted to guns for photoinjectors, where causality plays an important role, and one must address the non-ultrarelativistic behaviour of the emitted particles. Finally, we will discuss the simulation of these effects in the CLEAR facility at CERN.
The Extremely Brilliant Source (EBS) at the European Synchrotron Radiation Facility (ESRF) is a 4th generation light source operating with a horizontal emittance of 135 pm. This low horizontal emittance reduces the lifetime in filling modes with high current per bunch. This will be alleviated in the future with an active 4th harmonic cavity. In order to simulate the effect of the 4th harmonic cavity on the EBS performance, beam loading needed to be added included to PyAT (Python – Accelerator Toolbox). Here, we introduce the beam loading model and show the benchmarking simulations with theory and other simulation codes.
The Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab employs recirculating linac SRF technology to generate a high polarization 12 GeV electron beam
for nuclear physics users. New opportunities to study multipass energy recovery have also emerged with the proposal of a 5-pass energy recovery demonstration, ER@CEBAF. New beam optics with minimized beta functions have been developed and tested to avoid collective beam instabilities for multi-pass beams and meet the beam requirements of the nuclear physics community. To enable energy recovery for a common arc beam transport of five passes, achromatic and isochronous arc optics conditions were satisfied by re-designing the transverse optics of CEBAF. This paper
focuses on beam studies conducted to study the newly-designed, low-dispersion, lowest energy arcs for CEBAF operations and ER@CEBAF.
Beam-induced heating of equipment can have several undesirable effects, including rendering the equipment temporarily inoperative, equipment degradation and/or damage. Hence, to avoid these problems, it can be necessary to limit beam intensity. Beam-coupling impedance mitigation of existing devices and/or design optimization of new accelerator elements are essentials to overcome these limitations. In this framework a very good example is the optimization of the SPS kickers beam-coupling impedance for beam-induced heating mitigation. This paper describes the beam-coupling impedance measurements and simulation studies performed to identify and potentially remove the intensity limitation arising from the excessive beam-induced heating of a SPS injection kicker.
Laser-plasma electron beams are known for their large divergence and energy spread while having ultra-short bunches, which differentiate them from standard RF accelerated beams.
To study the laser-plasma beam dynamics and to design a transport line, simulations with CODAL [1], a code developed by SOLEIL in collaboration with IJCLab, have been used. CODAL is a 6D 'kick' tracking code based on the symplectic integration of the local hamiltonian for each element of the lattice. CODAL also includes collective effects simulations such as space charge, wakefield and coherent synchrotron radiation.
To validate the studies in the framework of Laser-Plasma Acceleratior developpement, results from CODAL have been compared to TraceWin [2], a well-known tracking code developed by CEA.
The comparison has been made using the outcome of Laser WakeField Acceleration (LWFA) particle-in-cell simulations as initial start particle coordinates from a case study of PALLAS project, a Laser-Plasma Accelerator test facility at IJCLab.
The Rapid Cycling Synchrotron is the key part of the China Spallation Neutron Source with the repetion rate of 25Hz. The lattice of the RCS is based on triplet cells with the superperiod of four. Due to ultilizing the trim quadrupoles in June 2021, the BPM OffSets were carefully measured, and the beam operation is more steady. In this paper, we will review the preparation of BPM OffSets measurements with the virtual accelerator, and the results of the measurements with beam.
A common feature in the design of low-emittance lattices is the small momentum compaction, which implies a short nominal equilibrium bunch length. A short bunch length can lead to beam-induced heating of the storage ring vacuum components, and, combined with the small transverse emittances, can degrade the beam quality and pose severe limitations on the beam lifetime. To mitigate the aforementioned issues and improve the lifetime and quality of the beam, a common procedure is to use a higher-harmonic cavity (HHC) system, which leads to an increase of the equilibrium bunch length without an increase of the energy spread. An important issue in the design of an HHC system is the proper choice of the multi-bunch configuration and the HHC parameters, both in terms of HHC performance limitations and beam stability. In this contribution we discuss numerical simulations of HHC effects, with parameters of a 3HC system for the NSLS-II low-emittance upgrade, addressing both beam stability and the performance limitation due to a gap in the uniform multi-bunch configuration.
The upcoming Jefferson Lab K-Long experiment at Hall D will require unique beam conditions with a much lower bunch repetition rate and atypically high bunch charge. To optimize the Continuous Electron Beam Accelerator Facility (CEBAF) injector for this experiment, we performed Multi-Objective Genetic Optimization (MGO) using General Particle Tracer (GPT) to determine the magnetic elements and RF settings necessary for the K-long bunch charge (0.64 pC) at 200 kV. We also investigated the transmission and beam characteristics of low to high charge per bunch electron beams through the injector for simultaneous operations of all four CEBAF Halls and characterized the transmission as a function of the photocathode laser spot size and pulse length. Our findings provide valuable insights into optimizing the CEBAF injector for the Jefferson Lab K-Long experiment, as well as for other experiments with similar beam conditions.
In the framework of the High Luminosity Upgrade of the LHC (HL-LHC) the beam intensity from the injectors must be doubled while keeping longitudinal beam parameters unchanged. As such, high-quality beams with high intensities are required also from the Proton Synchrotron (PS). The beam coupling impedance plays a crucial role and mitigation measures must be taken to remain within a stringent impedance budget. Kicker magnets are important contributors to the overall broadband impedance of the PS. Moreover, the detailed study of kicker impedances revealed additional resonant modes which may be critical for the beam stability. The longitudinal beam coupling impedance for the fast extraction kicker KFA79 is presented in this study, and a solution to reduce the impedance of the critical resonant modes is introduced. Electromagnetic (EM) simulations have been performed to determine the impedance behaviour. Finally, the insertion of transition pieces between magnet modules is presented as a measure for mitigating the low frequency resonant impedance contributions.
Following the successful implementation of the LHC Injectors Upgrade (LIU) project, the CERN injectors were re-commissioned in 2021 and have been delivering beam to the LHC since 2022. The operationally delivered beam is well within the specifications regarding its brightness. However, heavy population of non-Gaussian tails of the transverse beam profiles were observed.
These tails lead to high losses at LHC injection and degrade the luminosity reach of the LHC.
This paper follows the studies to characterize the transverse
profiles along the accelerator chain: the Proton Synchrotron Booster (PSB), the Proton Synchrotron (PS) and the Super Proton Synchrotron (SPS). The methodology to measure the emittance and the tail population as the studies aimed at reducing this population will also be discussed.
Neural network (NN) has been tentatively combined into multi-objective genetic algorithms (MOGAs) to solve the optimization problems in physics. However, the computationally complex physical evaluations and limited computing resources always cause the unsatisfied size of training set, which further result in the combined algorithms handling strict constraints ineffectively. Here, the dynamically used NN-based MOGA (DNMOGA) is proposed for the first time, which includes dynamically redistributing the number of evaluated individuals to different operators as well as some other improvements to handle constraint and preference of objectives. Radio frequency cavity is designed by this algorithm as an example, in which four objectives and an equality constraint (a sort of strict constraint) are considered simultaneously. As a result, DNMOGA considerably improves both the number and competitiveness of the final feasible individuals, and shows the potential to completely replace the manual procession in this question. In general, DNMOGA is instructive for dealing with the complex situations of strict constraints and preference in multi-objective optimization problems in accelerator physics.
(The corresponding paper has been accepted).
A 1.2-m-long superconducting wiggler with the peak field of 4.3 T and period length of 70 mm has been recently installed for the High energy Engineering X-ray (HEX) Diffraction beamline at Cell 27 of NSLS-II Storage Ring. The commissioning result for the orbit feedforward system will be presented, including the uncorrectable dispersive pattern in horizontal orbit and non-negligible hysteresis effects. The impact of large residual field integrals on the active interlock envelope will be also discussed.
The PETRA IV upgrade project is aiming at building a 6 GeV diffraction-limited light source. The storage ring’s off-axis accumulation injection scheme will allow generating a wide range of filling patterns for the needs of photon science users. To preserve high beam quality and low transverse emittances it is imperative to ensure beam stability against collective effects. In this paper we investigate the impact of different filling patterns on the coupled-bunch stability in the ring using a semi-analytical Vlasov solver.
We present a theory of coupled-bunch longitudinal instabilities for storage rings that employ a harmonic cavity to lengthen the bunch. We find growth rates associated with the m=0 and m=1 modes for both "optimally" and "overstretched" bunches; the former is a Robinson-like instability, while the latter corresponds to the "periodic transient beam loading" effect described in Ref *. By self-consistently including longitudinal feedback, we then show that controlling the instability may require feedback damping rates that are higher than the growth rate. For parameters considered, we find that controlling the the m=0 mode may require damping rates that are up to 2 times higher than the instability growth rate, while in many cases the m=1 mode cannot be stabilized with any feedback gain. We verify these predictions using particle tracking for APS-U like parameters.
A promising approach for compact linear accelerators in the THz frequency range is based on dielectric-loaded waveguides (DLWs). Higher breakdown fields expected at THz frequencies should enable higher acceleration gradients. However, the accelerating mode of a cylindrical DLW (TM01) is not the fundamental and only mode inside the waveguide at operating frequency. Therefore, a method is required to ensure excitation of the proper mode only. Here we present a coupler design to convert the guided electromagnetic TE10 mode in a rectangular waveguide to the TM01 mode of a cylindrical DLW. The symmetry of the structure and its feeding waveguides allow us to suppress all undesired modes and consequently increase the coupling efficiency to the desired mode. Moreover, this configuration shows an extremely wide bandwidth and low quality factor suggesting the coupler is also suitable for short THz pulses.
Korea-4GSR is a greenfield electron storage ring with circumference of 800 m and natural emittance of 60 pm. Preliminary conceptual lattice design of Korea-4GSR is fully periodic 28-cell H7BA. By keeping the conceptual design as much as possible, we have been exploring modification on the design for higher brightness and better nonlinear properties such as dynamic aperture and Touschek lifetime. We present which optics conditions can be satisfied upon the current lattice framework and how much cost is required in terms of magnet strengths and aperture radius.
Recently, a double-double bend achromat (DDBA) lattice is designed for Hefei Light Source (HLS), a second-generation synchrotron radiation light source, which reduced the natural emittance a lot. In this paper, to further reduce the emittance and improve the brightness, a DDBA-hybrid 6BA lattice is proposed and applied to the design for the potential HLS upgrade. With more bending magnets, the emittance is significantly reduced from 36.4 nm∙rad to 1.8 nm∙rad at the cost of two short straight sections. After nonlinear dynamics optimization, the dynamic aperture and momentum aperture are large enough for the requirements from beam injection and lifetime.
Expressions to quantify betatron mismatch and chromatic effects are frequently used in accelerator physics, but their derivations are not given in standard text books, making their interpretation difficult. First parameters describing betatron mismatch are introduced using normalization with respect to reference Twiss parameters describing a lattice. In a second step, the derivatives of these mismatch parameters with respect to the relative momentum offset are considered and lead naturally to the Montague W functions and a phase angle computed as well by standard lattice programs.
Synchrotron light sources of the 4th generation typically use varying radius dipoles (also called longitudinal gradient bends). The longitudinal variation of these magnets needs to be properly modeled as the preconditions of the common local 2D approximation are only fulfilled at certain places.
We describe our concept of modelling such magnets using basis functions (approximately) fulfilling Maxwell Equations and compare these models to the magnetic fields calculated for various magnets foreseen for BESSY II or BESSY III.
Multi-objective evolutionary algorithms (MOEAs) are usually used to optimize two or three objectives in the accelerator field and perform well. However, the optimization objectives are often equal to or greater than four for an accelerator, which causes severe deterioration of the performance of these algorithms. Recently, many-objective evolutionary algorithms (MaOEAs) that can solve the problems with four or more optimization objectives have received extensive attention. In this paper, two diffraction-limited storage ring (DLSR) lattices of ESRF-EBS type with different energies are designed and optimized using three MaOEAs and a widely used MOEA. The initial population has been found to have a significant impact on the performance of the algorithms, and this impact has been carefully studied. The performance of the four algorithms is compared, and the results demonstrate that the grid-based evolutionary algorithm (GrEA) has the best performance. MaOEAs are applied in many-objective optimization of DLSR lattices for the first time and lattices with the natural emittance of 116.70 pm∙rad and 23.08 pm∙rad are obtained at energies of 2 GeV and 6 GeV, respectively, both with reasonable dynamic aperture and local momentum aperture (LMA). This work provides a valuable reference for future many-objective optimization of DLSRs.
(The corresponding paper is under PRAB review)
In this paper we present the design and validation of a compact LEBT for the LINAC 7 project. Specifically, the LINAC 7 project focuses on building a new generation, low-energy, low-current compact accelerator. The core idea is to achieve an energy of 7 MeV in less than 12 m while maintaining enough current to generate isotopes for medical uses.
Through this work we explain the procedure we followed for the design, including the tests that we carried out to reach the final result.
This includes the iterations we needed to overcome various problems such as how to keep the LEBT compact and deal with cooling, when is the best time for packing factor calculation, how to solve mechanical problems,...
Although this LEBT is intended to be used with protons, further simulations have been carried out to show that it could be used for other species as well.
The Lanzhou Light Ion Cancer Therapy Facility (LLICTF) is a compact medical accelerator currently under construction. It is designed to treat cancer using a 230MeV, 30mA H+ beam and a 85MeV/u, 1mA 3He2+ beam. The facility comprises two ion sources, a low-energy beam-transport (LEBT), a Radio Frequency Quadrupole (RFQ), a medium-energy beam-transport (MEBT), and the main ring accelerating structure. Due to the presence of two ion sources, it is necessary to introduce a dipole magnet which is symmetrically focused as much as possible to meet the symmetrical focusing requirements of the LEBT beam. Therefore, a gradient dipole magnet has been designed to achieve this symmetrical focusing. This paper discusses the theoretical and simulated symmetric focusing of the gradient dipole magnet. It also analyzes the effect of fringe fields and space charge. Additionally, the paper presents the results of the model design with CST and the multi-particle simulation results with TraceWin.
For an experimental setup at the laser plasma accelerator (LPA) at the JETi Laser at Jena, Germany, an energy upgrade of a linear beam transport line has been studied. The transport line, originally designed to match the LPA beam to a transverse gradient undulator (TGU) at 120 MeV and successfully experimentally tested in 2014, will be upgraded to up to 300 MeV by employing stronger focusing quadrupoles. For these high strength quadrupoles, magnetic simulations as well as cooling and electrical calculations have been done. To develop fabrication procedures and magnetic measurement techniques, a prototype of the quadrupole magnet has been manufactured and tested at Karlsruhe Institute of Technology, Germany.
This paper is presenting the design, fabrication and magnetic measurement of the first prototype quadrupole magnet.
Lens based proton radiography is a powerful diagnostics technique capable of resolving ultra-fast processes on the ns-scale in dense matter with unprecedented micrometer spatial resolution. This unique performance is currently realized by the use of a chromatic imaging system consisting of four quadrupole magnets that are configured to suppress the most significant 2nd order position dependent chromatic aberrations of the proton distribution*. Systems of this kind are currently in operation in Germany (PRIOR-II at GSI, 4.5GeV p+) and in the US (pRad at LANL, 800 MeV p+).
As energy dependent 2nd order chromatic aberrations cannot be cancelled by any means, many experiments using dense targets suffer from a reduced depth of field caused by a large amount of energy loss straggling. This leads to a degraded image quality and also limits the physics output of those experiments.
In order to compensate for this, a prototype ion-optical achromatic imaging lens is currently being developed for low-energy 25MeV electron beams. Achromatic lenses are already in use at particle accelerator facilities in e.g. fragment separators, however, the developed system will be the very first of its kind designed solely for imaging purposes. The final 5-cell design consisting of 25 ion-optical elements has passed the design stage and is foreseen to be commissioned in 2024. It is planned to then expand this capability to the 800MeV proton beam of the LANSCE accelerator at LANL.
SLAC has been developing the parallel finite element electromagnetics simulation suite ACE3P (Advanced Computational Electromagnetics 3D Parallel) for accelerator modeling using high performance computing (HPC) platforms. ACE3P employs the parallel high-order finite-element method with conformal (tetrahedral) mesh for high-fidelity representation of geometry, and further accuracy can be obtained using quadratic surface and high-order elements resulting in reduced computational cost. Currently, the treatment of material properties applies to linear dielectrics and metals, wherein the electric displacement field is directly proportional to the electric field. There is a rapid need for new interaction regimes of high fields that would drive nonlinear response in materials which are in turn essential for novel accelerator applications. Moreover, efficient conversion between photons of different energies is needed for harmonic and THz generation, as well as quantum sensors which inherently require materials with second- or third-order optical nonlinearity. In this work we present the current status of the development of the nonlinear EM solver, in ACE3P which includes nonlinear response of the dielectric material. This utilizes parallel and scalable architecture to perform simulations and virtual prototyping on multiscale optical and quantum systems.
Particle accelerators require extensive optics measurement and correction. Due to the complexity of analytic treatments, numerical optimizations are often employed. A disadvantage of this approach is the lack of gradients, limiting optimization methods to derivative-free ones such as simplex or genetic algorithms. We explore a reformulation of beam optics that preserves gradient information by making use of efficient automatic differentiation tools from machine learning frameworks. First, standard beam dynamics computations are converted to a graph of operations on tensors that calculates objectives. Backpropagation is then performed to find parameter gradients and higher order derivatives. Using gradient-aware optimizer algorithms, we showed improved performance in beamline optics matching over existing tools. We also demonstrated an important use of differentiable models in Bayesian inference, whereby probabilistic estimates of magnet parameters and linear optics functions can be obtained from experimental measurements. Our results on test problems showed robust performance and estimates in agreement with standard LOCO methods.
An algorithm for determining the eigenvalues of the eigenfunctions of a
multilayer cylindrical waveguide is constructed. A relationship is found
between dispersion relations and impedances. A method for determining
the resonant frequencies of the wake field in the linear and helical
motion of a particle is described. The damping coefficients of
eigenmodes at resonant frequencies are determined.
The calculation of the volume of the phase-space stability region of hadron storage rings is currently performed through computer simulations of particles tracking in 6D coordinates, which are resource -and time- intensive processes. We have investigated in a previous paper the ability of an ensemble reservoir computing approach based on Echo State Networks to predict the long-term evolution of the radius of the phase-space region in which the motion of charged particles in hadron storage rings is bounded. Here, we perform a sensitivity analysis of the results of the Echo State Networks prediction with respect to different ways of splitting the original data set into a training, validation, and test set. This analysis confirms the validity of the splitting proposed in our previous paper and suggests that extending the validation phase too much is counterproductive.
Dynamic Aperture (DA) studies based on single-particle tracking simulations have proven to be a powerful tool for optimizing the performance of the Large Hadron Collider (LHC), as well as its future High-Luminosity upgrade (HL-LHC). The present paper presents the studies performed for the first year of HL-LHC operation at the beginning of the fourth operational run of the LHC. The main focus lies on the exploration of new optics scenarios such as flat optics, where the transverse beam sizes at the high-luminosity interactions points are not equal. Multi-parametric DA studies and Frequency Map Analysis are deployed to derive the best parameters for operation for the start and end of the luminosity leveling with flat optics.
A crucial common parameter for the new 4th generation machines is the reduced dynamic aperture at injection point.
Will be presented the analyzed strategies and what have already been done in order to reduce the emittance of the injected beam and garantee a good injection efficiency.
Limited dynamic aperture which is in the consequence of strong nonlinearities in a low emittance storage ring, is a challenging issue from beam dynamics point of view. In the present study, we have applied three families of focusing and defocusing octupoles to the storage ring lattice with the aim of increasing dynamic aperture and beam lifetime . We have discussed different methods to optimize of the position and strength of octupoles so that each octupole family fights a specific resonance driving term.
Hefei Advanced Light Facility (HALF) is a fourth-generation storage ring with an emittance lower than 100 pm∙rad. To assess the real performance, in this paper, static error effects are studied and corrected for HALF. Simulation corrections of closed orbit, linear optics and transverse coupling are presented and the results show that the HALF lattice has reasonable robustness. The emittance growth caused by error effects is acceptable and the nonlinear dynamics performance with errors considered is also favorable.
The beam screen for the Future Circular hadron-hadron Collider (FCC-hh) has a baseline design based on a copper (Cu) coating. Calculations have indicated that the resistive wall impedance will be the major contributor to the beam impedance for the FCC-hh at both injection and collision and that Cu might be on the limit to ensure beam stability. To increase the safety margin, it is desirable to reduce the resistive wall impedance. In this contribution, we present an approach to reduce the beam impedance based on the reduction of the surface resistance of the beam screen coating by using High-Temperature Superconductors based on REBaCu3O7-x coated conductors (REBCO-CCs). These HTS-CCs have transition temperatures around 90K, and critical current densities which are high enough even in the presence of strong magnetic field, being therefore good candidates to substitute Cu in the FCC-hh beam screen which will be operating at around 50K and under a magnetic field of 16T. Using experimental data generated on the surface impedance of REBCO-CCs, CST simulations have been performed and the beam impedance has been estimated for an elliptical beam screen with the same vertical dimensions as that of a pure Cu beam screen. A position and REBCO-CCs contribution dependence study to determine the optimum beam screen configuration will be shown. Resistive wall impedance studies using an ellipse is a step forward towards determining the performance of the REBCO-CCs on the FCC-hh beam screen.
We present the results of the first experiments on 4-dimensional phase-space tracking of a single electron in a storage ring, using a linear multi-anode photomultiplier tube for simultaneously measuring transverse coordinates and arrival times of synchrotron-radiation pulses. During the next few months, full 6D tracking will be implemented. This technology makes it possible to characterize the motion of a single particle, i.e. simultaneously tracking of amplitudes and phases for slow synchrotron oscillations and fast betatron oscillations. Complete tracking of a single particle enables the first direct measurements of dynamical properties, including invariants, amplitude-dependent tunes, and chaotic behavior.
Merging beams from multiple beamlines is critical to energy-recovering linear accelerators and beam-driven wakefield accelerators. Recently, a "straight-merger" beam line was proposed as a compact beamline to merge beams. The concept is based on a deflecting cavity with a superimposed dipole field. It provides a large deflecting kick at the injection phase where the RF and magnetic kicks add up ("deflecting mode") while a beam injected at a phase where the RF and magnetic field cancel out does not experience any net kick ("transparent mode"). A proof-of-principle beamline of this concept was built at the Argonne Wakefield Accelerator and experimentally tested. This contribution will discuss the experimental performances of the beamline.
Experimental beamlines often are regularly reconfigured to meet changing requirements of the experiments and to minimize beam losses. The configuration is usually done with the help of beam optics tools like MADX. These tools offer matching capabilities which allow to find solutions in terms of quadrupole strengths. However, such solutions are found by satisfying the given constraints only and do not take into account limited precision of actual quadrupole devices. Under the influence of quadrupole errors due to magnetic hysteresis, power converter trips etc, the original beamline optics often degrades. This results in beam losses or loss of focus at the experimental target. Readjustment of the optics costs valuable experiment time. Hence, it is desirable to operate a beamline configuration which not only meets the requirements but is also robust against quadrupole errors. Such a configuration will deviate from its nominal properties only by a small margin even when the quadrupole strengths deviate within specified intervals. We present the systematic exploration of beamline configuration space to identify robust configurations. The results are discussed for the BIGKARL beamline at Forschungszentrum Jülich and the findings are supported by experimental data.
The beam dynamics of a bunch both longitudinally and transversely play a major role in the design process of an RF cavity, from the feasibility of cavity lengths, to the focusing schemes required to maximise capture. Often, computer simulations track particles using computationally intensive numerical techniques, which can be extremely time-consuming to run. In this paper, we present a generalised analytical method to track macro-particles through RF structures, computing the 6D phase space elements at the end of each RF cell. The results show strong agreement with the well-benchmarked tracking code, ASTRA, however requires a significant reduction in computing power and run time. The results from this paper present a very promising means of streamlining future tracking simulations by increasing the computing efficiency with no significant detriment in accuracy.
Many accelerators employ axisymmetric structures, such as RF cavities, induction cells, and solenoids, to accelerate and transport charged particle beams. To analyze the motion of the beam in solenoids, it is common to make a transformation to the rotating Larmor frame. In the presence of an electric field, this transformation can be modified to obtain further simplifications in the equation of motion. In this paper, we explore the use of a complex Larmor phase to simplify the equations of motion in the presence of simultaneous axial electric and magnetic fields, such as those found in the induction cells of a linear induction accelerator (LIA). We also analyze the corresponding envelope equation and find that the natural emittance in this frame can be expressed in terms of familiar quantities.
In the lattice design of the BESSY II successor, the diffraction-limited, Multi-Bend-Achromat (MBA) storage ring BESSY III, HZB follows the approach of deterministic lattice design. MBA lattices are composed of rather simple sub-structures: the repetitive unit cell, two dispersion suppression cells at the end of the achromatic section, and the focusing doublet or triplet with the straight section. As demonstrated in earlier papers, these sub-structures can be strategically optimized, once the optimization criteria are clearly defined. This paper deals with the optimal distribution of the bending angle between the (identical) unit cells and the two dispersion suppression cells, aiming at the lowest emittance. Further, options for utilizing different numbers of chromatic sextupole families are investigated with respect to their impact on the tune shift with momentum. Finally, the need for and benefit of harmonic sextupoles are treated.
This paper is the follow-up of a previous one where we reported symmetry breaking as the main factor that establishes transverse resonance island buckets (TRIBs) close to a third-order random resonance in one of BESSY III design lattices by using a single knob. Here we present a more complete picture of the analytical framework and we show that there are two types of resonances close to which islands can be implemented. We give a brief overview of how this framework can be applied by using the BESSY III multibend-achromat (MBA) lattices as examples.
Corrugated structures have been used widely in X-ray free-electron laser facilities for chirp control, fresh-slice applications, and diagnostics. In this paper, we present a general method for calculating the short-bunch wakefield of corrugated structures with arbitrary shapes. At zeroth order, we give analytical solutions via the method of conformal mapping. At first order, we give steady-state wake calculation by solving a set of integral equations.
The Generalized Gradient (GG) formalism of Venturini and Dragt for describing static magnetic or electric fields has been implemented in the Bmad toolkit for accelerator simulations. In conjunction with this, a new method for calculating GG derivatives from a field table has been developed which avoids some of the problems of the Venturini and Dragt method. Generalized gradients are also implemented in the PTC toolkit developed by Etienne Forest which is interfaced to Bmad. This allows for construction of spin/orbital Taylor maps useful for nonlinear analysis and rapid tracking.
The growth rate of the Head-Tail mode 0 instability is related to the real part of the transverse beam coupling impedance. The SPS transverse impedance model, which includes the major impedance contributions in the machine, can be benchmarked through measurements of growth rates as a function of chromaticity. This paper summarizes the methodology established to explore a wider range of chromatic frequency shifts, and presents the measurements performed after the LHC Injectors Upgrade (LIU) for two sets of machine optics: nominal and low gamma transition. The measurements are compared with the current Impedance model to further study its degree of accuracy.
A solution is presented for the radiation field of a particle moving along
a helical trajectory in a cylindrical waveguide with multilayer walls. The
number of layers and their filling is arbitrary. The solution was obtained
by the partial domain method and is a generalization of the solution for a
resistive waveguide obtained earlier.
J-PARC MR is a high intensity synchrotron that accelerates protons from 3 GeV to 30 GeV. In MR, beam study for 1.3 MW upgrade plan is now in progress. The upgrade is done by shortening the repetition period and increasing the number of protons, and it is crucial to understand their effects on beam motion. Especially, the betatron function is one of the most important parameters that determines the beam motion. In MR, the betatron function has been measured by using turn-by-turn signal of the beam position monitor. Betatron function has been adjusted to match with model within 3% accuracy in relative error in low energy period. However, in evaluating the effects of space charge forces and eddy currents on beam optics whose impact will be largen by the upgrade, the accuracy of betatron function measurement during the injection and acceleration period will be even more important. In this study, we have attempt to match betatron function to model within 1% accuracy in relative error both in injection and acceleration period which has never been achieved in MR, by performing beta function measurement using COD response from the steering magnets in MR.
Pulsed electron beams probe the dynamics of matter out of equilibrium with high spatial and temporal resolution. Ultrafast electron diffraction in particular is sensitive to sub-angstrom, sub-picosecond scale atomic motion. To collect all the structural information available in an electron diffraction pattern, the experimentalist must control the angular magnification onto the detector plane. We present a case study demonstrating the advantage of angular magnification: investigating periodic strain in moiré materials. Strain waves with 10 nm wavelength appear in diffraction as satellites closely clustered around brighter Bragg peaks. We describe a quadrupole lens triplet that varies the effective drift distance $M_{12}$ between sample and detector from 80 cm to 8 m for our 140 keV electron beam, allowing us to zoom in on these moiré satellites. Three independently powered quadrupoles make it possible to eliminate astigmatism from a point-like probe. With the field strength achievable using quadrupole magnets, this magnification technique is also suitable for MeV beam energies.
Current and historic tracking studies of the RHIC accelerator lattice find difficulty in explaining the transmission efficiency of spin polarization from the AGS extraction to
RHIC storage energies. In this paper, we discuss mechanisms that result in resonant depolarizing behavior, beyond the usual intrinsic and imperfection resonance structures. In particular, the focus of this paper will be on higher-order resonances that become apparent in the presence of snakes. The set of conditions that identify higher-order spin-orbit resonances are 𝜈 = 𝑗0 + 𝑗 ⃗ ⋅𝑄⃗for integers (𝑗0, 𝑗) ∈ ℤ^4, where 𝜈 is the spin tune and 𝑄⃗ contains the orbit tunes. Note that we do not use the closed-orbit spin tune 𝜈0 but rather the amplitude-dependent spin tune 𝜈(𝐽𝑥, 𝐽𝑦, 𝐽𝑧) that depends on the phase-space amplitudes. While Sibrian snakes keep 𝜈0 at 1/2, the amplitude-dependent spin tune can deviate from 1/2 and can cross resonances during acceleration.
Crab Cavities (CCs) are a key component for the HL-LHC luminosity upgrade. To significantly reduce the Long-Range Beam-Beam (LRBB) effects a large crossing angle scheme is needed . The installation of 4 CCs per beam in each of the two main interaction points aims to restore the luminosity loss caused by the crossing angle. Noise injected through the Low-Level RF (LLRF) system in these cavities is known to be affecting the growth of the transverse bunch emittance. In this paper a new numerical study has been developed thanks to the new tracking tool Xsuite to study in depth this detrimental effect of both phase and amplitude LLRF noise. Both Long Range and Head On Beam Beam effects are included in the simulation together with the CC noise to evaluate the effects of the interplay between these strong non-linearities and the external noise. Furthermore, transverse bunch measurements show that the transverse distribution can be modeled as an heavy tailed q-Gaussian. To take this into account a particular focus is given to the linear matching and subsequent tracking of a multivariate q-Gaussian distribution in the lattice. The Emittance Growth Rate induced on both a Gaussian and a q-Gaussian bunch is computed. This study could serve as a basis to evaluate the cross-talk between the two beams introduced by their head-on interaction in this heavy tailed scenario.
In the presence of a tune spread induced by chromaticity or amplitude detuning, decoherence will lead to the damping of the beam centroid motion after a single transverse excitation. This in turn has implications for the analysis of turn-by-turn based optics measurements, as it affects the precision of the spectral analysis. In the past, it has been shown how the effect of decoherence on spectral lines in a single plane can be accounted for. In this paper, this work will be extended to include the effect from both transverse planes. The derivations are then applied on data taken at the IOTA ring at FNAL to study resonance driving terms.
In order to maintain the continuity of the vacuum system wall and comply with beam stability limits, radio frequency contact bridges are utilised as transitional elements in beam vacuum line interconnections. These radio frequency contact bridges must absorb and correct longitudinal, angular, and transverse misalignments brought on by mechanical motions during assembly, alignment, operating phases and thermal influences during accelerator operation. A deformable thin-walled copper beryllium structure is the foundation of a novel deformable radio frequency contact bridge concept that satisfies the above criteria without using conventional sliding contacts. To assess the feasibility of implementing such deformable radio frequency contact bridges in the High-Luminosity LHC, the longitudinal, dipolar, and quadrupolar components of the beam impedance in the two transverse planes were determined using electromagnetic simulations.
Sirius is a 4th generation synchrotron light source at the Brazilian Center for Research in Energy and Materials in Campinas, Brazil. The storage ring is currently operating with a normal conducting seven-cell cavity and an upgrade of the whole RF plant is foreseen to take place in the beginning of 2024. Two CESR-B superconducting cavities will be installed in the storage ring and comb-type RF-shielded bellows will be placed in the 100 mm diameter sections. This paper presents the results of the bellows wakefield simulations carried on to estimate the power deposited by the beam, the thermal simulations and the status of the prototype.
Impedance modeling is an important subject in diffraction limited storage rings based light sources, due to the adopted small beam pipe as well as the tight requirements from beam collective effects. Therefore, a batch of impedance bench measurements are performed or planned for the dominant impedance contributors in HEPS, including resistive wall impedance of the NEG coated vacuum chambers, as well as the geometrical impedance of components with large impedance for single element or that show large contributions due to large quantities. In this paper, the impedance measurement of the key elements in the HEPS will be discussed, and the main results are given and compared with the theoretical estimations.
Recently, the Korean government decided to construct a fourth-generation storage ring (4GSR). Compared to a third-generation storage ring (3GSR), emittance is significantly smaller so that we can achieve higher photon beam brightness. This small emittance enables because of a multi-bend achromat (MBA) which necessitates high magnetic field gradients. Accordingly, the vacuum chamber aperture is several times smaller than the 3GSR and the small apertures lead to high impedances that cause various beam instabilities. Hence, estimating the impedance of the components and mitigating the beam instabilities are key tasks during the 4GSR construction. Here, we present the impedance of some Korea 4GSR components calculated through numerical and analytical methods.
Impedance-induced tune shifts and instability growth rates in the CERN Proton Synchrotron are studied thanks to the recently updated impedance model of the machine. Calculation of these beam observables are obtained using both Vlasov solvers and macroparticle tracking simulations, and are compared with those observed during dedicated measurement campaigns. Thanks to improvements in the measurement procedure, including the careful monitoring of losses, bunch length, linear coupling and chromaticity, uncertainties on the tune shifts were noticeably reduced compared to previous years. Finally, the effect of linear chromaticity on tune shift slopes and growth rates has been examined, allowing for a detailed comparison with both past measurements and simulations.
Nonlinear integrable optics (NIO) are a promising novel approach at improving the stability of high intensity beams. Implementations of NIO based on specialized magnetic elements are being tested at the Integrable Optics Test Accelerator (IOTA) at Fermilab. One method of verifying proper implementation of these solutions is by measuring the analytic invariants predicted by theory. The initial measurements of nonlinear invariants were performed during IOTA run in 2019/20, however the covid-19 pandemic prevented the full-scale experimental program from being completed. Several important improvements were implemented in IOTA for the 2022/23 run, including the operation at higher beam energy of 150 MeV, improved optics control, and chromaticity correction. This report presents on the improved calibrations of the NIO for nonlinear invariant measurements.
The commissioning of the APS Upgrade storage ring will need to be completed fast in order to minimize the dark time for APS users. To help speed up commissioning, lattice commissioning simulations were developed that allow to test commissioning algorithms and automate the entire process. In this paper, we describe recent improvements and additions to the commissioning simulations. We cover the addition of the transfer line commissioning, handling of larger than expected errors, use of survey results in the first-turn trajectory correction, and discuss lattice correction results.
Passive superconducting harmonic cavities may cause two types of instabilities when operated in bunch lengthening mode. One is the mode-zero Robinson instability and the other is the periodic transient beam loading instability. In this paper, these two instabilities will be briefly introduced using the parameters of the Hefei Advanced Light Facility storage ring.
Residual gas atoms, ionized by the electron beam, may create two effects in an electron accelerator. One is the trapping of ions in the beam channel by the Coulomb forces of the beam and the other is the fast beam ion instability, a dynamic mutual transverse oscillation between ions and electrons.
While the strongly reduced beam emittance of the accelerator upgrade SLS 2.0 is helpful in that situation, it will not suppress ion related effects completely. To avoid ion trapping, a small ion clearing gap of 30 buckets is still required. Enlarged pressures of 1e-9 mBar, as expected before complete vacuum conditioning, may lead to sufficient build up of ions during the passage of the bunch train to provoke fast beam ion instabilities, requiring to employ multiple clearing gaps. At nominal conditions with 1e-10 mBar, a stable operation is expected.
Korea fourth generation storage ring (Korea-4GSR) is the low emittance storage with an emittance of 61 pm and a circumference of 800 m. The design has been updated to add an injection straight section, where the beta function intentionally made to have high value to relieve the requirement of the off-axis injection. With the injection straight section, the improvement of the injection efficiency was confirmed through the tracking simulation considering various storage ring errors. We also investigated the nonlinear properties of the updated lattice including intrabeam scattering effect and Touschek lifetime.
Proposals to measure a possible Electric Dipole Moment (EDM) of protons in an electro-static machine are studied by a world-wide community. The machine is operated at the so-called magic energy to satisfy the "frozen spin" condition such that, without imperfections and the well-known magnetic moment of the particle, the spin is always oriented parallel or antiparallel to the direction of movement. The effect of a finite EDM is a build-up of a vertical spin component. A small average radial magnetic field leads as well to a build-up of a vertical spin component, which cannot be disentangled from the effect due to a finite EDM, and thus generates a systematic error of the measurement. Essential ingredients of the concept are to install the machine inside a state-of-the-art magnetic shielding and to measure the vertical orbit separation of two counter-rotating beams, enhanced by choosing a very low vertical tune, with high precision pick-ups. In this paper, we analyse limitations of this method and, in particular, the impact of wanted ("strong focusing" lattice) and unwanted variations of the betatron functions and of coupling.
At the NSLS-II ring, a 1.2 m long superconducting wig- gler with the maximum 4.34T magnetic field has been in- stalled at a low-β straight section (cell 27) to drive the high energy engineering X-ray scattering (HEX) beamline. To mitigate the potential performance degradation due to the linear optics distortion, a local compensation scheme was adopted and confirmed with the online beam measurement. A feedforward control to enable a dynamic compensation of the linear optics distortion was deployed. It can maintain the storage ring lattice performance when the device main coil current ramps.
The compact STorage ring for Accelerator Research and Technology (cSTART) project aims to store electron bunches of LPA-like beams in a very large momentum acceptance storage ring. The project will be realized at the Karlsruhe Institute of Technology (KIT, Germany). Initially, the Ferninfrarot Linac- Und Test-Experiment (FLUTE), a source of ultra-short bunches, will serve as an injector for cSTART to benchmark and emulate laser-plasma accelerator-like beams. In a second stage a laser-plasma accelerator will be used as an injector, which is being developed as part of the ATHENA project in collaboration with DESY and Helmholtz Institute Jena (HIJ). With an energy of 50 MeV and damping times of several seconds, the electron beam does not reach equilibrium emittance within the storage time of about 100 milliseconds. Therefore, the initial phase space distribution influences the later dynamics and beam properties. We perform longitudinal particle tracking simulations to investigate the evolution of the bunch lengths and phase space densities for different initial beam distributions.
The proposed upgrade of ALBA to a 4th generation light source, ALBA-II, will involve several changes in the beam dynamics. The most significant change in the longitudinal plane is the addition of a harmonic RF system, which is expected increase the bunch length by at least a factor of three and raise the Touschek lifetime by a similar amount. However, RF systems with harmonic cavities can be limited by their own set of instabilities, hindering them from achieving optimal working conditions and reducing their lengthening performance. In this context, we present a preliminary assessment of the beam stability of ALBA-II in terms of longitudinal dynamics, along with an evaluation of the RF system performance based on the chosen RF parameters.
The worldwide first in-vacuum elliptical undulator, IVUE32, is being
developed at Helmholtz-Zentrum Berlin. The 2.5 m long device with a
period length of 3.2 cm and a minimum gap of about 7 mm is to be
installed in the BESSY II storage ring. The device follows the Apple-II
design and features four magnet rows. Both the two bottom and two top
rows can be shifted longitudinally. This shift needs to be permitted by
the shielding foils that cover the permanent magnets. The proposed
solution calls for a longitudinal slit in the top and bottom shielding
foils, which gets folded into the gap between the top and bottom magnet
rows respectively. The manufacturer states that the folding process can introduce a small sinusoidal error to the slit width. We will present wakefield simulation studies that investigate the effect of different possible foil gap variations.
Magnetic Field Tools is an open source library being developed by the Insertion Devices and Magnets group at the ESRF. It is dedicated to the analysis of static magnetic field values obtained from simulations and measurements. Magnetic field models such as 2D and 3D multipoles in various geometries, as well as boundary element models, can be built from sets of field samples. The library was designed in order to be easily extendable to other types of field models. It is implemented in C++ and a Python binding is available. Application to undulator magnets, 3D multipole fringe fields and solenoids will be presented.
The APS Upgrade storage ring will keep the same rf system that is currently used at APS. This rf system has amplitude and phase noise dominated by the lines at 60, 180, and 360 Hz. APS presently operates with a synchrotron frequency close to 2 kHz, which is far away from the rf noise frequencies, but APS-U will operate with a bunch-lengthening cavity, which could lower the synchrotron frequency down to the range between 100 to 500 Hz depending on the cavity setup. Such low synchrotron frequency could lead to resonant amplification of the energy variation-induced orbit motion. In this paper, we describe measurements of the orbit motion at APS in a specifically designed low momentum compaction lattice that allowed us to lower synchrotron frequency below 300 Hz. We also show good agreement with our simulations.
The ESRF presently operates with the HMBA lattice that features beta-functions of 6.9 m and 2.7 m in the horizontal and vertical planes at the center of the the straight sections. These are not optimal for a length of in-vacuum undulator of approximately 2 m that is used at ESRF. New optics with reduced beta functions at the center of the straight section were designed to better match the electron and photon beams, allow for a reduction of the in-vacuum undulator gap and increase the brilliance delivered to the beam line. This paper presents the optics design, brilliance calculation and plans for experimental validation at the ESRF.
Sealab (SRF Electron Accelerator LABoratory) is composed of an SRF photo gun and an SRF booster, followed by a diagnostic line and a recirculation path for ERL applications. It is the follow-up project of bERLinPro, which ran from 2010-2020 at HZB. In an SRF injector, a single solenoid is sufficient to optimally focus the beam for small emittance. The alignment of the solenoid is crucial, as it is the dominant source of trajectory distortions in the facility. Polynomial Chaos Expansion (PCE) is a technique developed for risk management and uncertainty quantification. It is well suited for application in accelerators, although not well known. In this paper, PCE is used to set up a surrogate model from calculated or measured data to determine the misalignment of the solenoid in Sealab.
As a follow on to the 12 GeV upgrade to the Continuous Electron Beam Accelerator Facility, the front end of the DC photo-gun-based injector has gone through a phased upgrade. The first phase focused on the beamline between the gun and the RF chopper system, and the second phase addresses the beamline after the RF chopper system including replacing the capture section and quarter cryomodule with a new booster module containing a 2-cell and 7-cell cavity string. Throughout the design process, we maintained and developed three models, one for the existing injector and one for each of the upgrade phases. With these models, we evaluated proposed hardware upgrades, evaluated and determined optimized beamline element positions, developed buncher voltage requirements, and settings for optimal injector running. In this paper, we will describe the models and results from these various studies and provide a brief summary of Phase 1 commissioning.
Electromagnetic processes of charged particles interaction with oriented crystals provide a wide variety of innovative applications such as beam steering, crystal-based extraction/collimation of leptons and hadrons in an accelerator, a fixed-target experiment on magnetic and electric dipole moment measurement, a positron source for lepton and muon colliders, X-ray and gamma radiation source for radiotherapy and nuclear physics as well as plasma acceleration in the crystal media. One of the main challenges is to develop an up-to-date, universal and fast simulation tool to simulate these applications.
We present a new simulation model capable to simulate both steering and radiation electromagnetic processes in oriented crystals implemented into the Geant4 simulation toolkit. We validate the model with the experimental data and benchmark it with other simulations*. We discuss the advantages and perspectives of this model for the applications of oriented crystals mentioned above.
Fixed Field Alternating Gradient Accelerators (FFAs) that follow the conventional scaling law have – by definition – high order multipole components in their magnetic fields. It is the presence of these nonlinearities that in many cases determines several important properties of the machine, including amplitude-dependent tune shift and dynamic aperture. Consequently, understanding of the nonlinear dynamics in these machines can be critical to design and optimisation processes. Study of these properties is made challenging by the complicated nature of closed orbits in many FFAs and the presence of edge angle effects (which are exploited by design in certain lattice configurations, such as the F-D spiral design chosen as the baseline for the FETS-hFFA prototype ring). This poster presents a novel method of nonlinear analysis based on the combined application of harmonic analysis and truncated power series algebra-derived techniques.
We expanded the capability of the nonlinear optics from off-energy closed orbits technique proposed by Olsson et al. to include harmonic sextupole correction in storage rings. The existing technique was successfully used to correct the errors of chromatic sextupoles on the MAX-IV machine. However, it was not applicable to harmonic sextupoles, which are widely used in $3^{rd}$-generation light sources, and even some $4^{th}$-generation diffraction-limited machines. By introducing vertically dispersive orbits with skew quadrupoles, we were able to observe a measurable dependency on harmonic sextupoles. We used both simulations and beam measurements at the National Synchrotron Light Source II storage ring to demonstrate the expanded capability of our technique.
A new set of nonlinear beam manipulations have been recently proposed, with the goal of extending the transverse beam splitting that is routinely used at the CERN PS to deliver beam to the SPS for fixed-target physics. Using a simple Hamiltonian model, it has been shown how the transverse emittances can be shared by crossing a two-dimensional nonlinear resonance. Moreover, it has been shown how an AC-dipole can be used to split transversely the beam. In this paper, numerical simulations of these manipulations performed using a realistic model of the PS ring, including longitudinal motion, will be presented and discussed in detail.
SIRIUS is the 4th generation storage ring-based synchrotron light source built and operated by the Brazilian Synchrotron Light Laboratory (LNLS). Beam accumulation at SIRIUS storage ring occurs in an off-axis scheme, using a nonlinear kicker (NLK), for which the efficiency depends on a sufficiently large dynamic aperture (DA). This work reports on the application of online optimization using the Robust Conjugate direction Search (RCDS) algorithm on SIRIUS sextupoles, which resulted in improvements to injection efficiency and DA in three different machine working tunes.
The new generation of storage rings aims to push the limits of the luminosity and the size of the electrons beam that can be achieved. One of such planned machines is the e+/e- Future Circular Collider (FCC-ee) with 100km circumference. The FCC-ee lattice components can be subject to random misalignments and field errors. These errors can adversely affect the beam's closed orbit and beam optics properties, resulting in a significant reduction in the future collider's performance. This issue requires linear optics correction methods to be utilized, One of these methods is linear optics from closed orbit (LOCO) in which the measured ORM is fitted to the lattice model in order to determine the appropriate quadrupole strengths. n this study we demonstrate the application of closed orbit-based optics correction LOCO for FCC-ee lattices.
The code was implemented using the Python accelerator
toolbox (PyAT). The impact of alignment errors on FCC the
lattice optics parameters were studied.
In shanghai, a hard X-ray free electron laser facility named SHINE is under construction which is composed of three undulator lines. As part of the facility, it is preferable to incorporate a beam distribution system just before the undulators to provide suitably tailored beams for diverse experiments. In order to drive a FEL, a good overlap between the electron beam and the radiation is very essential. As a result,evaluating the beam position jitters at the entrance to the undulator is a must. In this paper, the total impact of all the jitter sources, as well as the individual contribution of each jitter source, was calculated. Data was compared and analyzed.
During Long Shutdown 2 (2019-20), the injector chain of the Large Hadron Collider (LHC) has been upgraded to reach the High Luminosity LHC goals in terms of beam intensity and brightness. In the CERN Proton Synchrotron (PS), this upgrade consisted in hardware modifications to double the intensity at extraction, while preserving the transverse emittance available from the CERN PS Booster. The gradual beam brightness ramp-up in the PS after the restart in 2021 brought to light several impedance-induced instabilities. Each of these instabilities has been thoroughly studied in order to understand the impact of several key beam parameters (chromaticity, RF voltage, damper gain). Instability observations, mitigation strategies as well as comparisons with macroparticle tracking simulations will be presented in this paper.
Transverse resonance island buckets (TRIBs) have been successfully observed at the Cornell Electron Storage Ring (CESR) after optimizing the distribution of seventy-six sextupoles to achieve the desired amplitude-dependent tune shift and the resonant driving term near a third-order resonant line (3vx=2). A novel knob is created to adjust the resonant driving term h22000 while minimizing the change of h30000. Interestingly found from simulation, the knob can change the TRIBs locations in the phase space, which is then confirmed experimentally at CESR. Theoretical calculation of the fixed points (stable and unstable) in the phase plots are explored with PTC, which shows excellent agreement with the tracking results and provides theoretical understanding of the TRIBs in the phase space. In addition, the island locations in the real x-y space are explored by adjusting a skew quadrupole to change the x-y coupling.
A beam collimation in the distribution system is designed to protect the undulator and beam pipe in the SHINE FEL.A tracking with a big initial distribution provide a result of the collimation efficiency. Detailed simulation studies about the evaluation of the available collimation design limits for the acceptance of the undulator is described.
The compensation of the long-range beam-beam interactions by DC wires is currently being investigated as an option for enhancing machine performance in the framework of the High-Luminosity LHC Project. In this paper, we report and comment on the potential of wire compensation during the first HL-LHC run. The results are based on numerical simulations and optimisations of the machine dynamic aperture varying the wire position and current, taking into account the latest optics and beam scenarios and the constraints imposed by the corresponding settings of the HL-LHC collimation system.
Recent efforts at SLAC aim at developing high-power accelerators powered by compact, high-efficiency rf sources such as klystrons and Inductive output tubes (IOT). In particular, a high-efficiency IOT is an electron-beam-driven RF source employed in the UHF band that offers high efficiency at variable output power levels. Due to the improved linearity, high efficiency, and reduced size, it is the RF amplifier of choice in the TV broadcast market. Stellant Systems (formerly L3Harris Electron Devices) has long pioneered the IOT design and recently leveraged its power toward various accelerator applications [1]. In this talk, we show the progress of developing a 1.3 GHz HEIOT in terms of design and performance. We also show results of 3D space-charge beam dynamics simulation of an L-Band inductive output tube (IOT) RF electron gun using the accelerator code ACE3P as a transformative approach to HEIOT design. We also show an optimization scheme of the rf output cavities that results in >100 kW of average power with an upward of 80% power efficiency.
FCC-ee is a proposed lepton collider with a circumference close to 100 km to produce an unprecedented amount of luminosity. The FCC-ee optics tuning working group is addressing one of the most critical aspects of the FCC-ee, that is the recovery of the optics design performance in presence of realistic imperfections.
Various teams from laboratories all around the world have got together to assess field quality tolerances and review and share experience gained at synchrotron light sources and lepton colliders such as SuperKEKB. This paper reports the latest results on optics measurements and tuning simulations for various techniques, the development of simulation tools, and possible layout design changes to optimize the tuning performance.
The ALBA-II upgrade lattice to a diffraction limited soft X-rays storage ring calls for an emittance smaller than 200 pm*rad in a 269 m circumference at an energy of 3 GeV. In this paper we report on progress of the 6BA lattice with distributed chromatic correction. This lattice relies on transverse gradient dipoles and reverse bends to suppress the emittance. Several modifications to the lattice presented in 2021 have been introduced in order to easy the injection with high horizontal beta function and a longer section for the septum, to make more efficient the chromaticity correction with the sextupoles, and to provide room for the orbit correctors. The last performances of the linear and non-linear beam dynamics are presented in this paper.
The SOLEIL II storage ring project will require an injected beam with small transverse and longitudinal sizes. To meet this requirement, a new multi-bend 14BA Higher-Order Achromat lattice has been de-signed to reduce the booster emittance from the pre-sent 140 nm.rad to 5 nm.rad @ 2.75 GeV. In this paper we report the progress in the booster beam dynamics studies, considering the linac energy increase from 110 to 150 MeV, and all errors coming from injection mag-nets, injected beam parameters, booster magnets and RF system, whereas the resistive wall study is reported elsewhere. The progress in designing the magnets, the vacuum system, the ramped power supplies, and the diagnostics is presented.
Tracy, the code base used for designing synchrotron light sources with predictable performance, has been significantly refactored. Furthermore it now uses mad-ng gtpsa library.
We describe the achieved progress, discuss its python interface. We show how to use it for achieving a robust design for a modern synchrhotron light source.
Vacuum chambers of flat aspect ratio are source of a quadrupolar component of long-range resistive wall wake fields whose amplitude only depends on the trailing test particle.
In multi-bunch filling this leads to an accumulation of the long-range quadrupolar resistive wall wake field which expresses in multi-bunch tune shifts on both planes. The tune shifts were measured at the ALBA storage ring and the results were compared to the model of Chao, Heifets and Zotter *
and the model of Blednykh et al.**. As ALBA runs with only 8 insertion devices of which 3 are in-vacuum undulators in relatively short sections with low beta-functions, the quadrupolar detuning is
dominated by dipolar vacuum chambers and the standard vacuum chamber around the ring. The effect of the in-vacuum undulators will be also discussed.
ER@CEBAF is an effort to demonstrate multi-GeV multi-pass energy recovery with a low beam current in CEBAF. The race-track-shaped CEBAF geometry allows its linacs to accommodate multiple energy beams simultaneously. However, five energy recovery passes complicate the beamline optics design process. Individual recirculating arcs each transport one beam energy, and are shared between accelerating/decelerating beams. Present CEBAF optics needs to be redesigned to accommodate this additional multi-pass ER scheme. Isochronous arcs are retuned to match with the solutions obtained from optimized 10-pass beamline. In this paper, we discuss the optics redesign process with the existing beamline for ER@CEBAF.
A algorithm is demonstrated which performs first-principles tracking of relativsitic charged-particles for determining the power they deposit into their surroundings (in particular, blackbody cavities and pillbox accelerating cavities). A computationally costly, but highly accurate covariant approach is used, which employs retarded vector potentials for trajectory integration instead of performing field calculations.
The peak vector potential and related Lorentz force in the direction of travel is shown to increase asymptotically for high $\beta$ particles approaching a conductive surface or another charged particle. This effect produces a very strong field distribution at small angles from the source particle's direction of travel, which, for high-intensity beams, can deposit significant power onto the surface surrounding a cavity's exit aperture.
Changes in momentum of a charged particle occurring after a cut-off of external fields are shown to be non-conservative, such that any resulting power deposition causes a recoil effect on the cavity.
We present benchmark cases for this framework and results for two-particle simulations as well as small-bunch simulations using a macroparticle formalism.
One of the interesting topics among accelerator physicists in the last decades has been the resistive wall impedance of vacuum chambers with general cross sections. The resistive wall impedance of a round pipe was calculated more than half a century ago, followed by parallel plates, rectangular pipes, and, in more recent years, oval shapes. Analytical solutions usually require some approximations to simplify them. It is possible to solve Maxwell's equations in the vacuum chamber with simulation codes in order to obtain an exact solution for Resistive wall impedance. Although some of them show promising results, the need for a versatile code that can calculate resistive wall impedance and wakefield in a general cross-section vacuum chamber is still necessary. VACI-suite is a finite element solver that tries to solve this problem. Compared to well-known theories and simulation codes for well-known geometries, the code's results show remarkable agreement.
The ultra-low emittance specification of the SOLEIL II storage ring requires a challenging lattice design of the booster that will inject the beam into it. The dimension of the vacuum chamber in the new booster must be reduced compared to that in the present machine. The resistive-wall (RW) instability is then expected to become more important than in the current booster. However, the Amplitude-Dependent Tune Shift (ADTS) is also expected to be stronger due to the strong sextupole magnets necessary for chromatic error correction in the new lattice. It could then be an important effect in fighting against this instability. Therefore, evaluating this instability is important to ensure the machine's feasibility. This work studies the beam dynamics along the ramp in the RW instability regime using the code mbtrack2. The turn-by-turn tracking allows us to see the evolution of the beam thoroughly and understand how RW, synchrotron radiation, and ADTS impact the beam stability.
Abstract
A geometric control theory method is outlined & pre- sented to improve the on & off-momentum dynamic aper- ture for synchrotrons. And applied to the two lattice op- tions/solutions for BESSY III. A guideline is also provided for how to estimate the resulting performance for the “real lattice. The so-called tune confinement approach [32].
RUEDI, the Relativistic Ultrafast Electron Diffraction and Imaging facility for the UK, is a planned facility that will deliver single-shot, time resolved, MeV electrons for imaging and ultrafast (~10 fs) diffraction. The facility naturally separates into two lines, both fed by the same RF gun. The first line is for microscopy and imaging whereas the second is dedicated to diffraction. Microscopy can be done in two ways, the first is by building a line with solenoid lenses and the second is by building the same line with quadrupole lenses. Here, we explore the advantages and disadvantages of both. Starting with a description of how the microscope is built using solenoids and extending this to look at various options with quadrupoles.
With the development of Mega-electron-Volt ultrafast electron diffraction technology, electron microscopy based on photocathode radio-frequency (RF) electron guns has become a promising tool for high spatiotemporal resolution and shows obvious advantages of suppressing the space charge effect. An ultrafast electron microscopy is being developed at HUST. Russian quadruplet (RQ) based electron optics is selected to achieve simultaneous focusing and equal magnification in both vertical and horizontal directions. The RQ exit beam position must be highly dependent on the entrance beam position and independent of the entrance beam divergence to achieve a point-to-point image, which defines the first-order transfer matrix parameters. COSY INFINITY code is implemented for optics design. The simplified hard-edge model, the fringe field effects, and high-order lens aberrations are discussed and further optimized for the electron beam optics design.
A beam transport section using the scaling fixed-field alternating gradient-type (FFAG) magnets is designed to transport laser plasma accelerator (LPA) electron beams to a specific application. This beam transport section has a large momentum acceptance, which is able to collect and transport the LPA beams with a momentum acceptance of up to 10%. Also, using the periodical FFAG magnet cells, the optical functions are identical at the beginning and end of this beam transport section, which makes it capable to be placed in any arbitrary designed beam transport line when transportation to a longer distance is required.
Modern SRF applications require precise control of a wide range of material properties, from microscopic material parameters to macroscopic surface structures. Historically, Nb has been the primary superconducting material in SRF cavities. The past decade has seen increasing amounts of research into the development of cavities using next generation materials, such as Nb3Sn. These materials have great promise for improving SRF performance, but their small coherence lengths require even greater control of surface and material defects. Mesoscopic simulation of superconductors has proven itself to be a powerful tool in SRF development, connecting the results of ab initio/quantum calculations to the mesoscopic structures of the material, allowing for investigation of many phenomena which are difficult to probe experimentally. One particular phenomenon of concern is the field enhancement effect, which causes increased magnetic field near rough surface features, potentially leading to vortex nucleation or other dissipative processes. We outline a two-domain finite element framework of the Time-Dependent Ginzburg-Landau equations which allows for the simulation of magnetic field enhancement due to supercurrent screening near rough surface features. We apply this framework to several different candidate surface structures which may occur in Nb3Sn, and determine their impact on dissipation and vortex nucleation. We discuss the implications of these results for SRF cavity design.
The Figure-8 storage ring (F8SR) concept for fusion reaction research in context of astrophysics is under development at Frankfurt University. In contrast to traditional storage rings, a guiding longitudinal magnetic field is used for confinement of very low energy charged particle beams continuously with high transverse momentum acceptance. Due to the strong magnetic field level (B=6 T), low energy proton and ion beams (W < 1MeV) of several amperes can be confined. Many characteristic and unique features (e.g. injection system, collider mode) and key components were developed in the past. The current developments are concentrated on the design of a beam-target area and detectors. Particle-in-cell (PIC) simulation of high current beam propagation through a target area and interaction with an internal gas target will be presented and discussed. Possible space charge compensation through confined electrons will be assessed. Investigation of the large target area for colliding beam mode will be presented and discussed as well.
In the KIT storage ring KARA (Karlsruhe Research Accelerator), two parallel plates with periodic rectangular corrugations are planned to be installed. These plates will be used for impedance manipulation to study and eventually control the electron beam dynamics and the emitted coherent synchrotron radiation (CSR). In this contribution, we present simulation results showing the influence of different corrugated structures on the longitudinal beam dynamics and how this influence depends on the machine settings in the low momentum compaction regime, which are related to the bunch length changes.
Third-order resonance lines will have a detrimental effect on the high-intensity operation of the Recycler Ring (RR), under the current Proton Improvement Plan (PIP-II) for the Fermilab Accelerator Complex. Increasing intensity will increase space charge effects, leading to the excitation of normal and skew sextupole lines. Dedicated normal and skew sextupoles have been installed in order to mitigate the effect of these resonance lines. By measuring the response matrix of the third-order Resonance Driving Terms (RDTs) to the currents of these dedicated elements, this study shows how several resonance lines can be compensated simultaneously. Resonance compensation is experimentally verified through loss maps and emittance growth measurements using the Ion Profile Monitor (IPM) system in the Recycler.
Bunch lengthening with a double radio-frequency (rf) system combining fundamental and harmonic cavities (HCs) is essential in achieving extremely low emittance along with suitable lifetime as required for ring-based fourth-generation synchrotron light sources in the low-to-medium energy range.
Recent studies have pointed out that, in many cases, an unstable beam motion, as so-called “periodic transient beam loading effect1” or “coupled-bunch mode l=1 instability2”, prevents from reaching the optimum bunch lengthening condition. One effective way to raise the bunch lengthening limit is to reduce the total R/Q of the HCs. However, there is also a limit to the reduction of their R/Q due to the need for generating sufficient HC voltage for bunch lengthening.
We have then considered using active (powered) HCs with conventional rf feedback loops, coupled-bunch mode damper and direct rf feedback, which were modeled and introduced in the particle tracking code, mbtrack. The tracking results for the SOLEIL-II ring case show that the direct rf feedback is quite effective in suppressing the beam instabilities thanks to its ability of reducing the cavity impedance as seen by the beam. The features of the implemented rf feedback loops and the simulation results are reported.
This report presents new investigations on beam dynamics for the separation beamline which allows to transport and compress electron bunches from the second electron source MIST to the first acceleration section of MESA. Several beamline configurations are compared concerning the capability for transport of elevated bunch charges.
The Accelerator Toolbox (AT) is a multipurpose tracking and lattice design code relying on a C tracking engine. Its MATLAB interface is widely used in the light source community for beam dynamics simulation and can be integrated in control systems through the MATLAB Middle Layer. In recent years major effort was made to develop a python interface to AT: pyAT. In this framework, several features were added to pyAT, in particular, the introductions of the 6D optics dynamic aperture and lifetime calculation, single and multi-bunch collective effects simulations and parallelized tracking capabilities. A python ring simulator was also developed based on pyAT for offline modeling of the accelerator control system. Following a presentation of the structure and main features of AT, an overview of these recent developments is provided.
MAD-X is a popular beam optics code used to design, model and operate a large number of synchrotons and linacs. In this paper, we present the features added in the most recent versions and improvements we intend to make in future releases. Physics models have been added and improved to support the needs of the Future Circular Collider (FCC) and the Electron Ion Collider (EIC), regarding machine-detector interface, complex beamline layouts, and synchrotron radiation. More precise physics models have been implemented for some elements, and a complete set of exact coordinate frame transformations are now available. The tracking module has been extended to support frozen space-charge models. To improve interoperability with scientific ecosystems, MAD-X relies on the cpymad Python interface which offers a fine-grained control of MAD-X simulations, exceeding the capabilities of the internal MAD-X language.
SOLEIL, the French third-generation synchrotron radiation facility, is in the TDR phase of its upgrade to a new fourth-generation synchrotron light source, called SOLEIL II. Its storage ring lattice design has evolved over the last year to better adjust its parameters taking into account the results of the mechanical integration, more realistic magnet design~[1], and the geometrical constraints for the extraction of the photon beams. A new configuration of girders has been introduced, and the correction strategies have been refined. A new corrector budget and updated results with more statistics are presented in this paper.
Superconducting dipoles with a strong curvature (radius smaller than 2 meters, for an aperture of about 100 mm and a length of 1-3 meters) are required for applications where compactness is key, such as the synchrotron and gantry for Carbon-ion therapy developed within the European program HITRIplus.
Such magnets challenge several assumptions in the field description and put to the test the range of validity of beam optics codes. In particular, the equivalence that holds for the straight magnets between the transverse multipoles description obtained from the Fourier analysis (used for magnet design and measurements) and the Taylor expansion of the vertical field component along the horizontal axis (used in beam optics) is not valid any longer. A proper fringe field modelling also becomes important, due to the curved geometry and the aperture being large compared to the magnetic length.
We explore the feasibility and the limits of modeling such magnets with optics elements (such as sector bends and multipoles), which allows parametric optics studies for optimization, field quality definition and fast long-term multi-pass tracking.
The High Energy Photon Source (HEPS), which is a 6 GeV diffraction-limited storage ring (DLSR)-based synchrotron light source, is under construction in Beijing, China. HEPS consists of a Linac, a booster synchrotron, and a storage ring. The HEPS booster is proposed to operate in multi-bunch mode. And the 5-cell PETRA-type cavity, which is rich in high-order modes (HOMs), is chosen to be used in HEPS booster. For the related coupled-bunch instabilities (CBI), comprehensive studies are performed. In this paper, we present the studies of CBIs both at the two fixed energy points (500 MeV and 6 GeV) and with the consideration of the energy ramping process in the HEPS booster.
The ongoing FCC-ee collider design aims at optimizing beam parameters and developing the different accelerators systems. For this reason, the coupling impedance modeling is in evolution following the design of the collider vacuum chamber and hardware components. Respectively, studies of collective effects and instabilities are continuously updated and refined. In this paper we describe the current FCC-ee impedance model and discuss results of the single bunch instabilities studies. Possible mitigation techniques for these instabilities are also considered.
Beam-beam interaction in FCC-ee can be seriously affected by the vacuum chamber coupling impedance resulting in a safe tune areas reduction, tune shifts and spread, bunch length and energy spread variation. The interplay of the two effects have a drastic impact on the stability of colliding bunches and respectively on the achievable luminosity. In this paper beam-beam collisions in FCC-ee with 4 interaction points are studied including the updated transverse and longitudinal impedances.
Intra-beam scattering (IBS) is one of the prominent effects for low-emittance rings resulting in a significant growth of the emittance, energy spread, and bunch length. This effect is partially mitigated by the bunch lengthening caused by the longitudinal impedance. However, a significant bunch lengthening provided by higher-harmonic cavities is needed to keep the emittance low enough for achieving the designed brightness. For low-emittance lattices considered as options for the NSLS-II upgrade, we studied a combined effect of the IBS, impedance, and harmonic cavities using analytical formulae and computer simulations.
We present a study of the systematic uncertainties in beam size determination using sextupole strength variations. Variations in strength of a sextupole magnet in a storage ring result in changes to the closed orbit, phase functions and tunes which depend on the position of the beam relative to the center of the sextupole and on the beam size. We take advantage of the beam-based measurements of sextupole alignment errors and calibration correction factors obtained in 2022 to improve our model of the Cornell Electron/positron Storage Ring optics and assess accuracy limits in the beam size determination. Two measurement sets for the 76 sextupole magnets are compared: 1) the commonly used method of measuring tune variation for a single sextupole strength change at a given set of beam positions in the sextupole, and 2) using the linear term in the dependence of orbit and quadrupole kicks resulting from a set of sextupole strength changes. The latter are determined from polynomial fits to the difference orbits, phase functions and tunes arising from the sextupole strength changes. The first analysis neglects the effect of the beam size, leading to a small error in the offset determination. The second method fully accounts for the beam size and gives a second estimate for the alignment error. The differing sources of uncertainty in the two methods are assessed and discussed.
In this paper, the nonlinear coupling resonance $2 Q_x -2 Q_y = 0$ is studied by means of a Hamiltonian model. The detailed analysis of its phase-space topology unveils the possible phenomena that can occur when crossing adiabatically such a resonance. These considerations are probed by means of numerical simulations carried out using a symplectic map and the results are presented and discussed in detail.
Classical canonical Lagrange for the electromagnetic potentials has been formulated for beam-wave interaction enclosed by periodic structure or slow wave structure (SWS). The analysis procedure is based on expanding the potentials in the Lagrange of the given SWS in terms of the solenoidal and irrotational eigenmodes of a canonical cavity with cross-section enclosing that of the original cavity. Floquet-Bloch theorem are used in the expansion for the potentials. We conclude some numerical results demonstrating the importance of this formulation.
The effect of both existing and the planned insertion devices on linear optics, dynamic and momentum aperture was modeled using the kick map approach. Cross check for some IDs have been done with different tracking codes. Mitigation strategy for avoiding the crossing of a 4th order resonance line, excited by some of the IDs, is proposed.
The Rapid Cycling Synchrotron (RCS) of the Electron Ion Collider (EIC) is the injector of the Electron Storage Ring (ESR). The dynamic range of the RCS is from 0.4 GeV to 18 GeV. The RCS will use normal conducting dipoles, quadrupoles, and sextupoles. With errors to the main dipole field and misalignment to the elements included in the model, an orbit correction scheme has been developed. These magnet to magnet variations to the main field of the elements were studied as well as the effects of the multipole field errors. The impact of these errors and misalignments on the dynamic aperture will be presented.
The resistive contribution of the vacuum chamber is a significant part of the impedance budget. Due to the NEG-coated re-designed ILSF vacuum chamber, the resistive-wall effects must be carefully studied. The resistive impedance of the insertion devices and general cross-section of the storage ring was calculated by CST and WI2D code. In addition, the fast-correctors containing a resistive insert with a conductivity different from the rest of the pipe were simulated in CST. Finally, the not negligible effect of the heat load and threshold current was studied. The single-bunch calculations were done by ELEGANT code. The final results in longitudinal and transverse planes are presented here.
Recent studies have shown that accelerating $+19^{\circ}$ off-crest in all RF cavities in the MAX-IV linac reduces voltage-induced timing jitter from the klystrons. The current bunch compressors in the linac have fixed first-order longitudinal dispersion, and the RF phase is varied to control the amount of compression. Variable bunch compressor designs have been considered at MAX-IV in recent years, these would allow us to regain control over compression while the accelerating phase is fixed to reduce timing jitter. Particle tracking studies have been performed on the MAX-IV linac with the addition of arc-like variable bunch compressors.
The Hefei Advanced Light Facility (HALF) storage ring will be an ultralow emittance storage ring with 2.2 GeV beam energy, less than 100 pm·rad emittance, 480 m circumference and 350 mA nominal current, which is designed with 20-long and 20-middle straights, so more insertion devices can be installed for users. To facilitate its high performance, the beam-coupling impedance effect must be considered and controlled in a safety margin. The present impedance model of the HALF storage ring, including the resistive wall impedance and main geometrical impedance, will be shown in this paper.
The transfer line that carries the electron beam from the plasma to the undulators is certainly a critical line in EuPRAXIA@SPARC_LAB as in all plasma driven Free Electron Lasers.
This machine section must serve multiple purposes: capturing the highly divergent bunches at the plasma exit, separating the driver bunch from the witness and finally matching the witness to the FEL undulators.
In addition, the line must be as compact as possible so as to best contain the chromatic outbreak of the beam.
In this paper we present the results of the design and optimization phase of the transfer line taking into account important collective effects such as space-charge and coherent synchrotron radiation emission in the chicane.
Moreover, we show here our evaluations on the expected effect of chromatism after the plasma extraction on the witness and its core and the filtering procedure of the witness halo.
The quest of laser plasma accelerators is of great interest for various applications such as light sources or high energy physics colliders. This research has led to numerous performance improvements, particularly in terms of beam energy versus compactness [1] and ultra-short bunch length [2]. However, these performances are often reached without the achievement of sufficient beam quality, stability and reproducibility. These are the objectives of PALLAS, a test facility at IJCLab, that aims to advance laser-plasma from acceleration to accelerators.
To this end, one of the main lines of research is the electron beam control and transport.
The primary goal is to have a lattice design that allows for a fine characterization of the output beam as a function of the laser-plasma wakefield acceleration target cell and laser parameters, while paying a particular attention to preserving the quality of the beam during its transport.
I will present the approach, considered for PALLAS, on the problematic of chromaticity and divergence for the transport of laser-plasma accelerated electron beams.
After the LHC Injectors Upgrade (LIU) project, the CERN Proton Synchrotron Booster (PSB) operates with a new injection kinetic energy of 160 MeV and an extraction energy of 2 GeV. In light of this, several measurements have been performed to characterize the behaviour of the accelerator in terms of beam stability and beam coupling impedance in the new energy range. In particular, the horizontal instability observed in 2021 at about 1.7 GeV (between the old and the new extraction energy) has been deeply investigated and betatron coherent tune shift measurements have been carried out to further benchmark the PSB transverse beam coupling impedance model. Regarding the horizontal instability, although a mitigation strategy has been identified, measurements and studies have been conducted to understand and explain its source.
The growth time of transverse coupled-bunch instability (TCBI) in the vertical direction was
measured at SuperKEKB rings. Resistive wall (RW) impedance is the primary source of driving
TCBI. As a collider, special vacuum chambers are remarkable sources of RW impedance in
addition to RW impedance from regular chambers. Such chambers include collimators where the
chamber gap is very small and interaction region where the vertical beta functions are very
large. The classical theory of TCBI based on uniform filling patterns is used to estimate the
growth time and compared with experimental results.
The International Muon Collider Collaboration is currently investigating the possibility to build a muon collider with a center of mass energy of 3 TeV in a first phase, with an option to build a 10 TeV collider in a second phase. The muon beam decay is the global challenge of such a collider and fast acceleration is required to reach high luminosities. A series of three or four Rapid Cycling Synchrotrons are currently proposed as the last acceleration stage before injecting the muon beams into the collider ring. The transverse collective effects in these synchrotrons have been analysed in detail. Both the higher-order modes of the numerous RF cavities needed for the fast acceleration, and the ceramic chamber needed to avoid eddy current effects, have been looked at in detail along with possible mitigation measures. Promising results have been obtained considering for the moment a single muon bunch.
In the framework of the International Muon Collider Collaboration, a 10 TeV muon collider ring is being studied, with the option of an intermediate 3 TeV collider stage. The decay of high-energy muons represents a great challenge in terms of heat load management and radiation shielding for the superconducting magnets of the collider ring. Materials such as tungsten are being considered to shield the cold bore of the magnets from decay products. The transverse beam coupling impedance and related beam stability have been investigated in detail for several vacuum chamber designs to identify the minimum vacuum chamber radius and transverse damper properties required for stable beams.
Several studies have been performed in the 2021 and 2022 runs to build a better understanding of the behaviour of the accelerator with high intensity beams. Transverse beam instabilities at injection energy are known from previous measurements and simulations to be a potential limitation to reach the LHC Injectors Upgrade (LIU) target beam intensity. This paper summarizes the limitations introduced by transverse instabilities and the experience gained during 2021 and 2022 runs. Special emphasis will be given to the vertical coupled-bunch instability predicted by simulations and observed for the first time after the Long Shutdown 2 (LS2) during the 2021 run. This instability together with the horizontal one, which has been deeply characterized before LS2, is expected to impose constraints on the chromaticity, octupole current and tune working point. The stabilization strategy at the LIU intensity has been demonstrated during the 2022 run. Beam lifetime and quality for the explored operational settings will also be discussed.
The tracking code RF-Track has been updated to include a large set of single-particle and collective effects: beam loading in standing and travelling wave structures, coherent and incoherent synchrotron radiation, intra-beam scattering, multiple Coulomb scattering in materials, and particle lifetime. This new set of effects was focused on the simulation of high-intensity machines such as linacs for medical applications. In these apparatuses, the beam propagation into air and water significantly impacts the beam propagation to and through the patient. Now, these effects can be included by design. Additionally, RF-Track can now simulate the cooling channel of a future muon collider.
The lattice design process for BESSY III is based on a systematic & deterministic approach where sub-structures of the MBA lattice are analyzed and optimized before the lattice is composed. During this process, 5 standardized Higher-Order-Multi-Bend-Achromat (HO-6MBA) lattices were developed utilizing different combinations of homogeneous and gradient bends in the unit and the dispersion suppression cell. All lattices yield basically the same emittance, momentum compaction factor, working point, maximal field strengths, and drift lengths. Therefore, they are equivalent to the linear optics. This enables us to attribute any differences in their nonlinear behavior to the specific lattice structure. A detailed description and analysis of the trade-offs of these standardized lattice structures are given. Based on this analysis, the choice of the BESSY III lattice type is motivated.
The Rapid Cycling Synchrotron (RCS) in China Spallation Neutron Source (CSNS) is a high intensity proton accelerator, the impedance can drive collective instabilities and limit the machine performance. Due to new component installation, the impedance model should be updated. A thorough estimation of the coupling impedance is presented and the impedance model in the RCS is obtained.
This paper presents the design concept of the dipole magnet with 50 mm aperture, 20 T nominal field and 13% margin based on a six-layer cos-theta (CT) hybrid coil design. Due to the high stresses and strains in the coil at high field, Stress Management (SM) elements are implemented in the CT coil geometry. The results of magnet magnetic analysis are presented and discussed. The key parameters of this design are compared with the parameters of similar magnets based on block-type and canted cos-theta coils.
Seen in the light of finding ways to reduce the CO2 footprint in the Big Science world and at the same time make big saving in operating cost due to 90% lower LHe consumption I will in the presentation share the following insights:
1) initial idea and economic business case for 10-20 kA current leads
2) the 13 kA Hybrid Current Lead design by using LN2
3) the application in a test cryostat
4) detailed engineering, production, and timeline
5) performance after installation in the test cryostat
6) next steps
The presentation will be rich with photos from the production/installation.
Besides giving a PowerPoint presentation also a poster session is prepared.
Background:
Mark & Wedell has been supplying current leads to CERN, GSI, CEA etc. over the last 20+ years.
Grid-controlled electron gun usually uses specially designed power supplies to supply power, the performance of the power supplies can directly affect the beam performance of the accelerator. In this paper, a nanosecond power supply for a grid-controlled electron gun is designed. It uses avalanche transistors and superimposes Marx generators to improve the power. Finally, its rise edge is less than 1 ns. The power supply can be used in the thermal cathode grid-controlled electron gun, the electronic source scheme of Hefei Advanced Light Facility (HALF), which is practical and feasible.
For the Elettra 2.0 upgrade project, a new class of DC power converters have been internally designed and eventually installed in a number of around 1000 pieces to power multipole and corrector magnets in the synchrotron storage ring. In order to fulfill evolving scenarios over the expected lifecycle of the accelerator, the power converters will be supervised by one of the most advanced digital controllers actually available on the market. In particular the controller provides a double ethernet interface, the first one is used mainly for device management, while the second is designed to support daisy chain or one-to-many (broadcast) current setting schemes, at a maximum of 100 kHz setting rate. Results of static and dynamic tests of the first 20 A prototype of the corrector power converter connected to the control system realtime framework will be reported in the following article.
Organic and inorganic Optical Fibers (OFs) are increasingly utilized in space and medical applications, including accelerator and reactor environments to monitor beam currents and shapes, doses, temperatures, and pressures [1-5]. OFs are ideal as they can be radiation hard, small in size, independent from electro-magnetic environments, and linear over a large measurement range. Here we present a new application in conjunction with a medical cyclotron, where a collar of four Ce-doped silica fibers is mounted onto a beam line. In our experiments, measurements of the OF scintillation signal from prompt neutrons and gammas produced by the proton beam as its bombardment position changes in a beam dump are made. This is an extension of our previous work with a similar setup to monitor beam delivery onto a medical isotope target at a cyclotron [6]. The advantage is that the OFs are outside of the vacuum and do not need to intercept the beam. Initial testing shows that monitoring of a 150 nA beam of 18 MeV protons into a beam dump is possible. The monitor can measure relative beam current and beam displacement in X and Y as a function of magnetic steering. Further testing is underway.
Acceleration for a muon collider will have to be extremely fast to ensure efficient transmission of the decaying beams, with acceleration times of the order of 1ms. One of the proposals for such a machine is centered around a rapid cycling synchrotron (RCS), a hybrid lattice of cells with alternating superconducting and resistive dipole magnets. Resistive magnets will swing from negative to positive field level, providing the magnetic flux variations (more than 3600 T/s) that are required for the quick acceleration of the muons, while the superconducting magnets will give a field offset. The resistive magnets will have to be supplied with extremely high peak power levels, in the order of few tens of GW, to provide the necessary magnetic field variations. For the extremely quick magnetic field ramp, this application is unique in the field of the RCS and related technologies. This paper analyses the application of a two harmonics circuit with additional active filter to the powering of the four RCS stages of the muon acceleration to the ultimate 10 TeV energy level
Klystrons and IOTs are widely used in accelerators as high-power RF sources. Development and optimization of klystron and IOT designs is aided by the use of different simulation tools, including highly efficient large-signal codes. We present an overview of the advances in the code development and modeling using Naval Research Laboratory (NRL) set of TESLA-family of large-signal codes, suitable for the modeling of single-beam and multiple beam klystrons (MBKs) and IOTs. Original 2.5D large-signal algorithm of the code TESLA was developed for the modeling of klystrons based on (relatively) high Q resonators and is applicable to the multiple-beam devices in an approximation of identical beams/beam-tunnels. Parallel extension of TESLA algorithm (code TESLA-MB enabled an accurate, quasi-3D modeling of multiple-beam devices with non-identical beams/beam-tunnels. Added into TESLA algorithm procedure for proper treatment of ‘slow’ and ‘reflected’ particles enabled accurate modeling of high-efficiency klystrons and contributed into the development of klystron with 80% efficiency. Recently developed more general TESLA-Z algorithm*** is based on the impedance matrix approach and enabled accurate, geometry-driven large-signal modeling of devices with such challenging elements as multiple-gap cavities and filter-loading. Examples of applications of TESLA-family of codes to the modeling of advanced single-beam and multiple-beam klystrons and IOTs will be presented.
It is often required to estimate the effect of small perturbations of design parameters on various performance metrics of RF sources as a part of optimization and sensitivity analysis. The direct approach, assuming an accurate simulation code is available, is to change slightly the value of an input variable of interest; a simple example is a calculation of how a small change in klystron cavity spacing would affect output power. The trouble with this approach is that, when there are many, N, design parameters of interest, for example cavity spacing, cavity dimensions, magnetic field, beam voltage, current, then N+1 runs of the simulation code are required to compute all the partial derivatives. N can be very large when considering the detailed design of RF sources for accelerators (), (). By computing the solution of the adjoint of the perturbed equations governing the beam-wave interaction, we have shown (**) that all N partial derivatives might be computed with only three runs of the simulation code, no matter how large N is. Once known, these partial derivatives may be used to specify manufacturing tolerances and/or used in a design optimization calculation. Example of the latter include (3) for a traveling wave tube. We will discuss an application of adjoint perturbations to klystron design in our presentation.
The cost of a klystron for the SNS is estimated to be in the $200K range. A magnetron with the same power level is about one-fourth the cost. With ancillary equip-ment to functionally duplicate the performance of the klystron and allowing for the reduced lifetime of the magnetron compared to the klystron, about half the cost. Additional operational cost savings are related to the 805 MHz magnetron 90% efficiency, which for some applica-tions is twice that of a corresponding klystron.
Hefei Advanced Light Facility (HALF), a planned key mega-science facility approved by the Chinese government in 14th five-year plan, will be constructed in Hefei, China, and National Synchrotron Radiation Laboratory (NSRL) is responsible for the construction. HALF is a 4th generation diffraction limited synchrotron radiation light source which includes a 240 m injector, a 180 m transport line, and a 480 m storage ring. Comparing to the 3rd and earlier generation light source, it requires much higher alignment accuracies. This paper instructs the alignment strategy for it, including alignment accuracy requirements for different parts, alignment procedures and techniques for different stages of the project from civil engineering to the installation of components in the machine and the deformation monitoring system.
This study primarily discusses a unique topology for constructing a double full bridge circuit. The study establishes a push-pull inverter model and analyzes the balance circuit in its architecture. This allows the power supply to initiate the balance circuit and ensures the TPS booster magnet power supply operates smoothly in a safe and balanced voltage region when magnet energy is re-covered. We employ the approach of adding Y circuits to mitigate the impact of common mode noise. Adding a Y circuit effectively suppresses the common-mode noise generation, improving the quality of the output current of the TPS dipole magnet power supply at low currents state and ramping the beam current energy from 150 MeV to 3 GeV. Furthermore, the reproducibility and stability of the injection point can enhance the injection efficiency of the TPS booster magnet power supply. This study presents the results obtained from these efforts.
The CERN’s Electrical Power Converters group is responsible for around 4000 power converters controlled, monitored, and diagnosed using Function Generator/Controller (FGC) devices. These devices run either on in-house designed embedded hardware (FGC2, FGC3) or in Front-End Computers. The latter flavour of devices is encoded in the FGCDv1 framework, which also implements the logic interfacing CERN’s control system to communicate with operational tools, applications, and services.
This paper presents the new version of the FGCD framework, the FGCDv2, developed from the ground up using the modern C++20 language and designed with modularity in mind, allowing for multi-platform compilation (x86, AArch64), easy extensibility and maintenance. The pool of modules available in the FGCDv2 framework will be the basis for the process running in the Front-End Computers and the process running in the new embedded hardware platform, FGC4, promoting code reusability. Finally, to export the FGCDv2 framework to external laboratories through the CERN Knowledge Transfer program, the interface to the industrial control standards TANGO and EPICS will be integrated in the design from the very beginning.
CERN's North Area comprises several target and experimental systems and is a zone of interest for future development. Provision of beam to this area relies upon several beam-intercepting devices located in various branched transfer lines from the Super Proton Synchrotron. In several lines, these include a primary production target system of beryllium plates followed by a combined collimation, attenuation and dump device made from a set of aluminum, copper and iron blocks and known as a 'TAX' (Target Attenuator [for] eXperimental areas). These may operate in a range of configurations depending on experimental needs. Future operational regimes with higher beam intensities (increased from a current specification of 1.5×10^13 to 4.0×10^13 p+/pulse), shorter pulse times (4.8 s reduced to 1.2 s), greater repetition rates (14.4 s cycle time reduced to 7.2 s) and ten times the annual intensity place more stringent thermo-structural demands on these existing devices, beyond their original specification. This contribution outlines the engineering analysis, including beam-matter interaction studies and thermo-structural simulations, carried out to assess their robustness under such conditions.
In 2017, a proton-impact test HL-LHC collimator materials was carried out in the HiRadMat facility at CERN. The experiment, called “MultiMat”, enabled the testing of bulk and coated materials developed at CERN for different beam collimation functionalities. Manufacturing of these materials was then passed to the industry, leading to a series production for use in the collimators installed in the LHC during Long Shutdown 2 (LS2). The industrial versions of bulk and coating materials were tested in HiRadMat in 2021 in the “MultiMat-2” experiment, that efficiently re-used of the same experimental test bench as for “MultiMat”. This new experiment proved the reliability of the absorbers installed in LS2, and confirmed the possible use of alternative materials and coatings for the next LS3 collimator production. This paper describes the preparation and beam parameters of “MultiMat-2”, the experimental and data-acquisition equipment and the main results of the experiment.
The Upgrade from the third to the fourth-generation light source of the SOLEIL synchrotron requires significant work on the reorganization of the equipment in the storage ring. Higher performance such as low emittance, small transverse size and high brightness are expected but requires redesigning the lattice. New constraints appear, requiring innovative designs of insertion device (ID) in order to keep the spectral range currently offered to users as large as today. The current straight sections can welcome two juxtaposed undulators to allow the beamline to cover a wide spectral range. However, the average space of straight sections dedicated to ID of SOLEIL II will be decreased in the future by 30%. SOLEIL Insertion Group studied several technical solutions combining two magnetic periods in a shorter space. Bi-periodic undulator project would make it possible to design a unique compact device with special magnet arrangement allowing to operate the ID alternatively with one periodicity to its triple value by means of longitudinal displacement of magnet arrays. Such an undulator enables to cover a wide spectral range of photons and only requires short space. A complete magnetic design with magnetic and spectral/optical performance will be presented and compared to usual solutions. Impact on the electron beam dynamics and magnetic forces will be also considered to have a complete knowledge on the feasibility of this project.
CERN-MEDICIS is an isotope mass separation facility for biomedical R&D located in a class A laboratory, receiving up to 50% of the 1.4GeV PSB protons. It was commissioned with radioactive ion beams in 2017. MEDICIS has operated for the past 5 years in batch mode, with targets irradiated in a dedicated beam dump station at HRS, and with external sources provided by cyclotrons and nuclear reactors MEDICIS partners, notably during Long Shutdown LS2 [1,2]. Recent additions to the CERN-MEDICIS facility are the MELISSA laser ion source, radiochemistry on implanted isotopes, and online gamma implantation monitoring.
In 2022, we introduced key performance indicators (KPI’s) to monitor the facility for collected efficiencies, the optimization of the radiological risks and impact of modifications of the irradiation station, like the yearly integrated luminosity serves as one of the KPI's for LHC. Defined KPI’s cover different aspects in the operation cycle, such as planning in CERN schedule, target irradiations, process duration, radiological risk mitigation, facility downtime, developments and maintenance. MEDICIS KPI’s can help distinguish which of the elements in the operation and in the facility life-cycle thus requires immediate intervention, developments or consolidation.
Those deal with the irradiation stations, beam-lines (parallel collections), target and ion sources (reliability), robot handling and infrastructure, or the separation process itself.
The Future Circular Collider (FCC) study is developing designs for a new research infrastructure to host the next generation of higher performance particle colliders to extend the research currently being conducted at the Large Hadron Collider (LHC) once the High-Luminosity phase (HL-LHC) reaches its conclusion around 2040. CERN’s Integration Office aims to fulfil the requirements of different stakeholders, which includes reviewing alignment defining tunnel cross sections and supporting underground civil engineering designs. After investigating different scenarios, a first layout of an FCC machine tunnel with an inner diameter of 5.5m was defined. This paper describes the integration process for future projects i.e., decisions made and challenges that had to be overcome along the integration studies, from typical cross-sectional dimensioning to 3D machine design.
The insertion device for FAXTOR, the new hard XR tomography beamline at ALBA, is a 54mm-period in-vacuum wiggler. The device is of hybrid PM-type, consists of 11 poles for a total magnetic length of 362mm, and it will operate at a minimum mechanical gap of 5mm. The device has been manufactured by AVS Company. During the manufacturing process, the field quality of each individual magnetic arrays was checked and adjusted, but it was not possible to verify the magnetic performance of the whole device once the arrays were integrated on the final support structure. This last step has been carried out at ALBA magnetic measurements laboratory upon the delivery of the device, using our Hall probe bench for closed structures and a flipping coil bench. In this paper we present the results of the magnetic characterization and the final adjustments that have been implemented, as well as the integration of the device into ALBA Storage Ring.
In this paper, the dynamic response measurement of fast corrector at the High Energy Photon Source (HEPS) is reported. The measurement system for the fast corrector of the HEPS is based on a flat coil with high cut-off frequency. Both amplitude-frequency response and step response are measured. The measurement results indicate that the open-loop bandwidth of the fast corrector is higher than 5 kHz.
The RF Accelerator Research Division at SLAC is developing fully integrated linear accelerator systems for low energy applications, with a smaller footprint and higher efficiency than facility-scale accelerators. These systems are packaged as single units that include the high voltage power supply, RF sources, controls, and the linac structure itself. A considerable part of the effort is in developing high efficiency RF sources (klystrons) with minimal size and weight. Peak power for the klystrons is on the order of hundreds of kW per RF amplifier. Sources have been designed for X-band and C-band, with 60 kV beam voltage to eliminate the need for oil insulation and custom high voltage components. By developing a single “building block” topology of pulsed RF amplifiers with stable and repeatable phase and amplitude control, these compact klystrons could be deployed in small numbers for portable accelerator systems, or in mass produced arrays for powering larger-scale facilities for fundamental science. The intent is to enable a diverse set of applications using a common high power pulsed RF source topology, regardless of scale, to incentivize cost-effective RF power solutions via high volume production. In this presentation, a summary of SLAC’s recent design and test developments in compact RF sources will be discussed.
The Iranian Light Source Facility (ILSF) is in the detailed design phase. It will operate at 3 GeV and 400 mA with an ultra-low horizontal emittance of 0.27 nm. rad. The main storage ring combined dipole magnet has a 0.56 T magnetic field and a -7 T/m gradient. It can serve as a soft X-ray source, and there are several ways to achieve hard X-rays; one is to use a high-field dipole. It is designed with a permanent magnet and consists of three parts; a high field part that provides a 3 T magnetic field and two low field parts on either side of the high field one. The basic design of the super-bend dipole magnet is presented here.
The standard injection scheme of ILSF is composed of 2 septum and 4 kicker magnets installed in a 7-meter-long straight section. Further tuning of the 4 kicker devices to reduce perturbations has proven to be almost impossible since it requires having 4 identical magnets, electronics, and Ti-coated ceramic chambers. Different from pulsed dipole kicker magnets used in a conventional local-bump injection, the single nonlinear or multipole kicker provides a nonlinear distribution of magnetic fields, which has a maximum value off the axis where the injected beam arrives and a zero or near-zero value at the center where the stored beam passes by. So, here the designs of different multipole kickers, including sextupole, octupole, and a nonlinear kicker, have been investigated and compared.
The Spallation Neutron Source (SNS) Radiofrequency (RF) Systems have operated at over 98.5 percent availability for the last several operational periods. The implementation of a more stringent goal for the SNS RF – to exceed 99 percent availability – coupled with the more general desire to increase reliability for accelerator-driven systems has required a more subtle approach to reducing downtime. Close examination of the top downtime sources revealed that power supplies are the second leading contributor to system interruption in both frequency and duration. Power supply maintenance is nearly always reactive and there is not currently a confirmed method at the SNS to predict when they will fail. The SNS RF Systems engineering team has developed a concept, analogous to methods employed in 3-phase induction motor fault detection and mechanical vibration analysis, that uses frequency domain measurements over time to predict supply failure. This paper will describe the concept, present existing reliability data, and outline the implementation plan.
It took a decade to develop the 500-MHz module for the Solid State Power Amplifier (SSPA) in NSRRC. Performance of a single module was gradually improved to reach a steady output power of 960W by using the RF chip IC-BLF578XR. Heat dissipation unit and high-efficiency power supply are key issues in improving integral performance (49.5% RF power) of the single module. A 110-module SSPA tower was first constructed to generate 80 kW CW RF power. Next this 80-kW tower was successfully combined with a 100-kW klystron-type RF source to generate 140 kW RF power to finish the conditioning of power couplers (CPL) and off-line high-power test of a KEKB-type SRF module in the RF laboratory. Based on these operation experience, four towers of modified SSPA were then constructed and successfully combined to generate 320 kW RF power, in which the RF chip in each module is upgraded to IC-BLF578. This 320-kW SSPA station is applied to the on-line high-power test and CPL aging of a KEKB-type SRF module in 2021-2022. However, reduction on module damage rate during CPL aging, higher operation stability, greater energy efficiency, and suppression on acoustic noise are the challenges foreseen.
For the upgrade of the 6 GeV synchrotron light source PETRA III into a diffraction-limited storage ring PETRA IV it is planned to replace the 23 m long double-bend achromats by hybrid six-bend achromats (H6BA). The high packing density of elements in the H6BA cells requires that the distance between magnets are small with only a few centimeters between the yokes for some of the magnets. Overlapping fringe fields of the magnets will result in substantial magnetic cross talk. The change of the main field component of quadrupoles due to magnetic interference will lead to a change of the optical functions of PETRA IV. In this paper results of magnetic field cross-talk calculations between magnets will be presented. The influence of the cross-talk on the optics of PETRA IV, its integration in the lattice model and its correction will be discussed.
NHa and IBA are collaborating to develop a new cyclotron dedicated to hadron therapy.
This cyclotron is based on two symmetric NbTi superconducting coils, cooled at 4,3 K in helium bath. The cold mass is 15 tons, the diameter of the cryostat is about 5 meters. 470 liters of liquid helium are cooled by cryocoolers, and the coils are maintained at superconducting temperature by using a thermosyphon circulation principle. Due to the very expensive cost of commercial helium, a compact close loop cooling system has been developed to allow liquefaction of gazeous helium, and to allow re-liquefaction of the vaporized helium after a quench. The overall expected cooling time is lower than 60 days, and the recovery time after quench is shorter than 10 days. This liquefaction / recovery system is very compact and efficient, it will be set as close as possible to the cyclotron and service turret of the cryogenic coils.
The manufacturing of the cyclotron, as well as its main cryogenic systems, are in advanced stage.
In this poster will be presented the cryogenic process principles, the equipment developed and the manufacturing progress.
Significant developments in the future of linear accelerators including the operation of high gradient cavities, novel cathodes, and improved magnet designed are enabled by cryogenic operation of various subsystems and components. In order to address the growing needs of traditional infrastructure operating in a new low temperature regime, we have commissioning infrastructure for the testing of materials and complex components at low temperatures.We will present here several systems under study for developing enabling technologies for a very high brightness cryogenic normal conducting RF photogun.
The damage mechanisms and limits of superconducting accelerator magnets caused by the impact of high-intensity particle beams have been the subject of extensive studies at CERN in the recent years. Recently, an experiment with dedicated racetrack coils made of Nb-Ti and Nb3Sn strands was performed in CERN’s HiRadMat facility. In this paper, the design and construction of the sample coils as well as the results of their qualification before the beam impact are described. Furthermore, the experimental setup is discussed. Finally, the measurements during the beam experiment such as the beam-based alignment, the observations during the impact of 440 GeV protons on the sample coils and the obtained hotspots and temperature gradients are presented.
We have designed and fabricated a new DC septum magnet for modern accelerators. Septum magnets feature a dipole magnetic field deflecting designated beams at one side of the septum while providing no deflecting field on the other side. Conventional direct-drive type DC septa is embedded with coils inside the magnet gap, which usually results in rather high current density in the thinner septum conductor as the septum thickness is required as thinner as possible upon request from beam trajectory design. It can, however, lead to failures in coils due to harsh heat cycles and faults in high-current power supplies. We propose an alternative septum magnet design to significantly reduce the current density by an order of magnitude. The new design has achieved a high flux density of 1.2 T with the current density of as low as 5 A/mm2 with the 5 mm thick septum that comes in a dogleg shape for optimizing the magnetic field configuration on the both sides of the septum. We present our new magnet design and the measured performance of the magnet.
The Hefei Advanced Light Facility (HALF) is a future soft X-ray diffraction-limited storage ring at National Synchrotron Radiation Laboratory (NSRL), which aims to decrease the horizontal emittance to improve the brilliance and coherence of the soft X-ray beams. The lattice of the ring depends on the use of many short and high field multipole magnets, dipole-quadrupole magnets with high gradients (DQ) and dipoles with longitudinal gradients (DL). Due to the high gradient of DQs, it is a better choice to obtain the ideal field with an offset quadrupole design. The longitudinal gradient dipoles are electromagnets with different gaps for the requirement of the field adjustment. The design of all multipole magnets relies on a new optimization method based on NSGAII and the good results have been achieved. The design has been completed and the prototype of DL2 is under construction.
The PETRA IV storage ring is a project planned to upgrade the synchrotron light source PETRA III at DESY. The main aim is to decrease the horizontal emittance as low as 20 pmrad. This nominal emittance will be achieved by a hybrid six bend achromat lattice (H6BA) and a series of damping wigglers. The magnets used in this lattice will be a combination of resistive quadrupole and higher multipole magnets and permanent dipole magnets.
Three different types of permanent combined-function dipole-quadrupole magnets are presently developed, including one with an additional longitudinal gradient. The design structure is a further advancement of the well-proven ESRF-EBS dipoles with longitudinal gradient. Due to its moderate value, the transverse gradient can be implemented by a slanted pole design. This contribution presents the design status of these novel magnets, discusses the expected magnetic field characteristics, and outlines the mechanical design for a prototype.
This paper describes the design progress of the electron gun, and solenoid of 50 MW class klystron at C-band frequency (5720 MHz) for CEPC LINAC. The beam optics is designed in DGUN code for a space charge beam current of 318 A at an acceleration potential of 350 kV with average cathode loading of less than 6.0 A/cm^2. The maximum surface electric field at the beam optics and high voltage ceramic seal is reduced to be less than 18.65 kV/mm and 3.81 kV/mm, respectively. The magnet design transports the beam with low scalloping parameter less than 5.0 % with laminar flow downstream. Gun envelop and magnetic field are designed in POISSON code.3-D CST simulation is under progress for validation of 2D simulation results.
In order to provide hard X-rays with a 1.5 GeV electron ring, a new superbend-magnet will be used in the middle of each standard cell at Wuhan Advanced Light Source (WALS). The design, assembly, and detailed magnetic measurement of the superbend-magnet prototype has been finished. It is a three-stage combined magnet, with a high-field permanent magnet in the middle and two low-field electromagnets with transverse gradient on each side. The results of magnetic measurement show that the central magnetic field reaches 3.67 T in a gap of 14.72 mm, and the range of high field region(＞3.5 T) is larger than 40 mm in the longitudinal direction. The uniformity of the field integral is controlled below 5E−4 across the good field region. Two low-field magnets are designed as water-cooled resistive magnets which can be used to correct the integrated dipole and quadrupole components.
The radio frequency system of High Energy Photon Source adopts a double-frequency design with a main frequency of 166.6 MHz and a third harmonic frequency of 499.8 MHz. There are six normal-conducting cavities on the booster, and each cavity will be driven by a 500-MHz 100-kW solid-state amplifier (SSA) with high modularity, high efficiency and sufficient redundancy. Five 166.6-MHz and two 499.8-MHz superconducting RF cavities will be installed on the storage ring, and each cavity will be driven by a 260-kW high-power SSA. All SSAs use cabinet design, where all amplifier modules and AC-DC converters are pluggable and installed inside the cabinets. The total RF power of the SSAs will reach 2.4 MW at HEPS. With the successful development of two SSA prototypes in 2021, and after a long operation period for various high-power tests, the high stability and high reliability of SSAs have been examined. Series production of all remaining SSAs as well as the subsequent performance tests are underway. Five sets of 500-MHz 100-kW SSAs and two sets of 500-MHz 260-kW SSAs have completed the factory acceptance tests and are ready to be installed at HEPS. The development and progress of the SSAs at HEPS are presented in this paper.
Since its operation in 2013, Taiwan Photon Source (TPS) has been constantly maintaining and developing new technologies to improve its power electronics systems. The availability of GaN FETs power devices with integrated drivers and protection functions has allowed designers to achieve new levels of power density and efficiency in these systems. This paper explains how to use GaN FETs for power supply development and PCB design, and how to incorporate them into the TPS correcting magnet power supply architecture, using a TI TMS320F28335 controller and GaN FETs power modules to increase output current band-width, complete PI compensation algorithms, high switching frequencies, PWM switching modes, and communication functions.
Finally, we implemented a GaN FETs based fully dig-ital TPS correction magnet power supply development platform, which provides strong support for future development of new TPS correction magnet power converters.
The extraction system of the superconducting AGOR cyclotron consists of an electrostatic deflector and three electromagnetic channels. As the electrostatic deflector has only a moderate field strength (<100 kV/cm), the first electromagnetic channel has to generate a rather strong dipole component resulting in current densities up to 169 A/mm^2 in water-cooled copper coils.
In the original design the coils consist of sections of hollow conductor, parallel to the beam path, vacuum-brazed to machined “bridges” over the beam aperture. These “bridges” consist of several vacuum brazed parts. Altogether there are over 200 brazings made in three subsequent cycles in the three coils (dipole, quadrupole and first harmonic corrector).
In 25 years of operation two channels of this type have been “consumed”. The channels developed water leaks due to erosion of the copper by the high speed cooling water flow in the “bridge” regions that ultimately could not be repaired anymore.
To remedy this problem the channel has been redesigned using bent conductors. A production technique for small radius bends and a new joining method to avoid vacuum brazing have been developed. The coil support taking up the 10 kN/m Lorentz forces on the windings are now made from insulating material instead of anodized aluminium to prevent grounding errors. The new channel is now in operation for two years without any failure.
A detailed comparison of the old and new design will be presented.
The invention relates to a special power supply for injection of a compact electronic storage ring and an injection method, belonging to the technical field of special power supply for particle accelerators. The power supply includes a DC power module, a switching power module, a high-frequency resonant capacitor and a control circuit. The invention adopts the series resonance scheme, drives the switching power module through the control circuit as the excitation of the resonant circuit, and the high frequency resonant capacitor and the load perturber form the LC resonant circuit. The resonant frequency can be adjusted by changing the capacitance of the capacitor. The H-bridge circuit composed of silicon carbide MOSFETs can excite resonance twice within one electron injection pulse width, effectively compensate the sine wave amplitude attenuation caused by circuit impedance, and effectively improve the injection efficiency. The invention makes use of the characteristics of the resonant circuit and combines multiple H-bridge circuits in parallel to realize the high-frequency sine wave high-power current source required by the compact electronic storage ring to inject the perturber, and solves the problem of low injection efficiency of the conventional injection method.
An air-core pulsed magnet named Ceramics chamber with integrated Pulsed Magnet (CCiPM) was developed as a fast dipole kicker at first. A prototype of a dipole CCiPM was designed and tested successfully at KEK Photon Factory (KEK-PF). Because of the feature of an air-core magnet, a CCiPM can also generate an octupole magnetic field for pulsed multipole magnet injection. Compared with the pulsed iron-core magnet, the CCiPM almost does not have eddy current effects which may induce the stored beam oscillation. One prototype has been developed for the beam injection at PF ring. To examine the performance of the octupole CCiPM, some experiments has been conducted such as durability test, current excitation test and magnetic field measurement to evaluate the mechanical performance and magnetic field quality. The design and experimental results will be reviewed.
After 20 years of use, the Hall-probe system at the Na-tional Synchrotron Radiation Research Center (NSRRC) has poor measurement reproducibility. The granite bench is 6m long and is robust but the Hall-probe stage with air bearings has deteriorated. To create a reasonable operat-ing space for field correction for an insertion device (ID), the distance between the ID and the measurement system must be increased so a more stable and accurate stage is required. The developed system has a new structure to isolate the imbalance in the forces that act on it when the Hall probe stage is moving and the cable drags. An opti-cal position sensitive detector (PSD) is also fitted to measure the change in the position of the hall probe in space. The positional error in space for the Hall probe is now less than 15um. This is achieved by measuring and correcting the position in real time.
Permanent Magnet (PM) based bending magnets are state-of-the-art concepts to gain stable beam operation and to reduce the power consumption of the magnetic system in an accelerator. This is even more true in injector and beam transport beamlines with fixed beam parameters and low repetition rates. An example is the B2PT magnet in the BESSYII transfer beamline between booster and storage ring. It is the last dipole magnet for the final 7.8 deg bending into septum. This one meter long, compact, high current dipole will be replaced by three 300mm long Variable Permanent Hybrid Magnets. They combine a PM driven strong and stable magnetic field with a small field variability via compact corrector coils. With this new magnet we can reduce fringe fields and vibrations next to stored beam, as well as the total power consumption of the injector by almost 30 kW. In this paper, the design and construction process of the new B2PT magnet will be presented.
The Advanced Light Source Upgrade (ALS-U) project at Lawrence Berkeley National Laboratory (LBNL) is major upgrade of the ALS that involves the design and installation of a new Accumulator Ring and an upgraded Storage Ring. The RF High Power Amplifier (HPA) with 60 kW CW output power at 500 MHz is a complex and very costly piece of equipment that will provide high power RF to the accelerating cavities in Accumulator Ring. This paper presents the main technical specifications / requirements, features, development status and construction details of various subsystems of the HPA which is being built under con-tract by R&K Company and with engineers at LBNL providing technical oversight and inputs. The HPA detailed design and construction drawings / documents were completed by the vendor and the Final Design Review was successful. Presently, manufacturing of the HPA is in progress. The HPA is self-protecting and the main features consist of a distributed control system employing extensive monitoring of various signals; slow and fast interlock responses; finite state machine controls; and built-in fault tolerance to RF or DC power supply module failures. The theoretical high reliability (MTBF ~ 135000 hours) and high availability (~99.997%) requirements of the HPA requires redundancy in RF modules and DC PS modules for delivering a minimum 48 kW RF output under module fault conditions.
As multipurpose synchrotron radiation facilities, the Korea-4GSR is being promoted in Korea from July 2021 to the end of 2027. The construction project includes linac, 4 GeV booster, and storage ring. The circumference of the storage ring is about 800 meters, the beam emittance is 58 pm.rad, and there are more than 40 beamlines with 28 superperiods. A large number of electromagnets are used in these facilities. This presentation describes the design of the dipole quadrupole (DQ) magnets used in the storage ring. The DQ magnets are basically offsetted standard quadrupoles for design simplicity. The poles are optimized for minimum harmonic content and maxi-mum B’ with tapering. All DQ magnets should have trim coils for dipole component that will be used to keep the dipole field while quadrupole field changes.
Solid-state RF amplifiers (SSAs) are being developed to compose SIRIUS storage ring’s RF plant for operation with superconducting cavities. Each amplifier must deliver up to 65 kW of RF power at 500 MHz and a high AC-to-RF efficiency is desired to minimize operation costs. To this end, amplifier modules able to deliver 900 W with approximately 70 % DC-to-RF efficiency were designed. To combine the output of 80 modules, a cavity combiner was simulated and a prototype was assembled. This paper presents the performance of the RF modules obtained from a pilot batch, as well as measurement results from the cavity combiner at low RF power. Finally, a summary on the ongoing development of solid-state amplifiers is presented.
The EIC Crab Cavity Low-Level Radio Frequency system will have to regulate the crabbing and uncrabbing voltages, while also keeping their sum close to zero. The system will have to reduce the crab cavity impedance to prevent transverse instabilities. It will also have to maintain extremely low RF noise levels injected to the beam. This work presents an estimate of the required performance for each of these conditions and a summary of the specifications to achieve them. The significant tradeoffs between these requirements are also explored.
Elettra 2.0 is the Project finalized to upgrade the Storage Ring (SR) and part of the beamlines (BLs) of Elettra. The machine optics requires a significant number of magnets and additional coils to energize individually. More than 1200 DC power converters (PCs) are foreseen. A synergic design of the magnets and the associated PCs led to a great standardization: four current ranges (300 A, 100 A, 20 A, 5 A) and, consequently only four different types of PCs.
While the 20 V/300 A PCs (72 units) have been ordered on the market with a “built-to-specification” procedure, the 15 V/100 A and the 10 V/20 A units (together account to about 1000 units) are an in-house design and their procurement will follow a “built-to-print” procedure. The 15 V/5 A type (not less than 250 units) is still under design and will follow the same approach of the 100 A and 20 A ones.
This paper gives an overview on the magnet power converter system, the results of the tests on the prototypes and the installation strategy.
An experiment to study damage caused by the impact of 440 GeV/c protons on sample superconducting racetrack coils made from NbTi and Nb3Sn strands was recently carried out at CERN's HiRadMat facility. This paper reports on the detailed Monte Carlo simulations performed with FLUKA and Geant4 to evaluate the energy deposition of the 440 GeV/c proton beam on the sample coils positioned in the experimental setup. using the measured beam parameters during the experiment. The measured hotspot temperatures and temperature gradients reached in the sample coils are presented and compared with the simulations. In addition, comparisons between the simulation results from FLUKA and Geant4 are discussed in detail.
The European Spallation Source (ESS) will accelerate a beam of protons with a beam pulse width 2.86ms long and pulse repetition frequency 14Hz. The acceleration will be provided by 155 cavities, out of which 97% of the cavities are superconducting.
The first section of the ESS superconducting linac is the Spoke linac. The spoke linac increases the beam energy from 90MeV to 216MeV using the 26 superconducting Spoke cavities, resonant at 352MHz, situated in 13 cryomodules. The spoke cavities are powered by Spoke RF Power Stations (RFPS). The maximum power requirement for the spoke RFPS is 400kWp@352MHz. Outputs of two tetrode TH595A based amplifiers are combined to achieve 400kW output.
The RFPS are delivered by Elettra as a part of Italian in-kind contribution towards the construction of ESS. The detailed design of RFPS is done by ESS and Elettra. At present, 27 RFPS are delivered to ESS. Out of these, 20 RFPSs are installed and commissioned at ESS gallery. Out of these, four RFPSs are under soak testing at 400kWp and four RFPSs are under soak testing at 300kWp. The present paper discusses test results, issues faced during soak testing and their possible mitigations.
A source for polarized positron beams at the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab is being designed. The Polarized Electrons for Polarized Positrons (PEPPo) concept is used to produce polarized e$^+$e$^-$-pairs from the bremsstrahlung radiation of a longitudinally polarized electron beam interacting within a high-Z conversion target. The scheme under consideration includes a 4 mm thick tungsten target that absorbs 17 kW deposited by a 1 mA continuous-wave electron beam with an energy of 120 MeV. The concept of a rotating tungsten rim mounted on a water-cooled copper disk was explored. The results of ANSYS thermal and mechanical analyses are discussed together with FLUKA evaluations of the radiation damages.
The new fourth-generation synchrotron radiation source PETRA IV at DESY (Hamburg) will use a fast orbit feedback system to meet stringent orbit stability requirements. To this end, hundreds of fast orbit corrector magnets will be installed to minimize orbit distortions from external sources. These magnets are operated at high frequencies, creating strong eddy currents that result in Joule losses and a time delay between the applied voltage and the aperture field. User experiments impose stringent requirements on beam operation to preserve the point of the radiation source. To meet the demanding feedback requirements, finite element simulations are needed to understand the characteristics of the fast corrector magnet and its environment.
However, due to the low skin depths at high frequencies and the laminated structure of the magnets' yoke, conducting finite element simulations of the fast correctors is computationally very demanding. Therefore, we homogenize the laminated yoke which drastically reduces the computational effort but still captures the eddy current effects accurately.
The homogenization technique reduces simulation times from several hours to just a few minutes, allowing us to conduct extensive studies of the power losses, the field quality, and the integrated transfer functions of the magnets.
This paper presents the magnetic design, mechanical design and assembly tooling design for four 500T/m Hybrid Halbach Quadrupoles with an aperture radius of 4mm. The quadrupoles will be used for capture of a 1-5 GeV electron beam produced in a plasma acceleration stage at the Extreme Photonics Application Centre which is currently under construction at Rutherford Appleton Laboratory in the United Kingdom. In order to meet the stringent requirement dictated by beam dynamics studies, that the peak gradient of the four quadrupoles should vary by less than 1% in the presence of economically achievable engineering tolerances and magnetic field uniformity of the permanent magnet blocks, the design features a novel ‘3-bit tuning system’ in which three steel rods can be inserted in 8 different combinations into each steel magnet pole to tune the gradient in evenly spaced steps of 0.8% over a full range of 6%. This 3-bit tuning system can be used to ensure the specification on uniformity over the four quads is achieved.
We developed high-precision digital control magnet power supplies (MPSs) aiming at next-generation light sources such as SPring-8-II. The system consists of a high-precision ADC circuit and an FPGA that processes a proportional-integral control and pulse-width-modulation. Using the system, the current ripple and long-term stability (8 hours) of the MPS are controlled within 20 ppm. The MPS can be made to fit various magnets by readily adjusting feedback parameters. We also developed functions of a pattern mode and a multi-channel synchronization. In the pattern mode, the output current comes in a 0.5 Hz sine-wave that can be applied to a beam-based alignment and other purposes. The multi-channel synchronization can precisely synchronize the timing of three outputs for 6-pole steering magnets etc. The newly develop MPSs have been introduced to the next-generation 3 GeV light source, NanoTerasu, in Japan. There, large current MPSs with 50 - 650 A are used for family magnets, and DC-link type MPSs with +/-5 - 20 A are used for steering magnets in the storage ring, and various magnets in the injector linac. We will report an overview and performances of MPSs.
A new 1.3 GHz solid-state high-power RF amplifier (SSA) has been built for the Lighthouse project in close cooperation between Cryoelectra and RI Research Instruments. The amplifier was developed by Cryoelectra as a scalable compact system with an RF-power density of 40 kW/m². Its industrial design is very reliable and easy to maintain. The SSA delivers a continuous RF output power of more than 130 kW with a wall-plug efficiency of 64% and with very low phase noise.
The power is generated by 40 patented RF amplifier modules each containing 8 GaN transistor units. Their outputs are combined by a coaxial 8-way combiner in the center of the module. Each module is connected to the 4x10-way cable-free wave guide combiner network and can be exchanged in case of faults within minutes thanks to quick connectors. A sophisticated control system continuously monitors the state of all components for reliable machine and personnel protection.
MedAustron is a synchrotron-based ion therapy center in Wiener Neustadt, Austria, constantly working towards the performance improvement of cancer treatment. A major improvement opportunity comes from the scanning magnets system – a crucial element of dose delivery system at MedAustron - that is influenced by the bandwidth and power density of the magnet power supplies. Therefore, a novel highly modular power converter, based on the latest GaN technology is being developed to tackle the aforementioned requirements. One sub-module of this power supply is based on two H-bridges that are operated in hard parallel and are integrated into a standardized 19” euro-crate card form factor with target output specifications of 300V and 33A. This design also includes a 4th-order output Bessel filter to meet the ripple requirements for clinical operation. Furthermore, those sub-modules offer the possibility of being connected, cascaded or interleaved, in order to meet different output power requirements, providing a high modularity aspect. The status of this development in terms of requirements, global topology, filter structure, modulation strategy and control structure is presented.
A superconducting (SC) 1.5 GHz (3rd harmonic) cavity is being developed for lengthening bunch and improving beam lifetime in the Hefei Advanced Light Facility (HALF) storage ring.This SC cavity is excited by an electron beam with 350 mA current, 1 nC charge, and ~6.7 ps length and requires strong damping of higher-order-modes (HOMs) in order to meet beam instability requirements. Two fluted beam tubes are employed to allow HOMs to escape from the cavity and to be damped by a pair of silicon carbide (SiC) rings which are located outside the crymodule. This contribution presents optimizations on both SiC dampers in detail. The high damping requirements for both longitudinal and transverse modes can be achieved with these dampers. In addition, the engineering design of cooling system for HOM dampers is also presented in this contribution.
Cryoelectra’s 3rd generation of solid-state RF amplifiers (SSA) for synchrotron applications is presented in the frame of a poster. The SSA delivers up to 160 kW cw RF output power at 500 MHz. The amplifier is of industrial design regarding space and maintenance requirements. Together with its redundant architecture this allows for a 24/7 operation over several months without any need of maintenance.
The output power of the amplifier is produced by 15 RF power modules of our patented “tower” design with 16 RF transistors each. With its advanced water-cooling scheme, cable-free 16-way high power combiner, and, reliability optimized RF transistor path, the “tower” module enables industry leading run-times. A newly designed compact 15-way wave guide combiner collects the output power of each RF module for a practically lossless combination. For a smooth operation of the solid-state amplifier and reliable machine and personnel protection, all components are continuously monitored by a sophisticated control system.
The heavy-ion accelerator of the Rare Isotope Science Project (RISP) in Korea has been developed. There are three types of SRF cavity, which are 81.25MHz quarter-wave resonator (QWR), 162.5MHz half-wave resonator (HWR), 325MHz single-spoke resonator (SSR). There are 22 QWRs and 102 HWRs in the superconducting linac#3 (SCL3), and 69 SSR1s and 144 SSR2s in the superconducting linac#2 (SCL2). The required RF power is 4kW for each QWR, 4kW for each HWR, 8kW for each SSR1, and 20kW for each SSR2. The high power RF SSPAs for the SRF cavities have been developed and fabricated with domestic companies. 325MHz 20kW SSPAs have been designed and fabicated to test the prototype of the SSR2 SRF cryomodule including six SSR2 cavities. They were designed to enable full-reflection operation at all times. It consists of four 6kW power-units, four 6kW circulator units, 4-way combiner, a control unit, a power distribution unit, and cooling water inlet/outlet manifolds in each 19“ rack. The power-unit has six 1.2kW pallets and circulators, and three power packs. This paper describes the design and fabrication of the SSPA systems for the RAON SRF cavities.
Solid-state power amplifier systems as RF sources for particle accelerator are paving their way into industrial products due to several advantages compared with established tube technology. Within this change a demand for optimized performance as trade off from power gain and efficiency rises to reach the high-power levels and for ensuring an electrical efficient operation. When combining hundreds of transistors within one system many parameters play a crucial role and the small design decision taken on the transistor amplifier module level will severely influence the overall performance of a multi hundred kW system. Within the development of a new generation of solid-state power amplifier we investigated the effect of the drain voltage applied on the system performance such as power gain, compression point, efficiency, and phase. In this presentation we will discuss the benefits and challenges which arise when changing the drain voltage in a running combined amplifier system as well as present measured data of the system performance. This is done by analyzing the performance of the individual subcomponents as well as the whole combined amplifier system. Thus, we are capable to understand more in detail the parameter affected by the drain voltage and hence being able to improve the efficiency of the high-power systems.ltage and hence being able to improve the efficiency of the high power systems.
The European Spallation Source (ESS) linear accelerator is designed to accelerate a 62.5 mA, 2.86 ms, 14 Hz proton beam up to 2 GeV for delivery to a rotating tungsten (W) target. The beam transfer sections between linac cryomodules and approaching the target contain over 200 quadrupole, dipole and corrector magnets for beam envelope and trajectory control. In addition, a raster magnet system comprised of dual-plane dipoles is used to reduce beam density on the target. All magnets have been provided to ESS by in-kind collaborators, universities and research institutes across Europe. Following the delivery of these magnets and their respective power converters to ESS, this proceeding presents the status of the installation together with the methodology and first obtained results from integrated testing phase.
The Radia code is used widely to model magnets for various particle accelerator applications, especially for insertion devices at synchrotron radiation sources. Although Radia provides many useful capabilities, including generally nonlinear relationships between applied fields and material magnetization, it previously lacked a full description of the hysteresis dynamics present in ferromagnetic materials. We have developed extensions to theRadia Python interface which currently include two models, Jiles-Atherton and Preisach, that enable users to account for fully hysteretic dynamics in their magnet simulations. Our contributions feature efficient numerical implementations as well as useful loop-tracing and interpolation methods to allow users to accurately model developing dynamics during a simulation.
One of the key issues in the technology of superconductors is the protection against quenches. When designing a superconductor as a magnet, a coil or even current leads, the design should be made such that the superconductor withstands all operational conditions as fast discharges, pulsed loads or even rapid transient background fields.
Computational modeling of pulsed-current characterization in a self-field NbTi racetrack sample coil has been performed using the finite element modelling software Opera as a step towards understanding the thermal and electromagnetic processes during a quench. The pulse was modelled to be generated by discharging a capacitor into an RLC circuit, which includes the NbTi racetrack coil as the sample under test. The coil was driven to the resistive state and the quench occurred by applying the pulse with a peak value exceeding the critical current of the sample coil.
This contribution presents the results obtained from investigating a pulsed NbTi coil in a model based on an electromagnetic analysis. In addition, a comparison to the theoretical expectations derived for the damped oscillations in the pulse-driving circuit is given. Finally, the results from a coupled analysis, where both thermal and electromagnetic properties are being considered, within a quench multi-physics study are presented.
An Injector upgrade at Jefferson Lab presented new requirements for the Wien filter magnets power supplies. In addition to raising the output amperage requirements from 10Amps to 20Amps, the new power supplies are required to drive loads with very low inductance, capacitive effects and stringent ripple limitations. Existing power supply solutions required loads with a minimum of 25mH to achieve the ripple requirements. A plan to develop a 100 parts per million (ppm) 20Amp DC power supply to drive specified loads was formulated. The specification and design choices for this power supply will be presented. A modulator approach to the design functions led to embedded controller and power amplifier implemented on two different printed circuit boards. This modular design allows for future flexibility to meet higher power requirements or obsolescence. The controller design uses modern technologies such as Field Programmable Gate Array (FPGA) for embedded controls, diagnostics and communications.
The design concept of the Electron Ion Collider (EIC), which is under construction at BNL, considers adding a 2nd Interaction Region (IR) and detector to the machine after completion of the present EIC project. Recent progress with development and fabrication of large-aperture high-field magnets based on the Nb3Sn technology for the HL-LHC makes it interesting for using this technology in the 2nd EIC IR. This paper summarizes the results of feasibility studies of large-aperture high-field Nb3Sn dipoles and quadrupoles for the 2nd EIC IR.
The synchrotron of XiPAF (Xi'an 200MeV proton application Facility) is a compact proton synchrotron, which can accumulate and accelerate 1e11 particles for 3-order resonance slow extraction, with H^- stripping injection and phase space painting scheme. Now XiPAF is under the challenge of more particle species for single event effect study, like He+, C4+ and so on. This paper report the lattice considerations and beam dynamic study for XiPAF-Upgrading Project, shows that XiPAF synchrotron upgrade is feasible by using original dipole, quadrupole and sextupole magnets.
The LHC low-beta quadrupole magnets, also known as “Inner Triplets”, are the final focusing magnets located on each side of the LHC interaction points. The design of the currently operated LHC Inner Triplets is based on NbTi superconducting technology. The magnets are operated in superfluid helium and use a longitudinal heat exchanger to extract the power deposited by the secondary particles coming from the proton collisions. The dynamic heat load in the Inner Triplet is proportional to the LHC luminosity and due to the recent upgrades of LHC and its injectors, the cryogenic capacity limit can be reached in ATLAS and CMS experiments where the luminosity can go slightly beyond the LHC ultimate values. This paper summarizes the history of the Inner Triplet cryogenics with the dedicated tests performed in the past to assess their cooling capacity. Then, it describes the optimization-oriented techniques implemented in the cryogenic process control system to handle the luminosity transients and finally presents a new process control interaction between the cryogenic system and the LHC levelling server, towards a high-level optimization of the achieved LHC luminosity without loss of the cryogenic conditions.
Logistics is not "rocket science" nevertheless a poor coordination and planning of procurement, transportation, and storage can cause congestion in the supply and movimentation of components and systems, increasing the risk of delays, damages and - worst of all - injuries to the personnel.
Upgrading an existing machine doubles the difficulties, handling the old parts and the new ones, almost at the same time.
This paper deals with the activities carried on so far for Elettra 2.0 Project, with main focus on the removal and handling of the existing Storage Ring (SR) and the associated systems.
Different approaches have to be adopted for what is contained in the SR tunnel – subject to radio protection verification – and what is external to the tunnel and can be more easily handled. Additionally, parts to re-use and those that must be temporary removed, protected and stored require different procedures from the other ones to discard and dispose.
The Hefei Advanced Light Facility (HALF) is a vacuum ultraviolet (VUV) and X-ray diffraction-limited storage ring light source. It has a relatively large dynamic aperture, and an injection scheme with a nonlinear kicker (NLK) was considered for the HALF. This kind of magnet was designed with a small gap shield in the central area to gain a flat magnetic field. A complete prototype has also been produced and the measurement of magnetic field was done. In this paper, an improved structure of the nonlinear kicker is presented based on the previous one. Simulation of the longitudinal impedance has also been done and will be given later.
An injection-locked amplitude modulated magnetron is being developed as a reliable, effi-cient RF source that could replace klystrons used in particle accelerators that have superconducting cavities. This paper will describe the magnet system which is designed to provide a reasonably uniform field over the magnetron interaction region (IR). Most of the field in the IR is provided by a large solenoid. A smaller trim coil inside the larger coil provides the ability to vary the field within a certain range. In anticipation of a large number of magnetrons needed for an accelerator the large solenoid would be replaced by permanent magnets to provide the IR field. This paper will describe the magnet system both with solenoid coils and with the permanent magnet option.
The transverse gradient undulator (TGU) concept is a way to enable short-gain length free electron lasers with laser-plasma accelerated electron bunches, although their energy spread is typically in the percent range. In this contribution, we report on the magnetic field measurements on a 40-period superconducting TGU designed, manufactured and commissioned at the Karlsruhe Institute of Technology (KIT). As the figure of merit for the field quality, tracking and radiation field simulations, based on the measured fields, will be presented.
The Elettra 2.0 project involves the installation of more than 600 new magnets for the upgrade of the existing light source. All the magnets will be measured in house in a new magnetic measurement laboratory to be built and equipped by 2024. The measurements will be carried out over a period of two years and will consists of acceptance tests, magnetic characterization and, to meet the demanding requirements of the new machine, alignment of magnet multiplets on a common girder. We report on the design and development of the measurement systems devoted to the aforementioned tasks. Specifically, two rotating coil systems employing high quality induction coils, fabricated on printed circuit boards, will be used for acceptance tests and characterization of multipole magnets, including reverse bend and combined function magnets. A 3D magnetic field mapper based on hall sensors will be used for the characterization of dipole magnets, sector dipoles with transversal gradient and superbend magnets. Moreover, a stretched wire system will be developed for the alignment of magnet multiplets.
he Advanced Light Source (ALS) at the Lawrence Berkeley National Laboratory (LBL) is going through an upgrade (ALS-U) where the ALS triple-bend achromat will be replaced by a nine-bend achromat storage ring (SR) with an on-axis injection using beam swapping from a triple-bend achromat accumulator ring (AR). About 700 magnets will be used for the ALS-U accelerator systems. The paper gives an overview of the stretched wire and rotating coil systems used for the magnetic measurements of the ALS-U magnets. We are also describing the fiducialization process, i.e. the mechanical and magnetic alignment of the magnets.
High-order corrector magnets will be required for the magnetic system of the HL-LHC inner triplets. These magnets are based on a superferric design thus the saturation of the iron poles affects the field generated in the aperture, i.e., the magnetic transfer function shows a nonlinearity. One of the challenges for the operations of these magnets is to find a suitable fit of the magnetic transfer function able to predict the field generated, given the current, within the acceptable level of 1%. In the LHC, the magnet operations rely on a magnetic field model (FiDeL) for deriving the current level from the required field strength. This paper presents a first iteration of the field modelling for the new high-order corrector magnets.
The new interest for a muon collider has motivated a renewed and thorough analysis of the accelerator technology required for this collider option at the energy frontier. Magnets, both normal- and super-conducting, are among the crucial technologies throughout the accelerator complex, from production, through acceleration and collision. In this paper we initiate a catalog of magnet specifications for a muon collider at 10 TeV center-of-mass. We take the wealth of work performed within the scope of the US-DOE Muon Accelerator Program as a starting point, update it with present demands for the increased energy reach, and focus on the magnet types and variants with most demanding performance. These represent well the envelope of issues and challenges to be addressed by future design and development. We finally give a first and indicative selection of suitable magnet technology, taking into account both established practices as well as the perspective evolution in the field of accelerator magnets.
A new kicker power supply using SiC-MOSFETs is under development at J-PARC. SiC-MOSFETs enables the fabrication of compact high-speed pulse power supplies to replace thyratrons switch power supply. The base circuit uses an induction voltage superposition circuit of the LTD method, and the semiconductor module circuit consists of a radial symmetry type that achieves low noise. The three main parts of an existing kicker power supply, the thyratron, PFN circuit, and end clipper, can be configured in a single module circuit. The power supply consists of a 1.25kV/2kA main circuit module board that forms a trapezoidal pulse and a 0.1kV/2kA correction circuit module board that compensates for droop of the flat section. The thirty-two main circuit module boards and twenty correction circuit module boards are connected in series in a hierarchical manner to achieve the waveform specifications required for J-PARC RCS kicker power supplies: output voltage of 40kV, output current of 2kA, and pulse width of 1.2us. In addition, an insulating cylinder for conductors has been developed that suppresses corona discharge and withstands continuous operation for long periods of time.
The CEBAF energy upgrade will require magnets with high fields to bend electron beams of up to 22GeV in the 80.6m radius tunnel. A peak field in excess of 1.5T, together with a large gradient of 40T/m or more, are used in its fixed-field arc lattice to bend multiple recirculation energies in a single pipe. Additionally, the magnet must have an open midplane to allow synchrotron radiation to be absorbed by a cooling channel.
A short 45mm section of NdFeB prototype has been designed and built as part of permanent magnet R&D at BNL. This satisfies all the above requirements and has had its integrated field tuned to better than 1 part in 10^3. This tuning process uses a technique with iron rods adapted from CBETA and miniaturised here, together with measurements at a new compact field-mapping stand that is accurate to 1 part in 10^4.
Cryogenic permanent-magnet undulators (CPMUs) have emerged as a focal point in the development of short-period undulators. At the Taiwan Photon Source (TPS), two 2-meter CPMUs have been developed using different magnet materials and cooling techniques. Spe-cifically, a PrFeB-based CPMU, equipped with cryocooler cooling, and a NdFeB-based CPMU, utilizing liquid nitrogen (LN2) tank cooling, have been developed. These CPMUs are currently stable operating at TPS storage ring under a constant beam current of 500 mA.
The energy of a collider is proportional to the field of the dipoles and to the length of the arcs available to dipoles. A way to increase energy without increasing the field or making a longer tunnel is to have a larger filling factor (fraction of the arcs covered by dipoles), ie to reduce the space dedicated to quadrupoles, correctors, interconnections ... In this paper we discuss three possible paths to increase the filling factor, namely (i) having longer spacing between quadrupoles, (ii) using a 60 degrees phase advance optics rather than 90 degrees , and (iii) spreading the quadrupole gradient in the dipoles, i.e. going for a combined function magnet. The case of both the HE-LHC and the FCC lattices are considered.
Permanent Magnets (PM) and Electro Magnets (EM) with conventional resistive conductors are widely used in particle accelerator. The different applications include all types of multipoles, bending magnets, chicanes, kicker and undulators.
Both types of Magnets have specific advantages and disadvantages, state of the art PM comprise expensive raw materials like Nd, Dy, Tb and Co and reach only limited flux densities. Whereas resistive Electro Magnets are comparable cheap to produce reach higher flux densities and can be easily adjusted or switched by controlling the exciting current. However running costs and energy consumption during use are much higher for the EMs and almost zero for the PMs. Therefore, the lifetime energy consumption and costs are lower for the PM. Both types of magnets are compared in terms of performance, production costs, running costs and CO2-emission. We discuss the latest PM materials and approaches to reduce energy consumption by substituting EM`s with PMs or to combine both types of magnets to hybrid structures.
A permanent dipole magnet assembled by Sm2Co17 was fabricated and measured at NSRRC. The main magnets were consisted of several small magnet blocks. A simple coil was wound to measure the total flux of permanent magnet. The flux coil was compared and calibrated by the Helmholtz coil using small magnet block. A flux sorting process was implement to obtain more homogeneity magnetic field. A NiFe alloy was used to compensate the magnetic flux fluctuation with temperature of permanent block. These methods were use in the accelerator upgrade in the future. The magnet circuit design, magnet assembly and field measurement results of permanent dipole magnet are presented in this article.
In order to ensure strict phase synchronization between power supplies, CSNSRCS resonant power supply receives 25Hz and 100KHz timing signals provided by the timing system. The 25Hz rising edge is used as the trigger signal of RCS cycle, and the 100KHz signal is the AD sampling clock of the power digital controller. These two signals are distributed by the timing system according to the clock demand of the whole accelerator. During the operation of CSNS, the thunder in the park caused the loss of the main timing of the timing system, and the RCS power supply reported various strange failures irregularly, resulting in the beam stop of the accelerator and damage to the power hardware. In this paper, the power supply action logic when timing loss occurs is studied in detail, and a timing signal loss detection method is proposed. The correctness of the program design is verified through programming and testing. At present, the timing signal detection subprogram has been added to the formal program, and it runs well.
The Insertion device development and measurement laboratory of Devi Ahilya University, Indore, India has ongoing activities on undulator design, development and measurements. A new type of undulator known as Asymmetric magnet pole with upper and lower structure having different period lengths will be designed and fabricated. Asymmetric magnet pole undulator has a special demanding field quality for suppressing the higher harmonic components of radiation and reducing on axis heat load from radiation.
The undulator will be a variable gap undulator with upper structure consist of 25mm period having NdFeB magnets of rectangular cross section 6.25 mm, 6.25 mm and 50mm and lower structure will be with 50mm period length with the same magnet material but having rectangular cross section of 12.5mm, 12.5mm and 50mm. In this paper the design details for an asymmetric magnet pole undulator will be presented.
The CERN ISOLDE facility is currently equipped with two uncooled iron blocks acting as beam dumps. In order to guarantee the reliability and safety of the installation for the years to come, a study has been launched to evaluate the possibility to exchange the ISOLDE beam dumps during LS3. The consolidation would also allow compatibility with the 2 GeV and intensity upgrade being discussed. The contribution will detail the challenges of the project and the path being proposed to tackle them.
This report discusses the design of a current feedback component for a TPS correction magnet power supply. The component utilizes a low-cost and small-sized TI INA253 resistor combined with a temperature compensation control circuit to improve the output current thermal equilibrium time. With these measures, the system achieves thermal equilibrium quickly, resulting in improved performance. Ultimately, we successfully developed a TPS correction magnet power supply with temperature compensation control. The system is compatible with the existing TPS control interface, reduces the cost of current feedback elements, and achieves a better thermal equilibrium time, which is highly beneficial to power supply development teams.
In CSNS, there are more than 350 devices in the accelerator power supply system, which respectively provide precise excitation current for the magnet load. Therefore, the stable operation of the power supply is an important prerequisite to ensure the beam quality, and also one of the necessary conditions for the normal operation of the CSNS.
In accelerator power system, digital controller is widely used because of its flexibility and reliability. However, with the accumulation of running time, the failure of power supply caused by the fault of the digital controller often occurs, which affects the operation efficiency of the accelerator. Through the analysis and detection of the failed digital controller, it is found that the failure is basically caused by the optocoupler failure.
In this paper, firstly, by dividing the digital controller into functional modules, it is equivalent to series system. According to the reliability principle of series system, the failure of any part will lead to the failure of the whole system. Secondly, according to the nature of the optical coupling failure is revealed, the reliability model of the controller considering the optical coupling failure is established, and the overall life evaluation of the controller is obtained. Finally, for the failure caused by optocoupler failure, a redundancy strategy is proposed for this part to improve the reliability.
As the precise sensor system for monitoring the rela-tive altitude changes among multiple points, the capacity hydrostatic leveling system (HLS) is widely used in particle accelerators. To expand its application in provid-ing the elevation constraint for the control network ad-justment, the research on the issue of the HLS for alti-tude difference measurement between multiple points is carried out. Based on the working principle of the HLS sensor, a comparison system composed of dual-frequency laser interferometer, high-precision Z stage, HLS sensors and others is designed and manufactured. The system is used to control multiple sensors to observe the same liquid level in the same coordinate system. The zero-position difference among sensors can be obtained by comparison. Then the altitude difference measure-ment can be realized, and it is verified that the measure-ment accuracy is better than 5 μm. In addition, a simula-tion experiment for 3D control network measurement is run, in which the HLS system provides the elevation constraint for the adjustment processing. The results show that for the 100m linear tunnel, the errors accumu-lation in the elevation direction is significantly improved compared to the classics adjustment.
The accelerators constituting the LHC injectors chain have been gradually built and commissioned since the CERN foundation in the fifties. The operation of the Proton Synchrotron, the Proton Synchrotron Booster and the Super Proton Synchrotron started in 1959, 1972 and 1976 respectively. During the Long Shutdown 2 (LS2) of the CERN accelerator complex in 2019 and 2020, a large upgrade of these machines has been performed in the context of the LHC Injector Upgrade (LIU) Project and consolidation programme. This paper presents the process of reverse engineering performed by the Integration Office within 3D CAD environment during the preparation phase of the LS2 to allow the spatial integration studies of the upgrades and ensure the reliability of the installations. It describes the methodologies and technologies used from 2D drawings to 3D models and data consistency check processes in accordance with reality. Process remains ongoing to treat the enormous quantity of data.
The Function Generator/Controller is CERN’s flagship controls platform for electrical power converters. Despite a proven track record, the current generation (FGC3) begins to show its age through performance limitations and component obsolescence. The requirements for its successor are ambitious: 100 kHz regulation rate (a 10-fold increase); reuse of a CERN-developed hardware platform (Distributed IO Tier), improving synergy between CERN departments; and a software stack based on Linux with modern programming environments. The solution must fit CERN’s accelerator control system, but also be fully usable at other institutions that use EPICS or TANGO through the Knowledge Transfer programme.
The paper discusses the software architecture, shaped by the need to separate real-time control processes from the Linux OS, which is achieved by dedicating separate CPU cores to each. Integration of CERN converter control libraries (CCLIBS) allows profiting from years of accumulated experience in the power converter domain. Results of performance characterization under different control scenarios are also presented, as well as lessons learned during integration in a test-bench environment.
The RF system for storage ring in TPS is adopted two sets of 500 MHz KEKB-type SRF modules, with total operating voltage of 3.2 MV. Its power is provided by two sets of klystron-type transmitters with an output power of up to 300 kW, and the RF feedback loop is controlled by analog LLRF system. Since the RF system started to operate, it has been continuously improved and introduced new technologies and functions. So far, the system is gradually stable, and the mean time between failures is gradually increasing.The construction of TPS phase III is in progress. To meet its power requirements, the third RF station was officially launched in 2018 for a period of five years. The system integration and performance testing were successfully completed in February 2022. However, the performance of the 4.5K LHe cryogenic system tends to degrade with operating time, which resulted in the newly built KEKB-type SRF module to remove from the operation. Subsequently, a scheme of combining two kinds of heterogeneous power sources to increase the operating power of two SRF modules is proposed and is in progress. TPS will be upgraded to the multi-bend achromat storage ring in the future, and the bunch length will become shorter. Thus, the design and manufacture of the third harmonic superconducting passive cavity was officially launched in 2019, and the system integration and testing are expected to be completed in 2024-2025.
A 4th generation storage ring based light source is being developed in Korea since 2021. It features < 100 pm rad emittance, about 800 m circumference, 4 GeV e-beam energy, full energy booster injection, and more than 40 beamlines which includes more than 24 insertion device (ID) beamlines. This machine requires about ~1300 magnets including dipole, longitudinal gradient dipole, transverse gradient dipole, sextupoles, and correctors. In this report, the current status and prototyping status of some key magnets are presented. Particularly, impact of the end chamfering of the quadrupole magnet on the integrated multipoles are analyzed and optimum and (hopefully universal) chamfering profile is suggested.
Wuhan Advanced Light Source (WALS) is a proposed 4th generation light source, which accelerators include a 1.5 GeV Linac, 1.5 GeV storage ring and one beam transport line. The ring lattice consists of 8 identical units of 7BA. In each unit, there are 7 longitudinal gradient dipoles with transversal gradients, 10 quadrupoles, 6 sextupoles, 4 anti-bending gradient dipoles. Moreover, a combined dipole which field arrives at 3.67T is located at the middle of unit, which is used for obtaining hard-X ray. In this paper, the status of WALS ring magnets will be presented and the key technical issues for the magnet performance, such as the method of permanent magnets, pole faces optimizations with NSGA-II methods, structures and assembly will be thoroughly discussed.
The MQXFB magnets are superconducting quadrupoles with nominal peak field on the conductor of 11.3 T. With their magnetic length of 7.2 m, they stand as the longest Nb3Sn accelerator magnets designed and manufactured up to now. Together with the companion MQXFA 4.2 m long units, built by the US Accelerator Research Program, they are at the heart of HL-LHC, as they shall replace the inner triplet quadrupoles at either side of the ATLAS and CMS interaction regions of the LHC. This technology has benefited from many years of development, and this specific design was validated with successful short models (MQXFS, 1.2 m long). More recently, several MQXFA magnets were shown to satisfy HL-LHC requirements. In this paper, we report on the cold test results of four MQXFB magnets, focusing on performance, training, behavior after thermal and powering cycles, and field quality. We then provide an update of the overall status, including ongoing verifications of design changes at the level of the coil fabrication.
Super Fragment Separator (Super-FRS) is the highest priority accelerator facility in construction of the FAIR at GSI, Darmstadt Germany. Super-FRS will provide desired exotic isotope beams to various experiment sites for fundamental researches. The high energy branch of Super-FRS will be the earliest to be built and will enable to execute the first experiment of FAIR.
Key elements of the Super-FRS that large aperture superconducting dipole magnets and multiplets, which contain quadrupole magnets and corrector magnets, determine performance of the beam separator, are being manufactured and tested intensively.
In Spain, super-ferric dipole magnets with combination of a warm iron yoke and a superconducting coil cryostat are manufactured, while bath-cooled multiplet cold masses in a large cryostat are produced in Italy.
These magnets are transported to a dedicated test facility at CERN, Switzerland, for a qualification of the performance. The testing are executed by a GSI team in collaboration with CERN. The test results are fully assessed by GSI experts including beam optical evaluations and an acceptance decision is made.
Accepted magnets are delivered to GSI and inspected at room temperature, and equipped with interface items to the accelerator infrastructure (pre-assembly) and stored for the installation into the FAIR building.
We will report status of the Super-FRS sc magnet production, testing, as well as pre-assembly, highlight some findings and the measures.
The proposed PETRA IV electron storage ring, that will replace DESY’s flagship synchrotron light source PETRA III, will feature a horizontal emittance as low as 20 pm∙rad. It is based on a hybrid six-bend achromat lattice. In addition to the storage ring PETRA IV, DESY IV booster synchrotron and the corresponding transfer lines will be renewed. About 4000 magnets will be manufac-tured. Some of the magnets have demanding specifica-tions due to high magnetic field in the poles. High pack-ing density of lattice elements implies short distances between the magnets and results in magnetic cross-talk.
This contribution presents the details of the design and prototyping of the storage ring electromagnets.
Xi'an 200MeV proton application Facility, as known as XiPAF, is upgraded to a heavy ion synchrotron, which replace H^- stripping injection with multiturn injection scheme. New synchrotron circumference is much bigger than original one for injection equipment installation space, which means that this heavy-ion lattice is much different from original proton lattice. Simulation is performed with pyorbit for resonance beam loss study, with or without space charge effect, the main beam loss is caused by 3-order incoherent resonance, i.e. vx+2vy=6, which is a structure resonance. Space charge and longitudinal synchrotron motion accelerate the beam loss process.
The Elettra 2.0 upgrade project is a new storage ring that will replace the existing Elettra. Among the project's flagships are those of three beamlines with a photon flux generated by dedicated bending magnets of up to 10^13 ph/ses at 50 keV. Since a magnetic field of around 6 tesla is needed to do this, the magnet designed for those beam lines will employ superconducting technologies, for what it's called superbends.
The installation of those three superbends is scheduled in the 2026 while the test of the first prototype at the beginning of 2025. This paper reports the main magnetic characteristics of the superbend model as well as the mechanical and cryogenic preliminary design.
At the Facility for Antiproton and Ion Research in Darmstadt, Germany, fast-cycled superferric magnets will be utilised for ion optics in the main accelerator SIS100. After an intense testing campaign, the full series of dipole magnets has been equipped with cryogenic beam vacuum chambers and is ready for tunnel installation. Currently ongoing is the procurement of the quadrupole and corrector magnets. By design, each main quadrupole is combined with at least one corrector magnet to form a so-called quadrupole unit. Two of such units are then, together with further functional elements, integrated into a common cryostat to form quadrupole doublet modules. Details on the processes of production, integration, and testing as well as an update of the progress will be presented.
Moreover, to sample the installation processes of SIS100, study collective effects in an module ensemble and gain experience in operation, several magnet modules and components are currently aligned at a test facility to model a cell of SIS100. An overview of this so-called String Test setup, its commissioning and first test results will be included in the presentation.
Elliptically polarized undulator (EPU) plays an essential role in providing circularly polarized light from the third generation to upcoming synchrotron light sources. To meet the demand of energy tuning, the operation is also discussed to change from the adjusted gap method to the adjusted phase method in many of the designs. However, the adjusted phase operation causes a transverse field gradient (TFG) which may exceed 100T/m. In addition to studying the TFG characteristics of EPU, our work also investigates how TFG affects synchrotron radiation (SR) using Gaussian approximation. With our results, one can know the effect of TFG on SR using the magnetic field characteristics obtained during the design stage. We also confirmed the validity of above methods and results by numerical simulation.
A new high intensity fixed target facility could be accommodated at CERN by fully exploiting the Super Proton Synchrotron. Multiple physics experiment proposals such as BDF/SHiP, NA62-BD, HIKE and SHADOWS are being considered. Amongst the different possibilities to locate such experiments and their respective target complex at CERN, the ECN3 hall in the North Area has been selected for further study. This contribution will detail the status of the design and physics optimisation of the target systems proposed for a high intensity upgrade in the CERN's North Area ECN3. Radiation protection considerations, remote handling strategy, services supply, installation, operation, maintenance, and decommissioning aspects are herein discussed.
Electromagnets have traditionally been used in accelerators due to their wide range of tuneability with high accuracy, but are a major factor in power consumption due to resistive losses in the coils and inefficiencies in power and cooling systems. Use of permanent magnets can greatly reduce power consumption, but it has proved difficult to produce the same range of tuning with comparable field accuracy and stability. A tuneable permanent magnet quadrupole has been developed at STFC Daresbury Laboratory that moves permanent magnet blocks relative to fixed steel structures that define the field, allowing strength to be changed while suitable field homogeneity is maintained.
This prototype magnet has been installed in the Diamond Light Source booster-to-storage ring transfer line, aiming to demonstrate the operation of ZEPTO (Zero-Power Tuneable Optics) technology on a real accelerator for the first time. We present results of beam-based measurements of gradient and magnetic centre and comparison with an existing electromagnet in the same transfer line, showing that it is capable of maintaining the same injection efficiency as a traditional resistive electromagnetic quadrupole during normal operation.
In preparation for the High Luminosity phase of the LHC at CERN, to start in 2029, a refurbishment of the electronics of the CMS electromagnetic calorimeter (ECAL) is planned. The ECAL barrel section is organized in 36 elements called Supermodules (SMs), 18 in each side. All SMs, weighing about 3 tons each, must be ex-tracted, upgraded and inserted again during the Long Shutdown 3 (LS3) using two large machines, Enfourneur n.1 (E1) and n.2 (E2) operating one per each CMS side. E1 – used for the original SMs installation - has been heavily upgraded to be compliant with the current safety norms, but the demands from the logistics of the CMS cavern and the tight schedule require to produce a second machine. The new E2 machine must meet some major engineering challenges: maintaining or improving func-tionality and safety in compliance with European regula-tions in terms of safety (Eurocodes and the Machinery Directive in particular), as well as being installable in the CMS plus side, which is only accessible through narrow shafts and tunnels. E2 was therefore designed in a modu-lar way, harmonizing functional and structural require-ments with the space and tools available for transport and installation. Functionality and safety have also been improved by replacing hydraulic actuation with electri-cally driven controls and motors, resulting in refined positioning capabilities and simplified procedures for handling heavy, voluminous, and extremely delicate objects such as supermodules. The E2 design is currently complete and the construction has started in January 2023.
The National Synchrotron Radiation Research Cen-ter (NSRRC) has developed a 320 kW solid-state am-plifier based on an 80 kW solid-state amplifier. In the design of the 80 kW amplifier, the DC power supply and solid-state amplifier racks were separated, with the DC power supply providing power to the solid-state amplifier power terminals through cables. This separa-tion allows the DC power supply rack to be movable and not take up space in the solid-state amplifier rack. However, this design requires additional ground space to accommodate the DC power supply rack and re-quires significant staff and time to wire the cable con-nections.
The 320 kW solid-state amplifier incorporates a bus bar design, which significantly reduces wiring space and time while also having a simpler appearance.
The High Luminosity Large Hadron Collider (HL-LHC) project is an upgrade of the LHC aiming to increase by a factor 10 the harvested integrated luminosity foreseen early 40s. During Long Shutdown 3, scheduled to begin at the end of 2025, nearly 1.2 km of accelerator components, including a range of services spread across surface and underground facilities, will be replaced with new equipment deploying innovative key technologies. Two 300-meter-long tunnels, with access shafts and large service caverns, were excavated in parallel to the LHC machine tunnel to house the new power converters, cryogenics, and other key systems. Ten buildings were constructed on the surface to house all the necessary new services. The civil engineering design, the system definition and equipment design phase have been managed in close synergy with the HL-LHC Integration Team, responsible for optimizing the allocation of volumes between the different stakeholders in order to guarantee the efficiency of installation, the maintainability, and the operability of the different systems. This work describes the process and the challenges that had to be overcome in the integration studies to meet the targets of maturity of the project, allowing the installation phase to start on a sound and solid basis.
The RAON accelerator facility which is under construction in South Korea consists of many subsystems. These subsystems have many control devices such as Programmable Logic Controller, Power Supply, Motor, and FPGA. In order to integrate these devices into the main control system, the RAON integrated control system consists of three parts which are the main control room, server & storage system, and control network. All accelerator control signals are integrated into EPICS and transmitted over a 200Gbps redundant backbone control network. In addition, the control signals sent from the device are controlled and monitored with a display wall-based system composed of 36 monitors in the main control room. In this paper, we will describe a design of the RAON integrated control system and the result of a performance test.
The RF group constructed a second radio frequency (RF) system for the Taiwan Photon Source (TPS) RF system. This RF system employs a high-power RF transmitter to deliver RF energy to the cavity. The RF transmitter is composed of multiple power supply modules (PSMs) that are installed in series. PSMs are critical and fragile components of the RF transmitter.
This article presents the maintenance history of PSMs from 2011 to 2022 and provides guidance on how to troubleshoot and diagnose fault problems. Furthermore, this article proposes an improvement strategy for preventing any failure events.
Superconducting (SC) undulators composed of high-temperature superconducting (HTS) tapes, which can be applied to compact light sources such as a table-top free-electron laser, are a part of research and development projects at Karlsruhe Institute of Technology (KIT). In order to minimize the beam heat loads in a cryostat including the compact SC planar undulator, a vacuum chamber (liner) positioned in the undulator gap is considered. In this study, we discuss the preliminary cryostat design based on a simple cooling concept with a cryocooler and report thermal and mechanical simulation results with the liner at cryogenic temperature.
The main ring (MR) of the Japan proton accelerator research complex (J-PARC) delivers the high-intensity proton beams to the T2K long-baseline neutrino experiment. To observe charge-conjugation and parity-transformation violation in the lepton sector with high accuracy, the upgrade of the MR toward the beam power of 1.3 MW is mandatory. One promising method for increasing the beam power is to shorten the repetition cycle of the MR. The crucial point in the success of this scheme is the upgrade of the magnet power supply system corresponding to the increase in the output voltages of the magnet power supplies and the power fluctuation of the electric system. During the long-term shutdown period of MR in FY2021, a wide range of works were carried out, including installations of new power supplies, rearrangement of existing power supplies, split of magnet families, and cable rewiring. The upgrade scheme of the power supply system in the J-PARC MR and the results of this upgrade will be presented.
Volume and precision are tightly related to magnetic components that are typically necessary in a power converter for filtering (inductor) or voltage adaptation (transformer) purposes.
This paper presents a methodology for creating an efficient design tool for magnetic components to be used in power electronics applications. Specifically, an air cored inductor is taken as an example. The method consists in using supervised machine learning to create a magnetic and an electrodynamics model, able to predict the inductance value and mechanical efforts on the winging, depending on dimensional input variables. The ANN model can predict the inductance value and is trained via Finite Element Analyses (FEA). Furthermore, it can predict the electrodynamic efforts in the winding, to prevent deformation (in relation to the power converter’s output current precision) or minimise acoustic noise emission.
The ANN-based model is then included into an optimisation process, where the input variables (dimensions) are selected in order to minimize the volume or the mass of the inductor and respect some constraints such as the desired inductance value or deformation constraints. This means that the ANN model is evaluated many times before finding an optimal solution. In this context we demonstrate the power of an ANN model, where the computation time is reduced by 60 times compared to a FEA approach.
Developing HTS dipole inserts producing fields larger than 5 T within 15 T Nb3Sn outserts is necessary to generate 20 T or higher fields for future high energy colliders. Dipole inserts based on the cos-theta coil geometry with various stress management concepts and Bi2212 super-conducting strand and cable are being developed at Fermilab both within and beyond the U.S. national effort. On paper, the potential reach for the maximum magnetic field in existing or planned Nb3Sn outserts is close to 20 T, thanks to the progress realized in Bi2212 wires’ critical current density. To achieve the Bi2212 potential in accelerator magnets, however, a number of technological challenges still have to be faced. These for instance include the need to design billets that are adequate for Rutherford cabling; developing insulation processes and materials that prevent leaks, which reduce transport current and increase the risk of shorts; control and limit Bi2212 coils’ stresses and strains; reconsider the Split Melt Process (SMP) to lower costs and simplify the processing. This paper reviews Bi2212 conductor properties and coil technolo-gies, and proposes new ideas to face the challenges that Bi2212 still presents as an accelerator magnet conductor.
We need something more than "adding" more women in our work context, we need to change the culture and our work organization. In these years we learned many things, mainly that if we want to change something we have to really include the gender dimension in our labs, in our researches, in our management tables. and when I speak of gender, I speak not only of women and for women, but for all.
Looking back while looking forward, a gender target would have seemed revolutionary in 1983. More recently, after ten years of gender and other diversity-related policies and actions, the Diversity and Inclusion Programme at CERN proposed a gender target strategy, “25 by ‘25”. Unanimously endorsed by the Senior Management in 2021, implementation is well underway and interim results are in. What is working and why? Beyond gender, let’s talk about how diversity and inclusion in STEM can be most effective when it is designed for, and with, everyone.
Light sabers, hyper speed and space fights – how do they all connect with the latest accelerator research?
Since 2017 Professor Welsch has hosted a number of Physics of Star Wars events in the UK. He used the iconic films to explain applications of accelerator R&D to science, society and commerce. Each event reached hundreds of people on the day, and Millions around the world through media coverage. This has helped improve public awareness and understanding of accelerator technology.
This talk will cover these highly successful outreach events, discuss the structure adopted for diverse audiences, and present the impact they have had and how this was assessed.
Developing Free Electron Lasers using Laser Plasma Acceleration open great hopes for compact laboratory scale light sources. The COXINEL line developed at Synchrotron SOLEIL (France) has been moved at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) (Germany) for using high-quality electron beam generated by the 150 TW DRACO laser. After proper electron beam transport, seed and undulator radiation temporal, spectral and spatial overlaps, the seeded Free Electron Laser driven by the DRACO laser plasma accelerator has been observed in the UV. Good agreement is found between measurements and simulations.
The analog LLRF system of the Taiwan Photon Source (TPS) booster ring was replaced by the DLLRF system at the beginning of 2018. The difference between setting points and measured values during the ramping process was controlled within 0.3% and 0.2° for the accelerating field amplitude and phase, respectively. Moreover, the sidebands of 60-Hz noise and their high-order harmonics were suppressed to lower than −70 dBc. However, for the storage ring operation with the DLLRF system, several difficulties have been encountered because of the high bandwidth of the digital controller and the heavy-beam-cavity–LLRF interaction, which may result in an oscillation of the accelerating field. The operation parameters for each RF station, therefore, must be tuned for stable operation under the heavy-beam-cavity–LLRF interaction. A long-term stability test for the DLLRF system was performed in October 2021. Under appropriate operational parameters, the TPS DLLRF system exhibited stable operation at 500 mA.
An easy to install method for controlling electron injection in relativistic plasma waves relies on a sharp density downramp that is achieved by introducing a hydrodynamic shock into the gas flow before it gets ionized. Although the leading-order, desired effect of the shock is the generation of a 1D longitudinal drop in the density profile responsible for well localized electrons injection, there can be higher-dimensional side effects, caused by the asymmetric shape of the shock. Such asymmetries can distort and cause asymmetries in the accelerating bubble’s shape; these, in turn, can negatively impact the accelerated beam’s quality. In a recent experiment at the HIGGINS high-power-laser laboratory at the Weizmann Institute of Science [1], we have observed the splitting of an accelerated electron beam, where the major part of the beam is oriented in the axial direction as expected, but a fraction of the beam splits off and is lost to an off-axis direction. This result was observed both experimentally (using a relativistic electron probe [2]) and in full 3D particle-in-cell (PIConGPU [3]) simulations. By understanding the causes of these quality degradations, we believe that they can be compensated by correctly designing the gas target and the laser pulse, in a way that will maximize the efficiency of the energy transfer to the accelerated particles.
Beam-driven plasma-wakefield acceleration is a promising avenue for future accelerators, where a high electric field gradient could reduce the size and cost of a high-energy physics or a photon-science facility. Successful experimental results in recent decades have demonstrated the feasibility of high-gradient acceleration in plasma. However, to meet the demands of current conventional accelerator users in terms of luminosity and brightness, there are more milestones to reach. Preservation of beam quality, high overall energy-transfer efficiency, and high-average-power operation comprise the three major research pillars of FLASHForward: a plasma-wakefield-acceleration research facility at DESY. Recent results from FLASHForward include per-mille-level energy-spread preservation; high energy-transfer efficiency of 42% from the wake to the accelerating bunch; and the in-principle operation of plasma accelerators at O(10 MHz) inter-bunch repetition rates — all demonstrating promise to shrink the footprint of future accelerator facilities without a loss in functionality or efficacy. In this submission an overview of the facility, recent results, and future outlook are presented.
Plasma based accelerators have achieved beams with multi-GeV energy, percent-level energy spread, micron emittance and stability over a full day however it remains a challenge to generate beams with all these properties simultaneously. External injection of a beam from a RF linac into a plasma-based accelerator holds the prospect of improving the beams from plasma accelerators by combining their high gradient with the high quality of RF accelerators. If the beam is matched to the plasma, then the initial beam emittance and energy spread can be preserved. This technique can also be used to investigate the staging of multiple plasma accelerator stages in a controlled manner by providing a stable beam to the plasma target being tested.
We present results of an experiment performed at the CLARA accelerator in the UK investigating the external injection of the 35 MeV, 20 pC electron beam containing from the linac into a laser driven plasma wave with accelerating gradient ~100 MV/m. The beam length was larger than the plasma wavelength resulting in electrons experiencing both positive and negative accelerating fields across several plasma buckets which broadens the energy spectrum rather than a pure energy gain. This proof-of-principle experiment is part of preparatory work aiming towards acceleration of electron beams with near perfect beam quality preservation. Simulations are also presented for beam parameters after a scheduled upgrade to CLARRA which inform future experiments.
The Compact Linear Collider (CLIC) beam-based acceleration baseline uses high-gradient travelling wave accelerating structures at a frequency of 12 GHz. In order to prove the performance of these structures at high peak power and short pulse width RF, two klystron-based test facilities will been put in operation this year. The first Southern Hemisphere X-band Laboratory for Accelerators and Beams (X-LAB) is under commission at the University of Melbourne, and it will operate half of the CERN X-band test stand system, called XBOX3.
XBOX3 uses a novel way of combining relatively low peak power (6 MW) but high average power klystron units whose power is steered to feed two testing slots with RF to the required power with a repetition rate of up to 400 Hz. Besides the repetition rate, peak power, pulse length and pulse shape can be customized to fit the test requirements. This novel way of combining pulsed RF high power can eventually be used for many other applications where multiple test slots are required.
Intelligent robotic systems are becoming essential for inspection, maintenance, and repair tasks, both for the validation of systems before installation as well as during operation. Aiming to increase personnel safety and machine availability, robots can perform repetitive or dangerous tasks that humans either prefer to avoid or are unable to complete due to hazards, size or access constraints. At the European Organization for Nuclear Research (CERN), robots are regularly used for such tasks in highly radioactive beam lines, as well as for decommissioning. This work describes the state of the art industrial and experimental robotics at CERN, as well as the application of artificial intelligence to robotics activities. It includes a review of the main types of interventions undertaken, focusing on the personnel safety impact and the improvement of accelerators availability. Research and development in robotics at CERN is also described, along with the results of commissioning and operation of novel robotic controls.
Sparks in TRIUMF's main cyclotron have to dissipate a lot of energy due to the large volume of the RF cavity, causing a trip of the system, resulting in down time of the machine and provide a risk of damaging the system if not reacted to immediately. A spark detection system evaluating the rate of change of the reversed power signal within the cyclotron when a spark occurs is employed but can currently not provide any information about its location.
Simulations with a detailed P-spice model including the entire RF infrastructure from the amplifier, the combiner station, the waveguide system, and the rather big cyclotron with a diameter of 18 meters will provide the necessary information whether the location of a spark in the system can be located. The evaluated signals are the rate of change of the falling DEE voltage and the RF signals in different locations of the RF system. These results and actual measurements of sparks in the system can then in the future be used to train a Machine Learning model to implement a real time spark detection and reaction system. Such a system provides fast diagnostics and enables preventative maintenance during scheduled maintenance times and hence can reduce the machine downtime significantly.
The international accelerator facility FAIR, one of the largest science projects worldwide, is being built in Darmstadt, Germany. At FAIR, matter that usually only exists in the depth of space will be produced in a lab for research. With the planned experiments scientists will be able to gain new insights into the structure of matter and the evolution of the universe from the Big Bang to the present. The existing GSI linac and heavy-ion synchrotron, UNILAC and SIS18 will become part of FAIR and will serve as first acceleration stage. The construction of the tunnels and buildings including the technical building infrastructure for the first project stage, including the SIS100 synchrotron and the Super-FRS (SFRS) fragment separator will be completed at the end of the year 2025. Component manufacturing, testing and delivery for the FAIR accelerator facility is progressing. Numerous components are completed, delivered and stored ready for installation. A clear plan is in place to address the replacement of the Russian in-kind contributions following the international sanctions due to the Ukraine war. Installation of accelerator components in the buildings will start at the beginning of the year 2024. Recent highlights are, for example, the progressing SIS100 string test and the successful SFRS magnet tests at CERN. A multi-stage strategy towards commissioning is under development aiming at the FAIR startup in the year 2028 with early science.
The Electron-Ion Collider requires several crabbing systems to facilitate head-on collisions between electron and proton beams in increasing the luminosity at the interaction point. One of the critical RF systems is the 197 MHz crabbing system that will be used in crabbing the proton beam. Many factors such as the low operating frequency, large transverse voltage requirement, tight longitudinal and transverse impedance thresholds, and limited beam line space makes the crabbing cavity design challenging. The RF-dipole cavity design is considered as one of the crabbing cavity options for the 197 MHz crabbing system. The cavity is designed including the higher-order mode couplers, fundamental power couplers and other ancillaries.
A 1.6 m long 16 mm period superconducting undulator (SCU16) has been installed and commissioned at the Australian Synchrotron. The SCU16, developed by Bilfinger Noell GmbH, is based on the SCU20 currently operating at at KIT. The SCU16 is conduction cooled with a maximum on axis field of 1.084 T and a fixed effective vacuum gap of 5.5 mm. The design and performance of the longest superconducting undulator at a light source will be presented.
The proton linac, for the European Spallation Source (ESS) currently in construction, will be powered by 155 high power RF systems. The RF systems will ultimately deliver in excess of 130 MW peak power, 5 MW of average power to a mixture of normal and superconducting accelerating structures at 352.21 and 704.42 MHz. ESS is a long pulse machine and will operate at 14 Hz with beam pulses of 2.86 ms. This paper will introduce the scope, system design and key technologies of the RF systems being deployed along the linac. We will present the installation and test status as well as initial experience from the operation of the first RF systems used for conditioning and first commissioning runs with beam. The RF systems have been designed to be as energy efficient as practical and we will present the results of a selection of the efficiency measures undertaken at ESS.
Climate change and its consequences require strong changes in our consumption modes and approaches. Large research infrastructures consume a large amount of various energy sources, from helium to electricity. Therefore, their societal impact in the current energy crisis is tremendous, as well as their environmental impact. The Energy for Sustainable Science at Research Institutes workshop, held every two years, gathers a large panel of institutes whose efforts and ideas aim towards a less energy consuming and impactful science.
The SPARC\textunderscore LAB test facility at the LNF (Laboratori Nazionali di Frascati, Rome) holds a high brightness photo-injector used to investigate advanced beam manipulation techniques. High brightness electron bunch trains (so-called comb beams) can be generated striking on the photo-cathode of a Radio Frequency (RF) photo-injector with a ultra-short UV laser pulse train in tandem with the velocity bunching technique. Beam dynamics studies have been performed with the aim of optimizing the dynamics of the double beam (driver and witness) used to perform particle driven plasma wake field acceleration (PWFA). In this scenario different scans on beam parameters were carried on adopting the ASTRA simulation code, in order to optimize the witness beam quality and improve the plasma booster stage performances. A benchmark of the simulations has been then performed, reproducing the experimental data obtained from the optimization of machine performances, and a good agreement was found.
Current analytical beam tomography methods require an accurate representation of the beam transport matrix between the reconstruction and measurement locations. In addition, these methods need the transport matrix to be linear as the technique depends on a simple mapping of the projections between the two areas, a rotation, and a scaling. This work will explore expanding beam tomography for transversely coupled beam and non-linear beam transports.
Gradient-free algorithms are commonly used because of the lack of knowledge about the derivative of the beam properties with respect to the accelerator parameters while running accelerator optimization simulations. However, similar to the automatic differentiation algorithms widely used in the AI/ML community, recent efforts have been made in the accelerator community to develop differentiable simulation models. In particular, differentiable space charge simulations benefit because computation time is usually critical in beam dynamics simulations. Recently, automatic differentiation of space charge simulations using truncated power series algebra (TPSA) has been proposed and shows its potential. In this study, we developed a differentiable self-consistent spatial charge model based on Green's function solver using the Hockney-Eastwood and Vico-Greengard-Ferrando algorithms.
[session-stream] https://www.youtube.com/watch?v=nIDDM4uK4qQ [/session-stream]
Nb3Sn will be a workhorse superconductor for building high-field accelerator magnets (dipoles, quadrupoles) for future energy-frontier circular colliders, but the performance of the state-of-the-art Nb3Sn conductors is still insufficient for this application. In the past few years a new type of Nb3Sn conductor with artificial pinning centers (APC) based on the internal oxidation method has been developed, and has demonstrated significantly superior performance relative to the state of the art. At present the APC Nb3Sn conductors have reached the critical current density (Jc) specification required by the 16 T dipole magnets for the proposed Future Circular Collider (FCC)-hh. In addition to the higher Jc at high magnetic fields, the APC Nb3Sn conductors also show several other interesting characteristics that are useful for high-field accelerator magnets.
Development of an accelerator-based tunable THz source prototype for pump-probe experiments at the European XFEL is ongoing at the Photo Injector Test facility at DESY in Zeuthen (PITZ). The proof-of-principle experiments on the THz SASE FEL are performed utilizing the LCLS-I undulator installed in the PITZ beamline. The first lasing at a center wavelength of 100 µm was observed in the summer of 2022. The lasing of the narrowband THz source was achieved using an electron beam with an energy of ~17 MeV and a bunch charge up to several nC. Optimization of beam transport and matching resulted in the measurement of THz radiation with a pulse energy of tens of µJ, measured with pyroelectric detectors. The THz FEL gain curves were measured by means of specially designed short coils along the undulator. The results of the first characterization of the THz source at PITZ will be presented.
In 1981 when I entered KEK, I did not know anything about accelerators and beam dynamics at all. Since then I have been helped by so many accelerator researchers in Japan and many countries. Here let me pick up a number of such people who could help me though my accelerator research. This prize is only made possible by those people.
The structural analysis of historical musical instruments is essential for the definition of restoration and conservation protocols, but also for the study of ancient manufacturing techniques and for the acoustic analysis of these precious objects. The use of synchrotron light microtomography has proved to be the ideal tool for a non-destructive approach in the analysis of instruments of historical importance such as eighteenth-century Italian violins or masterpieces in the history of music such as the first Neanderthal flute and the organs built with paper pipes for the most influential medieval families in Europe.
In collaboration with the Conservatorio di Musica "Giuseppe Tartini" - Trieste
The 288m long SLS 2.0 Storage Ring consists of several vacuum chambers with unique geometries. Complicated features, with many changes in the cross sections, are essential to provide the best impedance matching and to allow synchrotron light extraction under the tight geometrical constraints. In order to speed up the commissioning time, it was decided to NEG coat most of the vacuum chambers. A new magnetron sputtering setup has been developed in Paul Scherrer Institute, where the plasma length, defined by thin solenoids, is relatively small. The solenoids are then travelling over the entire vacuum chambers more than ten times per coating process to assure best possible thickness uniformity. Flexibility provided by this solution allows to coat various vacuum vessels in one assembly. This paper will describe this NEG coating setup and show results on SLS 2.0 vacuum chambers.
The production of high-current and intense spin polarized electron beams is of great importance in electron-based facilities. Tests are planned to produce such beams in 2023 using GaAs-based photocathodes installed in the Brookhaven National Lab RHIC Coherent electron Cooling superconducting radiofrequency (SRF) photogun [1]. A fast and efficient electron polarimeter operating in the MeV energy range is required to measure the beam spin polarization.
While Mott polarimeters provide larger measured asymmetries, a Compton Transmission polarimeter is well suited in the few MeV energy range. In this work, we report on a relatively compact and cost-effective Compton transmission polarimeter which has been built and calibrated at Jefferson Lab (JLab). First, we present the design of the polarimeter radiator, polarized target analyzing magnet, BGO detector assembly and data acquisition system. Next, results of a two-week commissioning study performed at the JLab Upgraded Injector Test Facility will be described. Here, a well-known polarized electron beam produced from a bulk GaAs photocathode in a dc high-voltage photogun was first measured in a 180 keV Mott scattering polarimeter, then used to characterize and calibrate the Compton transmission polarimeter as a function of the polarized target magnetization and beam properties. Finally, we report an effective analyzing power of the Compton polarimeter and compare experimental results with those produced via Geant4 simulations.
The growing interest in upgrading European XFEL to high duty cycle operation requires an adaptation of the current low-level RF system to the new machine specifications. In the current upgrade scenario, the principal change in the RF parameters will be the loaded quality factor (QL) of the superconducting cavities, which will increase from the current value of 4.6e6 to more than 5.3e7 to reduce the required RF power. As a result, the accelerating system will be an order of magnitude more sensitive to detuning disturbances, such as Lorentz force detuning or external microphonic vibrations. Therefore an MTCA.4-based chain to precisely measure the cavity RF signals, calculate the detuning error, generate a control signal and drive the piezoelectric tuner was developed both for single cavity and Vector Sum mode of operation. While the detuning measurement chain is implemented in programmable logic, the control algorithms are implemented on embedded processing systems of FPGA-enabled devices like DAMC-FMC25, DAMC-FMC1Z7IO, and DAMC-FMC2ZUP MTCA AMCs. This provides a flexible platform to develop resonance control algorithms. In this proceeding, the implemented architecture is discussed.
Particle accelerator projects are complex, and CERN’s current engineering tools already manage millions of documents that follow various lifecycles and workflows. Future projects will push size and complexity to yet higher levels, in addition to increased collaboration with external partners. As reliable data is critical for success of complex system design, CERN is now implementing a new PLM (Product Lifecycle Management) platform that outperforms previous disparate design data management systems in several aspects: Consolidation of legacy data in a consistent data model; Federation of data from different systems and external partners in a common structure; Processes with flexible Workflows and Lifecycles; Integration with Simulation, Manufacturing, Maintenance, and other services dealing with design and product data. The overarching goal for the new PLM platform is to act as a catalyser for improved quality and traceability of data (often known as the “Digital Thread”) and to serve as the foundation for Digital Twins of current and future accelerators with the aim to drastically reduce development times as well as operation and maintenance cost.
The Beam Interlock System (BIS) is the backbone of the machine protection system in CERN’s accelerator chain, ensuring that the beams are safely transported through the injector chain and circulated in the Large Hadron Collider. A new version of the BIS is currently under development and planned to be deployed in the SPS, LHC and the North Area experimental zone during the Long Shutdown 3 (LS3), while the recently installed BIS in LINAC4 and the PSB will remain in place. As a result, the current and the new system will be operated in parallel, and it is primordial that both systems can be supervised and monitored in the same way by the operation crews, the system experts, and reliability engineers. Consequently, it is planned to provide a data service with a unique API for both systems. This data service will leverage UCAP and chain transformations to expose data for anyone to consume, and to be logged as time series in NXCALS.
This paper recalls the current implementation of the BIS supervision. It then presents the solution that was developed with UCAP and the benefits of the chain of transformations. It then reviews the performance and limitations of this implementation, and details the future plans.
Ultrafast Electron Diffraction (UED) probes the dynamics of material structures which are triggered by a fs pump laser pulse. Some materials of interest for UED study, such as wide-bandgap insulators, require the use of UV pump lasers. Furthermore, UED with a probe size on the single micron scale requires high stability in the position, power, and size of the pump laser, which demands feedback systems and real time monitoring integrated in the full accelerator control system. Here we discuss a system currently implemented at a UED beamline at Cornell University for producing, monitoring, and stabilizing a UV pump lasers for UED with few micron probe beam sizes.
LIEBE (Liquid Eutectic Lead Bismuth Loop Target for EURISOL) is envisaged to enhance production of short-lived isotopes at higher beam powers. Radioisotopes produced at MEDICIS facility are extracted via mass separation, implanted in a small foil and delivered to other research facilities and targets like LIEBE. The high intense neutron and gama radiation produced in the liquid PbBi target results in a strong activation of the target. The activation and decay heat generation of the LIEBE target need to be assessed for maintenance, decommissioning and waste management purposes and the related safety analyses.
This paper presents the analyses performed within the study for providing up-to-date estimates of the activity inventories and the decay heat generation in the LIEBE target. To this end, a series of coupled MCNP transport and FISPACT-II inventory calculations were performed using the up-to-date LIEBE model and nuclear cross-section data from the FENDL-3.1 data library. Activity inventories and decay heat data were assessed for the target, consisting the PbBi, steel and other component materials.
The paper discusses the results obtained for the activity and the decay heat as a function of the decay time after radiation and also addresses the issue of the radiation dose loads which are to be expected due to the activated components/systems including PbBi eutectic.
During the 2022 maintenance outage, installation was completed for the new generation of spallation target-moderator-reflector-shield, known as Mark-IV at the LANSCE. The upper-tier of Mark-IV target requires precision Flight Path (FP) alignment, because of the line-of-sight view of the spallation disk within. This paper demonstrates the importance of using advanced Laser Tracker Survey (LTS) technology to inform geometry in the Monte Carlo N-Particle Transport (MCNP) code for beam spot simulation*. Based on LTS of FP14 we found out the FP14 axis to be intersecting the upper target emission surface is about 20% farther from the target center than depicted in the existing design drawings and the MCNP geometry. We have updated the MCNP geometry model based on the LTS data and used it to calculate detailed beam spot neutron intensity distributions in various neutron energy bins. The beam spot was experimentally measured by an active, high-speed, and gated PI-Max4 imager for each energy decade from 1meV to 1MeV and passive image plates. The experimental beam spot distributions agree very well with our MCNP simulations. Finally, we used our updated MCNP model to propose a realignment for FP14, along with redesigned external collimator to produce a uniform beam spot for FP14 experiments.
Modern Big physics experiments call for optimizations of machines in various aspects. Integration of an advanced control system is one of them, and timing system as controls’ backbone is most often required to be upgraded significantly or even designed and implemented anew. The complexity of experiments at HZDR ELBE and the range of varieties of its instruments and subsystems is combined with top-notch performance requirements. These, coupled with hardware obsolescence, dictate an implementation of a new timing system. It must generate trigger patterns in a range from a single shot on demand up to 26 MHz CW which requires a universal and complex implementation of the pattern composition and validity checks. The system must be compatible with all existing timing triggering patterns and must provide configuration options for new features. The design of such timing solution drives further adaptation and modification of the event-based timing system built on MRF HW. As a result, we realized the new Control Software with an extended range of functionalities. While maintaining the common functionality we made it suitable for the most demanding experiments today.
A unique muon linear accelerator (linac) for the muon g-2/EDM experiment at J-PARC is under development. Digital feedback (DFB) design employed in a low-level radio frequency (LLRF) control system is crucial to fulfilling the required RF amplitude and phase specifications in the RF cavities for a stable and continuous acceleration of the whole bunched particles. To this end, a micro telecommunications computing architecture.4 (MicroTCA.4)-based compact and in-house DFB design, using Vadatech commercial off-the-shelf (COTS) RF system-on-chip (RFSoC) advanced mezzanine card (AMC), is aimed for the muon linac. This feedback control system will employ a direct sampling method that reduces the project cost by requiring less hardware employment for ultra-high frequency (UHF) and L-band accelerating structures. The present status and first results of the project will be reported in this paper.
The design, execution, and analysis of light source experiments requires the use of sophisticated simulation, controls and data management tools. Existing workflows require significant specialization to accommodate specific beamline operations and data pre-processing steps necessary for more intensive analysis. Recent efforts to address these needs at the National Synchrotron Light Source II (NSLS-II) have resulted in the creation of the Bluesky data collection framework, an open-source library for coordinating experimental control and data collection. Bluesky provides high level abstraction of experimental procedures, instrument readouts, and data analyses to encapsulate data collection workflows. We present a prototype data analysis platform for integrating data collection with real time analysis at the beamline. Our application leverages Bluesky to provide data selection, in combination with a flexible run engine to execute user configurable Python-based analyses with customizable queueing and resource management. We discuss initial demonstrations to support X-ray photon correlation spectroscopy experiments and future efforts to expand the platform's features.
On AREAL RF photogun linac at CANDLE, time-separated ultrashort electron bunch pairs are generated by means of temporal shaping of the laser pulses driving the photocathode. The free-space interferometric delay line method used for the laser pulse shaping provides the means for tailoring the beam characteristics such as the charge contrast and relative delay of the bunch pairs in the train. In this contribution, the details on generation and characterization of temporally modulated beams will be presented along with the description of the set of available control parameters for various applications. In addition, results of ongoing studies of the effects of high-dose rate irradiation on structural and optical properties of transparent thin films and glasses will be presented and discussed.
The Argonne Tandem Linear Accelerator System (ATLAS) at Argonne National Lab uses an electronic shift log to record machine performance, save beam tune data, relay information between shifts, and track the facility's operational status for budget reporting. In early 2021, the legacy shift log was retired and upgraded to a modern platform to increase reliability and expand functionality. This contribution details the development and implementation, future expansion plans, and discusses 2 years of operational experience.
The High-Luminosity LHC (HL-LHC) project requires a doubling of the proton intensity transferred from its injector (SPS). Beam loading compensation in the SPS 200 MHz cavities is essential to limit losses when the beam is transferred into the LHC 400 MHz RF system. The SPS Low Level RF (LLRF) has been completely redesigned during the LHC Long Shutdown 2 (LS2, 2019 – mid 2021). The new system relies on a One-Turn delay FeedBack (OTFB) and a Feed-Forward for regulating the cavity field. The paper presents the performances achieved with the 2023 beam and compares these to the simulations performed during LS2. It also extrapolates the 2023 results to the HL-LHC beam intensity.
The Proton Testbeam At KAHVE-Lab project aims to accelerate protons to 2 MeV energy using a locally designed and built linear proton accelerator. An optimized Low Energy Beam Transport (LEBT) line is installed to transfer the protons from the ion source towards the Radio Frequency Quadrupole cavity operating at 800 MHz. The LEBT line includes a compact measurement station to determine the proton beam current and profile as well as the beam emittance using the pepper pot plate method and the locally developed image analysis software.
In this presentation, results from the beamline commissioning is shown: the low energy beam properties were measured at the diagnostics station for different focusing solenoid currents and compared to expectations from beamline simulations. Beam profiles obtained with different screens will be discussed for a comparison between scintillator materials. Finally, the ion source has also been upgraded from using electromagnets to a setup with permanent magnets. The initial results from this upgrade will also be shown
In order to steer beams through the center of focusing elements, the field center
with respect to adjacent Beam Position Monitors needs to be known precisely.
Often individual qudrupoles are varied to find the center, where the orbit does
not change, but this requires costly field control for each quadrupole. Here we
analyze beam-based Alignment(BBA) techniques that utilizes sextupoles that
are powered in smaller families. These methods usually involve altering the
strength of a sextupole to find the center, where the tunes do not change. How-
ever, these approaches do not hold up well for sextupoles powered in families,
as changing the strength of one sextupole in a family also changes the strength
of every other family member. To reduce the effects of other sextupoles in the
same family, a new method was developed and investigated that involves creat-
ing a closed three-kicker-bump around a sextupole and observing the effects of
the sextupole field on the kick settings. By changing the position at which the
beam enters the sextupole by controlling the bump amplitude, one can recon-
struct the sextupole center. Here, we explore the precision to which this method
can reconstruct the sextupole center and we derive an error equation used to
explain the degree of precision expected from this method.
1
Hefei Advanced Light Source is the fourth generation of synchrotron radiation light source based on diffraction limit storage ring, and its emission and brightness index design goal is the world's first, and will be the world's most advanced diffraction limit storage ring light source after completion. This paper is based on the Hefei Advanced Light Source Beam Measurement Project. CST software is used for electromagnetic simulation to adjust the physical size of the BPM. In this paper, the optimization design results of striped BPM are given. The difference ratio sum is calculated to obtain the beam position signal, and the beam position signal is adjusted to obtain the mapping diagram. Thermal simulation of button electrodes is performed in ANSYS software. Finally, the temperature distribution of the button electrode and the deformation due to heat during operation are obtained. to ensure the accuracy of the electrode measurement.
The European Spallation Source ERIC (ESS) is poised to be a high intensity and high energy neutron source for scientific applications. The source behind this high intensity neutron beam is a long pulse linear proton accelerator. In order to meet the stringent requirements on the proton beam, the protons need to be accelerated in stable accelerating gradients in the accelerating cavities. In order to achieve this, the LLRF system controlling the cavity gradients needs to be carefully calibrated. The presence of around 150 such LLRF systems, each with at least seven RF channels, and their corresponding calibration, poses quite a challenge. In this paper we present the automated calibration procedure that has been developed and is utilized at the facility. The process uses python scripts and integrated signal generator, power meter and the distributed control system (EPICS Channel Access) deployed at the facility to automatically generate the calibration tables, which are then deployed in the respective systems. The method utilizes statistical analysis of measurement data, and curve fitting procedures to generate calibration tables with high accuracy.
Vacuum chambers prepared from aluminium alloys bring unique fabrication challenges, and with recent experience preparing and testing a series of insertion-device vacuum chambers, new processes were developed and limits to mechanical design better understood. These challenges and new understandings are presented. Processes include: precision machining of almost 6 metre long aluminium extrusions with sub-millimetre wall thickness, radiographically inspected TIG welding of heterogeneous Al alloys, cleaning, ultra-high vacuum testing, alignment, and packaging for international shipment.
The normal conducting part of the European Spallation Source (ESS) linear accelerator (Linac) entered the phase of staged beam commissioning in 2021. To allow carrying out commissioning activities and operating the normal conducting Linac (NCL), safe conditions for personnel must be assured, for which the Personnel Safety Systems (PSS) at ESS play a substantial role. The Personnel Safety System 1 (PSS1) is the PSS for NCL, and its purpose is to restrict access to NCL area and to ensure that personnel are protected from being harmed by exposure to ionizing radiation in the NCL, generated by the proton beam and high power radio frequency (RF) systems. It is being realized in three phases, which follows commissioning plan of the NCL: beam up to and including radio-frequency quadrupole (RFQ), beam up to and including drift tube Linac (DTL) 1, and beam up to and including drift tube Linac (DTL) 4. PSS1 is a first PSS where Personnel Access Station (PAS) and Material Access Station (MAS) have been used to access the area, and interfaces with the RF systems realized to allow RF systems testing. It faced many challenges during the first two phases, and preparation for the third one, which will be described in this paper.
At the Ferninfrarot Linac- und Test-Experiment (FLUTE) at the Karlsruhe Institute of Technology (KIT) a new and compact method for longitudinal diagnostics of ultrashort electron bunches is being developed. For this technique, which is based on THz streaking, strong electromagnetic pulses with frequencies around 240 GHz are required. Therefore, a setup for laser-generated THz radiation using tilted-pulse-front pumping in lithium niobate was designed, delivering up to 1 µJ of THz pulse energy with a conversion efficiency of up to 0.03 %. In this contribution we study the optimization of the THz beam transport and environment.
Monte Carlo simulations are used to model neutron transport through matter for estimating backgrounds or to design adequate shielding for radiation safety. Detailed neutronics calculations require thorough descriptions of the geometry, so that the influence of all physical features and materials are captured. It is most convenient to import existing CAD models into Monte Carlo software to capture the needed precision in the simulation model. Variance Reduction algorithms are applied to enhance neutron fluxes on the far side of thick shielding for more accurate estimation.
We will describe the open-source OpenMC simulation code and its application to shielding design. We will show new variance reduction capabilities with applications for deep shielding problems. We will also demonstrate this with simulations of neutron fluxes from the Takasaki Ion Accelerator for Advanced Radiation Application (TIARA) shielding experiment. Finally, we will demonstrate a novel browser-based graphical user interface for the OpenMC software that offloads CPU-intensive simulation tasks to cloud computing resources.
ThomX is a 50-MeV electron accelerator made of a linac and a storage ring. Severe constraints on the RF-gun frequency have led to the choice of an heterodyne low-level radiofrequency distribution system. We report on the performances of this system during the first two years of commissioning of the machine.
Many vacuum applications, such as accelerators, optical chambers, superconducting cavities, SEM/TEMs, are particularly sensitive to dust and require an ultra-clean working environment. Non evaporable getter pumps with porous sintered elements are already extensively used in UHV and XHV particle-sensitive systems as well as in industrial applications, laboratories and large R&D facilities. In order to assess the compatibility of NEG pumps with ultra-sensitive devices in vacuum applications, in terms of particle release, SAES research team has been focusing on the development of optimized methods which allow to check, in a controlled and repeatable way, the deep level of cleanliness of a getter pump. In particular, the development of a robust method for particle counting is presented: the main challenges are given by the minimization of background effects and the detection of extremely low levels of counts.
The National Synchrotron Radiation Research Center (NSRRC) uses cryogenic fluids to create a low-temperature cooling environment for equipment and to conduct various experiments. However, exposure to these cryogenic fluids can cause frostbite, hypoxic suffocation, behavioral incapacitation, insanity, and even death in severe cases. To evaluate oxygen deficiency hazard (ODH) in the NSRRC, we adopted the Fermilab assessment methodology and conducted ODH assessments in the Cryogenic Compressor Room, Taiwan Light Source (TLS) Tunnel, and TLS15A hutch. The results of the evaluation of the Cryogenic Compressor Room and TLS Tunnel revealed that the ODH class is 0 both when the exhaust fan is operating normally and when the exhaust fan is damaged. The exhaust equipment in the TLS15A hutch is only for emergency use. Without the emergency exhaust fan, the ODH class in the area is 1. If the emergency exhaust fan is always on, the ODH class is 0. Therefore, we recommend that those in TLS15A should undergo safety education and receive hazard notifications. In addition, we strongly recommend installing oxygen detectors in the beamline hutch to ensure safety.
The existing heavy ion synchrotron SIS18 at GSI will be used as a booster synchrotron for SIS100 at FAIR operation. In order to reach the intensity goals, low charge state heavy ions will be used. Unfortunately, such ions have very high ionization cross sections in collisions with residual gas molecules, yielding in beam loss and pressure rise via ion impact stimulated gas desorption. To reduce the desorption yield, room temperature ion catcher providing low desorption surfaces have been installed.
Simulations with cryogenic surfaces show, that their high sticking probability prevents the vacuum system from pressure built-ups during operation with heavy ions. Such, the operation with heavy ion beams can be stabilized at higher heavy ion intensities, than solely with room temperature surfaces.
A prototype ion catcher containing cryogenic surfaces has been developed and built. The surfaces are cooled by a commercial cold head, which easily allows this system being integrated into the room temperature synchrotron. The development, laboratory tests, and improvements of this system will be presented.
High Energy Photon Source is a 6 GeV fourth-generation synchrotron light source currently under construction in Huairou, Beijing. It consists of 13 Radio Frequency (RF) stations. Each RF station consists of a solid-state amplifier, an RF cavity, an LLRF controller, an interlock controller .etc. To monitor the status of all 13 RF stations, approximately 60,000 process variables need to be acquired and archived, which shall require 600 terabytes of hard disk space for 3-year data storage. For a large number of historical data, the conventional RDB Channel Archiver does not perform well in data retrieval. Therefore the EPICS Archiver Appliance is applied and its performance was evaluated. The results indicate that the new archiving system is reliable and convenient for management and maintenance. Compared with the RDB Channel Archiver, the Archiver Appliance has the advantages of clusterable design, high read/write performance, and ease of expansion. The architecture of the data acquisition and archiving system is presented in this paper.
The Quench Protection System (QPS) of the LHC is crucial for integrity of the superconducting circuit elements. It also plays an important role in the acquisition of data from the circuit elements during the magnet qualification, equipment commissioning and accelerator operation. The new superconducting circuits for the HL-LHC era, which will be assembled and operated for a first time in the IT String facility, require finer and more comprehensive measurements during all of these steps. The required data throughput cannot be achieved with the current QPS data acquisition technology. Therefore, a new data acquisition stack called EDAQ has been developed to address this issue and provide further improvements, including accurate timing synchronisation down to the individual field agents. This contribution presents the technologies chosen for this new stack, their additional benefits, their assembly into a robust and high-performance prototype, its integration into the existing controls environment and the ongoing validation in successive steps towards the HL-LHC installation.
Protection of the superconducting circuits of the High Luminosity Upgrade of the LHC project (HL-LHC) will be ensured by a new generation of quench detection systems and various quench protection systems for the superconducting circuits and magnets.
The HL-LHC quench detection systems serve as well as high-performance data acquisition systems, that also provide essential input for the automatic analysis of events such as a superconducting magnet quench.
The supervision of the quench protection systems required the development of data acquisition and monitoring systems adapted to the specific characteristics of this equipment. Of particular importance are the protection device supervision units (PDSU), which are monitoring and interlocking the quench heater circuits and the Coupling Loss Induced Quench (CLIQ) systems.
All data acquisition and monitoring systems use Ethernet-based communication with precise timing instead of a classic serial fieldbus solution. This approach ensures the required data transfer rates and time synchronisation.
The contribution will discuss the specific functional requirements, the status of development and the results of extensive system validation testing. It will also report on the system integration and the preparation for the first deployment in the upcoming IT-String project.
The Hefei Advanced Light Facility (HALF) is a diffrac-tion-limited storage ring (DLSR) light source based on the compact multi-bend achromat (MBA) lattice. There-fore, the gaps between those focusing magnets are small. The commonly used ConFlat® flange, with a large axis dimension, is not suitable for the compact lattice in HALF. In this work, a stainless steel tapered flange fas-tened by a chain clamp has been designed for its smaller axis dimension. Two types of sealing structures are used, which are knife-edge and spring-energized metal C-ring structures, respectively. The copper gaskets with and without silver coating are used for knife-edge flange, respectively. Besides, the spring-energized metal C-ring is manufactured by SUS 304 with a tin layer of 50 μm. These flanges and chain clamps were made of SUS 304, and their vacuum properties were tested. The results indi-cate that these UHV flanges can meet the demands for the vacuum system of HALF.
The High Energy Storage Ring (HESR) has been designed for acceleration and storage of antiprotons and ions by Forschungszentrum Jülich (FZ-Jülich) for FAIR in Darmstadt.
The HESR kicker magnets have been designed for the injection of charged particles with magnetic rigidity of 13 Tm. Kicker magnets shall generate a total integral field of 57.8 mT during 500 ns with rise- and fall-times of less than 220 ns. To produce the neceassary injection field, a current pulse of up to 4000A/70 kV has to be sent through the magnets. Since the injection process using longitudional stacking should not destroy the stored beam, special attention has been paid to the flatness of the current pulse at flat-top ([I-I_0]/I_0<0.08) and to the current variation after ramp down (<10 A).
All the challenges of the kicker design have been successfully solved and the kicker system of the HESR has been produced. The system consist of four kicker magnets in two UHV tanks and one solid-state pulser with control system for every magnet. The pulsers, connected with magnet using a coaxial cable in Blumlein topology, are made of commercially available semiconductor based switches. Using a special tuning procedure the designed requirements for the pulse shape have been succesfully met. Main details of the designed system, achieved parametes and solutions used in the produced injection kicker system will be presented in this contribution.
The VSR DEMO SRF 1.5 GHz cavities require a large tuning range of 1 MHz to allow for the desired operation, including a cavity parking mode. The tuning system composed of blade tuner, stepper motor, release mecha-nism, and pre-loaded piezos installed into frames features mostly components already validated and used for other applications. However, the operational demands for the VSR application require adaptation of some of the com-ponents and testing to assess performance during aug-mented operation. Here the results of all component tests, most performed at cryogenic temperature, are presented.
The Beam Interlock System (BIS) is the backbone of the machine protection system throughout the accelerator complex at CERN, including the LHC. The present BIS needs to be upgraded to ensure the required level of dependability and maintainability for the lifetime of the HL-LHC, which is planned to become operational in 2029. The present BIS, designed more than 15 years ago, has proven its reliability but is becoming obsolete and can no longer be deployed in new installations. In this paper we present the progress towards the deployment of a new beam interlocking solution for the CERN accelerators, including several identified new requirements for the HL-LHC. The prototypes of the main interlock boards have been produced and the first tests to validate their functionality were conducted and are described in detail.
In the J-PARC linac, the low-level RF (LLRF) with the digital feedback (DFB) and the digital feedforwaed (DFF) of the cPCI system had been adopted to satisfy the requirement of amplitude and phase stabilities. It has been operated without a serious problem so far. However, more than 15 years have passed since the construction of the J-PARC linac and the life of the apparatuses used since the time of construction is approaching. Some apparatuses are now discontinued and cannot be purchased, and others have problems such as software development environments that only use on older OSs. Therefore, we are starting to develop the next generation LLRF system. Currently, the 324-MHz LLRF stations, approximately half of all systems, are replaced by new DFB and DFF system based on MTCA.4. As a next step, we will develop new 972-MHz DFB and DFF system. The analog boards cannot be shared with the 324-MHz DFB and DFF system due to the different frequencies. The digital board will be re-examined to reduce the latency. In this paper, we would like to introduce the plan to replace the DFB and DFF systems at J-PARC Linac and show the design study of the RF and clock generator board.
In modern accelerator facilities, femtosecond synchronisation between an optical master oscillator (OMO) that provides facility-wide timing pulses and an external experiment laser is needed to achieve the few-fs resolution required for experiments such as pump-probe spectroscopy. This can be achieved with a balanced optical cross-correlator (BOXC), which determines the timing delay between two laser pulses via the generation of sum-frequency radiation in a nonlinear crystal.
In this paper, a design for a two-colour fibre-coupled BOXC using waveguided periodically-poled lithium niobate (PPLN) crystals is presented. An all-fibre two-colour BOXC is highly desirable as it would be more robust against environment fluctuations, easier to implement, and can achieve greater synchronisation performance compared to free-space coupled BOXCs that are currently used in accelerator facilities. This proposed design can theoretically achieve 5 - 10 times greater sensitivity to relative timing changes between laser pulses than current free-space two-colour BOXCs, which can make sub-fs synchronisation between an OMO and an external experiment laser of different wavelength achievable.
Precision measurements of the permanent electric dipole moment (EDM) of fundamental particles require the development of new methods and techniques. The precursor experiments to measure the proton and deuteron EDM at the Cooler Synchrotron COSY in Jülich led to the of a ring concept with combined magnetic and electric field elements. The building of high-stability electric and magnetic field deflectors is one of the technical challenges of this project.
The previous studies on small-size deflectors have shown promising results in achieving high electric field strengths. For the present tests, a large-gap dipole magnet with a suitable vacuum chamber is equipped with a real-size prototype 1 m long deflector plates. Using high-voltage (200 kV) precision power converters we are aiming to achieve the design values of the prototype electrostatic ring of the order of 7 MV/m with 60 mm spacing between the electrodes in a presence of a necessary magnetic field.
The setup for studying the electric and magnetic field strength at various distances, as well as the results of the measurements, will be presented.
An X-ray detector is being developed for diagnostic measurement and monitoring of the Drift Tube LINAC (DTL) at the Los Alamos Neutron Science Center (LANSCE) at Los Alamos National Lab. The detector will consist of a row of x-ray spectrometers along the DTL which will measure the spectrum of X-rays resulting from bremsstrahlung of field emission electrons (FEE) and spilled beam. Each spectrometer will monitor a specific gap between drift tubes, and the broad array of detectors is intended to allow for location of beam spill and arcs in the DTL, a concept demonstrated to be feasible in previous measurements at the DTL. Two prototypes are under development: one with a LaBr scintillator coupled to a photomultiplier tube (PMT) along with a second LYSO scintillator that is also coupled to a PMT; and a prototype with two LYSO crystals each coupled to a silicon photomultiplier (SiPM). In both prototypes, LYSO provides a tagged gamma source with three peaks that are used for self-calibration. The LaBr-PMT module has better energy resolution than the LYSO-SiPM module, but is more expensive and more difficult to shield from background radiation. Both prototypes were tested at the LANSCE DTL to validate the feasibility of measuring gamma spectra, performing in situ self-calibration, and detecting spilled beam relative to nominal operating conditions in situ. Results from these tests and plans for future development and other possible applications will be presented.
The electron gun control system, which serves as the TLS LINAC's power source, has been in operation for more than two decades. Since some components of a previously designed circuit have aged and been discontinued, the control system will become unreliable and irreparable. A new control interface of electron gun pulser has been developed to improve the operational stability and future maintenance of the electron gun control system. To achieve remote control, a SBC (single board computer) equipped with a high-precision ADC/DAC expansion board was used as a control interface. The signal processing circuit module generates the Bias and B-plus voltages that are output to the electron gun and also provides instant feedback voltage readings. For easier maintenance, the new electron gun pulser control modules have been assembled into a single box. Furthermore, this software architecture of control interface has been based on the EPICS framework and integrated with an existing TLS control system. The efforts of rejuvenating electron gun pulser control system are described in this paper.
A new digital low-level RF (LLRF) system has been developed for the High Energy Photon Source (HEPS), a 6 GeV diffraction-limited synchrotron light source under construction in Beijing. The system is composed of a digital signal processing board (DSP), two ADC/DAC daughter boards and a RF front-end board. The FPGA of the DSP board has been changed from the original ALTERA Stratix III to Xilinx zynq-7000 which comes with a versatile Processing System (PS) integrated with a highly flexible and high-performance Programmable Logic (PL) section, all on a single System on Chip (SoC). The control algorithms were implemented in PL section while the EPICS-IOC was running on the embedded Xilinx Linux within the PS. The LLRF system has been tested with a 166.6 MHz mockup cavity in the lab and the RF field inside the cavity can be controlled within +/-0.02% in amplitude error and +/-0.02 degree in phase error (peak to peak). The requirements of HEPS were therefore fulfilled. The hardware design, control algorithms and the test results of the new LLRF system are described in this paper.
The high-energy beam transfer lines at GSI serve numerous experimental stations such as HADES, HTC and HTD as well as the fragment separator FRS and the storage rings ESR and CRYRING with a wide range of different heavy ion beams from the SIS18 synchrotron. The large amount of experiments carried out during beam times under different beam conditions require frequent changes of beam optics and beam steering in the transfer lines. In the past, the online model tool "Mirko Expert" was available for this purpose, which however is not compatible with the new control system infrastructure. Therefore, a new online model application based on the MAD-X beam dynamics simulation code and the JMad programming interface is under development in Java. This paper presents the concept and features of the new online model application, as well as possible future extensions. Efforts to overcome discrepancies in the present Mirko and MAD-X optics models are also discussed.
We are developing a fast pulsed power supply using Silicon Carbide (SiC) MOSFETs for a camshaft bunch kicker in KEK-PF. In the kicker system, the pulsed power supply needs to generate a high-precision short pulse with high power. A high repetition rate is also required due to the short circumference of the KEK-PF storage ring of 187 m. Therefore, the target specifications are 500 A pulsed current within a 1% uncertainty, a 100 ns pulse width, a timing jitter of less than 300 ps, a 15 kV voltage resistance, and a 1 MHz repetition rate. In addition, the power supply should have a high radiation resistivity because the power supply will be placed near the accelerator ring to reduce transmission impedance. To achieve the requirements, we have newly started the development of a pulsed power supply with a solid-state switching module using SiC-MOSFETs. We first developed a prototype power supply with a 14 kV switching module consisting of 16 SiC-MOSFETs in series. We confirmed the prototype power supply could deliver half-sine pulses with stable operation at a low repetition rate. The prototype power supply was also tested near the accelerator ring and worked successfully for about two months. We report the performance of the prototype pulsed power supply using SiC-MOSFETs.
Reliability in high power hadron accelerators is a major issue, particularly for Accelerator Driven Systems (ADS). For example, the Japan Atomic Energy Agency (JAEA) ADS maximum frequency of beam trips longer than 5 min was set to 42 per year. A significant number of breakdowns are caused by the failure of accelerating cavities or by their associated systems. Hence, we studied how these can be effectively reduced. To this end, we developed the numerical tool LightWin that aims to determine the compensation settings for any superconducting (SC) linac automatically and systematically [1]. This tool has been successfully used for the MYRRHA SC linac. In this work, we applied LightWin to compensate for several failure scenarios involving the last section of the JAEA linac and compared the associated retuned settings and beam performance to those found in a previous study [2] with TraceWin.
Beam commissioning is underway at STF of KEK. Since beam diagnostics are important to realize stable operation, as one of the beam diagnostics, we have developed a time-resolved beam loss distribution monitor. This monitor can observe a pulsed beam of about 800 µs, separated by every 100 µs, using up to 16 PIN photo diodes as X-ray sensors. Thus, 128 data can be acquired per bunch. The data is read out by an EPICS-based data acquisition system.
On the other hand, we are also developing an EPICS-based data acquisition system for sX-Map, which is inserted inside the stiffener ring at the iris for performance testing of superconducting cavities in vertical test. In this presentation, an overview of these EPICS-based data acquisition systems and their integration with the existing control system will be presented.
The Rare isotope Accelerator complex for ON-line experiments (RAON) is under construction in Daejeon, Republic of Korea. RAON is a device that accelerates various ions generated from ion generators such as Electron Cyclotron Resonance(ECR) and Isotope Separation On-Line(ISOL) system with a superconducting linear accelerator. The low energy superconducting linac(SCL3) is composed of 22 QWR(Quarter wave resonator) cryomodules, 34 HWR (Half wave resonator) cryomodules and 56 warm sections. The cryogenic distribution system for SCL3 has 45 valve boxes dedicated for the cryomdoules. The main purpose of the SCL3 control system is integrated control and monitor of the cryomodules, the vacuum system of the warm sections and the cryogenic distribution system. SCL3 was successfully cooled down to 4.5 K, and it is being commissioned since September 2022. This paper describes in detail the SCL3 control system developed based on Experimental Physics and Industrial Control System(EPICS).
The J-PARC 3 GeV Rapid Cycling Synchrotron (RCS) accelerates the beam pulses with different conditions to two facilities. Therefore, it is indispensable to be able to correctly monitor the beam conditions. Then, we developed the synchronized data system for RCS beam monitor. This system is enabled to provide real-time synchronized data and to also archive all synchronized data with no data loss. By this system, we could realize beam commissioning and beam supply with minimum beam loss from the beginning of RCS operation.
Current system is designed using Refractive Memory (RFM). However, recently, the use of RFM has made it difficult to integrate the various data into system. In addition, it is also difficult to upgrade to a system that can support larger size data because of RFM memory size limitation.
Therefore, we developed the extensible synchronized data system that has the same primary functions as the current system and can integrate the various data by data communicating via a LAN. Furthermore, this system is designed to provide and archive the larger size data. This paper presents the details of extensible synchronized data system and the results of its performance test.
Abstract
As part of the modernization of the Los Alamos Neu-tron Science Center (LANSCE), a digital low level RF (LLRF) control system for the LANSCE proton storage ring (PSR) is designed. The LLRF control system is im-plemented on a Field Programmable Gate Array (FPGA). The high resolution tunable 2.8MHz reference RF is gen-erated by a direct digital synthesizer (DDS) at the LANSCE front end and is transmitted to the PSR control system located half mile away. Since the digital LLRF control system is synthesized in the In-phase/Quadrature (I/Q) coordinate, the I/Q RF signals are generated by the Hilbert Transformer (HT) based finite impulse response (FIR) filter. For the stabilization of the cavity field, a Proportional-Integral (PI) feedback controller is imple-mented. In order to verify the performance of the LLRF control system before it is applied to the PSR, a FPGA based PSR cavity simulator is designed and its parame-ters are identified using the cavity field data obtained during the PSR beam operation. The low power LLRF testbench based on the simulator is constructed and the amplitude and phase stabilities of the digital LLRF sys-tem are verified.
The High Energy Photon Source (HEPS) is a 6 GeV, 1.3 km, 4th generation storage ring light source being built in Beijing, China. The HEPS storage ring is designed with an ultralow emittance of a few tens of pm rad. The development of high-level applications (HLAs) for HEPS started in early 2021. A new framework named PYthon-based Accelerator Physics Application Set (Pyapas) was developed for building HLAs. Based on Pyapas, the application development for Linac was completed in June 2022. And then the joint test with hardware system was performed, all the applications worked well in the Linac control room. Beam commissioning for the Linac began in March 9 of this year, and all the HLAs for the Linac are functioning well. The application development for the three transfer lines and the booster are essentially complete, with all the applications passing testing with virtual accelerator. Development of the HLAs for the storage ring began in November 2022. This paper will present a detailed progress on the development progress of HLAs for HEPS.
High Demand for stability, accuracy, reproducibility and monitoring capability were placed on accelerators LLRF systems, because of fundamental and applied experimental requirements. Meanwhile, availability of FPGA boards became better during last two decades. Nowadays, it is possible to implement FPGA based LLRF feedback using boards with S-band (or L-band) ADC&DAC (direct sampling technique) or boards with low-bandwidth ADC&DAC up to 60MHz (down-conversion technique).
If FPGA board with S-band or L-band ADC&DAC is not available, there are two options to implement feedback into the LLRF system. Both of them operate in down-conversion mode.
The first option employs external I/Q demodulator, I/Q signals digitization, phase and amplitude calculation, buffering into DDR memory, PI feedback, I/Q modulation and RF signal regeneration. This approach does not require an expensive, highly stable slave oscillator or slave signal generator to down-convert picked-up signals from RF cavity. However, the external I/Q demodulator has to be properly examined to define the phase and amplitude detection resolution.
The second option is almost the same, but I/Q demodulator is implemented into the FPGA logic. Picked RF signal frequency has to be down-converted with slave oscillator or slave signal generator.
Both approaches were implemented and tested at KEK LUCX facility. This report presents feedbacks’ performance results. Also, technical details are discussed.
ALBA is facing the upgrade towards a low emittance synchrotron light source machine. An active harmonic RF system operating at 1.5 GHz is foreseen to increase the longitudinal bunch length and therefore the Touschek lifetime. The main purpose of the DLLRF is to control the cavity voltage and resonating frequency of the cavity by means of the drive towards the amplifier and the plunger inside the cavity respectively. A prototype has been designed and built based on the SIS8300KU, SIS8864 and DWC8VM1 commercial boards provided by Struck. The prototype consist of a full self-contained rack, including not only the uTCA crate with the mezzanine boards, but also other auxiliaries to be able to operate the harmonic system such as intermediate frequencies generation or the driver motor controllers. In the framework of the collaboration between ALBA, HZB and DESY, the performance of the system is being proved in the BESSY-II ring using a 15 kW SSPA to feed the active Harmonic EU cavity designed by ALBA.
The Taiwan Photon Source (TPS) is equipped with 16 real-time radiation monitoring stations around the accelerator. Each operating scenario entails a different dose rate and accumulated dose. In this study, we assessed the beam current and injection efficiency of the accelerator and the dose rate and accumulated dose at the radiation monitoring stations in five scenarios. The background radiation level of the TPS is approximately 0.1 µSv/h. We observed that when the injection efficiency was over 85%, the accumulated dose was similar to the background level. When the injection efficient was low (~55%), the accumulated dose was high. When the beam trip focused on a hot spot, the accumulated dose was considerably high. The gamma-ray dose rate reached approximately 2,500 μSv/h. These results indicate that the machine should not be continuously operated in injection mode at low efficiency. Furthermore, in beam trip or dump beam mode, operators should pay particularly close attention to radiation safety.
The computation of residual gas density profiles in particle accelerators is an essential task to optimize beam pipes and vacuum system design. In a hadron collider such as the LHC, the beam induces dynamic effects due to ion, electron and photon-stimulated gas desorption. The well-known VASCO code developed at CERN in 2004 was already used to estimate pressure profiles in steady state conditions. Nevertheless, some phenomena are not taken into account such as the ionization of residual gas by the electron clouds and the evolution of the electronic density related to the electron cloud build up. Therefore, we proposed an upgrade of this code by introducing electron cloud maps to estimate the electron density and the ionization of gas by electrons to calculate pressure evolution in dynamic conditions. Results obtained with DYVACS reproduces with a good accuracy the experimental dynamic pressure recorded in the VPS beam pipes sector** of the LHC from the proton beam injection to the stable beam period, for several materials of vacuum chamber. Additionally, DYVACS was used as a predictive tool to compute the pressure evolution in the beam pipes for the Future Circular Collider e- e+.
Theoretically copper resistivity to a good approximation may be viewed as the sum of a term phonon-electron scattering term, and a constant term. The first follows the Bloch-Gruneisen formula; goes to zero as T5 at low temperature. The constant term corresponds to scattering off defects and magnetoresistance. The defect part is due to impurities and finite crystal size. Since copper coating maybe backup to sleeve insertion in RHIC, the constant term should be kept sufficiently small. Coatings of 10 µm thick copper films were deposited on RHIC pipes; their RF conductivity measured. One deposition had RRR of 1.2, while another deposition resulted in RRR of 2.3. Multiple measurements reveal that the only difference between these copper depositions was in the miniscule quantity of oxygen contamination 0.125% versus 0.03% respectively; consistent with predictions for O; but puzzling results for other impurities. Measurement results will be presented.
RadiaBeam has developed a novel design of high-power RF windows to be used in high-power proton accelerators, such as SNS. This design is based on the utilization of coaxial windows between two waveguides to coax transitions, instead of a ceramic window in a uniform cylindrical waveguide, which provides several significant benefits. First, the diameter of the ceramic disk in the coaxial line is reduced for the same RF power compared to in TE-mode waveguide design, since it operates in low impedance TEM-mode. For 500 kW average power at 400 MHz, the window size can be reduced from 13’’ to 8’’, which significantly reduces the fabrication complexity and improves structural stability, while keeping the TE11 mode cutoff frequency in the coax ~50% higher than the operating frequency. Second, the cooling of coaxial windows can be performed from both the inner and outer conductor sides. Then, the field distribution in the coaxial line is more uniform, which reduces dielectric losses and thermal gradients. Importantly, the multipactor discharge in coaxial windows can be suppressed by applying DC voltage bias between inner and outer conductors. Last but not least, coaxial windows provide wider RF bandwidth without requiring cavity resonances, which is important for accelerating cavity operation. In this paper, we will present the RF and engineering design of such windows.
For the x-ray free electron laser operation, the correlated energy spread of electron beam should remain optimized for the best performance. However, it could be varied owing to the drift of RF stations, even though a feedback system with low-level RF is operating. Non-destructive energy spread monitoring could stabilize such a variation and offer a tool to maintain the correlated energy spread of electron beam in the optimized condition. In this work, by using the electron beam produced by the photocathode, we experimentally investigated a feasibility of stripline-based monitoring system for the energy spread monitor at XFEL facility.
At Elettra-Sincrotrone Trieste (Italy), the Elettra 2.0 project aims to develop a new-generation storage ring. Taking into consideration the numerous constraints, we decided to adopt a new design of a vacuum chamber, while utilizing novel pumping solutions to overcome hugely reduced conductance compared to the current machine. Large sputter ion pumps (SIP) will be in majority replaced by distributed non-evaporable getter (NEG) coatings and small NEG cartridges and SIP pumps. For the synchrotron radiation handling, due to the tight space constraints imposed by the compact lattice, the photon absorption will be managed jointly with discrete and distributed solutions: photon absorbers have been carefully studied for combining compact form and high power density loads, while key sections of the new storage ring will be water-cooled. Throughout the whole development phase, we were using Monte-Carlo simulation codes like SynRad and MolFlow+ as effective tools supporting the design of new vacuum chambers and photon absorbers.
The current state of development for the Elettra 2.0 vacuum system, the challenges that we faced and the solutions that we adopted are here presented.
Emittance is one of the most important beam parameters in accelerators. Therefore, many emittance measurement methods such as Allison-type scanners, pepper pots, slit-scan methods, quadrupole scan methods, etc. have been widely used. In the case of the RAON heavy ion accelerator, an Allison-type emittance scanner is installed at the low-energy beam transport section. However, there is no other equipment that can measure 2D phase space downstream. To complement the measurements by the Allison-type emittance scanner, we suggest the emittance tomography with multiple wire scanners. By using feedback loop and tracking simulations, we reconstruct the 2D phase space of the beam and discuss the emittance evolution.
To better understand the beam-RF jitter at the Argonne Wakefield Accelerator Facility, a high-resolution bunch arrival monitor (BAM) is being developed. The BAM take advantages of a commercial, electro-optic modulator (EOM) to measure the bunch timing though optical modulation. This non-descructive technique is far superior and the resolution can be as high as several femto-second. A prototype has been developed.
ESS is poised to be a high intensity and high energy neutron source for scientific applications. The source behind this high intensity neutron beam is a long pulse linear proton accelerator. In order to meet the stringent requirements on the proton beam, the protons need to be accelerated in stable accelerating gradients in the accelerating cavities. In order to achieve this, the LLRF system controlling the cavity gradients needs to be designed and tuned precisely, so that cavity gradients may be maintained in the presence of long loop delay and gain and phase margin requirements. This makes it necessary to identify the characteristics of the active components involved in the RF signal chain and have accurate models of the same. The power amplifiers are one such major active component and in this paper we describe the method used to measure and model the S-parameters of the klystrons while they are made to operate at nominal conditions.
Conventional RF vacuum windows are made of metalized ceramics, hermetically brazed to a pillbox cavity. High-power windows, operating in UHF band, require the fabrication of ceramic disks with diameters on the order of 200mm (8’’). Furthermore, a Titanium Nitride (TiN) multipactor suppression coating must be applied to the ceramic surfaces. The large size and complex internal geometry of these windows create challenges in validating the coating in the fully fabricated assembly. This study evaluates a novel low-loss alumina AO479U, provided by Kyocera, and a reactive sputtering process suitable to deposit a 10-20nm thick TiN coating on a large diameter window. The paper will report the changes in the TiN coating through chemical cleaning and vacuum braze processes using contact profilometry, optical microscopy, Scanning Electron Microscopy (SEM), and Rutherford Backscattering Spectroscopy (RBS).
The Low-Level Radio Frequency (LLRF) control system is one of the most critical superconducting linac infrastructures responsible for the parameters of the beam acceleration. The LLRF system mainly focuses on the electromagnetic field parameters inside the cavity. While it incorporates fast feedback algorithms to optimize energy transfer to the passing particle beam it does not follow other cryomodule or cavity parameter changes. The Radio Frequency Protection Interlock (RFPI) system closely monitors various factors (like cryomodule vacuum, beamline vacuum, field emission probe current level, temperature, RF signal leakage, etc). Its simple but reliable logic has to provide an instant decision about the LLRF system or high-power amplifier output signal blocking in case of safety region excitation.
This contribution presents a new version of the RFPI system which logic is implemented in the FPGA chip. The initial work on the prototype of the new system design resulted in the PoC (Proof of Concept) device. The PoC offers the possibility of various protection logic configurations, input signals parameters evaluation, and modularity aspects verification. The structure and test results from the device evaluation are summarized and discussed in this contribution.
The handling of very sensitive bi-alkali antimonide photocathodes as the electron source for the SRF photoinjector of SEAlab is a critical procedure for its operation. After the growth of the photocathode, they have to be transferred in-situ under extreme UHV conditions using a vacuum suitcase and under particulate-free conditions to avoid the contamination of the SRF cavity. Therefore, we performed an in-situ photocathode transfer between two photoelectron spectroscopy systems to study the impact of the varying vacuum conditions on the surface chemistry of the photocathode. The photocathode substrate (plug) has to be transferred from the sample holder onto the plug holder (insert) at the SRF photoinjector. At the transfer system, which was setup under particulate free conditions in the clean room, we installed an in-situ particulate counter to investigate the appearance of particulates by transferring the plug onto the insert under vacuum conditions.
The MedAustron Ion Therapy Centre is a synchrotron-based particle therapy facility, which delivers proton and carbon beams for clinical treatments. Currently, the facility treats 40 patients per day and is improving its systems and workflows to further increase this number. Although MedAustron is a young and modern center, the life-cycle of certain crucial control electronics is near end-of-life and needs to be addressed. This paper covers the expansion of the direct sampling µTCA based LLRF system presented in posters at Linac2022 and IBIC2022*. These extensions are particle beam-based regulation loops, which allow regulation of the heavy ion beams in the synchrotron. At the moment a phase regulation loop, to align cavity phases to beam phases, and a radial position regulation loop, to keep the beam orbit centered in the beam pipe are realized. Both of these additions rely on the already implemented real time configurable NCOs, the cavity regulation and the position measurement already presented in the posters mentioned above. The regulation can act on the base frequency of the NCO or the requested cavity phase to attain the requested setpoint.
New generation low-emittance storage rings bring new challenges for vacuum system design and to industry partners. Vacuum chambers from copper alloys are more frequently required, and processes for forming, machining, welding, cleaning and non-evaporable getter coating have been developed in response to this demand.
The technical challenges, available processes, and examples of recent activities are presented to share an industry perspective. Current processes and those in development are presented to encourage discussion about ideal mechanical design of vacuum chambers for storage rings, to optimise functionality, cost and reliability of fabrication.
The SIS100 heavy ion synchrotron as core part of the Facility for Antiproton and Ion Research (FAIR) will be equipped with 14 accelerating RF stations in the first stage of realization. Each RF station consists of a tunable ferrite-loaded cavity powered by a tetrode amplifier. Further key components are a solid-state pre-amplifier, a power supply unit, and dedicated Low-Level Radio Frequency (LLRF) feedforward and feedback systems to control amplitude and phase of the cavity gap voltage as well as the resonance frequency. Each cavity has to provide up to 20 kV peak gap voltage in the frequency range from 1.1 to 3.2 MHz. While all components of the system have been successfully tested in the factory acceptance tests and transferred to the FAIR storage, the First-of-Series (FoS) RF station is still persistently operated at GSI to gain experience. For further insight into the LLRF part, especially the stability of the control loops, the inter-coupling of the three local control loops was analyzed with methods from control theory based on simplified but realistic models, which have been developed based on extensive measurements and analysis of the systems’ behavior. In this contribution, the modeling as well as the analysis of the coupling between the LLRF control loops are discussed and the results are presented in comparison with measurements on the FoS system.
The Electron Ion Collider (EIC) Hadron Storage Ring (HSR) will reuse most of the existing superconducting magnets from the RHIC storage rings. To comply with the more demanding operational scenarios imposed by the EIC hadron beams, the beam pipes of the reused RHIC magnets will be equipped with low surface impedance and low SEY screens.
The installation of these screens will be done with the superconducting magnets as installed, making it a critical operation for a timely EIC installation.
On one hand the beam screen installation radial clearance must be as small as possible to maximize the superconducting magnet aperture. But on the other hand, keeping enough clearance is critical to ensure a smooth beam screen installation.
In preparation for this work, an autonomous survey probe was designed and built to measure in-situ the magnet beam pipe inner diameter and provide critical data for the beam screen design and magnet aperture optimization.
This paper reports on the design of the high-precision probe and the findings from its survey campaign.
The Hefei Advanced Light Facility (HALF) is a diffraction limited storage ring (DLSR) being constructed. As the main component of the storage ring vacuum system, the vacuum chamber transports the beam and withstands the thermal effect of synchrotron radiation simultaneously. The thermal and mechanical condition of the vacuum chamber of HALF were quantitatively analysed by means of ANSYS WORKBENCH in this work. Combining the Computational Fluid Mechanics (CFD) and Finite Elements Analysis (FEA), the temperature and thermal stress maps of the vacuum chamber were calculated. The CFD calculation displays that the heat transfer coefficient between the water and the chamber is 7966-13093 W/(m2·℃). The thermal-mechanical simulation shows that the maximum temperature and thermal stress are 53.5 °C and 42.1 MPa, respectively. The static structural analysis was performed on vacuum chamber under the ultra-high vacuum condition, with the maximum stress of 1.7 MPa and the maximum deformation of 0.0003 mm. These results show that the vacuum chamber meets the design requirements and provide a critical theoretical basis for the design of the vacuum system of HALF.
A new real-time measurement system for accelerator control, named FIRESTORM (Field In Real-time Streaming from Online Reference Magnets), to measure the integrated bending field has been recently deployed and commissioned in six synchrotron rings at CERN. We present the operational experience during the preparation phase and the restart of the accelerator complex for Run 3, focusing on the metrological performance of the new sensors and electronics, and on the lessons learned during commissioning. We also discuss the prospects for the evolution of the system and its adaptation to related use cases.
Iterative Learning Control (ILC) is a technique for adaptive feed forward control of electro-mechanical plant that either performs programmed periodic behavior or rejects quasi-periodic disturbances. ILC can suppress particle-beam RF-loading transients in RF cavities for acceleration. This paper, for the first time, explains the structural causes of ``bad learning transients'' for causal and noncausal learning in terms of their eigen-system properties. This paper underscores the fundamental importance of the linear weighted-sums of the column elements of the iteration matrix in determining convergence, and the relation to the convergence of sum of squares. This paper explains how to apply the z-transform convergence criteria to causal and noncausal learning. These criteria have an enormous advantage over the matrix formulation because the algorithm scales as N^2 (or smaller) versus N^3, where N is the length of the column vector containing the time series. Finally, the paper reminds readers that there are also wave-like (soliton) solutions of the ILC equations that may occur even when all convergence criteria are satisfied. Illustrative examples are provided.
The building blocks of a scientific facility based on particle beams is made of magnets and electro-magnetic devices such as accelerating cavities. The optical design usually imposes a demanding accuracy with respect to their theoretically exact position and orientation. It is however frequent that the functional features are either not clearly defined – what is the « axis » of a magnet –, or not directly used along the lifecycle of these devices. Improving the ways to handle these functional features would contribute to meeting the demanding challenges.
The European Spallation Source (ESS) is aiming at providing a powerful proton linear accelerator and a target system to produce pulsed neutrons. The challenging complex design and integration yielded to introducing a tool shared in common by all stakeholders along the lifecycle: the "situation features", as defined in ISO GPS (Geometrical Product Specifications) standards. They are here developed and extended to beyond-mechanics cases. Two examples are presented: neutron beam optics; and fiducialisation and installation of quadrupole magnets. Perspectives of generic use are also highlighted.
The Argonne Tandem Linear Accelerator System (ATLAS) at Argonne National Lab is a superconducting ion linac capable of delivering beams ranging over all possible elements, from hydrogen to uranium, and at a wide range of beam currents and energies. The ATLAS scientific program is focused primarily on basic nuclear physics. In this contribution, we present the capabilities of ATLAS for high-rate radiation-damage studies for a variety of applications below the threshold of producing radioactivity. To date ATLAS has been used for such studies relevant to advanced reactors. These include studies of structural materials and damage induced by fission products in advanced fuel candidates. Such studies can be expanded to include in-situ measurements of response to damage in other materials used at high power densities such as for targets at spallation neutron sources and neutrino factories. ATLAS is in the process of a multi-user upgrade which adds the capability of simultaneously accelerating two ion beams and delivering them to different target stations. This enables ATLAS to deliver beams for nuclear physics research simultaneously with irradiation studies.
IC@MS is a modular and containerized web-based alarm management system. Scientific facilities need alarm management tools to increase effective operation. Experience shows that control systems face unexpected issues, that should be tracked and archived. The mature control system may require the involvement of many engineers to access the alarm list and focus on the most important ones. IC@MS allows users to group alarms and focus on important ones, remotely via a web browser. It is not only the extension and web equivalent to the PanicGUI desktop application but due to its modular architecture, other 3rd party applications can be easily integrated. IC@MS is supporting both PyAlarm and AlarmHandler, containerization makes deployment fast and effective. It introduces the different user roles that can limit functionalities for selected groups. The web-based alarm management system provides a better user-friendly user interface for everyday use with Integration with distributed directory services like Active Directory. IC@MS Web API that can be used by 3rd party applications.
The Forward Physics Facility (FPF) is a proposed experimental facility to be installed several hundred meters downstream from the ATLAS interaction point to intercept long-lived particles and neutrinos produced along the beam collision axis and which are therefore outside of the acceptance of the ATLAS detector. The construction of this facility, and in particular the excavation of the associated shaft and cavern, could take place in parallel to beam operation in the CERN accelerator complex.
It is therefore important to verify that the ground motion caused by these works does not perturb the standard operation of the SPS and LHC. In this work, the sensitivity to vibration and misalignments of the SPS and LHC rings in the vicinity of the affected area will be presented, together with the expected perturbations on beam operation following the experience gathered during the construction of the HL-LHC infrastructure around the ATLAS experiment.
The TLS (Taiwan Light Source) is a third generation of synchrotron light source which has been operated for more than 25 years, and its control system is a proprietary designed system. Due to component outage issues, the maintenance of the TLS control system is challenging. Some parts of the control system are being rejuvenated with the help of the EPICS framework used in the TPS (Taiwan Photon Source) control system to ensure that TLS continues to operate normally, saving both manpower and money. A new EPICS archive system was needed to efficiently record various machine parameters and status information during routine operation. As a result, the EPICS Archiver Appliance has been evaluated as suitable for deploying to archive TLS machine data which encapsulated the PV channel access. Specific graphical user interfaces and its API package have been supported for quickly retrieving archived data, as well as a plotting function for easy diagnosis. Furthermore, the performance of this new TLS archive system has been estimated, and related system resources will be manually adjusted for better service. The efforts will be summarized at this paper.
This paper describes the changes in the design of the MTCA-complaint Local Oscillator (LO) Rear Transition Module (RTM) board providing low phase noise clock and heterodyne signals for the 704.42 MHz Low-Level Radio Frequency (LLRF) control system at the European Spallation Source (ESS). Global chip shortage, as well as experience gained during the production and operation of Revision 1.2, influenced the modifications implemented in Revision 1.3.
The changes include a Field Programmable Gate Array (FPGA) Integrated Circuit (IC) offering more logic cells. Additional resources will be used to integrate new functionality, improving the performance of the module. The board reliability was also improved. A watchdog circuit controlling the proper operation of the module was added, and a more advanced reset scheme was implemented.
Properly managed asset and maintenance processes is key for minimizing unplanned downtime and to ensure efficient operations of any large-scale technical installation, including particle accelerator complexes. CERN has therefore over the last years significantly increased its use of a commercial EAM (Enterprise Asset Management) platform in order to support such efforts. With its advanced maintenance management functionality and built-in industrial best practices, more than 40 equipment groups at CERN are today relying on this software platform, to manage their installations. This does currently not only cover equipment inventories and work order management, but also storerooms with spare part handling and contract management capabilities for outsourced services. Several initiatives have in addition been launched to strive towards more elaborate maintenance practices such as condition-based and predictive approaches, using additional data sources including SCADA systems and IoT devices. While continuously extending and tailoring the EAM and its use at CERN, a strict policy of zero customization of it is applied, in order to stay 100% compatible with future versions.
Machine learning techniques have developed rapidly in the last decade and are widely used to solve complex scientific and engineering problems. Many accelerator laboratories internationally have begun to experiment with machine learning and big data techniques for processing accelerations. This paper presented the application of machine learning to the Hefei Light Source. Including the simulation of the tune and the calibration of the online experiment that met the design requirements and simulation of the beta parameter correction with deep learning. Based on this, online beta calibration will be carried out in the future.
In this article, the results obtained with a new designing approach for the active disturbance rejection control (ADRC) algorithm are presented, where loop shaping techniques are used in order to stabilize the controller and make it more resilient to delay. The objective of this work is to describe the experiment performed to test the microphonic reduction capability of the modified ADRC (MADRC), as well as to present and discuss the results obtained on the test system, which is a 9-cell super conducting radio frequency (SRF) cavity.
This is in respond to the need of a precise microphonics control in SRF cavities that are operated with high quality factors. Due to the stochastic nature of microphonics and the relatively large delay of piezoelectric actuators, feedback controllers tend to destabilize the system before an acceptable control bandwidth is obtained and, therefore, are quite limited. The objective of this new approach is to modify the basic structure of the ADRC in order to enable the study of its frequency response and then make it more robust via loop shaping techniques.
This project aims to develop a 100 MeV proton accelerator-based space environment chamber and create a radiation test database of electronic and optical components in the space environment. The chamber for the space radiation environment consists of various beam diagnostic equipment and control points. An integrated control system for remotely monitoring and controlling these signals has been implemented. The control system collects beam and sensor signals using ZYNQ and ADC chips, reads vacuum degree, temperature, cooling parameters, and controls gate valves and pumps. The interlock system for machine protection stops the beam trigger of the timing system and closes the beam shutter in an emergency. EPICS and modules were used for ADC data processing and communication with peripheral equipment in a single Zynq-based system, and the control system was connected with control network of the 100 MeV proton accelerator. This paper discusses the design and construction of an integrated control system for the space environment chamber.
The potential for developing compact, high-brightness particle and radiation sources has given a strong impetus to the development of the underpinning laser technology, including increasing the efficiency and repetition rate of the lasers. A result of this technological development can be seen in the new generation of ultrafast high-power laser systems working at a high repetition rate which have been built across Europe. A new high-power laser facility called I-LUCE (INFN Laser indUced radiation acCEleration) will be realized at LNS-INFN in 2024. The facility realization is funded by both EuAPS (EuPRAXIA Advanced Photon Sources) and Samothrace (Sicilian MicronanOTecH. Research And Innovation) projects financed by the PNRR Italian program. The Ti:Sapphire laser will have two outputs: the first one will be a 1 TW beam line (25fs,25-30mJ,10Hz) while the main beam line will be a 500 TW laser (25fs,10J,10Hz). I-LUCE will serve two experimental areas called E1 and E2. E2 will provide the unique worldwide combination of intense laser radiation with heavy ion beams generated with the Superconductive Cyclotron and Tandem (already installed at LNS) opening the door for interesting experiments in the field of plasma physics, nuclear physics and atomic physics. In addition, stand-alone experiments with intense laser beams will be carried out for several studies such as proton/ion acceleration laser generation. Instead, the E1 experimental room will be dedicated to electron acceleration.
KEK LUCX facility is a compact linear accelerator used for advanced accelerator technology and electron beam instrumentation R&Ds.
New LLRF (Low-Level RF) phase and amplitude feedback based on FPGA (Field-Programmable Gate Array) board was developed and tested during the LUCX facility routine operation. The RedPitaya 125-14 (also known as STEMLab 125-14) FPGA board was chosen due to its well-balanced specifications and the board-to-board synchronization ability. The LLRF feedback loop includes digitization of In-phase and In-Quadrature DC signals, PI controller for I and Q terms correction calculations, I/Q modulation and RF signal regeneration.
This report presents the LLRF feedback development and implementation status, as well as performance test results acquired during several LUCX machine runs. Also, the technical issues of the feedback implementation into the LLRF system of the KEK LUCX accelerator are discussed.
The Los Alamos Neutron Science Center (LANSCE) timing system leverages a commercial event-driven system from Micro Research Finland (MRF) which is in use at various (16+) accelerators facilities around the world. Recent upgrades to the LANSCE accelerator machine protection [Fast Protect] system utilizing MRF event receivers will address some long-standing issues that require non-intuitive work arounds to allow beam delivery. The complexity of the system stems from the fact that LANSCE is a multi-user facility which delivers uniquely time-structured pulsed beams of varying power levels “simultaneously” to up to 5 different user facilities. One of the remaining issues with the Fast Protect system is that a fault related to one user facility can, in some circumstances, prevent beam delivery to another user facility. This is caused by allowing unscheduled but permitted changes to the beam delivery destination. The paper will discuss all relevant aspects including the timing system, current fast protect implementation, observed operational issues, and proposed changes to the fast protect system which will take advantage of the existing capabilities of the timing system.
Modelling the fast orbit feedback (FOFB) system for the upcoming PETRA IV storage ring is in progress. The single-input-single-output (SISO) simulations provide an abstract insight into the FOFB system's performance and stability. Nevertheless, to investigate the orbit correctability in general and at spatial locations of interest, i.e. insertion devices, the simulations are extended to include the lattice model.
The multiple-input-multiple-output (MIMO) numerical simulations are being carried out in Python-based cpymad and Matlab-based Simulation Commissioning (SC) toolkit, and first results are presented.
The Los Alamos Neutron Science Center’s proton storage ring (PSR) extraction kicker systems consist of two thyratron switched blumlein modulators. The operating parameters of the PSR have changed over the years and the flattop voltage of the modulator outputs has become a limiting factor in the length of the beam pulse able to be extracted from the ring. The extraction voltage pulse travels upstream relative to the beam and thus needs to be longer than the beam pulse. A reanalysis of the voltage waveforms and the beam propagation times revealed that a longer pulse could reduce beam spill levels that have been seen during past run cycles. Reduced spill will allow operation at higher beam currents and thus increase the amount of beam current available for experimenters. We have upgraded the blumlein cables in both extraction kicker modulators with longer cables. We present test results of the modulator outputs and correlate their improvement with reduced beam losses at the PSR exit septum and improved beam delivery.
LA-UR-22-21024
CERN is currently developing a 40 kV proof of concept Inductive Adder (IA) for replacing the Proton Synchrotron (PS) complex pulse generators, which currently use 80 kV SF6 gas filled pulse forming lines. The experience gained during the design, commissioning and operation of this prototype device will be crucial for upcoming decisions on the type of future kicker pulse generators. The cross-sectional area (CSA), hysteresis curve, biasing and material of a magnetic core determines its volt-time integral. In a terminated mode IA this parameter dictates the maximum pulse width that can be delivered into the load at a certain voltage. It is therefore key to measure the magnetic core response at the expected rate of magnetization (T·𝜇s−1) to assess its capability. Measurements and analysis yield important information for choosing the core CSA per IA layer and develop an accurate simulation model. In this paper BH curve measurements under different excitations of a toroidal, tape wound, nano-crystalline core are presented and discussed. Based on the results, pulse length/amplitude limitations are outlined and the required core CSA per inductive adder layer is proposed.
NEG-coated chambers have been adopted as the beam ducts for large particle accelerators and synchrotron light sources for the sake of the lower yields of the photon stimulated desorption (PSD) and the photoelectrons (PE) from the NEG films in addition to their pumping performance. Measurement of the photoelectron yield (PEY) was performed at the BL19B (PSD) beamline of the 1.5 GeV Taiwan Light Source (TLS) which simultaneously measures the PSD-yield. An aluminium cathode was inserted in the tubes and a positive bias of voltage for extraction of the photoelectrons applied. The PEY was obtained by dividing the photoelectron current by the photon flux of the synchrotron radiation. Measurements of the PEY include various types of NEG-coated stainless steel tubes and the bare tubes of titanium and aluminium alloys for the comparison. The experimental system and the results will be described in this presentation.
At DESY, the technical design phase to upgrade the PETRA III storage ring towards the 4th-generation synchrotron light source PETRA IV is ongoing. This foresees a complete renewal of the machine including its existing timing and synchronisation system.
The new timing and synchronisation system needs to deliver precise clocking, which will be implemented by an application-specific hardware design. Further on, it has to provide trigger signals and beam-synchronous information to the subsystems located across the facility. The main hardware for the timing system will be based on the MTCA.4 standard. This platform has been successfully implemented here at DESY / EuXFEL. Because of new specific requirements for PETRA IV, the successor hardware has to be adapted and upgraded to a new design.
This paper describes the system design and the facility-wide distribution of precise clocks, trigger signals and timing system-related meta-information. We illustrate how the new MTCA.4-based AMC card (DAMC-X3TIMER) meets the requirements for PETRA IV. Insights into ongoing lab tests on components qualification and the status of the development will be presented.
Lambda-squared scaling of the ponderomotive potential makes long wavelengths preferable for certain regimes of laser-based particle acceleration, including the laser-wakefield acceleration of electrons at low plasma densities and the acceleration of ions from gaseous targets. Currently, multi-terawatt levels of peak power at long-wave infrared (LWIR) wavelengths around 10 μm can only be achieved via the amplification of a picosecond laser pulse in high-pressure CO2 laser amplifiers. Our state-of-the-art LWIR laser system employs chirped-pulse amplification in a mixed-isotope CO2 active medium (Oxygen-16 : Oxygen-18 ≈ 50:50) at a pressure of ~10 atmospheres to deliver up to 5 TW peak power in 2-picosecond pulses. This laser system has enabled several promising parameter-space optimization studies and proof-of-principle demonstrations of advanced techniques of particle acceleration and x-ray generation in recent years.
A next-generation LWIR laser is currently under active development. It will provide a sub-picosecond pulse duration (100 fs and 500 fs with and without post-compression, respectively) and ≥15 TW of peak power. Theoretical models predict that these laser parameters will enable new acceleration regimes, such as the blow-out regime of laser-wakefield acceleration with millimeter-scale accelerating plasma structures.
IFMIF-DONES* is a key device in the EUROfusion roadmap for studying and licensing materials for future fusion reactors. It will be a unique neutron fusion-like irradiation facility equipped with a linear particle accelerator impinging an intense deuteron beam (125 mA, 40 MeV) onto a liquid lithium target. In terms of safety analysis of the facility, relevant accidental scenarios are related to the technical impossibility of having a separation window between the liquid lithium target chamber and the accelerator vacuum chambers. In case of Loss of Vacuum Accident (LOVA), such as a sudden air/water inrush or leakage in the accelerator or target vacuum chambers, the beam duct could serve as a transport line and lead to air/water contact with liquid lithium, with the risk of exothermic reaction. The use of Fast Isolation Valves (70-100 ms closing time) is envisaged as mitigation mechanism for these events. The MuVacAS Prototype is an experimental setup to study in detail these scenarios and validate the Safety Credited mitigation requirements. For this purpose, it recreates the last 30 meters of the accelerator and target vacuum chambers and, it is equipped with dedicated instrumentation and modules for simulating LOVAs. This contribution presents an overview of the experimental setup together with preliminary numerical simulation of these accidental events.
Non-Evaporable Getter (NEG) development at DESY has been ongoing to accommodate PETRA IV machine requirements. While most of the PETRA IV beam vacuum chambers will be manufactured from oxygen-free silver-bearing (OFS) copper and coated with NEG, getter film performance on these substrates has not been tested as extensively as on the stainless-steel. In order to investigate pumping and impedance properties of the columnar NEG films, TiZrV and Zr layers with varying thicknesses were sputtered on four Cu-OFS tubes. The 1 μm films were activated repeatedly at 180 °C to determine how the sticking probability as well as CO pumping capacity develops over time after multiple saturations prior to increasing the activation temperature. By measuring the attenuation of the RF signal along the four tubes, resistivity of both NEG materials was calculated. The results were then compared to previously reported findings for columnar NEG films.
Controls of the White circuits for the booster synchrotron of Taiwan Light Source was developed in late 1990s. That design based on various analog circuitry to detect 10 Hz magnet amplitude and phase. The existed implementation consists of analog regulation for amplitude control and digital regulation for relative phase between magnet family. Modernized of the White circuits controls was implemented recently to avoid obsolesce of components of the existed system. Upgraded system adopt digital regulation for amplitude and phase loops. Improve performance and easy maintenance are the goals of this upgrade.
The Linac system at Taiwan Light Source (TLS) has been in operation for almost a quarter of a century and requires upgrades to improve its reliability. To achieve this, some components of the control system have been replaced with new digital low-level RF control units that use emerging technologies. A new unit is based on the open-source hardware platform which is named “Red Pitaya STEMlab” and offers a compact size and low power consumption. The unit features DAC blocks for downloading arbitrary waveforms with external trigger play and ADC blocks for waveform acquisition, enabling the development of real-time diagnostic toolkits. The new low-level RF control interface has been fully integrated into the existing EPICS software framework for system integration. The new digital low-level RF control system supports I/Q data with online amplitude and phase settings, and a waveform digitizer for inspecting low-level RF signals from the klystron modulator. Specific graphical applications have been designed and integrated into the existing operation interfaces. The system has been successfully achieved during routine operations. This paper describes the details of these efforts.
The Taiwan Light Source (TLS) is a third generation of synchrotron light source, and it has been operated since 1993. Legacy timing system of the Taiwan Light Source was delivered in early 1990s. To deal with obsolete com-ponents and improve functionality, upgrade to event-based timing system for TLS is under way. The system need coordinate the operation the linac, White Circuit based booster synchrotron, and the storage ring for beam genera-tion, injection, extraction, and beam accumulation. Sup-port top-up operation of the storage ring is needed. Due to more experiences on EPICS related framework, the cPCI (CompactPCI) based EPICS IOC (Input Output Control-ler) and expandable Fanless Embedded Computers have been adopted for new TLS Timing system to replace the existed VME based ILC (Intelligent Local Controller) to be as an easy-to-maintain control environment. Scheme deal with resonance excitation of the booster magnets with the event system need special care. Design ideas and implementation will be summarized.
Taiwan Light Source (TLS) delivery user service since 1993. Some legacy system have been updated recently to avoid obsolesce and to provide better performance to improve operation efficiency. Proprietary designed timing modules were replaced by event based timing system recently. The magnets of the booster synchrotron configured as three White circuits and drive by resonance excitation. Original control of the White circuit include analog amplitude loop and digital phase loop for regulation were replace by full digital regulation loops. Success upgrade of both system lead easy and smooth injection control possible with functionality and flexibility enhancement. The injection control includes foreground and background processes to coordinate the operation of e-gun, linear accelerator, booster synchrotron, and storage ring by the help of timing system. Scheme of fix time interval between injection was selected to meet user requirements. Injection control GUI provide an intuitive operation interface includes parameters setting and present all necessary information display like various timing value, stored beam current/lifetime, injection efficiency, filling pattern, kickers waveform. Energy saving mode of the White circuits are supported by the injection control to save electricity. Lifetime calculation of the storage ring is also synchronized with the injection process. Detail of the implementation and operation experience will be presented.
The CERN PS booster features four extraction kicker systems, one for each of the four superposed rings and three transfer kicker systems for recombination of the beams when being transferred towards the PS. Each of these systems consist of SF6 gas filled Pulse Forming Lines (PFL) which are resonantly charged and then fast discharged by thyratron switches into SF6 gas filled transmission cables, transferring the pulse to the magnets. This paper outlines the future refurbishment of PFL and transmission cables with the constraint of minimizing SF6 gas usage. The pulse requirements are presented since they limit the choice of technology together with the development cost for alternative SF6 free technologies. The optimization potential regarding technical pulse requirements versus beam performance is discussed. The paper concludes with the choice made and the technical design outline for the refurbishment of the PSB transfer and extraction kickers.
The European Spallation Source - ESS, has achieved its major construction in Lund, Sweden and is currently continuing in parallel the commissioning of its first systems. ESS aims to install and commission the most powerful proton LINear ACcelerator (LINAC) designed for neutron production and a 5MW Target system for the production of pulsed neutrons from spallation. In support of this ambitious goal, the Mechanical Measurements Lab (MML) at ESS provides an array of investigative solutions such as Resonant Ultrasound Spectroscopy (RUS), Transient Grating Spectroscopy (TGS), Modal Analysis and Strain and Stress Analysis, guaranteeing full support to all the groups that have the mandate to install all the different components of the machine. The scope of this contribution is to describe the current status of the undergoing studies, together with the applied methodology and the definition of the testing apparatuses.
Spatio-temporal couplings (STCs) [1] can have a detrimental effect on the intensity at focus of ultrashort femtosecond lasers. The laser spatio-temporal intensity profile control is a key issue for stable operation of laser wakefield acceleration (LWFA) [2]. Thus, it is necessary to measure and correct STCs. Techniques such as INSIGHT [3] or TERMITES [4] allow reconstructing the full spatial phase for different spectral components of the laser pulse using a phase-retrieval iterative algorithm. However this requires a computing time of the order of several minutes, making it inappropriate for single-shot online monitoring of lasers running at repetition rates of several hertz. We propose a method to characterize STCs in real-time using a multispectral camera [5] coupled with wavefront and temporal measurements and a machine learning algorithm. We will present the sensitivity characterization of the STCs measurement, which has been tested at 10 Hz for the optimization of a large optical compressor. Finally, we will discuss the status of the reinforcement learning implementation for full laser field reconstruction.
CERN’s digital Low-Level RF (LLRF) family for injectors is deployed on CERN’s PS Booster (PSB), Low Energy Ion Ring (LEIR), Extra Low ENergy Antiproton (ELENA) ring and Antiproton Decelerator (AD). It implements multiple capabilities, including beam and cavity feedback loops, bunch shaping, longitudinal blowup, bunch splitting and longitudinal diagnostics.
New capabilities are now available and the LLRF family is soon going to be deployed for tests also in CERN’s Proton Synchrotron (PS). This paper provides details on the operation and on the new capabilities of this LLRF family. Hints on future evolution are also given.
The CERN SPS injection kicker magnets (MKP) were developed in the 1970's, before beam power deposition was considered an issue. There are two types of these magnets in the SPS: MKP-S (small aperture) and MKP-L (large aperture) versions. The MKP-L magnets are very lossy from a beam impedance perspective: this would be an issue during SPS operation with the higher intensity beams needed in the future for HL-LHC. Hence, a beam screen has been developed, which is inserted in the aperture of each MKP-L module. The screen consists of silver fingers applied to alumina U-shaped chambers: the fingers have been optimized to achieve both adequately low beam induced power deposition and good high voltage (HV) behaviour. A surface coating, with a low secondary electron yield, is applied to the inner surface of the alumina chambers to reduce dynamic vacuum. The low-impedance MKP-L has been extensively HV tested in the lab before installation in the SPS. This paper briefly presents the design and focuses on the operational experience in the SPS, including heating and vacuum.
Emittance measurements are a universal requirement when operating particle accelerators. Many techniques exist to achieve these measurements, each suiting the specific requirements of a machine. Most are multi-shot or invasive, and struggle to function with low energy beams or where space-charge effects are dominant. Generally, these limitations can be restricting, but especially so in emerging sectors such as novel acceleration or energy recovery linacs. To this end, two all-optical single-shot emittance measurements are being developed. In both cases the measurement is analogous to an optical version of the common pepper-pot diagnostic. The two methods are complementary: the first uses a micro-lens array (MLA); the second a digital micro-mirror device (DMD). Both systems can operate away from a beam waist and separate the optical beam radiation into beamlets rather than the beam itself; leaving potential for a non-invasive measurement. The benefits of using optical beam radiation are reduced beam scattering, simple designs, and suitability for low-energy/space-charge dominant beams. Presented is a series of benchmarking measurements and simulations with laser sources. Initial beam simulations, plans for first measurements, and the application to a machine learning virtual diagnostic are also discussed.
Optical Transition Radiation (OTR) is commonly used in imaging systems of highly relativistic charged particle beams as the light yield and collection efficiency increase with beam energy. For low beam energies, scintillating screens are typically preferred but they saturate or even get damaged when using a high beam current. For such a beam, OTR screens can, therefore, still be an attractive diagnostic tool when using thermally resistant materials such as Glassy Carbon. This work presents the OTR-based beam imaging measurements of a high-intensity low energy (7~keV) hollow electron beam at the Electron Beam Test Facility (EBTF) at CERN. The mechanical design of the monitor, as well as the expected OTR angular distribution, are presented. Beam images obtained with an aluminium oxide scintillating screen are also shown and compared to the OTR results. This contribution presents the design of the monitor and discusses the initial results obtained with a hollow electron beam at the EBTF.
The PSB, PS, and SPS accelerators at CERN provide high-energy proton and ion beams to a wide range of experiments, from fixed targets to the world’s biggest particle accelerator: the Large Hadron Collider (LHC). In 2021 and 2022, their beams have reached unprecedented intensities thanks to the LHC Injectors Upgrade (LIU) undertaken during the Long Shutdown 2 (LS2) in preparation of the High-Luminosity (HL) LHC era. The operation of these accelerators results in beam losses that generate a mixed radiation field that can negatively impact the exposed electronic systems through cumulative and single event effects. To minimise the associated damage, including potential the machine downtime due to radiation effects on electronics, the evolution and distribution of radiation levels must be carefully monitored across the CERN complex to detect anomalies promptly, to propose mitigation measures to protect electronic systems when needed, and to plan the installation of new electronic systems appropriately. This contribution will give an overview of the new radiation levels across the CERN injector complex in 2021 and 2022.
During the Large Hadron Collider (LHC) operation small fractions of the beam are lost continuously, leading to mixed-field radiation. Whereas the 2022 radiation environment in the majority of the locations follows expectations established both through measurements and simulations, some discrepancies with respect to the Run 2 operation (2015-2018) were detected. This work presents an overview of the 2022 Total Ionizing Dose (TID) levels as measured by the Beam Loss Monitors (BLMs) distributed along the LHC, focusing on the similarities and most prominent discrepancies with respect to the Run 2 operation.
With LCLS-II commissioning started and transfer-to-operations being scheduled, users will have more choices to use different scales of X-Ray FEL. LCLS-I instrument hutches and the beam diagnostic systems at SLAC have the requirements to use the same facilities to detect the X-Rays or electron beams from both LCLS-I and LCLS-II accelerators. Synchronization of the phase reference systems between the two machines is the prerequisite to achieve this goal. The LINAC Locking System at SLAC replaces the LCLS-I stand-alone 476 MHz master oscillator with one derived from the LCLS-II 1300 MHz phase reference signal. The phase initiation is realized with the timing alignment of the LCLS-I LINAC event generator (EVG) to the LCLS-II timing pattern generator (TPG) using a common subharmonic frequency. The new low noise 476 MHz phase reference is to be distributed to LCLS-I LINAC master oscillator and the instrument hutches via RF-over-Fiber system over a 1km distance in an uncontrolled environment. This paper will discuss the system design architecture and the test results gathered during the system's commissioning.
Laser-driven proton beams are characterized by very high intensities per pulse with a very short duration, extremely high dose rates, and broad energy spectra. These specific features do not allow the use of the conventional dosimeters typically suggested by the international dosimetry protocols for conventional proton beams. Precise dosimetry for laser-accelerated protons is an ambitious task as well as a crucial prerequisite for successful radiobiological experiments. We will present the work done within the PRAGUE project funded by the H2020 in the framework of the MSCA-IF IV program and by the INFN. The main goal of PRAGUE was the design, simulation, realization, and characterization of a real-time depth-dose distribution detector system based on thin Silicon Carbide multilayers for conventional and laser-accelerated proton beams in the energy range between 30 MeV to 150 MeV. The detector developed was designed to work at the regime of extremely high dose rate beams and it allows the retrieval of real-time and shot-to-shot depth dose distributions with a high spatial resolution thanks to the development and use of a 10 μm, fully depleted 15x15 mm2 square SiC detector. A detector prototype was already realized, simulated, and tested with 30 and 70 MeV conventional proton beams. Potentially this newly developed detector could enable new detector technology capable of providing online information of dose delivered at a biological sample with a laser-driven proton beam.
The Superconducting RF system of Hefei Advanced Light Facility (HALF) can provide an accelerating electric field for the beam, and its stability is required to be of RMS ≤ 0.1% in amplitude and RMS ≤ 0.1° in phase. To achieve this, a LLRF controller is being prepared for the control of the HALF Superconducting RF system. This LLRF controller mainly consists of three modules of RF front-end, signal processing and the motor drive. The RF front-end downconverts the RF signal to the IF of 31.2375MHz (499.8/16), and then up converts the IF to the RF after being processed by the digital board. The LLRF includes four channels of down conversion (cavity sampling signal Pt, forward power signal Pf, reflected signal Pr and the reference signal Pref) and one channel of up conversion (power source drive signal). LLRF can realize three control loops and one interlock protection, namely cavity frequency tuning loop, cavity field amplitude control loop and cavity field phase control loop. The project progress of the HALF LLRF system will be introduced in this manuscript in detail.
Electron beam injection and extraction from the various stages of the SOLEIL II accelerator complex will be performed in three different locations, as it is done today. Injection of the LINAC beam into the upgraded booster and then its extraction use traditional on-axis & on-momentum schemes with single turn kickers and septum magnets. The main Top-Up injection scheme in the storage ring* will use an off-axis & on-momentum betatron injection scheme. In particular, this scheme requires the design of a new type of Multiple Injection Kicker (MIK) which significantly differs from the current generation. This article presents the technical proposals and design constraints for the pulsed magnets and power supplies – dipole kicker, MIK and septum magnets - foreseen in the upgrade of SOLEIL.
Polish Electronics Group (PEG) is one of the in-kind partners to the European Spallation Source (ESS) project. One of its tasks is testing the LLRF control systems before installation in the machine. To perform this task, the Cavity Simulator was developed. It simulates the behavior of an amplifier driving a superconducting cavity, both used in medium and high beta sections of ESS' linac. This device has proved its function while installing the medium beta cavities LLRF control systems, but the development process is still in progress. New functionality is still being added, extending the range of possible uses and applications.
This contribution describes the latest developments of the Cavity Simulator for ESS. The recent measurement results that present the device's performance are also shown together with the plans for the future.
The Safe Machine Parameter system (SMP) is a critical part of the machine protection system in CERN’s Large Hadron Collider (LHC) and the Super Proton Synchrotron (SPS). It broadcasts safety-critical parameters like beam energy, beam intensity, the beta functions and flags indicating safety levels of the beam to other machine protection elements. The current SMP will be replaced by a consolidated system during CERN’s Long Shutdown 3, foreseen to start in 2026. In this contribution the results of the reliability study of the new SMP system are presented. This study quantifies the criticality of end-users by identifying the hazard chains leading to potential damage of the involved equipment. Data-driven risk matrices are used to derive acceptable failure frequencies and reliability requirements. The study encompasses Monte Carlo simulations of sub-system level configurations to support the decision-making process in this project.
One of the crucial elements of any scientific installation, especially in particle accelerators, is the timing system. Timing systems are used for providing a common notion of time to all the elements of the facility as well as for the generation of discrete events and periodic signals that are shared by the different elements across the accelerator. In addition, it also can be used for radiofrequency dissemination across the whole facility.
In this work it is presented the timing system architecture currently under development by Orolia Spain for the distribution of synchronized triggers. The hardware, based on FPGA, is described. The system allows total flexibility when configuring the triggers in terms of direction, number of pulses, pulse rate, pulse period and delay.
Facilities are increasingly demanding better performance. The system proposed is intended to achieve high precision triggers with resolutions in the order of 5ps. The performance achieved will be shown in this work.
In accelerator beam chambers and RF waveguides, electron cloud and multipacting can be mitigated effectively by reducing the secondary electron yield (SEY). In recent years, it has been established that laser surface structuring is a very efficient method to create a copper surface with SEY close to or even below unity. Different laser pulse durations, from nanoseconds to picoseconds, can be used to change surface morphology. Conversely, the characteristics that minimise the SEY, such as the moderately deep grooves and the redeposited nanoparticles, might have unfavourable consequences, including increased RF surface resistance. In this study, we describe the techniques used to measure the surface resistance of laser-treated copper samples using an enhanced dielectric resonator with 12 cm diameter sample sizes operating in the GHz range. The quantification basis lies in a non-contact measurement of the high-frequency losses, focusing on understanding the variation of surface resistance levels depending on the specifics of the treatment and possible post-treatment cleaning procedures.
The FAIR complex at the GSI Helmholtzzentrum will generate heavy ion beams of ultimate intensities. To achieve this goal, low charge states have to be used. However, the probability for charge exchange in collisions with residual gas particles of such ions is much higher than for higher charge states. In order to lower the residual gas density to extreme high vacuum conditions, 65% of the circumference of SIS18 have already been coated with NEG, which provides a high and distributed pumping speed. Nevertheless, nobel and nobel-like components, which have very high ionization cross sections, do not get pumped by this coating. A cryogenic environment at moderate temperatures, i.e. at 50-80 K, provides a high pumping speed for all heavy residual gas particles. The only typical residual gas particle that cannot be pumped at this temperature is hydrogen. With an additional NEG coating the pumping will be optimized for all residual gas particles. The installation of cryogenic surfaces in the existing room temperature synchrotron SIS18 at GSI has been investigated. Measurements on a prototype chamber and simulations of SIS18 with cryogenic surfaces based on these measurements are presented.
In recent years, SAES has deepened its knowledge in the NEG coating field, aiming at uniformly coating vacuum chambers with challenging geometries and fine-tuning the film characteristics, according to the needs and requirements of the final users.
To achieve these goals, several complex vacuum chambers have been coated and studied, both at SAES and in collaboration with various research institutes around the globe. Tests made on NEG-coated samples include pumping speed and sorption capacity measurements, extensive film characterisations by XRF, SEM-EDS and XRD analyses, vacuum and plasma simulations, and photon-stimulated desorption yield measurements.
At the same time, SAES has been committed to the NEG coating of hundreds of vacuum chambers and of several prototypes for ongoing and upcoming machine upgrades, respectively.
An overview of the most significant achievements and results is presented, not only focusing on the technical challenges and the optimisation of few prototypes, but also giving an industrial perspective in terms of reliability, when large batches of tens or hundreds of vacuum chambers should be deposited.
According to the schedule, the commissioning of HEPS injector would start in 2023. The high-energy transfer line ‘BR’ is used to deliver 6 GeV electron beams from the booster to storage ring. Systematic simulation of beam commissioning was carried out for the HEPS high-energy transfer line. The simulation results suggest that it is feasible to deliver not only on-momentum but also slightly off-momentum beams through the transfer line. One key point is to evaluate the momentum deviation using a response matrix with dispersion. Based on the studies, a commissioning plan of the HEPS high-energy transfer line has been proposed and will be introduced in this paper.
In the CSNS RCS RF system, a combination of feed-back control and adaptive feedforward control was proposed in in the Low-Level Radio Frequency (LLRF) system to ensure stable beam acceleration. Although the effectiveness of the feedforward control has been confirmed in operation, a detailed study on it is still necessary. This paper presents a detailed study on the feedforward control based on Simulink simulations and proposes an optimization scheme to further improve its performance. The proposed adaptive feedforward control is reviewed, and the simulation results are presented and summarized.
The installation of the new Swiss Light Source - SLS2.0 will start in October 2023. All beamlines will profit from the increased photon beam brightness. Given the geometrical constraints of the new storage ring, high synchrotron radiation power densities must be dissipated on the crotch absorbers. For the bending magnets, as well as the insertion devices, absorbers have been adapted to maximize their efficiency and protect downstream components. A design in Glidcop, fitting a CF63 flange, has been developed to fulfill the space, vacuum and thermal requirements. This paper will describe the design, manufacturing and testing of first crotch absorbers of SLS 2.0.
The installation of the SLS2.0 storage ring will start in October 2023. Most of the vacuum chambers composing the 288 m long storage ring will be made out of copper to dissipate the synchrotron radiation heat and to decrease resistive wall impedance. The nominal inner diameter is 18 mm with a wall thickness minimum of one millimeter and distance to pole going down to 0.2 mm at some locations. In the 7 bend achromats dipoles, the chambers will have an antechamber ending with a glidcop crotch absorber. The whole ring will be NEG coated to speed up the vacuum conditioning. Each arc is about 18 m long without any bellows so that NEG activation can be made in an oven outside tunnel. The installation of this long arc in the magnet apertures will be a delicate crane transport. This paper will describe the design and production of the different vacuum components as well as the first components tests.
As part of the High Luminosity LHC (HL-LHC) project, the SPS (LHC injector) Low Level RF has been completely re-designed. Part of this project is a system that can measure the phase of each individual bunch (5 ns spacing), to be used for both diagnostic and as input to the Beam-Based phase loop. The system uses a 5 G samples per second (Gsps) ADC mezzanine card, mounted on the motherboard with a System On Chip (SOC) FPGA for the processing, all electronics on a uTCA platform. The paper presents the motivations for this upgrade, the overall architecture (RF frequency distributed via a White Rabbit link), the main algorithms, the hardware and the firmware.
Achieving femtosecond synchronization between charged particle beams and experimental laser systems poses a significant challenge for modern particle accelerators. In particular, tight synchronization of multiple remote accelerator systems is required to achieve femtosecond stability of the electron beam. This paper presents the development of the CLARA fibre-stabilized timing distribution network and beam arrival monitor system, and reports on the commissioning of the first stabilizing timing link at CLARA, which has achieved a long term stability of <5fs.
With the high beam current in storage ring, it is necessary to consider the instability problem caused by the heavy beam loading effect. It has been demonstrated that direct RF feedback (DRFB), autolevel control loop (ALC) and phase-lock loop (PLL) in the main cavity can lessen the impact of the beam effect. This paper regarded the beam, main cavity, harmonic cavity and feedback loops as double harmonic cavity system, and extended the transfer functions in the Pedersen model to this system. Some quantitative evaluations of simulation results have been got and conclusions have been drawn. In the case of a passive harmonic cavity, the optimization strategy of the controller parameters in the pre-detuning , ALC and PLL, as well as the gain and phase shift of DRFB were discussed. Meanwhile, it also involved the impact of the harmonic cavity feedback loop on the system stability at the optimum stretching condition when an active harmonic cavity was present. The research results can be used as guidelines for beam operation with beam current increasing in the future.
Digital twins have emerged as a powerful tool for monitoring and optimizing complex systems, including Synchrotron Light Sources. This paper describes the development of a digital twin for BessyII and MLS, two Synchrotron Light Sources, which allows for real-time monitoring of the machine status and easy integration of online analysis while measurements are taken. The digital twin is designed to provide accelerators with commissioning predictions and feedback capabilities, and offers greater flexibility in configuring the modelling part combined with ease of adding new features. To enable the various components developed in EPICS, Python, C, and C++ to work together seamlessly, a microservice design is adopted, with REST API services providing the interfaces between the components. End user scripts are implemented as REST API services, allowing for better data analysis and visualization. The paper also describes the integration of dash and plotly for enhanced data comparison and visualization. Overall, this workflow provides a powerful and flexible solution for managing and optimizing BESSY II digital twins, with the potential for further customization and extension to upcoming machines. The digital twin is also considered important for the design of complex systems and can serve as a natural interface for machine learning and AI approaches.
The "Facility for Antiproton and Ion Research" (FAIR) is a new international accelerator complex, which is currently built in Darmstadt, Germany. Part of this complex is the SIS100 heavy ion synchrotron with a circumference of ~1086 m. To inject ions into the SIS100, an injection kicker system will be required. For fast extraction of the particle beam from the SIS100, an extraction kicker is used. This extraction kicker will be capable of performing normal extraction or emergency extraction kicks depending on the requirements. To ensure the correct kick angle at any time, the emergency kicker is charged up to 80kV synchronously with the beam energy. Depending on the experiments and the kicker type, pulse durations can vary from 0.5 up to 7 us. Slow extraction of the ion beam will include an electrostatic septum, operating with voltages up to 180 kV. The actual design, progress in building and test results of these projects will be presented.
The 1.5-GeV electron storage ring of the synchrotron radiation source DELTA at TU Dortmund University is surrounded by a 1 m thick concrete radiation shielding wall with a height varying between 3.0 and 4.3 m without the top being covered. The installation of a new 7-T superconducting wiggler and tentative plans for a new building in the vicinity motivated recent studies of background radiation either directly escaping the open-topped radiation shield or being scattered by air or the roof of the hall (the so-called radiation skyshine). Spectra of gamma radiation were recorded under different conditions using a high-purity germanium detector. Long-term measurements were made with photo- and thermoluminiscence dosimeters. The paper presents the results together with calculations of the spectral distribution of wiggler radiation as well as a model for the spatial distribution of radiation emitted by the whole storage ring.
Bunch length measurement is an essential diagnostic for FEL facilities and now the interest of ultrashort bunch is continuously rising. The nondestructive methods with high resolution are now the favorite design for short bunches less than 1 ps. The technique of cavity bunch length measurement based on the monopole mode is discussed is this article. The influence of many factors on the amplitude of TM010 mode are analyzed, such as energy and beam offset. For 1 ps beam length measurement, a cavity of 19.04 GHz is design using CST software, which may provide a resolution of 10 fs with an 80 dB signal-to-noise ratio.
Coherent X-ray beam focus can be characterized using ptychography, a lensless imaging technique used at synchrotron X-ray light sources and free-electron lasers. Ptychography relies on collecting X-ray diffraction from a thin sample at overlapping regions and reconstructing an image from the data. Since the phase is not measured by the detector, ptychography can solve for the phase of the sample and the probe. This is useful for characterizing the beam focus, coherence, and energy dependence, and for exploring experimental conditions.
Ptychography, however, is challenging due to the time to collect data from each sample point and also for iterative reconstruction of the phase. Recently, AI-based ptychographic methods have shown promise in making ptychography-based beam characterization faster and more efficient.
This poster presents a study on the effect of various types of noise present in ptychographic data. A number of noise sources occur in ptychographic setups and include noise from parasitic scattering (background), outliers, correlated noise sources, cosmic rays, bad frames, beam jitter, motor jitter, fluctuating dark noise, beam miscentering, a static sloped background and fluence jitter.
This study explores the effect of random noise in experimental data used for AI-based ptychographic reconstruction and how it impacts reconstructed probe and object image accuracy. Results on noise impact using both AI-based and iterative ptychographic methods are compared.
The purpose of a Low Level Radio Frequency (LLRF) system is to control the amplitude and phase of the accelerating field in the cavity. To improve the RF field stability and to decrease the noisy sideband such as few kHz sideband from RF transmitter, a study for the application of active disturbance rejection control (ADRC) is ongoing. ADRC algorithm is based on an extended state observer, which can estimate the total disturbance acting on the system and then to cancelled them. The simulation results of the ADRC controller for the Taiwan Photon Source RF system will be reported in this paper.
One of the projects for upgrading at the Taiwan Photon Source (TPS) is the design and fabrication of an improved multipole injection kicker (MIK). The aim is to improve the injection efficiency using four kickers, to deliver transparent injections during the top-up operation. A uniform titanium coating on the inner surface of the ce-ramic substrate is required to reduce the impedance of the stored electron beam and to conduct the image current. The study results of the deposition of a titanium film on a ceramic substrate (30 cm × 6 cm ) in a long vacuum chamber show that the thickness uniformity of the thin film can be controlled within 5 % with an electrical resis-tivity of 2 × 10-4 ohm-cm. The adhesion between the ceramic substrate and the titanium film meet the highest ASTM-D3359 5B requirements (bonding strength 39.2 MPa). The details of the coating set-up, experimental processes and measurement method are described in this paper.
The beam orbit stability is the crucial indicator to evaluate the performance of the synchrotron radiation source. In order to obtain higher beam quality, higher stability requirements are placed on the beam orbit. The stability can be improved through accurate meas-urement of beam orbit by beam position monitors (BPMs) and appropriate feedback system. However, due to radiation of the synchrotron beams on the vac-uum chamber, the thermal effect of synchrotron radia-tion causes the thermal deformation of the vacuum chamber. The thermal deformation drives the BPM fixed on the vacuum chamber to move, which will induce error to the beam orbit. We analyze the effect of beam current on the vacuum chamber movement and the effect of vacuum chamber movement on the beam orbit. We also built an online vacuum chamber displacement measurement system on Hefei Light Source II (HLS II), which is used to validate and cor-rect our analysis. After analysis and verification, the vacuum chamber moves with the change of current. The larger the change of current, the larger the vacuum chamber displacement. The vacuum chamber dis-placement has a hysteresis compared to the current change.
In order to improve the sensitivity and long-term sta-bility of Hefei Light Source – II (HLS-II) for beam posi-tion measurement, it is necessary to improve the meas-urement method. The beam position monitor (BPM) electronics is used to measure the beam position and is an important part of the beam position measurement system. In this paper, we propose a beam position meas-urement system based on the compensated diode detec-tion (CDD) technology for electron storage ring. Since HALF under construction, we used the parameter of HLS-II to design the system and simulate the system circuits to verify its feasibility.
Surface annealing using intense nanosecond laser pulses is an emerging technique for SRF cavities. This technique can effectively reduce the cavities’ surface defects and improve their RF performance. However, previous studies in this field limited themselves on solid state lasers or gas lasers, which have very low average power and are not practical for processing actual SRF cavities with ~m2 inner surface area. IMP innovatively built a practical whole-cavity processing system with a kW-level nanosecond fiber laser, which is designed to process an SRF cavity within a working day. In this work, the system design and feasibility analysis will be given, together with the comparison between pristine Nb thin film samples on copper substrates and their fiber laser processed counterparts. The results show that our fiber laser system can deliver comparable surface treatment as that from the solid-state laser system, but with higher efficiency. The authors believe such results could boost the application of laser surface annealing technique in the particle accelerator community.
The performance of operating particle accelerators has been seriously affected by the electron cloud (e-cloud) effect. The secondary electron emission (SEE) and the e-cloud can be effectively suppressed through laser-etching the inner surface of the vacuum chamber. Oxygen-free copper (OFC) has become the first choice for the vacuum chambers of modern accelerators due to its high electric and thermal conductivity and effective radiation shield-ing property. It is necessary to study the vacuum proper-ties of the laser-etched OFC for the application in the particle accelerators. In this paper, the photon stimulated desorption (PSD) yield and the outgassing rate of the laser-etched OFC were measured. The results show that the laser-etched OFC presents lower PSD yield compared to the untreated OFC, while the outgassing rates of the laser-etched and unetched samples are similar.
The Super Separator Spectrometer (S3) is an experimental device dedicated to fundamental research in nuclear physics at GANIL laboratory in Caen, France. S3 spectrometer was designed in the framework of SPIRAL2 in order to take full advantage of the very high intensity stable ion beam delivered by the superconducting linear accelerator, LINAC.
In November 2022, the first beam of Argon beam has been accelerated to an energy of 7 MeV/u by the LINAC, opening the door for S3 experimental program. In the meantime, the installation of the spectrometer is being finalized and is due to accept the first beams by the end of 2024, for commissioning.
In order to achieve a mass resolution of 1/450 together with a high transmission, the superconducting magnets of S3 are designed with a large warm-bore aperture of 30 cm combined with a relatively high-gradient field. The technique*** used in these Superconducting Multipole Triplets (SMT) coils aims to generate a very precise multipole fields, able to correct 2nd and 3rd order aberrations. We believe that this technique is applied, at this scale, for the first time in a heavy ion spectrometer of the nuclear physics domain.
Detailed information of the progress of the qualification of the magnets and associated equipment, as well as the concept of the S3 spectrometer design will be presented.
The KEKB personal protection system (PPS) takes care of not only KEKB accelerator, but also PF-AR, Positron Damping Ring and their beam transport lines. The PPS is updated step by step. The new beam transport line to the PF-AR was constructed, and it makes possible that the injector supplies the beam to the 5 storage ring (KEKB LER,HER,PF-AR,PF and Positron damping ring) simultaneously. The positron damping ring was also constructed at the middle of the injector. The injector is not only supply the beam to the damping ring, but also is receive the beam from the damping ring. In this way, the accelerator operation scheme changed dramatically. The logic of the PPS has been changed to adapt the new accelerator operation scheme.
The Mu2e Experiment has stringent beam structure requirements; namely, it requires short (~200 ns) proton bunches separated by 1.5-2.0 $\mu$s. This beam structure will be produced using the Fermilab 8 GeV Booster, the 8 GeV Recycler Ring, and the Delivery Ring, which was formerly part of the antiproton accumulator system.
Out of time beam is limited to a fraction of level of no more than $1\times 10^{-10}$, a requirement known as "extinction". Achieving this level of extinction requires a system of resonant magnets and collimators, phased such that only in time particles will pass through. The Mu2e magnet system involves two components: a 300 kHz component, timed such that the 600 kHz beam will pass through the collimators at the nodes, and a 4.5 MHz system to reduce the slewing of the in-time beam. These two systems must be precisely phase locked to the bunch rate coming from the Delivery Ring, which itself must be phased to match beam transfers coming from the Recycler.
This poster describes the control system for the magnets, which is based on an Intel Arria FPGA, which handles phase locking of the magnets to the Delivery Ring, including the phase jumps required to match transfers from the Recycler.
High resolution bunch length monitors are an important diagnostic for the optimisation of any accelerator, from typical linacs or storage rings to novel acceleration systems. Given the availability of synchrotron radiation (SR) in these systems, studies have been carried out into how the spatial profile of the radiation changes with bunch length. Understanding these profile variations offers a non-invasive method of studying bunch profile characteristics. This contribution presents coherent SR simulations carried out in Synchrotron Radiation Workshop (SRW) for bunch lengths less than 100 fs, which are of interest to free electron lasers and novel acceleration facilities. These simulations have been carried out for the short pulse facility (SPF) situated in MAX IV. This is the location of a previously developed coherent transition radiation (CTR) monitor, which is currently being utilised as a compression monitor. The results of these simulations will be used to train a machine learning model to predict bunch profile characteristics, following the application of this process with the CTR monitor.
The CERN SPS Low Level RF (LLRF) has undergone a major upgrade, including the complete redesign of the 200 MHz Cavity-Controllers [1,2] and the Beam-Control [3]
during the Long Shutdown two (LS2) in 2018-21. Two major goals motivated the upgrade, first the required doubling of the proton beam intensity injected from the Super Proton Synchrotron (SPS) for the High Luminosity Large Hadron
Collider (HL-LHC) project, second the implementation of the slip-stacking of two families of ions bunches, 100 ns spacing, to generate a 50 ns spacing after interleaving. This paper presents new features of the 200 MHz Cavity-Controller part,
that is responsible for the regulation of the accelerating field in a single SPS cavity. Unlike the pre-LS2 implementation, the new system supports 100% Amplitude modulation (AM) and Frequency Modulation (FM) for the One-Turn delay FeedBack (OTFB) and for the Feed-ForWarD (FFWD).
The AM was commissioned and used with physics proton and lead ions beams during the SPS 2022 run. The new elements required for the modulations are reviewed
and details are provided on the implementation: delay and phase compensations to synchronize the cavity voltage measurement for the cavity field regulation with the AM and FM, synchronization of multiple cavities, and the velocity compensation for the heavy Ion acceleration. Finally, results of the cavity field regulation with amplitude modulation in 2022 are presented.
The CERN SPS Low Level RF (LLRF) has undergone a major upgrade, including the complete redesign of the 200MHz Cavity-Controller and the Beam-Control during the Long Shutdown (2018-21). This upgrade was motivated by the required doubling of the beam intensity in the SPS for the High Luminosity LHC project (HL-LHC). This paper covers the embedded acquisition core used in both the 200MHz Cavity-Controllers (one per cavity) and the Beam-Control systems. These acquisitions measure the internal signals of the LLRF inside the Field Programmable Gate Array (FPGA) such as cavity voltages, amplifier power, beam phase and radial position, synchro loop error, all essential for the beam commissioning. The embedded acquisition core allows standard decimation or peak detection of any signal and can also provide a turn-per-turn decimation to track the evolution of selected bunches through a longer time scale. The latter can be used to study Coupled-Bunch Instability (CBI) growth rates or longitudinal diffusion.
The described embedded acquisition architecture and some advanced features accelerate the commissioning and offer new beam observation which greatly improves the operational efficiency of the accelerator.
The interlock systems of the CERN Experimental North Area will be consolidated in CERN’s Long Shutdowns 3 and 4, planned to start in 2026. The new interlock systems will guarantee the safe and efficient operation of the machine protection systems for the coming 25 years. The consolidation work includes not only the primary beam areas but also the secondary beam lines and possible new beam lines, as part of the Physics Beyond Colliders program.
This contribution describes the limitations of the present North Area interlock systems in terms of reliability and response, and gives the details of the proposed new interlocking systems based on CERN standard hardware, the Warm Magnet Interlock Controller (WIC) and the Beam Interlock System (BIS). The WIC protects the magnets against overheating and additionally interfaces with the power converters and the BIS. The BIS collects operational information from many different systems. The BIS will be SPS machine-cycle dependent and will act on the beam dump system in the SPS and on the beam intercepting devices in the North Area beam lines.
Non-evaporable getter (NEG) coated vacuum cham-bers are widely used as a vacuum solution in modern particle accelerators.
In the development and testing of new NEG coatings to produce better vacuum, the pumping properties are evaluated.
In this paper, Test Particle Monte-Carlo Simulations are created to investigate whether small bends in sample tubes may affect the results of pumping speed measurements, and therefore lead to a set of inaccurate results.
With the preference to move towards smaller beam emittance in new accelerators, the required aperture of the beam vacuum chamber is getting smaller as well. The chambers are thus becoming more delicate (less mechanically stable), and able to be bent, therefore creating the risk that when NEG-coated samples are created, a bend in the tube is skewing the results.
Findings have shown that a bend of less than 1° could lead to a change in results by a factor of 10 in a sticking probability, which is a severe difference that cannot be ignored. The results have a strong correlation with the molecular beaming area from the bottom to the top of the modelled tubes.
In future, it will be important to define how straight a tube must be to obtain accurate pumping property measurements.
The Frascati linear accelerator was built in 1996 to be the electron and positron source and the front end of the DAFNE injector, is now also being used to support the DAFNE accelerator complex and the Beam Test Facility (BTF).
The Frascati linear accelerator system consists of four S-band high-power klystron and modulator systems, fifteen accelerating structures, and four SLAC-type energy doubler cavity sleds all running at 2,856-MHz frequency.
The Low Level RF distribution and status was upgraded starting from 2017.
The original design of the TITAN BETA Low Level Radio Frequency system for the FRASCATI linac was briefly described and the upgrades applied in last years are discussed.
Once completed, the Facility for Antiproton and Ion Research in Europe GmbH, FAIR, is to be one of the leading nuclear physics laboratories in Europe and one of the largest and most versatile accelerator complexes worldwide. FAIR can serve a number of experiments simultaneously, using fast-cycling synchrotrons. In this context, safety of personnel has the highest priority. The essential function of the Personnel Access System (PAS) is to prevent the presence of personnel in areas with particle beam or its secondary radiation. A particular challenge for FAIR is the large number of areas where personnel can access. For efficiency, it is required that during access to some areas, the beam operation continues in other areas of FAIR. For other hazards (e.g. electrical hazards, RF, laser beams) in certain areas, the PAS ensures that only personnel with adequate authorization can access and provides a safety signal to switch off hazardous equipment. Based on safety PLCs for the control system, the PAS uses some novel technologies such as hand vein scanners and safety radar systems.
The CiADS linac is a superconducting linear accelerator which has hundreds of RF cavities. The stable phase reference line is essential for effective control of accelerating fields in RF cavities, it provides phase reference signals for low level radio frequency systems, beam position monitor systems and timing system with low phase drifts. The phase reference line of CiADS SC linac is a coaxial cable based RF phase distribution system, a new phase averaging scheme has been designed to minimize the phase drifts in the main distribution line, which is hundreds of meters long. Instead of controlling the temperature of cable, the phase averaging scheme compares the forward and reflected signals at each tap point to get the reference phase. The new phase averaging scheme can overcome the VSWR ripple, which is the main disadvantage of using the traditional phase averaging reference method. This paper describes the design scheme and the prototype test results.
The Structured Laser Beam (SLB) is a type of optical beam characterized by an intense, sharply defined, low divergence core at its center, similar in its transverse intensity distribution to a Bessel beam. The SLB can propagate over a theoretically infinite distance, and has recently been tested up to a distance of 900 m. This test confirmed the low divergence of the SLB core, of about 0.01 mrad in this case. Furthermore, a hollow SLB (HSLB) can be created by feeding the generator with vector beams. These properties open the possibility of creating new types of optical alignment systems that could be used over long distances, for example for particle accelerators. Investigations are on-going to optimize the SLB and fully evaluate its alignment potential. Methods are under development to accurately detect the center of the SLB, based either on the beam intensity distribution or on the measurement of particular polarization states of the HSLB. Moreover, in order to deal with alignment in harsh environment, systems based on passive elements are also of interest. This paper summarize these studies and includes a discussion of phenomena such as the straightness of the SLB.
At the SPES (Selective Production of Exotic Species) facility, intense Radioactive Ion Beams (RIBs) are produced by the interaction of a 40 MeV proton beam with a multi-foil uranium carbide target employing the Isotope Separation On-Line (ISOL) technique. The Target Ion Source (TIS) unit constitutes the core of the isotope production process. TIS units are replaced on a periodic basis during operation to maintain high performance. An automated storage system has been designed to accept highly radioactive TIS units and house them during a cooling period prior to decommissioning. The system is conceived to meet strict functional and safety requirements. Its peculiar design allows for improved reliability and availability during critical operations, as well as minimization of staff exposure to ionizing radiation during maintenance tasks. This contribution describes the design and control architecture of the Temporary Storage System (TSS). The equipment is part of a structured framework of remote manipulation, consisting of various machines interlocked with the Access Control System (ACS) and the Machine Protection System (MPS).
We report on the behaviour and tuning of the diagnostics of the ThomX
Compact source during the accelerator commissioning. These diagnostics
consist of Beam Position Monitors, screens used to measure the beam
profile (YAG and OTR), charge monitors, bunch length monitors, beam loss monitors and
synchrotron radiation monitors. For each diagnostics we report on the
performances measured with the beam and the difficulties encountered.
The pulsed magnet control system at KEK electron positron injector LINAC changes the magnetic field every 20 ms to realize the simultaneous injection for four target rings, 2.5 GeV PF, 6.5 GeV PF-AR, 4 GeV SuperKEKB LER and 7 GeV SuperKEKB HER. It receives the trigger signal from the event timing system which varies for different beam modes. Then the output of a PXIe DAC board responds to the trigger and sets the current of the pulsed magnet. The combination of Windows 8.1 and LabVIEW was utilized to implement the control system since 2017. However, the discontinued support of Windows 8.1 requires an upgrade of the current system. Linux is choose to replace Windows and EPICS driver for PXIe devices is thus required. The development of the new Linux-based pulsed magnet control system is introduced in this work.
For X-ray spectroscopy applications it has been verified that Germanium detectors are enable to detect efficiently photons of considerable higher energy with respect to Silicon detectors. On the other hand, another advantage for cases like fluorescence detectors for absorption spectroscopy (XAFS), Germanium detectors do not show artifacts due to features like the escape peak interfering with interesting peaks being measured. In this context, the European project LEAPS-INNOV has launched a Research and Development program dedicated to creation of a new generation of Germanium detectors for X-ray detection.
From the thermal mechanical point of view, in order to optimize the efficiency of the new Germanium detector, finite element analysis (FEA) studies have been carried out on different geometrical models. In this paper, the thermal mechanical calculations of the current prototype are presented, as well as the details of the modifications implemented since the beginning of the project, with the main objective of optimizing the operating conditions of the Germanium sensor and its associated components. For the numerical simulations, ANSYS WORKBENCH software has been used.
For vacuum scientists and the accelerator community, it is of paramount importance to find solutions for high energy machines to mitigate : (i) pressure increases induced by the desorption of electrons, photons and ions; (ii) clouds of ions or electrons inducing beam instabilities, heat deposits on the vacuum chamber walls or stimulated molecular desorption; (iii) multipactor effect in superconducting rf cavities. The solutions call for specific surface treatments, including the use of deposits of thin films whose nature and morphology should lead to the improvement of the surface properties, in particular to reduce the secondary electron emission yield (SEY). We present a comparative study of several thin layers (CuO, TiNC, TiN, TiVZr, Zr, amorphous-C) whose SEY as well as the surface chemistry were characterized before and after conditioning by electrons. We focused in particular on the conditioning rate as a function of the nature of the thin film. This investigation highlights the influence of thickness and roughness of thin layers on the surface properties for accelerator applications.
The low level RF system of TPS booster ring was replaced by the DLLRF in 2018. After that, the phase drift compensation loop for energy saving operation and the tuner loop were also implemented into the DLLRF system sequentially. We used altera-DE3 to build the core of DLLRF and to handle the high speed ADC/DAC procedure for RF signal sampling. As facing to the tuner control requirement, we choose an another low cost board, altera-DE0-Nano, to develop the tuner loop for 5-Cells-Petra-Cavity. It has an eight channels 12-bits-ADC, ADC128S022, to detect two tuners’ positions and two transmit powers for power balance function. The phase information of forward power and cavity gap voltage will get from altera-DE3 to tell the tuner loop in altera-DE0-Nano that the cavity is resonance or not. The tuner loop controls the cavity to work not only at resonance frequency but also with balance electric field distribution. In this study, the architecture of the tuner loop is presented including locking resonance frequency and field balance functions. The performance of field balance function is observed by the archive data of two tuners’ positions and two transmit powers.
Thyristors triggered in impact ionization mode find their dI/dt capability boosted by up to three orders of magnitude. This innovative triggering requires applying an important overvoltage on the anode-cathode of the thyristor with a slew rate > 1kV/ns. Compact pulse generators based on COTS components would allow the spread of this technology into numerous applications, including fast kicker generators for particle accelerators.
Our approach for such a compact pulse generator begins with a HV SiC MOS with an ultra-fast super-boosting gate driver. Super boosting in the gate of a 1.7kV rated SiC MOS allows to reduce its rise time by a factor of > 25 (datasheet tr = 20ns vs. measured tr < 800ps), resulting in an output voltage slew rate > 1kV/ns and an amplitude > 1kV. Parallel MOSFETs triggered in synchronisation deliver higher current at this stage.
Next, additional boosting is obtained by a Marx generator with D2PAK thyristors, reaching an output voltage slew rate > 11kV/ns. Finally, creating sufficient current necessary for the triggering of a big thyristor presents a new challenge. In this paper, we present an upgraded board design with a higher current output capacity.
The ALPI accelerator radio frequency (RF) control system at LNL (Legnaro National Laboratories) is currently undergoing a series of upgrades which will extends its lifetime and provide enhanced performance. This is a multi-year project where the upgrades are delivered incrementally while avoiding disruptions to the accelerator schedule. The first phase includes the development of new Low Level RF (LLRF) controllers, tuner and coupler stepper motor boxes and power amplifiers interfaces. The control system software and graphical user interfaces have been completely rewritten based on EPICS, supporting both the new and old LLRF controllers. A second phase is undergoing with the installation of the new software and hardware, while still using the old LLRF controllers, on the low and medium beta cavities of the ALPI accelerator. In the next phases the upgrade of the whole accelerator to the new software will be completed and the new LLRF controllers will be installed. This paper describes the technical solutions adopted and the status of the project.
The medium energy beam transport (MEBT) of the SPIRAL2 superconducting linac contains a single bunch selection system equipped with a 7.5 kW beam dump (SBS dump). This device, originally designed with a long plane slope to decrease the power density so that the maximum operating temperature was 170 °C, was impacted by Coulomb scattering generating two side effects: heating of the downstream beam transport components and degrading of the beam current measurement uncertainty. The paper relates the way these two problems were solved.
The LNL accelerator complex is equipped with two stable ion beams injectors, employing respectively negative and positive ion sources. In particular, a sputtering-type negative ion source and an Electron Cyclotron Resonance Ion Source (ECRIS) are installed on high voltage platforms, to provide the optimum injection energy in the downstream accelerators. Recently, the two injectors have been object of upgrades and developments, in order to improve the overall safety and reliability of the two systems, as well as the beams available for the users. This contribution describes the work related to the above mentioned activities, the technical choices employed and the latest results on ion beams production.
The Shanghai soft X-ray free electron laser facility has made significant progress in recent years with the rapid, upgraded iterations of the High Level software, including but not limited to energy matching, orbit's feedback and load, beam optimization, etc. These tools are key components in operation and experiment of free electron laser facility. Some key applications are presented in this paper.
In the context of Time Sensitive Networking (TSN), the Ethernet standards are being extended with new capabilities for deterministic communication, allowing standard Ethernet to be used in new fields of application. In addition, more and more companies now offer TSN compatible devices and software tools. In accelerator control systems (ACS), which need synchronization in the range of some hundred ns, TSN provides the necessary mechanisms for a one-cable timing system with deterministic low latency and best-effort data transfer in parallel. These techniques include message-based timing and fast back channel capabilities for front-end controllers, leading to high safety in medical applications. Nowadays, time synchronisation below 100 ns of up to 250 devices can be achieved using the IEEE 802.1AS standard, based on PTP (Precision Time Protocol). Deterministic communication can be guaranteed by a time-based scheduler according to IEEE 802.1Qbv standard, protecting critical traffics. This fulfils the needs of a next generation ACS for a synchrotron-based ion beam therapy facility. Time measurement results of test set-ups, using TSN capable switches and SoMs (System-on-Modules), will be reported as well as conceptual designs, which will be realized soon to implement multi-energy operation at HIT.
The large-acceptance Superconducting Fragment Separator (Super-FRS) at the Facility for Antiproton and Ion Research (FAIR) at GSI Darmstadt poses peculiar challenges for its vacuum systems. Although the vacuum levels ranging from 1E-5 to 1E-7 mbar for the single-pass beamline are rather undemanding in absolute values, a combination of high level of prompt and residual radiation in the target and pre-separator area, highly outgassing and self-sealing inserts, and large volumes not usually encountered in accelerator systems are setting exceptional demands on the design of the vacuum systems. The radiation environment also has an impact on regular maintenance and emergency intervention strategies as well as on radiation hardness requirements of the standard vacuum components. We present the vacuum layout of the Super-FRS, giving an overview of the major vacuum requirements with pressure profiles from analytical as well as Molflow+ simulations of selected vacuum sectors. Additionally, the solutions implemented for remote handling of the standard and special vacuum components are discussed.
The Photo Injector Test facility at DESY in Zeuthen (PITZ) utilizes slit scan technique as a standard tool for reconstruction of horizontal and vertical phase spaces of its space charge dominated electron beams. A novel method for 4-dimensional transverse phase space characterization, known as Virtual Pepper Pot, is proposed at PITZ, that can give
insight to transverse beam phase space coupling. It utilizes the horizontal and vertical single slit scans to form pepper pot-like beamlets by careful crossing and post-processing of the slit scan data. All the elements of the 4D transverse beam matrix are calculated and used to obtain the 4D transverse emittance and coupling factor. The proposed technique has been applied to the experimental data with coupled beam
phase space in order to demonstrate the diagnostic capability. The loss of signal at tails of the beamlets due to low signal-to- noise (SNR) ratio is considered in the algorithm and the systematic error resulting from crossing of the beamlets is also explored.
Dielectric gratings are used in Dielectric Laser Acceleration due to their high damage thresholds in high acceleration gradients. When an electron bunch passes close to these gratings, it emits radiation, and the features of this radiation will be dependent on the beam position relative to the grating, the bunch charge, and the bunch length. A compact high-resolution diagnostic device will be developed that consists of multiple dielectric gratings with different periodicities; these types of devices are required for the accurate operation of future compact accelerators which are currently undergoing development and testing.
The ARES linac at DESY is able to provide sub-fs electron bunches and has a range of high-resolution diagnostic devices installed, such as the PolariX Transverse Deflecting Structure, which will allow for performance verification of a new diagnostic. The electron bunches can be altered, allowing for the measurement and analysis of the emitted radiation for different bunch lengths and charges. This work will present the current progress in this area, including the presentation and discussion of simulations, and a discussion of the planned experiments at ARES.
High-brightness photoinjector has been an indispensable electron source driving X-ray free electron lasers (FEL). To improve the performance of the next-generation FEL, a high-quality electron beam with a small emittance, e.g, 0.1 micrometers for 100 pC bunch charge, will be of vital importance. A consecutive double-slit emittance meter has been proposed to measure such a small-emittance beam accurately. Analytical evaluations have been performed based upon the beam parameters of a C-band photocathode RF gun being constructed in the China Spallation Neutron Source.
Reinforcement learning (RL) algorithms are investigated at KIT as an option to control the beam dynamics at storage rings.
These methods require specialized hardware to satisfy throughput and latency constraints dictated by the timescale of the relevant phenomena.
The KINGFISHER platform, based on the novel Xilinx Versal Adaptive Compute and Acceleration Platform, is an ideal candidate to deploy RL-on-a-chip thanks to its ability to execute computationally intensive and low latency feedback loops in the order of tens of microseconds.
In this publication, we will present the integration of the KINGFISHER system at the Karlsruhe Research Accelerator (KARA), as a proof-of-principle turn-by-turn control feedback loop, to control induced transversal oscillations of an electron beam.
Beam monitoring for Ultra High Dose Rate (UHDR) radiation therapy using pulsed beams, i.e. Very High Energy Electrons (VHEE), is a major challenge. The lower pulse repetition of VHEE beams means a larger dose-per-pulse is necessary to achieve the mean dose rates required for UHDR therapy (so-called FLASH). The currently used transmission ion chambers suffer drastic recombination effects under these conditions. A proposed detector consisting of a 2D array of silica optical fibres connected to a photodetector which measures the Cherenkov radiation emitted by the VHEE beam as it passes through the fibres could be a promising alternative due to its high spatial and temporal resolution and its low material budget. First measurements with such a detector, consisting of silica optical fibres with a diameter of 200 μm, have been conducted at the CLEAR facility at CERN using 200 MeV electrons up to the UHDR required for FLASH. Measurements on the dynamic range of the fibre detector showed that it had a linear response at mean dose rates of over 300 Gy/s. Such results show that this fibre-optic based beam monitor is able to provide fast direct real-time measurements of the VHEE beam dose and profile up to the UHDR. This makes them an excellent candidate for online dosimetry and beam diagnostics in future clinical FLASH machines with VHEE and other beam types.
Contaminated photon beams which comes from upstream and downstream dipole magnet in between an Insertion Device (ID), the main light source, often cause a critical measurement error on blade-type Photon Beam Position Monitors (PBPMs). The reason of such misreading is that the center position of the beam is calculated by only with the weak photoelectric current generated from both ends of the blade. Instead of direct photoelectric effect on metal blades, we considered an ionization of residual gas as a main detecting principle of photon beam position to remove the measurement error caused by the contamination. Realistic photon beam profiles which comes from the ID and dipoles were generated, and they were used as a photon source of beam-gas interaction calculation in order to get a distribution of ionized electrons. The electrons were tracked inside a conceptually designed model that consisting of residual gas chamber, electrodes and uniformly distributed electric field. In this paper, we introduce a Monte Carlo simulation method of gaseous type PBPM and a preliminary result of the parameter optimization
Thin targets, in the form of wires, stripes, or foils, are often used in accelerators to measure the properties of particle beams. Motivation for a small thickness, typically between several and to hundred micrometers, is diverse and depends on a particular case. For instance, small diameters of wires allow for precision measurement because it is probing a small fraction of the beam transverse profile. In case of high-power beams, the critical argument is small energy deposits and good cooling because of the large surface-to-volume ratio. In certain beam conditions, the temperature of the target can be very high and lead to thermal damage. This paper attempts to give an overview of the conditions under which the breakage occurs and the damage mechanisms for various materials.
Developments in current and future experiments in the SPS North Area (NA) and PS East Area (EA) fixed target beam lines at CERN, including the “Physics Beyond Colliders” (PBC) program, require accurate determination of the number of protons on target (POT). The re-calibration of Beam Secondary Emission Intensity monitors (BSI), recently completed in one of the NA branches, reduced the estimated uncertainty on the absolute POT to a few percent. The calibration is based on an activation technique, applied to metal foils (Al, Cu), installed in front of the BSI and irradiated with the nominal proton intensity for a short period. The number of protons is determined from offline gamma spectrometry analysis of the foils and compared to the total integrated signal of the BSI. A description of the method, data analysis and results, will be presented and followed by considerations intended to standardise the procedure for future regular use in all SPS NA beamlines.
Capacitive Pick-Ups (PUs) are typically used for monitoring the beam position and measuring the relative intensity of bunched beams. We explore the potential usage of capacitive PUs for measuring the absolute charge in a bunch over the full range of beam energies, transverse beam offsets and bunch lengths found at ion accelerators. The results suggest that absolute charge measurements can be performed, however a correction specific to the design and installation of PUs is required.
In this contribution, the field simulation results for a typical PU design installed at GSI UNILAC and CRYRING@ESR for a standard beam parameter range are shown. Historical experimental data from comparative measurements between PUs and current transformers performed at CRYRING@ESR support the simulation results.
To harness the full potential of the ultrafast electron diffraction (UED) and microscopy (UEM), we need to know accurately the electron beam properties, such as emittance, energy spread, spatial-pointing jitter, and shot-to-shot energy fluctuation. Owing to the inherent fluctuations in UED/UEM instruments, obtaining such detailed knowledge requires real-time characterization of the beam properties for each electron bunch. While diagnostics of these properties exist, they are often invasive, and many of them cannot operate at a high repetition rate. Here, we present a technique to overcome such limitations. Employing a machine learning (ML) strategy by training a model on a small set of fully diagnosed bunches, we can accurately predict electron beam properties for every shot using only parameters that are easily recorded at high repetition rate by the detector while the experiments are ongoing. Applying ML as real-time non-invasive diagnostics could enable some new capabilities, such as online optimization of the long-term stability and fine single-shot quality of the electron beam, filtering the events and making online corrections of the data for time-resolved UED, fully realizing the potential of high repetition rate UED and UEM for life science and condensed matter physics applications.
The Heidelberg Ion-Beam Therapy Centre (HIT) provides proton, helium, and carbon-ion beams with different energies and intensities for cancer treatment and oxygen-ion beams for experiments. For several experiments and possible future applications, such as helium ion beam radiography, a low-intensity ion beam monitor integrated into the dose delivery feedback system for the accelerator control is a necessary pre-requisite. The updated 2D prototype for this purpose consists of scintillating fibres with enhanced radiation hardness, silicon photomultipliers (SiPMs) to amplify the emitted light, and a dedicated front-end readout system (FERS) to process and record the generated signals. This setup was tested successfully on monitoring ion-beam position and profile horizontally and vertically, as well as the beam intensity, for all four ion types with energies from 50 to 430 MeV/u and intensities from 1E2 to 1E7 ions/s. Additionally, time-of-arrival (ToA) measurements on single ions have been successfully performed for a limited intensity range, allowing for ion tracking in a further update. This will reduce noise, and will also improve the accuracy and usability of ion radiography.
Physics models, particularly for online operations, such as for our MAD-X or Bmad models, depend on a good understanding of the magnet characteristics. While we often measure the magnets or some subset of the magnets, those measurements are only meant to verify that the magnets meet specifications before being installed. We often have magnets that are not precisely understood. As a result, we end up adjusting the coefficients in our models to match beam-based measurements with little or no theoretical basis. In this work, we present a new method for deriving these coefficients using orbit response matrix (ORM) methods. This new approach utilizes a neural network (NN) surrogate model to establish the mapping between ORM measurements and quadrupole kicks. The NN model is trained to identify quadrupole kick as a source of error by observing the difference between measured ORM and model ORM with no quadrupole kick. With actual kick values from the NN model and power supply current values from the control system, we can calculate the magnet transfer function coefficients using a polynomial fit. We will present results from preliminary beam studies in the AGS Booster.
At a heavy-ion linac facility, such as ATLAS at Argonne National Laboratory, a new ion beam is tuned once or twice a week. The use of artificial intelligence can be leveraged to streamline the tuning process, reducing the time needed to tune a given beam and allowing more beam time for the experiment. After establishing the required automatic data collection procedures, we have developed and deployed machine learning models to tune and control the machine. We have successfully trained online different Bayesian Optimization (BO)-based models for different sections of the linac, including the commissioning of a new beamline. We have also demonstrated transfer learning from one ion beam to another allowing fast tune switching between different ion beams. And more importantly, we have demonstrated transfer learning from the simulation to the online machine model using Neural Networks as the kernel for the BO optimization instead of Gaussian Processes (GP). This latest development allowed fast convergence even when including a multitude of variable parameters. We have also explored Reinforcement Learning (RL)-based models which showed some promising results but will require more development. These models will be later generalized for the whole ATLAS linac and can, in principle, be adapted to control other heavy-ion linacs and accelerators with modern control systems.
The CNAO orbit measurement system consists of 20 electrostatic pickups. They are based on a nineties’ design and reliably working from over fifteen years, despite a not very effective calibration system.
At beginning 2020, a new control software was installed, with two significant improvements: firstly, pickups signal is acquired continuously and beam orbit is saved every cycle; secondly, it allows to perform the calibration procedure very simply, from the pickup user’s interface, in a fast and non-invasive way. These features gave us the instruments for a comparative study of position and calibration measurements, that brought about the definition of a quantity able to predict accurately position fake shifts caused by changes of eletronics transfer function. This allows to isolate the electronics contribution from the true beam shift, resulting in a more reliable orbit measurement system.
Calibration measurements have revealed some causes of electronics response variations, while others have to be understood yet. Anyway, a new monitoring plan has been started from a few months, to follow the trends closely, to better understand the causes and to promptly intervene with a software compensation, aiming to an increasingly reliable orbit measurement system.
After the upcoming upgrade, the storage ring in the Advanced Photon Source (APS-U) will have over two thousand magnet power supplies. They will be constantly monitored in order to prevent impeding failures, when possible. The new data acquisition system (DAQ) will deliver 22600 samples of each power supply’s current per second. The data can be saved at this rate for a short period of time around a suspected anomaly. However, continuous data logging is more feasible at a smaller rate. In this contribution, we present (1) a statistical plug-in for the DAQ, which allows to reduce the data rate for logging, while capturing the most important statistical properties of the raw data, (2) a number of machine learning models for anomaly detection in the compressed data, and (3) an application with a graphical user interface to review the detected anomalies.
The energy consumption in accelerator structures during beam downtimes is a significant fraction of the overall energy budget. Accurate prediction of downtime duration could inform actions to reduce this energy consumption. The LCAPE project started in 2020 and develops artificial intelligence to improve operations in the FNAL control room by reducing the time to identify the cause of a beam outage, improving the reproducibility of labeling it, predicting their duration and forecasting their occurrence.
We present our solution for incorporating information from ~2.5k monitored devices in near-real time to distinguish between dozens of different causes of down time.
We discuss the performance of different techniques for modeling the state of health of the facility and we compare unsupervised clustering techniques to distinguish between different causes of down time.
Since its commissioning, operators at the Argonne Tandem Linear Accelerator System (ATLAS) have used an analog current meter to manually record beam current measurements from Faraday cups along the beamline. Recently an automated process using a digital picoammeter was developed for beam current measurements. This automation has streamlined daily operations, increased the precision of measurements, and expedited the generation of digital data for use with ongoing artificial intelligence and machine learning work (AI/ML).
The CERN SPS Beam Dump System (SBDS) is responsible for disposing the beam in the SPS in case of any machine malfunctioning or end of cycled operation.
This is achieved by the actuation of kicker magnets with predefined pulses, which aim to: i) deviate the beam towards the absorber block (TIDVG); ii) dilute the particle density. Evidently, a malfunction of this system may have negative consequences, such as the absorber block degrading if the beam is not sufficiently diluted, unwanted activation of the surroundings or even damage to the vacuum chamber in case of complete failure.
By leveraging a combination of real images from a beam screen device and data from simulations, we train an online monitoring system to identify potential failures of the SBDS from real-time images. This work improves the safety of the operation of the SPS and contributes towards the goal of automating the operation of accelerators.
Beam arrival time is one of the key fundamental parameters for free-electron laser (FEL) facilities to ensure an accurate synchronization between an electron bunch and a seeded laser. Thus a high-performance beam arrival time/flight time measurement (BAM) system is indispensable for an FEL. A cavity-based BAM system has already been established at the Shanghai Soft-X-ray FEL test facility three years ago. To further optimize the system performance, the impacts of the local oscillator, signal processing window, and temperature around the electronic devices were analyzed, and the related subsystems were upgraded and optimized accordingly. Currently, the upgraded BAM system has been applied at the Shanghai Soft-X-ray FEL user facility. This report will focus on the evaluation of the upgraded BAM system performance and the analysis of the beam instability caused by the beam energy jitter by both analytic calculation and beam test. The beam test results show the deviation of beam flight time can reach 10 fs. Besides, a linear correlation between the beam energy and beam flight time is found and the energy jitter can contribute 33 fs to 65 fs to the beam flight time RMS jitter.
The ionization profile monitors (IPMs) are used to measure the transverse profiles of the beams accelerated at the Brookhaven National Laboratory (BNL) AGS. These devices use multi-channel plates (MCP) to collect electrons generated by ionization of the residual gas to get an image of the beam projection onto the two transverse planes. The gains of each of the 64 channels in the MCP can vary from channel to channel due to both initial fabrication variations and over time as the channel exposed to more signal degrade and become less sensitive. There are also systematic errors associated with varying delays in the digitization paths for different groups of channels. We describe a reinforcement learning approach to accounting for and calibrating these errors using historical data from the Brookhaven AGS IPMs.
Parameter tuning is a regular task and takes considerable time for daily operations at FEL facilities. In this contribution, we demonstrate SASE pulse energy optimization at the European XFEL with Bayesian optimization (BO) as an alternative approach to the widely used simplex method. Preliminary experimental results show that BO could reach a comparable performance as the simplex method, even with an out-of-the-box implementation. Compared to previous attempts, our version of BO does not require setting hyperparameters via additional measurements, thus effectively reducing the required effort for machine operators to use it during operation. On the other hand, BO has the potential to be further improved by introducing prior physical knowledge about the task and fine-tuning the algorithm to specific tasks. This makes BO a promising candidate for routine tuning tasks at particle accelerators in the future.
The X-band lineariser linac planned to be installed on CLARA will be aligned using beam induced higher order modes (HOMs). Higher order modes in the cavity were studied using a bead-pull measurement technique. A software application was developed in LabVIEW to control the 3D motorised bead position scanning setup and VNA for S-parameter measurements. Propagation of HOM frequencies in the linac were verified, identifying the most suitable HOMs to use. Progress in development of HOM signal processing hardware system with dynamic control is also discussed in the paper.
The Mainz Energy recovering Superconducting Accelerator (MESA) is currently being installed in the final area of the Institute for Nuclear Physics at Johannes Gutenberg-University in Mainz. To optimize and operate the accelerator reliably luminescence screens, wire scanners and RF cavity monitors are used. In this paper we will present the ongoing development of the beam diagnostics foreseen at MESA.
Many beam instrumentation systems at Brookhaven National Laboratory’s Collider-Accelerator complex are over 20 years old and in need of upgrading due to obsolete components, old technology and the desire to provide improved performance and enhanced capabilities. In addition, many new beam instrumentation systems will be developed for the future Electron Ion Collider (EIC) that will be housed in the existing Relativistic Heavy Ion Collider (RHIC) tunnel. A new BNL designed custom hardware architecture is planned for both upgrades in the existing facility and new systems for the EIC. A general-purpose carrier board based on the Xilinx Zynq Ultrascale+ System-on-Chip (SoC) will interface with a family of application specific daughter cards to satisfy the requirements for each system. This paper will present the general architecture that is planned, as well as details for some of the application specific daughter cards that will be developed.
The Beam Loss Monitoring (BLM) system of the Large Hadron Collider (LHC) at CERN is essential for the protection of machine elements against energy deposition from beam losses. Employing around 4000 detectors placed around the 27-km LHC ring, the BLM system measures secondary particles continuously and can trigger beam extraction in less than 3 turns, in case the signals exceed certain predetermined thresholds. Thanks to its high dynamic range and sensitivity, a signal-to-lost-particle calibration of this system is suited to provide accurate information about the LHC beam loss patterns. This includes online monitoring of the beam lifetime and even the identification of the plane of losses, making it an asset to follow up the performance of the accelerator.
In this contribution the principle of the monitor calibration is explained, as well as a description of the machine tests used to acquire the calibration data. Finally, an analysis of the beam lifetime during the first year of the LHC Run 3 is presented together with examples of selected LHC fills.
The Fermilab Linac is a roughly 145 meter linear accelerator that accelerates H- beam from 750 keV to 400 MeV and provides beam for the Booster and the rest of the accelerator chain. The first section of the Linac is a Drift-Tube Linac (DTL), which in its current state, suffers from a lack of instrumentation along its length. As a result, operational staff do not have access to the diagnostic information needed to tune the critical components of this accelerator, such as the quadrupole magnets within the drift tubes. This work presents an effort to utilize both fixed and translating scintillation detectors to investigate beam loss along the first two tanks of the Drift-Tube Linac.
Beam Loss Monitors will be installed along the primary SPES beam line to detect proton beam losses in the cyclotron area. They will be connected to the cyclotron Machine Protection System (MPS), as it is significant for the proper management of the accelerator during the operation. This report shows the work of characterization of such devices.
Preliminarily, the characteristics of models used in other facilities with features similar to SPES (Proton beam energy= 40-70 MeV and current= 200-500 μA) were analyzed.
Instrumentation Technologies-Libera, a company that makes potentially suitable devices for the SPES facility, was contacted as a possible supplier. They offer a system designed for beam loss measurements based on scintillators integrated on Photomultiplier, flash ADC and data acquisition. The gain is controlled by dc voltage managed by the system.
Detectors and electronics have been tested in two steps:
1. Irradiation with gamma and neutrons static sources;
2. Irradiation with the CN accelerator beam (zero-degree line).
From the tests, the detectors resulted very reactive to gamma and neutron radiation, so they could be suitable to be implemented at SPES as beam loss monitor purposes.
Moreover, to characterize the detector on the operational conditions is fundamental. For these reasons, testing the detector’s behavior at the SPES cyclotron in normal operation (current= 200 μA and proton energy= 40 MeV) is mandatory and is planned for the next future.
The mitigation of heat loading is one of the important issues for beam instrumentation to measure the high-power proton beam. Recently, the highly-oriented pyrolytic graphite (HOPG) material was used for the target probe of the bunch-shape monitor at the front-end in the Japan Proton Accelerator Research Complex (J-PARC). Since the thermal conductivity of the HOPG is high, it is suitable to measure the beam profile under the condition of high heat loading. As an application of the HOPG, for example, the thin HOPG may be used as a substitutive material of the target wire for the transverse profile monitor such as the wire scanner monitor. The possibility of the HOPG target for the beam profile monitor is discussed from some results of the test experiment using the 3-MeV negative hydrogen ion beam at the test stand.
Advancements in low-emittance x-ray sources have required the exploration of various diagnostic techniques to push the resolution limit. Here we will present the two techniques to measure the size of the electron beam using X-rays: zone plate transmission microscope and a multi-crystal diffraction-based beam property analyzer. Both techniques have been tested at the Swiss Synchrotron Light Source (SLS), with encouraging results. With the zone plates, it is possible to measure the beam profile in 2D simultaneously. However, with the diffraction-based method, only the vertical beam size was measured. We have built and tested a diffraction-based system that is able to measure the beam size in both dimensions. This concept was also built to be compact and does not require long x-ray beamlines such that it could afford beam size monitoring for light sources with limited space.
In recent work, it has been shown that reinforcement learning (RL) is capable of outperforming existing methods on accelerator tuning tasks. However, RL algorithms are difficult and time-consuming to train and currently need to be retrained for every single task. This makes fast deployment in operation difficult and hinders collaborative efforts in this research area. At the same time, modern accelerators often reuse certain structures within or across facilities such as transport lines consisting of several magnets, leading to similar tuning tasks. In this contribution, we use different methods, such as domain randomization, to allow an agent trained in simulation to easily be deployed for a group of similar tasks. Preliminary results show that this training method is transferable and allows the RL agent to control the beam trajectory at similar lattice sections of two different real linear accelerators. We expect that future work in this direction will enable faster deployment of learning-based tuning routines, and lead towards the ultimate goal of autonomous operation of accelerator systems and transfer of RL methods to most accelerators.
Bunch-by-bunch systems are developed at the Taiwan Light source and the Taiwan Photon source to monitor the transverse position and filling pattern. This system consists four channels with 500 MHz sampling rate which synchronizes with the radio frequency of the accelerator. This system is used to diagnose the injection transition due to the kick mismatch and beam oscillation coming from the damped betatron oscillation and wake field.
In order to fulfill the target performance of Elettra 2.0 light source, a brand new button type beam position monitor detector has been developed. From a theoretical point of view, the transfer function which relates beam position information to electromagnetic signal intensity induced on pick up electrodes is well known. In practice, due to a number of constraints, a real device implementing this transfer function is difficult to manufacture. In this paper, a series of practical design considerations involving electromagnetic, mechanical, vacuum, maintenance, and cost issues are reported to illustrate the advantages and disadvantages of the conceived constructive solutions.
A set of twelve Polycrystalline Chemical Vapour Deposition (pCVD) diamond detectors are installed in the beam injection, extraction and betatron collimation areas of the Large Hadron Collider (LHC) as fast beam loss monitoring detectors. Their high-radiation tolerance and time resolution in the order of a few ns makes them an ideal candidate to monitor bunch-by-bunch losses in the LHC beams, which have a nominal bunch separation of 25 ns. Considering their location in some of the most critical areas for beam loss studies, a signal-to-lost-particle calibration of these detectors provides a useful insight of the various LHC bunch-by-bunch beam loss mechanisms.
This contribution shows the principle of the calibration of the LHC diamond Beam Loss Monitors (dBLMs) as well as a description of the machine tests run to study and perform this calibration.
Capacitive beam position monitors (BPM) are widely used as diagnostics tools in particle accelerators. Typically due to a large number of BPM in an accelerator, their contribution to the beam coupling impedance cannot be neglected. In addition to the broadband part at low frequencies, the impedance exhibits resonant peaks at higher frequencies due to electromagnetic fields trapped around the BPM button and in the feedthrough assembly. Coupling of these peaks with beam spectrum lines can result in the BPM overheating. In this paper, we discuss the BPM design optimization aimed at the beam coupling impedance minimization while keeping/improving the BPM signal sensitivity (transfer impedance).
The Future Circular Collider (FCC) R&D study was started in 2021 as a comprehensive feasibility analysis of CERN’s future accelerator project encompassing technical, administrative and financial aspects. As part of the study, Beam Instrumentation (BI) is a key technical infrastructure that will have to face unprecedented challenges. In the case of electron-positron FCC-ee, these are represented, among others, by the size of the accelerator, the amount of radiation produced along the ring and in machine-detector interaction region, the presence of the top-up booster and collider ring in the same tunnel. In this contribution we will present the current FCC-ee BI study and discuss its status and perspectives.
Supersonic gas jets are useful tools in particle accelerators used in both scientific and medical applications. They can provide real-time, longitudinal and transverse beam profile measurements for charged particle beams in accelerators and are also being used as a plasma source in wakefield accelerators. For gas jets to be used effectively as beam profile monitors, the density profile of the jet must also be well-known. This can be calculated by measuring the phase shift produced by the gas jet inside a laser beam due to the difference in density between the gas and the surrounding vacuum environment from the Lorentz-Lorenz relation.
In this contribution, multiple techniques for measuring gas jet profile and density will be compared and analysed; Mach-Zehnder and Nomarski interferometry. A 532 nm laser will be used for both of these methods, with a gas jet backing pressure of 7 bar. Multi-pass interferometry will also be used to increase the phase shifts by a factor of 4, and therefore sensitivity to lower density gas jets. This method involves retro-reflecting the interferometry beams, passing them through the gas jet multiple times. These techniques will be compared and their suitability for gas jet density characterisation will be assessed.
The generation of Cherenkov diffraction radiation when a charged particle beam passes in close proximity to a dielectric target is being studied and developed for various non-invasive beam instrumentation applications. One such instrument is a beam position monitor (BPM) composed of four cylindrical dielectric inserts. A challenge of using the conventional stretched wire technique to characterize the BPM is the coupling of higher order modes (HOMs) into the inserts that are dielectric-loaded circular waveguides. To minimize the generation of HOMs and excite mainly the transverse electromagnetic (TEM) mode as a model of the beam field, a set-up comprising a dielectric insert mounted on a slab line with 50 Ohms characteristic impedance was tested. The results and comparison with numerical simulations in CST are presented.
To support commissioning and early operation of the ESS normal-conducting linac, a variety of beam instrumentation systems have been deployed. These include beam chopping systems, Faraday cups, beam current monitors, and beam position and phase monitors as well as specialised systems such at wire scanners, emittance measurement units and neutron beam loss monitors. Commissioning has proceeded in three campaigns: proton beam through the Radio-Frequency Quadrupole to 3.6 MeV in 2021, through the first Drift Tube Linac (DTL) tank to 21 MeV in 2022 and through the first four DTL tanks to 74 MeV in 2023. In preparation for each campaign, the diagnostics team verified the measurement and protection functions of this instrumentation suite without beam. These functions were then verified with a low duty factor beam before finally declaring the systems operational. Throughout these verification activities and the succeeding commissioning stages, a rich data set was archived and analyzed. This paper describes the early experience with the ESS NCL instrumentation and, with a focus on lessons for future facilities, summarizes the data analysis techniques and results.
The oscillator-type mid-infrared free-electron laser at Kyoto University named Kyoto University FEL (KU-FEL) has achieved the extraction efficiency of 9.4% and the micro-pulse duration of 4.2 cycle with the electron bunch charge of about 200 pC by the photocathode operation of 4.5-cell thermionic RF gun. Then the micro-pulse energy obtained was 100 micro-J. A new and dedicated 1.6-cell RF gun for the photocathode operation was fabricated and installed for increasing the electron bunch charge up to 1 nC and increasing the micro-pulse energy up to 1 mJ. The RF gun has curved cavity profile and elliptical cross-section of the connection between the half and full cell with a demountable cathode. This cavity design reduces the surface field of the inner cavity wall**. This improvement is important for having long macro-pulse (~10 micro-s) operation of the gun, which is essential for the oscillator-type FEL. The commissioning of the RF gun is undergoing. Results of commissioning experiments will be presented in the conference.
We built a test stand for evaluating the performance of the thermionic electron sources for the electron lens project at the Integrable Optics Test Accelerator (IOTA) in Fermilab. The lens will be used to study nonlinear dynamics and electron cooling of 2.5 MeV protons with strong space charge. The test stand will validate the characteristics of the thermionic sources and the main parameters of the generated beams. In this paper we present the results of the commissioning of the UChicago test stand and validation of the hollow beam source.
In this paper we present a systematic benchmark between the simulated and the measured data of radiation monitors useful for Radiation to Electronics (R2E) studies at the Large Hadron Collider (LHC) at CERN. The radiation levels in the main LHC tunnel on the right side of the Interaction Point 1 (ATLAS detector) and 5 (CMS detector) are simulated using the FLUKA Monte Carlo code and compared against Single Event Effect (SEE) measurements performed with the Radiation Monitor (RadMon) system. Considering the complexity and the scale of the simulations as well as the variety of the LHC operational parameters, we find a generally good agreement between measured and simulated radiation levels, typically within a factor of 2 or better.
On the one hand fault occurs with high cost in accelerator operation, on the other hand operation data is treasure for modelling the accelerator from the other side.
Due to limited capacity of data processing, massive data is discarded in accelerator operation. However, regular data recorded can not meet the need for measuring the damage of fault. Therefore, a balanced design to capture as much data as possible to reconstruct the fault scene is valuable.
Dedicated wakefield-generating structures are capable of measuring the electron beam current profile, and of removing residual energy chirps (dechirping). Furthermore, at Free-Electron Laser (FEL) facilities they can be used to measure* or shape the photon pulse power profile. We motivate and present the mechanical design of the rectangular, double-sided corrugated structures used at SwissFEL, and compare it to similar designs employed at other facilities.
The Cryogenic Current Comparator (CCC) is able to provide a calibrated non-destructive measurement of beam current with a resolution of 10 nA or better. The non-interceptive, absolute intensity measurement of weak exotic ion beams (< 1 µA) is essential in heavy-ion storage rings and in transfer lines, as the ones in FAIR. With traditional diagnostics this measurement is challenging for bunched beams and virtually impossible for coasting beams. The CCC is able to provide reliable values of beam intensity for current of this order of magnitude or lower, independently of beam bunching, ion species and without tedious calibration procedures. The test of the CCC in the heavy-ion storage ring CRYRING@ESR at GSI confirmed its viability, and suggested several improvements to the detector hardware. Therefore, an upgrade of the CCC system was performed and tested in laboratory environment. A review of these improvements will be presented, with a deeper discussion of the improvements and of the next steps for the development of the final version of the CCC for FAIR.
Measuring transverse beam profiles using thin wires is a very successful and widely used method. The signal is generated either by measuring scattered particles outside of the vacuum chamber or by measuring the current of the secondary electrons emitted from the wire. In high-brightness accelerators, the heating of the wire induced by the direct beam interaction or by coupling to RF fields can lead to the thermionic emission of electrons, which disturbs the measurement. The spectra of the electrons are different, but they overlap, therefore the typically used method of biasing the wire only partly reinstates the original beam profile. This study investigates the mixing of current signals from both phenomena and tries to address the question of the optimal bias voltage and potential reconstruction of the original beam profile. The estimations are compared to measurements performed on high-brightness beams of PSI HIPA machines.
Electro-optic diagnostics are able to non-destructively resolve the longitudinal charge profile of highly relativistic bunches without complicated calibrations and ambiguous phase recovery techniques. The most implemented technique is EO spectral decoding as it is simple and reliable, and has an easy to interpret output. However, its resolution is limited to the geometric mean of the transform limited and stretched probe laser durations. Until very recently, efforts to improve on this have resulted in designs that lose the attractive properties of spectral decoding. On the CLARA accelerator at Daresbury Laboratory we have demonstrated a new EO system that exploits common-path spectral interferometry, 'EOSI', which removes the geometric mean limitation. The system was used to measure 35 MeV/c bunches live at 10 Hz, ranging from 150 pC down to 2 pC, and at a range of compressions from several ps down to ~300 fs rms. We explain the technique, describe the measurements, and outline issues and improvements. The technique differs from a spectral decoding system by only a single optical element, potentially allowing current EO systems to be upgraded.
Ultrashort electron beams with high brightness are of vital significance in probing nanoscopic dynamics on the pico-to-femtosecond temporal scales. Electron sources are the most critical element in such apparatuses, whose advancements are expected to further improve the resolving capabilities. In this contribution, we report on the development of a DC photocathode electron gun aiming at delivering optimal-quality electron beams for ultrafast electron scattering and photocathode studies. The 200 kV gun features simplicity and adjustability in fabrication and assembling, and is compatible with INFN/DESY/LBNL-type photocathode plugs. The design, fabrication and conditioning processes of the gun are discussed in detail, along with preliminary beam measurement results where nm-scale emittance is demonstrated.
The CLARA accelerator facility at Daresbury Laboratory, UK, was originally designed to operate as a free-electron laser test facility. To improve the user exploitation of the facility a dedicated full energy beam exploitation (FEBE) area has been designed and is currently being installed in a separate experimental bunker on the CLARA accelerator. This facility will allow users to conduct experiments combining a 250 MeV electron beam of up to 250 pC bunch charge with laser pulses up to 100 TW in a large target chamber. A second downstream chamber contains room for a number of diagnostics that are customisable to the experiments being conducted.
The ability to combine a laser and electron beam in FEBE presents the possibility of novel acceleration experiments. FEBE is designed to allow user experiments which aim to further accelerate the electron beam from 250 MeV to 600 MeV, or 2 GeV at a reduced repetition rate. To measure the output of these experiments an innovative in-vacuum permanent magnet spectrometer dipole has been designed with modular construction to measure broadband electron energy spectra. The modular nature allows the length of the installed dipole to be tailored to the experiment, allowing room for additional diagnostics in experiments where maximum energies below 2 GeV are expected.
Medical isotopes are used for diagnostics and cure of tens of millions of patients worldwide every year. For the largest parts they are produced in fission reactors from enriched Uranium-235 leaving behind long-lived nuclear waste. Around the world organizations are therefore working to make medical isotope production more sustainable.
RI Research Instruments was commissioned by the Institute for Radioelements (IRE, Belgium) with the design of a superconducting electron linac (75MeV, 40mA, CW) for the industrial production of Mo-99.
The short development time and high requirements on availability (23h/d, ca. 360d/y) lead to the use of proven concepts from the Cornell CBETA accelerator and a redundant design with two DC photoguns able to produce the initial electron beam.
We report on the innovative aspects of this design. They include a merger feeding e-beam from either of the guns into the linac, a beam splitter dividing the beam 50/50 for illuminating the target from opposite sides, beam dynamics for low-loss beam transport, and a machine protection system able to switch the beam off in <1µs. For the region near the target, where high gamma and neutron doses occur, a radiation-hard design using pillow seals was developed.
For risk mitigation prototypes of the critical components were developed and are currently being tested. This involves especially the DC-photogun, which is described elsewhere.
Test of a DC-photogun Injector for the Lighthouse facility, IPAC 2023.
The Extreme Photonics application Centre (EPAC) is a new national facility to support UK science, technology, innovation and industry currently under construction at the Rutherford Appleton Laboratory, UK. EPAC is designed to facilitate a wide variety of user experiments with 1PW 10Hz laser systems. It is anticipated that early experiments will include laser-plasma acceleration of electrons to energies ranging from 100 MeV up to 10 GeV, with later experiments using these electrons as a beam once stable generation is achieved.
EPAC is designed to be flexible, allowing users to select the relevant central electron energy for their experiment. To achieve this goal EPAC and the Accelerator Science & Technology Centre (ASTeC) at STFC Daresbury Laboratory have been working on the design of a beamline to capture laser-plasma driven electrons with broad energy spread, measure their energy spectrum, perform selection of specific energies if necessary and deliver these electrons to a user interaction point. We present here the conceptual design of the proposed spectrometer and energy selection system.
A high-average-current VHF electron gun operating in the CW mode is under construction at Shanghai Advanced Research Institute, which is the key component of a kW-power-order free electron laser facility. The average current and the frequency of this electron gun is 1-10mA and 217MHz, respectively. To validate the performance of this instrument, a test platform has been designed. The R&D of its vacuum and diagnostics are presented in this work.
The Electron Ion Collider (EIC) is being built at Brookhaven National Laboratory (BNL). Early preliminary design phase efforts are underway. In addition to upgrading the existing RHIC instrumentation for the EIC hadron storage ring, new electron accelerator subsystems that include a 400 MeV Linac, rapid-cycling synchrotron, electron storage ring, and a strong hadron cooling facility will have all new instrumentation systems. The scope of the instrumentation includes devices to measure beam position, loss, current, charge, tune, transverse and longitudinal profiles, emittance, and crabbing angles. A description of the planned instruments and the present design status will be presented.
The Electron-Ion Collider (EIC) facility at Brookhaven National Laboratory is in the preliminary design phase and advancing towards establishing the project baseline. One challenging task is to design cryogenic BPM pick-ups for the Hadron Storage Ring (HSR) that will ensure reliable beam position measurements over a large dynamic range. The BPM pick-up design must take into consideration potential elevated heating concerns caused by resistive wall effects for a radially shifted beam during normal operations, in the buttons and cryogenic signal cables. The geometric impedance associated with the button configuration and housing transition to the adjacent HSR beam screen must also be minimized. This paper focuses on the evolution of the button BPM design and describes simulation results of the impedance characteristics, position-related voltage signals, and beam-induced losses on the metallic BPM buttons due to the radial offsets.
KoBRA (Korea Broad acceptance Recoil spectrometer and Apparatus) of RAON (Rare Isotope Accelerator complex for ON-line experiments) in Korea is preparing for producing rare isotopes with stable ion beams from SCL3(Superconducting Linac 3) at an energy range of 5 - 25 MeV/u in early-phase experiments. Due to quite a lengthy transport beamline from the end of SCL3 to the target of KoBRA (SCL3-KoBRA beamline), the required bunch length of incoming ion beams for KoBRA production target wouldn’t be satisfactory, if the ion beam energy is less than 15 MeV/u. Therefore, this suggested a rebuncher system for longitudinal focusing within the SCL3-KoBRA beamline is absolutely needed.
In order to suppress the bunch length, the velocity bunching technique will be used, and to have the lowest possible RF power, we compared various RF cavities, such as QWR, HWR, and IH-DTL. We simulated the electric field and shunt impedance of RF cavities with CST STUDIO to estimate the effective voltage of RF cavities with different types, design βvalues, and the number of RF gaps for beam energy range of interest. Because one rebuncher cannot cover the entire beam energy range of less than 15 MeV/u, we selected normal conducting 5-gaps IH-DTL (Interdigital H-mode Drift Tube Linac) as a rebuncher for 5 - 15 MeV/u beams. Moreover, another rebuncher for less than 5 MeV/u beam is planned. This report presents the design study of the rebuncher system for KoBRA focusing on the selection process.
Characterizing the phase space distribution of particle beams in accelerators is a central part of accelerator understanding and performance optimization. However, conventional reconstruction-based techniques either use simplifying assumptions or require specialized diagnostics to infer high-dimensional (> 2D) beam properties. In this work, we introduce a general-purpose algorithm that combines neural networks with differentiable particle tracking to efficiently reconstruct high-dimensional phase space distributions without using specialized beam diagnostics or beam manipulations. We demonstrate that our algorithm reconstructs detailed 4D phase space distributions with corresponding confidence intervals in both simulation and experiment using a single focusing quadrupole and diagnostic screen. This technique allows for the measurement of multiple correlated phase spaces simultaneously, enabling simplified 6D phase space reconstruction diagnostics in the future.
Comprehensive simulations for the FETS laserwire have been made with the developed Geant4 laser package. Feasibility of the longitudinal mode laser to provide full 6D beam characterisation has been made. Simulation results have been used to outline minimum detector requirements. The detector necessary for measuring the 6D phase space requires a drift distance of at least 2.5m between interaction point and detection plane, a 1mm2 spatial resolution, across a total transverse area of 40mm2 for the transverse measurements. To include longitudinal data the time resolution of the detector would need to be 200ps or less. The Timepix4 is proposed as a candidate detector due to its tile structure enabling custom size detector, a <100 μm spatial resolution, and a 195 ps time resolution.
A new dedicated materials irradiation beamline and target station was developed and recently commissioned at the ATLAS facility at Argonne National Laboratory. The new ATLAS Materials Irradiation Station (AMIS) is located just downstream of the first linac section (PII) and designed to receive heavy-ion beams with energies of 0.5 - 1.5 MeV/u. The main activity at AMIS is the irradiation of samples for radiation damage studies of nuclear materials. The facility will provide a unique accessible platform for accelerated testing of nuclear fuels and materials that support the testing and deployment of new materials for advanced reactors in a short period of time, which otherwise can take years of testing in conventional reactors. Although the focus of the AMIS line is to irradiate and investigate materials for nuclear energy applications, other research and applications are welcome. In particular, more beam time will be available following the completion of the ongoing ATLAS multi-user upgrade which will allow simultaneous beam sharing between different experimental stations. The development and commissioning results of the AMIS beamline will be presented and discussed.
A quantum gas jet-based beam scanner is under development at the Cockcroft Institute (CI) in the UK. This device is based on detecting the ionisation induced in a gas jet by a beam of charged particles. It aims at generating a dense gas jet with a diameter of less than 100 μm by exploiting the quantum wave nature of neutral gas atoms to generate an interference pattern with a single maximum. Work analogously to a mechanical wire scanner while being minimally interceptive, a tightly focused gas jet promises superior position resolution and high signal intensity.
This contribution gives an overview of the design and functioning principle of the monitor, presents initial modification in the system for gas density measurement, as well as results from beam profile measurements obtained with a 5 keV electron beam.
The emittance of fourth-generation storage ring(4GSR) will be built in Cheongju-Ochang, Korea, is expected to be 100 times smaller than the existing third-generation storage ring. As the emittance decreases, more precise beam stabilization is required. To satisfy this, the resolution of the Beam Position Monitor (BPM) should also be further improved.
We have performed an optimization study of 4GSR BPM to minimize wake impedance and power dissipation in small size of 4GSR vacuum chamber. Moreover, The cut-off frequency of feed-through antenna was designed to be high by using a material with a low dielectric constant. As a result, the BPM output signal is fully decayed and supressed within a bunch interval of 2ns. In this presentation, we will describe that the more detailed current status of the design and development of the beam position monitor for Korea 4GSR.
Standard methods of measuring the transverse beam profile are not adaptable for sufficiently high-intensity beams. Therefore, the development of non-invasive techniques for extracting beam parameters is necessary. Here we present experimental progress on developing a transverse profile diagnostic that reconstructs beam parameters based on images of an ion distribution generated by beam-induced ionization. Laser-based ionization is used as an initial step to validate the electrostatic column focusing characteristics, and different modalities, including velocity map imaging. This paper focuses on measurements of the ion imaging performance, as well as the dependence of Ion intensity on gas density and incident beam current for low-energy electron beams (<10 MeV).
A suite of diagnostic was designed to fully characterize a high current electron beam in a short section of a beamline. The entire suit of diagnostics is housed in ~1.2 m in length and contains 7 diagnostic assemblies that have 78 fast channels and two cameras. The suite contains a slit-harp emittance diagnostic, energy analyzer, two beam position monitors, a Faraday cup/beam stop with 14 sampling cups, OTR camera for 2D imaging, and streak system with temporal 2D reconstruction. The system was designed to accommodate large and small diameter beams up to 1.5 kA of electron beam. The paper will outline the utility and regime of operation, along with anticipated measurement accuracy.
The Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory is currently undergoing an upgrade known as ALS-U. As part of this upgrade, the existing Triple-Bend Achromat (TBA) storage ring lattice is being replaced with a Multi-Bend Achromat (MBA) lattice, which allows for the tight focusing of electron beams to approximately 10 um, reaching the diffraction limit in the soft x-ray region. However, accurately measuring the beam size in such a tightly focused beam presents a challenge. This paper presents a diagnostics beamline design for ALS-U that utilizes a 2-slit interferometer technique to achieve a sub-micron resolution for beam size measurement. The impact of beam jitter, optics vibration as well as the incoherent depth-of-field effect on the measurement are also discussed.
Digital beam signal processor is critical for the beam diagnostic resolution and on-line application performance. High speed & high precision ADC, high performance FPGA are the key devices for the evolution of the processor. At present, ADC technology has entered the era of RF direct sampling, which bandwidth is up to 9GHz, sampling rate is higher than 2GSPS, and sampling bits is up to 14 bits. If the beam signal is sampled directly and processed with an FPGA, the beam diagnostic system structure will be much more concise and stable. In this paper, a developed direct RF sampling processor for beam diagnostic in SXFEL and SSRF will be introduced, and the first application on cavity BPM system will be shown.
A beam position monitor based on Cherenkov diffraction radiation (ChDR BPM) is currently under investigation to disentangle the electromagnetic field of an electron bunch from that of a proton bunch travelling together in time and space in the beam-line of the AWAKE plasma acceleration experiment at CERN. The signals from a horizontal pair of ChDR BPM radiators have been studied under a variety of beam conditions at the CLEAR electron beam test facility. This paper summarizes the results using microwave signal processing at different frequency ranges.
In the novel device described in this presentation uses a simple, strip cathode provides a sheet beam probe for tomography instead of a scanning pencil beam that was used in previous electron probe bunch profile monitors. The apparatus with the strip cathode is smaller, has simpler design and less expensive manufacturing, has better magnetic shielding, has higher sensitivity, higher resolution, has better accuracy of measurement, and better time resolution. With this device it is possible to develop almost ideal tomography diagnostics of bunches in linear accelerators and in circular accelerators and storage rings. Currently we are planning to build a prototype tomography system will be built for testing in a proton or ion beam.
Beam position monitors (BPMs) are fundamental diagnostic tools for lightsources: thanks to their data readout, machine orbit can be stabilized and corrected by control systems. New generation machines need better performances on these diagnostic devices due to increased demands, such as smaller photon beam size and long-term stability. This article outlines all the devices that will make up the future Elettra 2.0 BPM system, based on pilot tone compensation. The entire signal acquisition chain will be described, from the pickups to data delivery to the control system. After a brief introduction about the electronics (analog signal conditioning, digital conversion and processing), more emphasis will be given to the description of timing and synchronization functionalities, machine protection system integration and machine feedback
The high luminosity specifications for future linear colliders, such as the Compact Linear Collider (CLIC) require extremely small vertical beam emittance at the interaction point. This relies on minimizing the emittance growth in the collider sub-systems. One major source of emittance growth is the Main Linac, mainly caused by misaligned quadrupoles and accelerating structures. The current budget for the normalized emittance growth is 5 nm due to the static misalignments and another 5 nm due to the dynamic imperfections. The budget for the static imperfections is achieved through the use of beam-based alignment, such as one-to-one correction, dispersion-free steering, and the realignment of accelerating structures. This paper explores the use of additional emittance tuning bumps to further decrease the emittance growth, thereby increasing the luminosity.
At the KIT storage ring KARA (Karlsruhe Research Accelerator), a far-field electro-optical (EO) experimental setup to measure the temporal profile of the coherent synchrotron radiation (CSR) is implemented. Here, the EOSD (electro-optical spectral decoding) technique will be used to obtain single-shot measurements of the temporal CSR profile in the terahertz frequency domain. To keep the crucial high signal-to-noise ratio a setup based on balanced detection is under commission. Therefore, simulations are performed for an optimized beam path and the setup is characterized. In this contribution, the upgraded setup and first measurements are presented.
The Superconducting RF photo-injector with the prototype 1.4 lambda/2-cell Niobium cavity of the bERLinPro Energy Recovery Linac (ERL), recently renamed to SEALab, was tested and characterized in a dedicated beam test facility called Gunlab to analyze its performance for the ERL. After dismantling and refurbishing of the cavity, a small surface defect was found close to the cathode opening and by simulated reconstruction of the set-up it was demonstrated to be the main source of the dark current measured at Gunlab. Later, a method was found to remove that defect**, but still the question remains, what amount of dark current is acceptable for an ERL injector, especially for the SRF systems? In this contribution, we show a fully 3D simulation based emulation of the dark current measurements in Gunlab and extrapolate the impact on the complete injector at bERLinPro (SEALab). Here, it can be shown, that besides a small meshed beam loss diagnostics, methods need to be found to determine the amount of field emitted current dumped into the SRF systems.
Older cyclotrons still find a variety of applications in research and education, but in many cases the beam dynamics of these machines is not well understood, which can be a limitation to achieving their ultimate performance.
The cyclotron at the Crocker Nuclear Laboratory at UC Davis is a capable of accelerating protons, deuterons, or alpha particles to variable energies up to a maximum of 67 MeV for protons. Recently, we have been trying to improve the performance of the machine for a variety of applications, with particular emphasis on increasing the alpha beam, for use in producing the isotope 211-At, which has great promise for cancer treatment. This effort is hampered by the lack of an accurate model of the cyclotron and extremely limited instrumentation for the beam as it accelerates.
This poster describes a series of beam measurements made using a segmented beam probe with the time resolution to measure individual bunch structures and sufficient lateral segmentation to measure horizontal and vertical motion of the beam as it accelerates. These are compared with models to try to understand such motion at a fundamental level.
Achieving a high signal-to-noise ratio is challenging in electron scattering experiments that require low average probe current or low total electron dose, e.g., time resolved hard-matter or radiation-sensitive soft matter experiments. A promising method for improving the signal-to-noise ratio when electron counts are low is to structure the electron wavefunction with optical fields and then retrieve the image via reconstruction algorithms in a single pixel imaging approach. When the electron-optical interaction is inelastic, such a scheme requires an electron energy filter. Here, we present numerical simulations of a time-of-flight energy filtering scheme for use in ultrafast electron microscopy, where a radiofrequency deflector cavity placed at the bottom of an electron microscope column provides a time-dependent momentum kick, dispersing the energy bands of the beam on a downstream detector. We estimate the filtering performance for electron single pixel imaging with an electron beam wavefunction shaped by a high intensity, highly coherent ultrafast light pulse and discuss future practical aspects.
The accelerator upgrades of SLS and Elettra will use newly designed kickers adapted for their small aperture beam pipes.
The striplines of the transverse kickers conform closely to the aperture of the beam pipe with special grooves to avoid synchrotron light on the blades. The multitude of trapped higher order modes, caused by a high beam pipe cut-off frequency and dangerous in terms of stability and heat up, is suppressed by lossy silicon carbide dampers. The devices feature integrated pumping ports. The transverse shunt impedance improves by a factor of four compared to the current SLS/Elettra kicker.
The longitudinal kicker is a heavily coupled cavity at 1.875 GHz (3.75 * RF) with four input and four output couplers for driver and loads. A nose cone design optimizes the shunt impedance resulting in a 20% improvement over the current SLS/Elettra kicker. Also here, the high cut-off frequency of the beam pipe caused problematic higher order modes, which needed to be damped by higher order mode couplers. A dedicated field sensor pickup will be used to synchronize the feedback to the bunch train.
Protons are dominant radiation source in the space environment causing radiation effects such as SEE(Single Event Effects), DD(Displacement Damage) to EEE(electrical, electornics and Electromechanical) parts of spacecraft. Until now, radiation effect test for space EEE parts have been carried out by using a 100 MeV proton irradiation facility (BL102) at KOMAC(Korea Multi-purpose Accelerator Complex). For this kind of the accelerated ground test of such radiation effects on devices to predict their performance in space, the new space radiation environment simulation apparatus, which can simulate ultra high vacuum and thermal cylcling (-55 to +125 celcius degree) as well as 100 MeV proton irradiation, have been developing under way. For the new space environment test for space EEE parts, the Determination of dose or Fluence is the key parameter. Although the BL102 facility usually provide the the users the beam intensities range from 1E6 to 1E8 protons [cm-2 s-1], In order to match the demand of the space testing community of the South Korea, the new real-time beam flux monitoring system was developed by the combination of the high sensitivity in-air ACCT(AC current transformer) and the Bragg peak chamber detector which have the measurable range from 1E4 to 1E8 protons [cm-2 sec-1] and the beam flux can be measured by the pulse to pulse in real time. In this paper, new space radiation environment test apparatus and its beam flux monitoring system will be introduced.
The Karlsruhe Research Accelerator (KARA) is an electron storage ring, which features an electro-optical near-field monitor within the beam pipe in vacuum as a tool for longitudinal bunch profile measurements. The device performs very well in single-shot turn-by-turn measurements during single-bunch operation and over the years. The design has been optimized to be prepared for measurements in multi-bunch operation. The ability to work with multiple bunches and short bunch spacing is an important step to make the device suitable for more application purposes such as a diagnostics tool for the Future Ciruclar Collider for electrons and positrons (FCC-ee). This contribution provides first tests of the monitor during two-bunch operation with minimum 2 ns bunch spacing. Challenges like crystal heating due to an increased beam current are discussed and strategies for mitigation are presented.
SPES (Selective Production of Exotic Species) is an ISOL type facility for production and postacceleration of exotic nuclei for forefront research in nuclear physics, for the operation it must be equipped with a safety system compliant with the Italian regulatory framework.
The object of this work is to report how the Safety Requirement Specifications, generated from the safety analysis, are mirrored in the Functional Architecture of the System, showing the accordance with IEC-61511. It is explained how the main tasks of the system have been developed in the organization of the safety hardware, starting from the description of the elementary logic unit, describing the features of the safety PLCs and illustrating the arrangement of the system on the field.
At FAIR, GNU Radio* is being used as part of the generic monitoring and first-line diagnostics for acceleratorrelated devices, and to further support equipment experts, operation, and FAIR users in developing basic to advanced top-level measurement and control loops.
GNU Radio is a free and open-source software development toolkit supporting hundreds of low-cost to high-performance industrial digitizers with sampling frequencies ranging from a few MS/s to GS/s~\cite{gnuradio, gnuradio_github, gnuradio4_github, FAIR_Digitizer, FAIR_Digitizer2}. At its core are directed signal flow graphs expressing arbitrary post-processing and feedback control loop logic that are both numerically highly efficient as well as providing an intuitive yet detailed nuts-and-bolts representation. This facilitates to inspect and/or to reconfigure existing systems by accelerator-, control- or other system domain-experts alike with little to no prior required programming experience.
This contribution describes the community-driven improvement and modernisation process leading to GNU Radio 4.0 supporting improved type-safety, improved performance, and new features such as event-driven data processing, nanosecond-level synchronisation using White-Rabbit, and slow feedback loops.
Presently, superconducting radio frequency (SRF) cavities with high intrinsic quality factors are used in particle accelerators, as a high intrinsic quality factor allows for increased energy efficiency. As such, this technology benefits new research into light source linacs such as in the new LCLS-II system. However, due to the narrow bandwidth attributed to large quality factors, the use of these SRF cavities requires more accurate control to mitigate the effects of vibrations within the cavity and maintain a fixed frequency. In a paper by Banerjee et al., it was proposed that the current practice of actively suppressing such vibrations using fast tuners may be improved through the implementation of a narrowband active noise control algorithm (NANC) that makes use of gradient descent. It is the aim of this research to explore which gradient descent methods work best for active resonance control
An electro-optic beam position monitor is in development for the HL-LHC to enable high-bandwidth monitoring of crabbed bunch rotation and intra-bunch instabilities. Following in-air beam tests of a prototype at HiRadMat and the Clear facilities at CERN in 2021 and 2022, a new in-vacuum version is being prepared for operation in the SPS during LHC Run 3. We report on progress toward the design aims and investigate a novel method of readout of single shot pulsed bunch signals at high bandwidth, while acquiring data at lower bandwidths using an optical time-stretch technique.
The technological evolution of analog-to-digital and digital-to-analog converters increases the amount of data that can be processed in the digital domain. Therefore, direct digitization enables many advanced signal processing techniques and is attracting more and more attention in the field of accelerator instrumentation. The future HL-LHC Beam Position Monitor (BPM) data acquisition system to be installed near the ATLAS and CMS experiments is a clear example of an application with demanding signal processing requirements that could greatly benefit from this trend. The investigated architecture is based on an RF System-on-Chip from Xilinx, which allows fast RF conversion and high-performance digital processing to be integrated in a single chip for multiple channels. This paper compares the estimated performance and cost of such an integrated solution with an architecture based on discrete components.
Magnetic field errors pose a limitation in the performance of circular accelerators, as they excite non-systematic resonances, reduce dynamic aperture and may result in beam loss. Their effect can be compensated assuming knowledge of their location and strength. Procedures based on orbit response matrices or resonance driving terms build a field error model sequentially for different accelerator sections, whereas a method detecting field errors in parallel yields the potential to save valuable beamtime. We introduce deep Lie map networks, which enable construction of an accelerator model including multipole components for the magnetic field errors by linking charged particle dynamics with machine learning methodology in a data-driven approach. Based on simulated beam-position- monitor readings for the example case of SIS18 at GSI, we demonstrate inference of location and strengths of quadrupole and sextupole errors for all accelerator sections in parallel. The obtained refined accelerator model may support set up of corrector magnets in operations to allow precise control over tunes, chromaticities and resonance compensation.
The Hollow Electron Lens (HEL) was proposed to actively remove the beam halo of the proton beam for the HL-LHC upgrade. Currently, the concept of generating such an electron beam is being tested in a dedicated Electron Beam Test Stand (EBTS) at CERN. It currently produces a hollow electron beam with 7 keV energy and 0.4 A current 25 us pulsed with 2 Hz which will be confined in a strong solenoid field. A gas curtain-based beam profile monitor was developed to characterize the beam non-invasively during operation. It injects a directional gas sheet at 45 degrees to interact with the electron beam. Gas particles are excited and emit fluorescent photons which are collected by an intensified camera system. This allows the reconstruction of the profile of the hollow electron beam.
This contribution presents the design of the monitor and discusses the initial results obtained with a hollow electron beam at the EBTS.
Beam-based alignment (BBA) for quadrupoles is a routine process for circular accelerators to steer beam orbit through the magnetic centers such that the orbit is unperturbed when the strengths of quadrupoles are varied. The random errors associated with BBA are well known, but a type of systematic error appears to be neglected by the community. A standard measurement procedure involves variation of the quadrupole gradient. This systematic error is introduced when there is a non-zero dipole component after quadrupole strength is changed. This dipole component can be also interpreted as a shift in the magnetic center. The analytical formulas for this error and its amplification factor with respect to the magnetic center motion have been derived and confirmed with simulations. We demonstrate the significance of this error, potentially on the order of hundreds of microns, through both simulations and recent experimental results at NSLS-II. In addition, a special term in this error that is not extractable from orbit measurements alone will be discussed in detail.
The longitudinal phase space tomography, which reconstructs the phase space distribution from the one-dimensional bunch profiles, is used in various accelerators to measure longitudinal beam parameters. At the J-PARC, an implementation of the phase space tomography based on the convolution back projection method has been used to measure the momentum spread of the injected beam. The method assumes that the beam distribution rotates without significant deformation during the synchrotron oscillation. Because of the nonlinearity of synchrotron motion with sinusoidal RF voltage, the method can be used only in limited situations such as small amplitude synchrotron oscillation. Algebraic Reconstruction Techniques (ART) in conjunction with particle tracking, which is implemented in CERN's tomography code, allows accurate reconstructions even for nonlinear large amplitude synchrotron oscillations. We present the overview of the application of CERN's tomography code to the J-PARC synchrotrons. The results of benchmarking are also reported.
Methodical studies to improve the existing e-beam Longitudinal Phase Space (LPS) tomography were performed at the Photo Injector Test facility at DESY in Zeuthen. Proof-of-principle simulations were done to address some core concerns e.g. booster phase range, space charge effects and noisy artefacts in results. Phase advance analysis was done with the help of an analytical model that determined the booster phase range and step size. A slit was introduced before the booster to truncate the beam and reduce space charge forces. The reconstruction method adopted was image space reconstruction algorithm owing to its assurance of non-negative solution. An initial scientific presumption of LPS from low energy momentum measurements was established to reduce artefacts in the phase space. This paper will explain the proof-of-principle simulations highlighting the key aspects to obtain accurate results. Reconstructed LPS for different experimental cases will be presented to demonstrate the diagnostic capability.
The LHC interlock BPM system is used as part of the beam abort system to insure that beam trajectories in those regions are conform with a safe extraction of the beams from the main ring to the dump lines.
After more than 10 years of operation, the system has shown some limitations in bandwidth and dynamic range and a study was initiated to look for improvements.
Nowadays, with the availability of multi giga sample per second sampling rate ADC converters, there is poten-tial to greatly improve the performance of the system.
In this paper a wideband architecture with direct acqui-sition of the BPM electrode signals, time interleaved on the same read-out channel is presented with emphasis on the design and construction of the critical components, and on the measured performance of a prototype system tested in the LHC during the 2022 run.
The Los Alamos Neutron Science Center (LANSCE) employs the use of BPPMs (Beam Position and Phase Monitors) to track the position and phase of beam throughout the site. In the past, BPPMs in the 805MHz CCL (Coupled Cavity Linac) section of the site used a 201.25MHz reference over facility network fiber, using RF media converters. This fiber reference distribution gave rise to give a large diurnal phase & temperature dependency causing a large error in beam phase measurement. A system was devised to use the site’s temperature controlled 805MHz reference divided by 4 as a 201.25MHz reference, with the n*90˚ phase uncertainty eliminated though measurement of phase between 805MHz divided by 4 and fiber 201.25MHz alongside a switched hybrid coupler network. Deployment of 7 phase reference units in 2022 allowed for greatly reduced error in beam phase measurement.
SuperKEKB is an asymmetrical lepton collider with a circumference of 3 016 meters, which collides 7 GeV electrons with 4 GeV positrons. To optimize the luminosity, which recently reached a world record of 4.71 10^34 cm-2 s-1, all the undesirable effects on beam parameters must be analyzed in detail, especially close to the interaction point where the Belle II detector is operated. The presented study investigates the influence of mechanical vibration on the luminosity. For this purpose, four seismic sensors (Guralp 6T) were installed and collect data 24 hours a day, two on the ground and another two located on the supports of the two cantilevered cryostats, inside which the last focusing magnets on both sides of the interaction point (the most critical for vibrations) are mounted. The luminosity is measured thanks to the LumiBelle2 fast luminosity monitor, which is based on diamond detectors installed in both beam lines. Vibration-induced disturbances in the luminosity frequency spectrum are investigated for several types of perturbations, in particular the ones resulting from ground motion amplified by the dynamical behavior of the cryostat, as well as also from external vibrations sources.
The Collider Accelerator Complex at Brookhaven National Lab (BNL) contains millions of control points. Monitoring tolerances for these control points is crucial for the system and is a challenging task. Catching early signs of failures in those systems will be very beneficial as they can save extensive downtime. Anomaly detection in particle accelerators has been highlighted and can significantly impact the system. Autoencoder is one of the most commonly used techniques for detecting anomalies. In this contribution, we apply an autoencoder method to analyze the historical data for runs 21 and 22 to find precursors for trips (and actual trips) of Air Conditioning (AC) systems based on local thermostat readbacks. Results from the existing system are presented, showing that the new method can catch early signs of AC trips so that advance notices can be sent for the operators to take prompt action.
Superconducting radio-frequency (SRF) photoinjectors offer a broad range of electron beam parameters and are therefore suitable for many applications such as energy recovery linac (ERL) driven lightsources, particle colliders, or for ultrafast electron scattering experiments. We are now nearing completion of the setup a SRF photoinjector with a SRF gun and SRF booster linac at the SEALAb accelerator test facility at HZB. The goal here is to realize an electron source with high brightness and high average current. In this work, the general planning for the commissioning phase, the operation modes and investigations into the diagnostic tools for achieving the expected beam parameters will be presented. The focus of the instrumentation is to provide information on the beam parameters at large dynamic range and on mechanisms for beam loss generation.
The Los Alamos Neutron Science Center (LANSCE) continues to invest into the future of its facility. In 2022 and after a 11-year effort the original and reliable RICE (Remote Instrumentation and Control Equipment) system was decommissioned. It was replaced with a modern customized control system in small stages during each annual 4-month outage. Since 1972 when the first proton beam was delivered through the near mile long accelerator, the control system was in a continuous state of modification. Thus, an extensive amount of non-RICE equipment was added over the years to expand the capabilities of the facility. Some of that equipment is now up to ~40 years old. Hence, the effort to replace the lingering obsolete and end-of-life equipment must continue to ensure reliable beam operations enabling scientific success in LANSCE’s five experimental areas. This paper discusses the scope of the designated Instrumentation and Controls Modernization project. We describe our technologies of choice and remaining challenges we face before we can implement them. The boundary condition for the whole project, as usual, is that we must implement these changes on a running accelerator.
The synchrotron light source BESSY-II has been in operation for almost 25 years and modernization measures are needed to maintain competitiveness until its successor BESSY-III comes online. One measure is to replace the old analogue LLRF control units with new, state of the art mTCA.4-based digital ones. The so-called “single cavity” firmware developed by DESY is being used together with the ChimeraTK adapter to connect the mTCA to the EPICS control system. A pair of SIS8300KU and a DWC8VM is used, while the tuner is driven by a PhyMotion chassis connected to the EPICS system. We discuss the implementation of the system.
We present an approach for detection of anomalous behavior of magnet power supplies (PSs) in storage rings, which may serve as an early indication of an impending PS trip. In this new method, we train a Long Short-Term Memory (LSTM) neural network to predict the temperature of several components of a PS (transistors, capacitors) based on the PS current, PS voltage, room temperature, and cooling water temperature. For training and testing, years of historical data are used from the Advanced Photon Source (APS). The neural network is trained on the data corresponding to the normal operation of the PSs. Anomalous behavior of a PS can be detected when the observed PS temperature starts to deviate significantly from the LSTM prediction. This may allow for preemptive action by the operators or PS group.
The MAX IV 3 GeV linac delivers electron beams to two synchrotron rings and to a dedicated undulator system for X-ray beam delivery in the Short Pulse Facility (SPF). In addition, there are plans to use the linac as an injector for a future Soft X-ray Laser (SXL). For both SPF and SXL operations, longitudinal beam characterisation with a high temporal resolution is essential. For this purpose, a transverse deflecting cavity (TDC) system has been developed and installed in a dedicated electron accelerator line located downstream of the 3 GeV linac. This accelerator line consists of two consecutive 3 m long transverse S-band RF structures, followed by a variable vertical deflector dipole magnet used as an energy spectrometer. This conference contribution presents the beam dynamics calculations for the beam transport along the TDC line, and in particular the optics configurations for slice emittance measurements. The operation of an analysis algorithm for use in the control room is presented. The aim is to provide 1 fs temporal measurement resolution to access the bunch duration of highly compressed bunches and slice parameters for sub-10-fs bunches.
The Alternating Gradient Synchrotron (AGS) is a particle accelerator at Brookhaven National Laboratory (BNL) that accelerates protons and heavy ions using the strong focusing principle. In this work, we perform simulation studies on the AGS ring of a machine error detection method by comparing simulated and measured orbit response matrices (ORMs). We also present preliminary results of building two machine learning (ML) surrogate models of the AGS system. The first ML model is a surrogate model for the ORM, which describes mapping between orbit distortions and corrector settings. Building a self-adaptive model of ORM eliminates the need to re-measure ORM using the traditional time-consuming procedure. The second ML model is an error identification model, which maps the correlation between measurement errors (differences between measurement and model) and sources of such errors. The most relevant error sources for the error model are determined by performing sensitivity studies of the ORM.
Longitudinal beam diagnostics are a useful aid during tuning of particle accelerators, but acquiring them usually requires destructive and time intensive measurements. In order to provide such diagnostics non-destructively, computational methods allow for the development of virtual diagnostics. Existing Fourier-based reconstruction methods for longitudinal current reconstruction, tend to be slow and struggle to reliably reconstruct phase information. We propose using an artificial neural network trained on data from a start-to-end beam dynamics simulation to combine scalar and spectral information in order to infer the longitudinal phase space of the electron beam. We demonstrate that our method can reconstruct longitudinal beam diagnostics accurately and provide the reconstructed data with adaptive resolution. Deployed to control rooms today, our method can help human operators reduce tuning times, improve repeatability and achieve pioneering working points. In the future, ML-based virtual diagnostics will help the deployment of feedbacks and autonomous tuning methods, working toward the ultimate goal of autonomous particle accelerators.
The temporal profile of the electron bunch is of critical importance in accelerator areas such as free-electron lasers and novel acceleration. In FELs, it strongly influences factors including efficiency and the profile of the photon pulse generated for user experiments, while in novel acceleration techniques it contributes to enhanced interaction of the witness beam with the driving electric field. Work is in progress at the CLARA facility at Daresbury Laboratory on temporal shaping of the ultraviolet photoinjector laser, using a fused-silica acousto-optic modulator. Generating a user-defined (programmable) time-domain target profile requires finding the corresponding spectral phase configuration of the shaper; this is a non-trivial problem for complex pulse shapes. Using a physically informed machine learning model, we demonstrate accurate and rapid shaping of the photo-injector laser to a wide range of arbitrary target temporal intensity profiles on the CLARA PI laser. Additionally, we discuss the utility of this expanded range of laser pulse shapes to potential applications in FELs and novel acceleration.
Linac is the first machine in the accelerator chain at Fermilab where H$^{-}$ ions are accelerated from 35 keV to 401.5\,MeV and then injected into a synchronton known as Booster where they are stripped of their electrons to become protons. One of the tools used during tuning of the Linac extraction energy is two beam pickups known as Griffin Detectors. Our goal is to control the output energy using machine learning techniques to increase the reliability and quality of the beam delivered from Linac. The first step is to understand the data from the diagnostics to develop reliable and accurate energy measurement, and control methods before implementing machine learning techniques. Two methods of energy measurement were studied, and their results are compared. The first method was the time of flight measurement using Beam Position Monitors that provide beam phase measurement. The second method used the relation between beam transverse positions and dispersion values to calculate momentum variation. The results of these two measurement methods are found to be consistent.
The work goal is to present the concept and the model for the reconstruction of the beam emittance from the spectrum of the scattered photons. The Compton process is a back-scattering of a laser pulse on the relativistic electron beam and is at the base of X-ray sources, as for instance, the project STAR. In the scattering process, the scattered photons get energy boost. The energy boosted photons carry also informations about the transverse momentum of the initial electron bunch. In this work we present the theory and the model implementation on how the beam emittance can be reconstructed from the spectrum of the scattered photons.
The bunch length in linacs is an important parameter to characterize the beam as well as to tune and optimize the final accelerator performances. In linear machines this observable is typically determined from the bunch imaged on a screen located downstream of a Transverse Deflecting Structure (TDS) used to impinge a time dependent kick along the longitudinal coordinate of the beam. This kind of measurement is typically performed during the machine setup and only sporadically to check the beam duration, but it cannot be continuously repeated, because time consuming and invasive. A non-invasive method to determine the electron bunch length was already presented in the past [1]. This method is based on the analysis of the synchrotron radiation light spot emitted by the bunch passing through a magnetic chicane provided that the energy chirp impinged on the bunch by the upstream radiofrequency structures is known. In order to overcome a systematic discrepancy affecting the SRM based results compared to the absolute TDS based ones, we implemented and optimized a Machine Learning (ML) approach to predict the bunch length downstream of the two SwissFEL compression stages - from about 10 fs up to about 2 ps - as well as the beam longitudinal profile at the first one.
[1] G. L. Orlandi, R. Xue, H. Brands, F. Frei, Z. Geng, V. Thominet, and S. Bettoni, Bunch length and energy measurements in the bunch compressor of a free-electron laser, Phys. Rev. Accel. Beams 22, 072803 (2019).
The widely used transverse parameters characterizing particle beams are the Twiss parameters. These parameters can be measured experimentally but they do not fully characterize the beam since they do not account for possible correlations in particle distribution between two transverse coordinates. These correlations may occur due to uncompensated magnetic field at the cathode or misalignment of focusing quadrupoles in the transport beamline. We propose a novel diagnostic for diagnosing full 4D beam matrix which may be used to identify such imperfections. The diagnostic is based on transporting the beam through the beamline which includes a quadrupole and a skew quadrupole magnets and measuring the resulting 2D beam distribution at the screen downstream. Such a measurement can be viewed as measuring a 2D projection of the 4D distribution. Different settings of the quads provide measurements of different slices of the phase space. The reconstruction of the original beam matrix from a number of measurements is done using machine learning algorithm, which provides a fast and reliable way of reconstruction for an arbitrary configuration of the scanning beamline. We study the performance of such a diagnostic, estimate its accuracy, and demonstrate that the uncertainty in the reconstructed sigma matrix can be smaller than the error of the measurements if the number of scans is large enough.
To realize more stable operation of a high-intensity ion beam accelerator with a minimum beam loss, we have developed a non-destructive beam profile monitor detecting photons produced by interaction between the beam and a gas sheet injected into the beam line. The gas-injection-type profile monitor should induce scattering of the beam particles, and the beam emittance is considered to become larger. On the other hand, the beam-gas interaction may also induce space-charge neutralization of the beam. The plasma produced by the beam-gas interaction cancels the electric potential of the beam, and emittance growth due to the beam space-charge force is inhibited; the emittance relatively becomes small. To evaluate the effect of gas sheet injection on the beam, we have measured the phase space distribution of the 3 MeV, 60 mA H- ion beam with/without the gas sheet injection. As the result, the root mean square value of the beam emittance was constant or decreased against the increase in the amount of the injected gas-sheet flux.
At the Karlsruhe Research Accelerator (KARA), an analytical online model of the orbit response matrix (ORM) has been developed and tested. The model, called the bilinear-exponential model with dispersion (BE+d model), is derived from the Mais-Ripken formalism describing coupled betatron motion. Compared to the standard approach of measuring the ORM, this method continuously adapts to changing beam optics without a dedicated measurement. It is especially useful for storage rings without turn-by-turn capable beam position monitors (BPMs) as the online model also gives access to estimates of the coupled optical functions. In the following, experimental orbit correction results and a comparison of fitted and simulated optical functions are presented.
OpenDigitizer* is an open-source modernisation of FAIR's modular digitizer infrastructure and graphical user interface based on OpenCMW, WebAssembly, and the GNU Radio 4.0 frameworks.
Already used to provide generic monitoring and first-line diagnostics for accelerator-related devices, it further supports equipment experts, operation, and FAIR users in developing basic to advanced top-level measurement and control loops. Supporting hundreds of industrial digitizers with sampling frequencies ranging from a few MS/s to GS/s, the core relies on directed signal flow graphs to express arbitrary post-processing and feedback control loop logics that are both numerically highly efficient as well as provide an intuitive high-level yet detailed nuts-and-bolts representation to inspect and/or to reconfigure existing systems by accelerator-, control- or other system domain-experts alike with little to no prior required programming experience.
The diagnostics UI tools are compatible with WebAssembly (WASM) allowing their native deployment, on mobile as well as on any browser-based platform, facilitating their flexible use both in the accelerator tunnel during commissioning, trouble-shooting, as well as in the control room.
The current injector system, composed by a linac and a synchrotron booster, will be used to inject into the new storage ring.
After 15 years of operation, some upgrade of the instrumentation devices are required to well characterize the beam parameters extracted from the booster, before and after the implementations in action to reduce the beam emittance.
Brookhaven National Laboratory Accelerator Test Facility is working on development software tools to achieve automated instrument for tuning and alignment of electron source and beam transport line. The end goal is a robust, efficient, and autonomous method of alignment that can operate on a generalized notion of beam fitness, that can optimize any quantifiable metric about the beam (size, shape, position, intensity, etc.) with live feedback. The algorithm should be able to operate with as little prior knowledge of the problem as possible and be adaptable to the preferences of a user. The developed set of tools will be made available for other beamlines at BNL and beyond and will help to reduce the preparation time for the scientific experiments at these facilities.
The project aims to address the alignment/tuning tasks with the help of Machine Learning (ML) based optimization tools as well as domain-specific simulation codes, seamlessly integrated with the Bluesky data collection framework (https://blueskyproject.io). The beam transport model will be applied through Sirepo-Bluesky interface which will let to use “digital twins” of the actual beamlines represented in the Sirepo simulation framework (https://www.sirepo.com) with the same Bluesky data collection system as in operating the beamlines.
A beam profile monitor using gas jet technology is being designed and manufactured at the Cockcroft Institute for high intensity electron beams. It generates a thin, supersonic gas sheet that traverses the beam at a 45-degree orientation and measures the beam-induced fluorescence interactions to produce a 2D beam profile image. The gas sheet acts similar to a scintillating screen, but remains non-invasive. This contribution summarises the method developed towards optimising the injection of a gas jet monitor for the example use-case of the Hollow Electron Lens. A multi-objective genetic algorithm is used with a Monte-Carlo particle tracking simulation to optimise the geometric features of the jet injection chambers. The algorithm optimises for several key features of the jet that will improve it as a diagnostic tool. Specifically, at the point of interaction, the jet’s density, uniformity and geometric dimensions are considered. The work developed in this contribution is not limited to diagnostics and can be expanded upon in other disciplines such as plasma wakefield gas injections.
Beam-based alignment and feedback systems are essential for the operation of the Free Electron Lasers (FELs). Cavity BPMs having the advantage of high position resolution are widely used in the field of accelerators. Systematically analyze the impact of the key parameters of each subsystem on the performance of the whole system, so that the key technical indicators of each subsystem can achieve the optimal and balanced allocation, is the primary issue to be considered when designing a CBPM system. In this paper, the relationship between the relative amplitude extraction uncertainty of the CBPM system and the key parameters of each subsystem is proposed based on theoretical analysis. And this method has also been applied in the development of the CBPM system for the Shanghai High repetition rate X-ray Free Electron Laser and Extreme Light facility (SHINE). Based on the beam test bench in the Shanghai Soft X-ray FEL facility (SXFEL), the position measurement uncertainty of the CBPM system can reach 40 nm at the bunch charge of 100 pC, which is consistent with the theoretical analysis results and better than the requirements of the SHINE.
Following works aiming at optimizing photonic focal spot size measurement conditions on AIRIX, we decided to improve our electron beam picture processing software with a goal of studying a potential relationship between AIRIX electronic and photonic focal spot size dimensions. AIRIX electronic focal spot size is obtained from an OTR measurement chain established by adapted optics and an intensified camera. One of the photonic focal spot size measurement techniques is built by inserting an annulus pinhole into the AIRIX source collimation. Pictures are obtained from a gamma-camera. Our new electron beam picture processing software calculates physical electron beam dimensions (up to now, these dimensions were given as the statistic projection = “RMS dimensions”) and allows to define a transformation coefficient allowing us to find again the photonic focal spot size values (established from a Lorentz fit of the photonic PSF) from electronic ones. We also showed the conservation of the electron PSF inclination degree after interaction with the AIRIX X-ray conversion target. A first photonic spot size estimation is given for the last hydrodynamic experiment at EPURE facility and implies great potential of such a diagnostic for the second stage of EPURE project, mainly in terms of duration optimization for the operating process of our next three radiographic axes.
One of the Grand Challenges in beam physics relates to the use of virtual particle accelerators for beam prediction and optimization. Useful virtual accelerators rely on efficient and effective methodologies grounded in theory, simulation, and experiment. This work extends the application of the Sparse Identification of Nonlinear Dynamical systems (SINDy) algorithm, which we have previously presented at the North American Particle Accelerator Conference. The SINDy methodology promises to simplify the optimization of accelerator design and commissioning by discovery of underlying dynamics. We extend how SINDy can be used to discover and identify underlying differential systems governing the beam’s sigma matrix evolution and corresponding invariants. We compare discovered differential systems to theoretical predictions and numerical results. We then integrate the discovered differential system forward in time to evaluate model fidelity. We analyze the uncovered dynamical system and identify terms that could contribute to the growth(decay) of (un)desired beam parameters. Finally, we propose extending our methodology to the broader community's virtual and real experiments.
The 3 GeV storage ring light source at the MAX IV Laboratory in Sweden is currently operating with 10 insertion device beamlines. Each of them is equipped with a pair of photon beam position monitors (XBPMs) in the beamline front end. During the past years these XBPMs have been developed to be a reliable monitoring tool for measuring photon beam stability during beamline operation. As a complement to the RF BPMs for the electron beam, the XBPM system offers an evaluation of the performance of the electron beam orbit feedback from a photon beam stability point of view.
The concept of a feedback on the electron beam orbit from measured photon beam position in the front end was demonstrated during machine study shifts and results will be presented, along with an evaluation of the potential benefits of such a feedback.
Compared to classic proton therapy, proton minibeam radiation therapy (pMBT) further spares normal tissue. To fully study this potential with small animal experiments focused minibeams with a sigma of 50 micrometers, a beam current of 1 nA and approx. 4 cm Proton-range (water) is needed. We present a preclinical pMBT beamline concept based on the 68 MeV cyclotron of the Helmholtz-Zentrum Berlin (HZB). The beamline was designed in first-order using the beam dynamic code TRACE 3-D. The maximum beam energy is defined by a first degrader after the cyclotron. A second degrader placed close before the target further reduces the energy, forming a spread-out Bragg peak in the target. Along the beamline, various slits shape the transverse beam profiles. A high magnetic field gradient triplet lens focuses the beam on the target while scanning magnets rasterscan it over the target. A small animal radiation research platform (SARRP) is used for positioning and imaging of the target. This beamline concept fulfills all the basic needs for the planned small animal minibeam irradiation studies. The results will contribute to the construction of a preclinical pMBT facility for small animals at HZB.
Bunch length is an important metric for user experiments at the Compact Linear Accelerator for Research and Applications (CLARA). A prototype Bunch Compression Monitor (BCM) based on Coherent Transition Ration (CTR) was recently installed and commissioned to support recent user experiments. The intensity of CTR is measured using a pyroelectric detector. A noise cancellation scheme based on a second detector offset from the focus of the CTR was used to reduce the noise caused by the broadband nature of pyroelectric detectors. Qualitative measurements of the bunch length as a function of RF phase are presented, along with an overview of the system design. Plans for an improved system are also presented.
Recent studies showed significant improvement in quantum efficiency (QE) by negative electron affinity (NEA) GaAs nanopillar array (NPA) photocathodes over their flat surface peers, particularly at 500 ─ 800 nm waveband. However, the underlying physics is yet to be well understood for further improvement in its performance. In this report, NEA GaAs NPA photocathodes with different dimensions were studied. The diameter of the nanopillars varied from 200 ─ 360 nm, the height varied from 230 ─ 1000 nm and the periodicity varied from 470 ─ 630 nm. The QE and photocathode lifetime were measured. Mie-resonance enhancement was observed at tunable resonance wavelengths. Simulations was also performed to understand the mechanism of photo-absorption and possible ways to further improve the photocathode performance to meet the stringent requirement of the electron sources in large scale electron accelerators.
Acknowledgement
Authored by Jefferson Science Associates, LLC under U.S. DOE contract no. DE-AC05-06OR23177. The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for U.S. Government purposes.
*mrahm008@odu.edu
As one of on-line single-shot and non-destructive absolute measure methods with high resolution, Electro-Optical (EO) techniques have been wildly utilized in Free Electron Laser to measure the longitudinal bunch profile. A bunch length monitor with 100 fs resolution is required for Shanghai Soft X-ray FEL (SXFEL) facility. The solution based on Electro-Optical Temporal Decoding (EOTD) method has been developed and tested during the past year. This paper will present the whole design according to SXFEL condition and its first test results.
The Large Hadron Collider at CERN is equipped with instruments that exploit collisions between beam particles and gas targets, one of them being the Beam Gas Vertex monitor. By design, its operation generates secondary particle showers used to measure beam properties, that also result in radiation levels in the tunnel proportional to the beam intensity and gas pressure. In this work, the radiation showers are characterised using measured data from LHC Run 2 operation and Monte Carlo simulations with the FLUKA code, and predictions are made for the operation of these devices in the HL-LHC era.
We will propose a novel high resolution method for surface scanning. Optical glow discharge spectroscopy (OGDS) devices are simpler and less expensive than secondary-ion mass spectrometry (SIMS),and can provide excellent spatial resolution. A small change in the design of the discharge device makes it possible to localize sputtering on a small portion of the target and to obtain the distribution of elements over the surface of the sample with micron resolution.
Miniature single-board cameras have been used for several years to monitor beam-induced residual gas fluorescence. This work gives an overview of the use of so-called Raspberry Pi cameras in accelerator experiments. These devices are installed in vacuum at hard-to-reach locations. They have been tested in strong magnetic fields with low energy proton beams from 2 keV to 60 keV. They have also been tested in the high energy range with 4.8 MeV/u, $^{48}Ca^{10+}$ beams. Nitrogen and argon were used as residual gas and the pressure was varied from $1\cdot10^{-5}mbar$ to $1 mbar$.
The use of artificial intelligence (AI) has the potential to significantly reduce the time required to tune particle accelerators, such as the Argonne Tandem Linear Accelera-tor System (ATLAS). Bayesian optimization with Gauss-ian processes is a suitable AI technique for this purpose, it allows the system to learn from past observations to make predictions without explicitly learning representations of the data. In this paper, we present a Bayesian optimiza-tion method with deep kernel learning that combines the representational power of neural networks with the reliable uncertainty estimates of Gaussian processes. The kernel is first trained with physics simulations, then the model is deployed online in a real machine, in this case a subsec-tion of the ATLAS linac, to perform the optimization. In addition to the kernel, we also modelled the mean of the Gaussian process using a neural network trained with simulation data and later with experimental data. The results show that the model not only converges quickly to an optimal tune, but it also requires very little initial data to do so. These approaches have the potential of signifi-cantly improving the efficiency of particle accelerator tuning, and could have important applications in a wide range of settings.
The beam emittances at the MAX IV 3 GeV fourth generation storage ring are evaluated using synchrotron radiation in the UV to visible energy range. The methods used are combined measurements with various diffraction obstacles and controlled light polarizations. The resolution capability is well covering the needs for the design emittances of the ring. However, accelerator studies often go beyond the design criteria, and in this report, we have especially studied the resolution limit of the vertical emittance measurement.
The brightness of the beam in any linear accelerator can be no greater than at its source. Thus characterization of source initial conditions, including spatial and momentum distributions, is then critical to understand brightness evolution in a linac. Often measurement of the initial momentum distribution is hampered by imperfect knowledge of either the spatial source distribution or the downstream particle optics. Here we describe a method of recovering the transverse momentum space of a beam at the particle source without prior knowledge of the electron optics used to obtain the
phase space or any source parameters; only linearity of the transport is assumed. We then demonstrate this method experimentally by measuring a 4D phase space using an aperture scan and subsequently recover the transverse phase space of a beam emitted by an alkali antimonide photocathode.
The transverse size of the electron beam in a storage ring can be measured using the synchrotron radiation of a bending magnet. Due to the diffraction limit, many facilities exploit beam size monitors in the X-ray regime. On the other hand, the visible part of the emitted radiation delivers spatial information via an interference pattern after passing through a double slit. Assuming a Gaussian beam distribution the size of the beam can be easily obtained with an analytical formula. If this assumption is not fulfilled, the calculated beam shape will vary from the real distribution. This can appear for instance in case of exotic beam optics settings or complicated filling patterns, that are widely used in modern storage-ring-based light sources. In this paper the idea to reconstruct the electron beam distribution by measuring the absolute visibility and its phase with a spectral-resolved set-up is introduced.
As part of the High Luminosity upgrade for the Large Hadron Collider, several new directive-coupler (stripline) BPMs will be installed near the ATLAS and CMS detectors where the two counter-rotating beams exist within a single beampipe. In the worst case scenario, the bunches of the second beam arrive at the BPM location just 4 ns after those of the first and the BPM signals from the two beams overlap significantly. Using simulations of the expected BPM output, a novel scheme for digitally processing these two-beam signals in order to extract the true position of each beam has been developed. The offline validation of this technique requires genuine two-beam signals. In October 2022, suitable signals were gathered using an early proof-of-concept digital BPM processor connected to an existing room-temperature stripline BPM close to the CMS detector. During this period of data acquisition, RF cogging was used to vary the difference in arrival time of the two beam at the BPM location and orbit bumps were used to vary the beam-beam displacement in order to ultimately be able to determine the performance of the digital processing scheme.
The present BPMs of the J-PARC Main Ring have adopted mechanical relays in its processing circuits. Frequency range is limited less than 10 MHz by LPFs. Mechanical relay is chosen due to its good isolation. But the drawback is contact failures due to insulating materials after long suspension period of months. Methods of recovery and checking are reported. Recovery of contacts are performed with injecting dummy pulses. Contact is checked examining consistency comparing four independent position pairs (x, y) calculated from 3 electrodes out of four electrodes. The hermetically seal reed relays will be implemented in the new processing circuits under development.
Optimal control is inherent issue in particle accelerators, mainly due to nonlinear and time-varying effects caused by unknown errors such as external environment changes, misalignment, and fabrication defects. In this regard, machine learning techniques are promising to go beyond heuristic methods or traditional optimization algorithms. Reinforcement learning is suited to solve the beam orbit correction problem in which various error factors, control magnets, and diagnostic devices are involved through combinatorial optimization. The training environment implemented based on the beam physics simulator and the learning results are addressed for the KOMAC proton linear accelerator.
Beam currents of particle accelerators used for cancer treatment are often on the nanoampere level. These currents are too low for standard beam current diagnostics used in other fields of particle accelerator science, e.g. current transformers. This led to the general adoption of ionization chambers for beam current and dose rate determination in medical accelerators. However, the development of the so-called FLASH radiation therapy requires beam currents too high for normal ionization chambers yet still too low for standard current transformers.
Resonant cavities have shown their capability to precisely detect nanoampere to microampere beam currents which renders them interesting for FLASH radiation therapy accelerators. After the design of a resonant cavity at Paul Scherrer Institut (PSI), a collaboration between PSI, Instrumentation Technologies, and Bergoz Instrumentation was established with the goal to develop a complete turn-key beam current diagnostics system readily available for medical accelerators. Two prototype systems were manufactured, installed, and tested at PROSCAN/PSI. We discuss the layout of the measurement systems and compare expected performance to beam current measurements.
Measuring beam parameters in the vicinity of fixed target experiments or interceptive devices like beam dumps is essential to ensure efficient fixed target physics and safe beam operation. At the same time the beam diagnostic reach is very often challenging in terms of robustness and performance. This paper reviews the CERN instruments exploited to measure protons at different CERN fixed target facilities (ISOLDE, PS East Area, AD, SPS North Area, HIRADMAT) and beam dumps (SPS, LHC), focusing on recent developments/results, limitations and future plans. Emphasis will be given to beam size and beam position monitors systems and their response to high power and/or density proton beams at target locations, thus involving radiation hardness, background and power deposition issues. The discussion will also refer to new materials studies and modern machine learning techniques developed to enhance the monitors overall accuracy and reliability.
For SRF cavity systems operated in continous wave (CW) at low effective beam loading as in Energy Recovery Linacs or Free Electron Lasers with rather low beam current, control of the tuning and counteracting any detuning caused by microphonics or Lorentz force driven coupled ponderomotive instability is mandatory to deliver and preserve a stable beam in longitudinal phase space regime.
To develop beyond the currently employed mTCA based LLRF systems, a compact RF on a chip system was developed, which features several potential applications.
Those range from a digital PLL to test and characterize the RF performance of cavities to a selection of detuning control algorithms, we have worked on in recent years, as e.g. a Kalman filter based state estimator controller [1] or an adaptive feedforward algorithm [2].
Here, we will show our first experimental findings with a TESLA style nine-cell SRF cavity operated in CW at our horizontal test facility HoBiCaT.
Particle accelerators require continuous adjustment to maintain beam quality. Several machine learning (ML) approaches are being explored for this task. At the Advanced Photon Source (APS), we have recently proposed the adaptive Bayesian optimization (ABO) algorithm and have shown it to be effective experimentally in the APS injector complex. Further testing has suggested several improvements, on which we report here. We introduce dynamic kernel switching, deep kernel learning, and surrogate model prior means, resulting in improved robustness. We also extend our code with multi-dimensional time kernel support and predictive constraint avoidance to make it applicable to a wider range of systems. These changes also improve the general ABO performance, but more importantly expand ABO applicability to systems with rapid or unexpected changes in either optimization parameters or time properties. Notably, this allows for rapid and automated fallback to conservative parameters when optimizer confidence degrades, with alarms raised for further operator review. These features will permit further operational ML adoption at APS.
A compact TDS (transverse-deflecting system) has been proposed for diagnostics of extremely short electron bunches (up to single-digit femtosecond range). The main idea is to use terahertz radiation, produced from optical rectification of the facility’s electron gun laser pulse. This provides an intrinsic synchronization between the electron bunch and the laser pulse. The proposed system is to be constructed at the test facility FLUTE (Ferninfrarot Linac- und Test-Experiment) at Karlsruher Institut für Technologie (KIT), which provides the opportunity to create electron bunches of variable length and at medium energy (7 MeV up to 90 MeV). Simulations in CST MICROWAVE STUDIO are carried out in parallel with the experimental activities to optimize the design of the system. In the present paper the simulation results for several possible designs will be presented.
FLUTE (Ferninfrarot Linac- Und Test-Experiment) is a compact linac-based test facility for accelerator and diagnostics R&D located at the Karlsruher Institute of Technology (KIT). A new accelerator diagnostics tool, called the split-ring resonator (SRR), was tested at FLUTE, which aims at measuring the longitudinal bunch profile of fs-scale electron bunches. Laser-generated THz radiation is used to excite a high frequency oscillating electromagnetic field in the SRR. Electrons passing through the 20 µm x 20 µm SRR gap are time-dependently deflected in the vertical plane, leading to a vertical streaking of the electron bunch. During the commissioning of the SRR at FLUTE, large series of streaking attempts with varying machine parameters and set-ups were investigated in an automatized way. The recorded beam screen images during this experiment have been analyzed and evaluated. This contribution motivates and presents the automatized experiment and discusses the data analysis.
At the visible light diagnostic (VLD) port at the Karlsruhe Research Accelerator (KARA), it is possible to measure the energy spread of electron bunches by measuring the horizontal bunch profile of the incoherent synchrotron radiation. KALYPSO, a MHz-rate line-array detector has been used to measure the bunch profile. Recently, the KALYPSO system has been upgraded to a version incorporating a microstrip sensor based on TI-LGAD. The performed measurements have shown that the overall sensitivity of the system was significantly improved, which enables measurements at low bunch charges. In this contribution, a brief overview of the upgraded setup and preliminary measurement results will be presented.
One of the crucial control systems of any particle accelerator is the Low Level Radio Frequency (LLRF). The purpose of a LLRF is to control the amplitude and phase of the field inside the accelerating cavity.
The LLRF is a subsystem of the CEA control domain for the SARAF-LINAC instrumentation and Seven Solutions has designed, developed, manufactured and tested the system based on CEA technical specifications. The final version of this digital LLRF has been already installed in the SARAF accelerator in Israel at the end of 2021 and the first results are going to be shown.
The architecture, design and development as well as the performance of the LLRF system will be presented during this talk. The results of the integration of the LLRF onsite will be shown.
In designing the synchrotron light sources like NSLS-II, non-linear perturbation from the sextupoles are thoroughly studied to secure dynamic apertures large enough for the high-performance operation. Also, it can be well understood that the offsets in sextupoles affect the overall machine performance, closed orbit, linear optics, coupling and dispersion. In this paper, we introduce various beam based alignment (BBA) algorithms measuring the orbit offsets in sextupoles and compare the results.
Cherenkov Diffraction Radiation (ChDR), which is emitted when relativistic charged particles pass around dielectric materials, has recently been presented as non-invasive beam diagnostics in various studies. We intend to measure transverse beam size using ChDR in e-LABs, a 100 MeV electron experimental accelerator at the Pohang Accelerator Laboratory (PAL). The electron energy of e-LABs is low, so the intensity of photons generated by ChDR is absolutely small. Therefore, a cumulative dielectric radiator with a length of 157 mm was designed to increase the photons incident on the detector. This contribution shows the characteristics of ChDR simulated numerically at low energies. Furthermore, we present an experimental configuration for measuring transverse beam size with some considerations.
The 3rd ICFA Beam Dynamics Mini-Workshop on Machine Learning (ML) Applications for Particle Accelerators was held in Chicago, Il, USA, on November 1-4, 2022. This was an in-person workshop focused on ML techniques as applied to accelerator operations, design, and simulations. There were 76 attendees representing 26 institutions from around the world. A total of 59 abstracts were submitted allowing us to build a diverse program with both oral and poster presentations. The workshop was sponsored by the Center for Bright Beams (CBB), with support from the National Science Foundation and by RadiaSoft, an industry leader in high-level research and design and scientific consulting for beamline physics and machine learning. CBB supported eight graduate students for this meeting. The workshop was approved as a mini workshop by the International Committee for Future Accelerators (ICFA) Beam Dynamics Panel. We will provide a summary of the work presented at the workshop and the outlook for future efforts.
Accelerator physics simulators accurately predict the propagation of a beam in a particle accelerator, taking into account the particle interactions (a.k.a. space charge) inside the beam. A precise estimation of the space charge is required to understand the potential errors causing the difference between simulations and reality. Unfortunately, the space charge is computationally expensive, needing the simulation of a few dozen thousand particles to obtain an accurate prediction. This paper presents a Machine Learning-based approximation of the simulator output, a.k.a. surrogate model. Such an inexpensive surrogate model can support multiple experiments in parallel, allowing the wide exploration of the simulator control parameters. While the state of the art is limited to considering a few such parameters with a restricted range, the proposed approach, LinacNet, scales up to one hundred parameters with wide domains. LinacNet uses a large-size particle cloud to represent the beam and estimates the particle behavior using a dedicated neural network architecture reflecting the architecture of a Linac and its different physical regimes.
The planned multi-pulse linear induction accelerator, Scorpius, will be used in radiographic experiments at the NNSS U1A facility. One of the many diagnostics, the emittance diagnostics, will provide information on the quality of the beam emanating from the injector and therefore the quality of the beam in the accelerator. A Slit-Harp design was chosen for the emittance diagnostic. COMSOL multi-physics parameter space modeling using modeled Scorpius input beams tunes drove both the slit and harp designs to achieve the measurement of the emittance. Additional modeling for energy deposition/heat dissipation/x-ray reduction drove material choices for the slit (aperture) and harp wires. The signal chain is designed around constraints of signal extraction, biasing against secondary electrons which would cause errors in the emittance reconstruction calculation, and individual multi-pulse record capability. The ensemble of materials, electrical, and mechanical aspects of the design to reconstruct the emittance from the injector of the accelerator will be discussed.
Ion profile monitors (IPM) are used to measure the beam size in synchrotrons. Both the Fermilab Recycler and Main Injector (MI) machines have IPMs. However, they were not well understood enough to provide confidence in their measurements. Accurately measuring beam size through the IPMs was crucial to recognize the loss mechanisms for accelerators and to keep the beam loss to a minimum. Thus, performing measurements with different parameters using the IPMs led to a better analysis on how changes in conditions affect the beam size. The IPM measurements are compared with that of multi-wires in the upstream transfer line after applying corrections. The results were compared with other diagnostics and the change in the beam size for different parameters are presented in this paper.
LhARA, the Laser-hybrid Accelerator for Radiobiological Applications, is a proposed facility for the study of proton and ion radiation biology. The accelerator is designed to deliver a variety of ion species over a wide range of spatial and temporal profiles at ultra-high dose rates. The facility requires that the deposited dose distribution be measured in real-time. For this purpose, an ion-acoustic dose mapping system has been developed that, exploits the ultrasound waves generated by the ion beam*. The feasibility of this approach is being evaluated using a two-stage simulation.
A water phantom modelled in Geant4 with beam energies up to 250 MeV is used to calculate the energy deposited by the beam as a function of position and time. The time-dependent 3D energy distribution is then used as the source in k-Wave to simulate the ion energy generation of acoustic (pressure) waves and their propagation in the three-dimensional space. A hemispherical acoustic sensor array is also simulated and its ability to reconstruct the generated pressure distribution is evaluated.
The results show that the 3D deposited-energy distribution can be reconstructed with sub-millimetre accuracy and suggest, that further development of the system can lead to real-time, non-invasive Bragg peak localization and dose deposition profile measurement during ion-beam therapy.
Using a calibrated permanent magnet spectrometer and a streak camera, a time resolved measurement is made for a multi-pulse beam. These measurements are cross calibrated with cell voltage monitors to have a reliable online energy measurement. The Dual Axis Radiographic Hydrodynamic Test Facility (DARHT) Axis-II produces a 16 MeV, 1.65 kA electron beam. Timing on the cell voltages is changed such that the beam has a varying kinetic energy spread. Multi-pulses are produced by a kicker at varying pulse lengths and selecting out different energies from the beam. This paper reports the results of these measurements.
Orbit feedback system (OFB) of the Taiwan Light Source (TLS) had been deployed two decade ago and upgraded to improve performance several times. The loop bandwidth was limited by existed hardware. The system cannot remove perturbation form fast source. Therefore, to improve orbit feedback performance, the system have been upgraded in 2008 [1]. It included the BPM electronics upgraded from analogy type BPM to digital BPM and the corrector power supply was also replaced by high performance switching type power supply with wide bandwidth in the same time. Later after Taiwan Photon Source (TPS) commissioning in 2015, to share resources between TLS and TPS control system, it has been decided that TLS’s control system would be migrated gradually to the EPICS (Experimental Physics and Industrial Control System) control system which has been adopted by TPS [2][3]. Orbit feedback system is one of the rejuvenated subsystem with EPICS support. Besides, the feedback computation unit is also upgraded to FPGA and increase calculating cycle from 2.5 kHz to 10 kHz. The integration of BPM, power supply control and fast orbit feedback will be summarized in this report.
For arrival-time monitors of the electro-optical synchronization system at the European XFEL, FELBE and other free-electron laser facilities, a novel concept based on rod-shaped pickups mounted on a printed circuit board is proposed. New simulation results show the huge potential for low charge applications foreseen at the European XFEL and FELBE for future operation modes. A theoretical jitter-charge product 𝜎t × 𝑄B of 9 fs pC was estimated for this pickup structure in combination with tailor-made ultra-wideband low-pi-voltage electro-optical modulators. The design meets the desired criteria for 1 pC operation, so it is planned to produce a prototype for first tests in FELBE. The structure is assumed to be sensitive to the production accuracy, manufacturing tolerances for different components of the pickup-structure are analyzed in this work. The results allow to identify critical dimensions and will help to predict the effect of inevitable geometric deviations.
Diffraction Limited Storage Rings, the 4th generation machines, provide transversely coherent beams with uniform phase, maintaining high photons flux and stability. Diagnostic systems play an essential role for both commissioning and operating tasks of Elettra 2.0. The small beam dimensions make measurements of both position and size challenging. Elettra 2.0 diagnostics will rely mainly on Beam Position Monitors and Synchrotron Radiation Profile Measurements. In this paper, an overview of all the beam diagnostics that will equip the new storage ring will be given, along with the diagnostic systems involved in the main machine control.
Before injection into the Karlsruhe Research Accelerator (KARA), the electron storage ring of the KIT Light Source, the beam energy is ramped up from 53 MeV to 500 MeV by a booster synchrotron. The whole booster is located in a concrete enclosure inside the storage ring and thus not accessible during operation. For the study of longitudinal beam dynamics, a cost-effective solution to leverage the synchrotron radiation emitted at the booster bending magnets is desired. To ensure durability of the setup and to not obstruct the removable concrete ceiling of the booster enclosure, it is required to place the radiation-sensitive readout electronics outside of the booster enclosure and outside of the storage ring. In this contribution a fiber-optic setup consisting of commercially available optical components, such as collimators, optical fibers and high bandwidth photodetectors is used. As a proof-of-concept we present experimental results of different components characterized at the visible light diagnostics port of the storage ring KARA. In addition, we report on first booster measurements along with planned future experiments.
Orbit feedback system of the Taiwan Photon Source (TPS) had been delivered since 2014. As long as more and more insertion devices installed, there are various wide-band disturbance produced. To further improve orbit stability, the fast orbit feedback (FOFB) system upgrade plan had been proposed in 2019. The upgrade plan includes both power supply controller revise and feedback computation rate increase from 10 kHz to 30 kHz. After upgrade, TPS fast orbit feedback bandwidth could be expanded from 250 Hz to 400 Hz in the vertical plane and from 200 Hz to 250 Hz in the horizontal plane. The integrated orbit power spectrum density could be effectively decreased around 20%.
Phase space tomography is a powerful technique for characterising beams in particle accelerators and has found widespread use at many facilities. However, conventional tomography techniques require significant computational resources, particularly when reconstructing the charge distribution for two or more degrees of freedom. Here, we describe a novel technique that employs machine learning and image compression for transverse phase space tomography in two degrees of freedom. The use of machine learning allows the beam distribution in 4D phase space to be reconstructed more quickly than by conventional tomography techniques, while the application of image compression can dramatically reduce the size of the data sets involved in the analysis. The new method has been deployed on the CLARA accelerator at Daresbury laboratory to characterise electron bunches with moderate energy (35 MeV) and charges up to 100 pC. We compare the machine learning technique against a conventional tomography algorithm (algebraic reconstruction) applied to the same data set, and show that the results are at least as good in terms of predicting the observed beam profiles for a range of quadrupole strengths.
The transverse beam size is a key parameter of electron bunches in the storage ring for beam quality evaluation. High-precision beam size measurement will offer better performance for accelerator monitoring and will be beneficial to study beam instabilities and optimizing machine operation. The interferometer system is a commonly used diagnostic tool for beam size measurement. High accuracy measurement can be achieved with low variation of beam size. It can also be used for very small size measurements by altering slit spacing. For future research on the physics and key technologies of high-brightness electron accelerators, we will build a turn-by-turn and bunch-by-bunch beam size measurement system based on the Shanghai Synchrotron Radiation Facility (SSRF) platform for related research. It will realize high-speed and high-resolution beam size measurements with the help of a multi-slit spatial interferometer and photomultiplier array (PMT). In this paper, we will introduce the construction of the overall system, discuss related problems, and give preliminary experimental results.
Reinforcement learning (RL) is a promising direction in machine learning for the control and optimisation of particle accelerators since it learns directly from experience without needing a model a-priori. However, RL generally suffers from low sample efficiency and thus training from scracth on the machine is often not an option. RL agents are usually trained or pre-tuned on simulators and then transferred to the real environment. In this work we propose a model-based RL approach based on Gaussian processes (GPs) to overcome the sample efficiency limitation. Our RL agent was able to learn to control the trajectory at the CERN AWAKE (Advanced Wakefield Experiment) facility, a problem of 10 degrees of freedom, within a few interactions only.
To date, numerical optimises are used to restore or increase and stabilise the performance of accelerators. A major drawback is that they must explore the optimisation space each time they are applied. Our RL approach learns as quickly as numerical optimisers for one optimisation run, but can be used afterwards as single-shot or few-shot controllers. Furthermore, it can also handle safety and time-varying systems and can be used for the online stabilisation of accelerator operation.This approach opens a new avenue for the application of RL in accelerator control and brings it into the realm of everyday applications.
One of the crucial monitoring systems of any particle accelerator is the Beam Position Monitor (BPM). The purpose of a BPM is to provide information on the position, phase and current of the beam at different points along the accelerator line.
The BPM is a subsystem of the CEA control domain for the SARAF-LINAC instrumentation and Orolia-Spain has designed, developed, manufactured and tested the system based on CEA technical specifications. A preliminary version of this system has been already installed in the SARAF accelerator in Israel at the beginning 2022 and the first results are going to be shown.
The architecture, design and development as well as the performance of the BPM system will be presented in this paper. The benefits of the proposed architecture and the first results obtained under different conditions will be detailed
Several machine learning (ML) projects on anomaly detection and optimization were recently started at the Advanced Photon Source (APS). To improve training data quality, and accommodate the upcoming APS Upgrade changes, a large increase in the number and size of log files is expected. Recent studies found performance bottlenecks in the current log analysis architecture, especially for large ML analytics tasks. We explored several approaches to improve both data density and throughput. First, we swapped lzma compression algorithm for modern alternatives like zstd and lz4, scanning presets to find an optimal one that increased decompression throughput by 10x for a 20\% file size increase. Several lossy compression schemes were attempted to take advantage of limited device resolution and ML quantization, yielding further size decreases with reasonable fidelity losses. Finally, we tested several analytics and time-series databases, finding them faster for both linear and random-access reads while maintaining good compression ratios. They also enabled offloading analytics computations to server nodes, reducing network load. Our results indicate that with some effort, it is possible to increase the amount of logged data significantly while improving ML analytics performance.
For any linear accelerator, a thorough understanding of the Longitudinal Phase Space (LPS) of the beam is a great advantage. At the synchrotron light source MAX IV the two storage rings are injected with electrons using a 3 GeV linear accelerator, which also serves to provide beam for a short pulse facility (SPF). A newly commissioned Transverse Deflecting Cavity (TDC) is used to reconstruct the full LPS in a separate branch in the SPF after the second bunch compressor. This diagnostic performs a destructive measurement to extract the LPS and can not be used simultaneously with the beamline in the other branch in the SPF. In this paper we present a new virtual diagnostics which utilizes machine learning methods to extract the LPS information from other, non-destructive signals in the MAX IV linac. This involves simulations of the linac including the TDC response, as well as the collection of real data from the new TDC, for use in training artificial neural networks to predict the full LPS.
The use of fast computational tools is important in the operation of X-ray free electron lasers, in order to predict the output of diagnostics when they are either destructive or unavailable. Physics-based simulations can be computationally intensive to provide estimates on a real-time basis. This proposed work explores the use of machine learning to provide operators with estimates of key photon pulse characteristics related to beam pointing. A data pipeline is set up and the method is applied to the SASE1 undulator line at the European XFEL. This case study evaluates the performance of the model for different amounts of training data.
Many complex systems require the use of different detector devices. The detectors usually acquire 1D or 2D data, but as the manufacturers differ, they all have diverse controlling interfaces. When the API and interface differ, it can become complex to control multiple different devices. The Lima library was created to overcome those obstacles. It unifies the usage of 1D and 2D detectors by exposing an interface which can, later on, be customized to use different detectors' APIs. The XH detector designed by STFC and used at ESRF is one example. The data collected by XH is sent to the server named "DA" acting as an API proxy and answers the string commands. The commands can both set the attributes and trigger the acquisition. All those complex commands and logic are wrapped into the Lima interface allowing transparent control over the device without additional knowledge and personal training.
The recent development of advanced black box optimization algorithms has promised order of magnitude improvements in optimization speed when solving accelerator physics problems. However, in practice these algorithms remain inaccessible to the general accelerator community, due to the expertise and infrastructure required to apply them towards solving optimization problems. In this work, we introduce the Python package, Xopt, which implements a simple interface for connecting arbitrarily specified optimization problems with advanced optimization algorithms. Users specify optimization problems and algorithms with a minimal python script, allowing flexible interfacing with both experimental online control and simulated design problems, while also minimizing the need for algorithmic expertise or software development. We describe case-studies where cutting-edge Bayesian optimization and genetic algorithms implemented in Xopt are used to solve online control problems at SLAC and Argonne National Laboratories. The same algorithms are also used to solve simulated optimization problems in high performance computing clusters using the same interface.
The APAM (Accelerators of Particles for Medical Application) Laboratory in the ENEA-Frascati Research Center developed a prototype of a self-shielded device dedicated to the treatment of breast cancer with the patient in prone position. It consists of a rotating X-ray source, based on a compact 3 MeV electron accelerator, placed under the patient bed which is provided with a circular opening through which the breast hangs down and can be irradiated. The system has been designed to suitably screen the patient body from the underlying accelerator. This setup improves target coverage and gives a valuable advantage in sparing healthy tissues: prone position increases the separation of the target and critical organs and in addition minimizes target motion caused by breathing. The prototype has been developed in the framework of the TECHEA (TEChnology for HEAlth) Project aimed to the realization and validation of prototype systems for applications to health protection. The paper describes the apparatus and reports the results of the experimental characterization of the X-ray source done in collaboration with the Laboratory of Medical Physics and Expert Systems of Regina Elena Hospital.
Progress in cancer therapy with ions heavier than protons, i.e., helium, carbon, oxygen and neon, requires research and development capability. Ion research activity, however, is limited from the absence of U.S. accelerator facilities offering ion beams for therapy – placing the U.S. significantly behind Europe and Asia. With dramatic advances in beam delivery and compact accelerators, the potential exists to create a facility that can play a leadership role in particle therapy and ion-based research. This paper announces summary details of a new center for ion therapy research under construction in Waco, TX, in collaboration with recognized accelerator entities both academic and industrial. The advanced accelerator technologies will produce beams for both clinical and research applications, offering a complete range of ions, intensities and energies required by the medical community, including the capability to perform ultra-high dose irradiation (FLASH) research. FLASH, a recent research initiative, which has the potential of reducing cancer treatment toxicities, is an important if not critical capability for a competitive research center – requiring beam intensities well beyond those provided by current medical accelerators. Building a state-of-the-art cancer research center within a comprehensive facility will provide the resources to promote ion therapy in the U.S, including, preclinical/clinical trials and protocols between modalities, and also support broad ion R&D.
A design study is currently underway at the University of Melbourne for a large energy acceptance beamline to enable future hadron therapy modalities. As part of the TURBO project, a beam delivery system demonstrator is being developed for a DC Pelletron accelerator, which will provide 3 MeV H+ beams. Fixed Field Accelerator optics will be used to maximise momentum acceptance, with dispersion minimised at both ends of the transport line. This project aims to be the first `closed dispersion arc' with fixed fields ever constructed. As part of the design process, the input beam phase space from the Pelletron has been characterised. Our results show that the Pelletron beam can be injected into the novel transport line successfully, and Zgoubi simulations show that near-zero dispersion at each end will be achievable. This is supplemented by error studies and magnet investigations, demonstrating that beam transport can be achieved under realistic circumstances. This initial study establishes the feasibility of this beamline design and work is continuing toward further optimisation for implementation.
Traditionally produced SRF cavities are characterized by many limiting drawbacks, such as welding lines and poor reproducibility of their properties. Additive Manufacturing, and in particular Laser Powder Bed Fusion (LPBF), may overcome these issues: with this technology, it is possible to create seamless components with reproducible characteristics. But 6 GHz cavities cannot see internal supports because they would not be easily removable. On the other hand, the down-skin self-supporting surfaces are extremely rough and unsuitable for the intended application. Indeed, very smooth surfaces are required since copper cavities are internally coated with superconducting materials (like Nb or Nb alloys): several surface treatments have been performed and studied; tests like tightness, resonant frequency and internal inspections have also been carried out before and after the post-printing smoothening and coating stages. Results are very promising and they will be shown in this work.
The Laser Powder Bed Fusion (LPBF) is an AM technology suitable to produce almost free-form metallic components. At Legnaro National Laboratories of the Italian National Institute for Nuclear Physics, the LPBF process was recently used to produce parts of the Forced Electron Beam Induced Arc Discharge (FEBIAD) ion source for the SPES Isotope Separation On-Line (ISOL) facility.
Such device is a critical component for the ISOL process, as its correct functioning is fundamental to ensure the availability of the radioactive ion beam to the experimental users. One of the main parts of the ion source is the tantalum cathode, a component that is electrically heated up to 2200°C and is subjected to thermal stresses.
Currently, the cathode is produced by subtractive manufacturing processes and TIG welding, which are not trivial in the case of Tantalum. Therefore, the cathode lacks dimensional/geometrical precision, affecting the performance repeatability and reliability of the ion source.
The LPBF technology allows to perform a morphological/topological optimization of the cathode aiming to overcome the intrinsic assembly limits of the present design and making more repeatable and reliable the ion source performance.
In this work, the production of the prototypical cathodes via AM, the results of dimensional–geometrical measurements, and the endurance high-temperature test are presented.
Taiwan Photon Source (TPS) is a 3-GeV synchrotron radiation light facility that was constructed in 2014. The magnets of the storage ring are installed on the girder system, and the girder system of TPS is an adjustable mechanism that is drove by motors of the cam mechanism. The control network of TPS is surveyed twice in ever year to observe the change of position of girders. The maximum changed location of girder system in storage ring is up to 1.5mm from 2014 to 2019. To improve status of storage ring, the girder system was re-aligned two times in 2021. This paper shows the procedure of realignment and the results of girders.
The aim of this work is to demonstrate the principal possibility to enhance the electron beam dose deposition in the depth of the sample for radiation therapy purposes. Trains of electron bunches of 22 MeV generated at PITZ are focused inside the sample using a dedicated fast deflector and a solenoid magnet. To explore the capabilities of the proposed setup, dose distributions are calculated for multiple electron bunches focused in a single point inside a water phantom. Electron beam focusing produces dose peaks with a tunable maximal dose depth which is interesting for healthy tissue sparing at the surface and enhancing treatment quality. The duration of the full bunch train is 1 ms. During this time interval, the FLASH effect could be efficiently triggered inside the irradiated target volume. Monte Carlo simulations based on the FLUKA code were performed to evaluate the depth dose curves distributions in a water phantom. Using the PITZ electron beam parameters, simulations have shown the possibility to produce a peak dose in water seven times higher than compared to the dose at the surface. Moreover, the RMS size homogeneous area around the maximal dose is approximately 25 mm.
The ANSI* steel penetration test is an important measure of the image performance capability of a cargo inspection system. Currently, the method for determining the arrow's visibility is completely subjective, as what one may deem 'visible', another may claim as not. An objective method is to calculate the contrast-to-noise ratio (CNR) between the steel plate and the arrow. A series of penetration scans were taken with the thickness of the steel plate ranging from 290-335 mm, and it was found that CNR decreases with increasing steel thickness. There is a point at which the CNR begins to level off - namely the 'limit of determination'. This is where the arrow can be objectively deemed as being no longer visible and, in this experiment, it was found to be at a CNR of around 0.23-0.25. Under-sampling the image data was also tested, and it was found that it did not have a detrimental effect on the CNR, and therefore the image performance. Once tested on more data sets, a definite value of the 'limit of determination' can be found. In future, this method has the capability of replacing the current method as an objective approach to determining the visibility of the arrow, and therefore measuring image performance using the steel penetration test.
Anodic bonding technology is a method which mainly by the aid of the electric field and temperature for connecting two materials such as glass-glass or glass-silicon wafer substrate by forming covalent bonding. The bent monochromator used in the synchrotron radiation which was made by high quality silicon wafer bonded onto concave cylindrical shape Pyrex glass base. In the past, it is made by gluing. The anodic bonding method for fabricating the bent monochromator which has more advantages than bonding by glue, such as tight bonging, non-intermediate, and simple process. This paper describes the detailed manufacturing processes and testing results.
The unique electronic band structure properties of two-dimensional (2D) materials allow for a multitude of cutting-edge applications involving electrical and optoelectronic devices. Atomically thin 2D materials such as MoS2 face major obstacles during synthesis and processing into precise electronic band gap properties adjustments. Few-layer MoS2 films are synthesized using alkali halide (NaCl) and, ion beams have been used to modify the electronic band gap and result in subsequent absorption properties of few-layer MoS2.
The band gap tuning in MoS2 is highly desirable for optimizing their applications in solar cells, photodetectors, and optoelectronic devices. We have already shown the effect of biaxial strain on the structural, elastic, and electronic properties of MoS2 [1]. In the present work, we are reporting 100 MeV Ni7+ ion irradiation-induced blue shift in MoS2, with ion fluences of 1×1011 to 1×1013 ions/cm2. UV-vis spectroscopy shows the absorption peak shifts from 680 nm to 674 nm for the A-peak and from 630 nm to 624 nm for the B-peak.
Boron Neutron Capture Therapy(BNCT) is useful for cancer therapy. To generate safe and efficient neutron beams, we accelerate 2.5 MeV protons and irradiate a lithium target. This is an endothermic reaction that avoids activation of the accelerator and produces neutrons of relatively low energy. We are designing a beamline to deliver such protons to a lithium target. Tokyo Institute of Technology has been developing a high duty factor RFQ in collaboration with Time Co. A 5% demonstrator is already in practical use. This paper describes a lossless beam transport system from the RFQ to the lithium target. The beamline consists of a quadrupole magnet, a bending magnet and a multipole magnet. The bending magnets prevent the backflow of neutrons into the RFQ. The expected beam current is 20 mA. The results of the design study of this beamline will be presented at the conference.
Real-time dosimetry for ultra-high dose-rates (UHDR) and Very High Energy Electrons (VHEE) is a challenge which is currently being studied using the electron beam at CERN Linear Accelerator for Research (CLEAR). These studies are motivated by the demand for reliable dosimetry for FLASH radiotherapy. This mode of irradiation relies on UHDR, a dose rate regime where conventional dosimetry monitors such as ionization chambers saturate. One potential approach is the use of a calibrated beam-based dosimetry method. The existing beam instrumentation provides real-time information on charge and both transverse and longitudinal profiles of the pulses, as well as making possible a measurement of the beam Twiss parameters. In the context of achieving a real-time prediction of the dose deposition, this paper presents experimental studies of the correlation of these parameters with the read-out of passive and dose-rate independent methods such as radiochromic films, and compares them with simulation results.
The Heidelberg ion beam therapy facility HIT has more than ten years experience in patient treatment. More than 7800 patients have been treated with protons and heavy ions, about 700 are treated every year.
Outside the beam time dedicated to therapy, quality assurance (QA) and machine tuning, we provide beams for a large spectrum of experiments in physics, biology and medicine which make use of various ion beam settings apart from the therapeutic application.
By slow extraction the HIT synchrotron produces a wide range of spill lengths between a few ms and more than 10s. The intensity can be varied accordingly: For biological FLASH-radiation experiments we provide more than 2e9 carbon ions/s, still applying the high-quality raster-scanning beam delivery method. On the other hand, we deliver very stable low intensity beams in the order of 1000 ions/s if sensitive detector equipment is mounted.
The layout of the facility was done for therapeutic ion beams with a maximum beam energy that corresponds to a penetration depth of ≈ 30cm in water and tissue accordingly. Especially for developments in ion beam radiography we now commissioned beams with higher energies for the light ions available at HIT (p, He).
This paper summarizes the large variety of accelerator settings for the different experimental activities.
Beam-Beam Long-Range Compensators employing current-carrying wires are considered as valuable options in hadron colliders to increase dynamic aperture at small crossing angles. This paper presents a simple design proposal for application at CERN LHC. The preliminary design allows for a certain scalability of the number of modules, current flowing in the wire, and dimensions. It complies with two key requirements: (a) the use of a thin, bare metal wire that allows for movement as near to the beam as necessary while minimising interactions with beam particles and meeting the specified DC current target; and (b) a wire support that is both an electrical insulator and a thermal conductor (ceramic).
A molybdenum wire, vacuum brazed on an aluminium nitride support, is proposed, and the design is conceptually proved through the realisation and extensive test of a demonstrator device. The wire brazing validation, as well as the system's heat management, which are the most critical aspects, are given particular regard.
Sub-millimeter precision is a crucial criterion for beam delivery in proton therapy. Nowadays, most of the therapy systems use the Pencil Beam Scanning (PBS) technique where single beams with regulated amount of protons are delivered sequentially to different locations within the target. Beam energy defines the depth of the beam propagation and scanner magnets deflect the beam to the desired lateral position.
The PSI Gantry 2 was among the first gantries to use the PBS technique. It makes use of 250 MeV protons produced by a superconducting cyclotron and degraded to a required energy. The beam scanning is performed just before the last bending magnet producing a nearly parallel and well- focused beam over the full scan range at iso-center. We developed a calibration algorithm for the scanner magnets in order to achieve the desired position precision in the target. Based on beam position measurement with a strip ion chamber in the gantry nozzle, we parametrized the propagation of the beam to the target calculating the beam angle at different scan positions as well as gantry angels.
During 10 years of operation, the system proved to be very stable and no parametrization update was required. Nevertheless, recently we re-evaluated parameters obtained during the system commissioning. In this contribution, we describe the calibration process of scanning magnets with respect to beam position at the iso-center and show the stability of this implementation over the time.
An ISO 14644-1 cleanroom is a contained environment where particle counts must be kept low in order for the cleanroom to function properly and meet critical certification criteria. These particles are typically dust, airborne microbes, aerosol particles, and chemical vapours. The Additive Manufacturing Department at Daresbury Laboratory was used to appraise the Cleanroom mechanical assembly process. This study has shown that 3-D printed materials can be utilised to meet ISO Cleanroom standards. Four printing methods were used, Fused Filament Fabrication (FFF), Direct Metal Laser Sintering (DMLS), Polyjet, and Stereolithography (SLA) to create nine DN16 ConFlat Flanges made from RESIN, MED610, PLA, and TI-64. A DN16 ConFlat Flange was chosen because it is a small component that will keep printing costs low, but it is also large enough to be particle counted successfully.
It has been demonstrated that ultrasonic cleaning can significantly reduce component contamination and, in some cases, raise the ISO level. The PLA DN16 CF Flanges were made clear and coloured to see if this factor affected the particle count. Because stainless steel is commonly acknowledged and used in the cleanroom industry, it will be chosen as the baseline for this study. In particle count readings, the RESIN and MED610 surpassed the Stainless-Steel. RESIN and MED610 will be utilised for configurable components such as tools, guides and bracketry in future processes that require ISO 4 cleanroom conditions.
In the field of Particle Accelerators engineering, the design of the cooling channels of its components has been extensively based on experimental correlations for the calculation of convective heat transfer coefficients. In this scenario, this work is focused on studying whether the experimental correlations are conservative when the flow is turbulent in fully developed and non-fully developed regions.
For this research, simulation models have been developed for turbulent flows in fully developed and non-fully developed regions, all of them for cooling channels with a 10 mm inner diameter. In the first case, for a circular channel, turbulence models have been studied, and comparative studies with respect to experimental correlations and previous studies performed at ALBA have been carried out. Simulation models based on the coefficients obtained from experimentally observed correlations, CFD models and an experimental validation of a mirror with inside cooling, have been performed in the second case.
In the extraction of booster to storage (BTS) for High Energy Photon Source (HEPS), four pulse bump magnets are applied to create a local bump to ease extraction. In this paper, a lot of characteristics of the pulse bump mag-net such as magnetic field, eddy current, induced voltage, vibration are introduced and thoroughly discussed. Ac-cording to measurements, four pulse bump magnets are satisfied with the physical requirements of beams extrac-tion in HEPS.
Very High Energy Electron (VHEE) beams represent a promising alternative for treating deep-seated tumors. However, VHEE beams generate quasi-uniform dose distribution along the beam path, leading to healthy tissue overexposed. Focused VHEE beams are a revolutionary radiotherapy technology that enables concentrating doses into a small and well-defined spot with an extremely high dose rate. This paper estimates the dose deposition and presents the influence of different focus depths. The contributions of secondary particles are further discussed. In addition, a focused beamline is designed using two triplets of quadrupole magnets to transport and focus VHEE beams onto the water phantom.
Niobium thin films are used in macroscopic SRF cavities for particle accelerators which are under study for microscopic superconducting qubits for quantum computing. The superconducting properties of niobium in microwave fields vary significantly with lattice defects and impurity content, where sub-at.% impurity level can reduce or increase microwave surface resistance by an order of magnitude. In this study, we investigated the microwave properties of Nb films deposited by bipolar HiPIMS, correlating microwave properties at dilution fridge temperatures with material properties characterized by surface analytical techniques. Nb thin films were grown on Nb substrates and, on the inside surface of 1.3 GHz TESLA-shaped single-cell Nb SRF cavities. We also studied the Nb thin film samples' microstructure, surface morphology, and superconducting properties. The SRF cavity performance was tested in Fermilab's VTS and dilution fridge systems. The intrinsic Q0 as a function of the accelerating gradient was measured at 2 and 1.5 K in the liquid helium dewar. Then the cavity was assembled into the dilution fridge without breaking the cavity vacuum and was tested from 20 mK to 40 K. The frequency and quality factor dependence as a function of temperature at low fields was investigated. The mid-T baking treatment was applied to improve the performance of the cavity. After mid-T baking treatment, cavity performance was tested again and compared with previous results.
Sirius is one of the first 4th generation synchrotron light source globally, currently in operation by the Brazilian Synchrotron Light Laboratory (LNLS). One of the components that will be part of the light source are the vacuum chambers defining the environment in which the electron beam travels under the influence of electromagnetic fields. This environment should be substantially free of gas molecules, since collisions between the electron beam and gas molecules can lead to the loss of stored electrons and a rapid decrease in the beam current. These chambers must be cooled and for chamber production, a joint of the silver-copper vacuum chamber alloy is required to be made to ETP copper by the process of soldering. This process achieved all the functional requirements of the project, being ultra-high vacuum tightness, low deformation, low oxidation, low temperature, and, low porosity. The development and characterization of the brazing process were carried out through tests of metallography, optical microscopy, microhardness, Scanning Electron Microscopy (SEM), and Energy-Dispersive X-ray Spectroscopy (EDS). With the results obtained through the tests performed, it was possible to characterize the solder and determine the intermetallic behavior after several types of heat treatment conditions.
While ion therapy provides an immense opportunity for advancement in the treatment of various cancers, present-day mechanical systems that deliver beam from the accelerator to the patient are large and complex. A new patent pending compact beam delivery system concept has been explored and is presented here. The concept is to provide a continuously rotating magnet system wherein the traditional gantry angle for beam delivery is determined by timing of the entrance of the beam to the gantry from the upstream accelerator. Longitudinal position of the beam at the treatment location is determined by a scanning magnet at the entrance to the rotating system. Beam transport is provided through a set of fixed-field gradient magnets of compact design. The combined-function magnets have gradients chosen to provide a zero or very small focusing effect in the bend plane of the gantry, while providing sufficient focusing in the out-of-plane direction. The final beam energy and hence final penetration depth is determined by a patent pending fast-response energy selection system between the exit of the final magnet and the isocenter. By minimizing the adjustments required of the main fields and through the use of a fast response scanning magnet, treatment times can be reduced significantly. A self-consistent design of the concept and its overall properties as well as possible directions for enhancement are described
In this talk, we describe the project status of a new class of simple, turn-key superconducting radio frequency (SRF) accelerators that will be used in environmental studies such as wastewater treatment, treating contaminants in municipal water, and industrial applications such as material processing, medical device sterilization, security, and other niche application. Leveraging recent R&D breakthroughs in high-temperature SRF cavities, cost-effective radio-frequency sources, modern cryo-coolers, and high-average current electron guns, Fermilab has developed a novel accelerator design for a compact SRF high-average power electron beam linear accelerator. We will describe the status of the active projects at 650 MHz and 1.3 GHz along with the results of this novel concept on conduction cooling of SRF cavities which removes the need for liquid Helium, thus making SRF technology accessible to industrial applications.
Our linac can generate electron beam energies up to 10 MeV in continuous-wave operation. We show through detailed thermal, RF and particle simulation that a single accelerator module can deliver average beam power as high as 250 kW and above. We can reach up to 1 MW by combining several modules. Compact and light enough to mount on mobile platforms, our machine will enable new in-situ environmental remediation applications, portable security applications, and novel applications for in-situ cross-linking of materials.
The high-brightness electron beam at the Photo Injector Test facility at DESY in Zeuthen (PITZ) is now also used for FLASHlab@PITZ: an R&D platform for studying radiation biology and the FLASH effect in radiation therapy. The available parameter space of the electron beam with a momentum of 22 MeV/c allows bunch charges from 10 pC up to 5nC, bunch durations of 0.1–60ps, and bunch train lengths up to 1 ms. The number of bunches in the single train can currently be varied between 1 and 1000 bunches, with an upgrade to 4500 foreseen in 2023. Radiation biology studies require accurate dose prediction, therefore Monte Carlo simulations based on the FLUKA code were performed. According to estimations, dose delivery of 0.002 Gy (low charge case 0.1pC) and 10Gy (high charge case 5nC) is possible, if the beam is confined to a circular area with a radius of 5 mm with a lead collimator. For the Monte Carlo simulations, the experimental setup was accurately modeled, including the exit window, lead collimator, etc. Dose measurements were used to compare simulations with experiments. Dose profiles were experimentally measured with Gafchromic films and then compared with Monte Carlo simulations. The first experiments at FLASHlab@PITZ in 2023 have demonstrated flexible dose options for studying the FLASH effect and radiation biology studies
Thanks to their superior dose conformality and higher radiobiological effectiveness with respect to protons, helium ions are considered as the new tool of choice in the fight against cancer using particle beams. A facility to produce helium beams at therapeutical energy can also accelerate protons, at energies permitting both standardised treatment and full body radiography, and heavier ions for treatment of shallow tumours and for research. Equipped with FLASH extraction, it will be able to couple the protection to healthy tissues provided by Bragg peak and FLASH effect.
This paper will present the basic layout of a facility based on a compact synchrotron of new design that can accommodate a wide research programme with patient treatment, sharing the beam between two treatment rooms and an experimental room. The linac accelerator may be designed to allow a programme for production of new radioisotopes for therapy, diagnostics and theragnostics using helium ions, in parallel with the operation as synchrotron injector.
Overall cancer and conventional radiotherapy statistics, along with an estimate on the number of patients that can benefit from this facility will be presented for the case of the Baltic States, a candidate for hosting the facility.
In recent years, there has been an increasing demand for high-intensity beams related to electron beam irradiation, such as mass production of nuclear-medicine examination by using 99Mo and high-efficiency production by material modification through material irradiation. While the acceleration of high-current beams can be realized by using a superconducting cavity, a compact accelerator is desirable for general-purpose irradiation beams. In this paper, we designed a 10 MeV, 50 mA high current beam irradiator for practical use based on the experimental results of highly efficient production of nanocellulose by wood irradiation. The conceptual design of the accelerator, which consists of the electron gun, the superconducting cavity, and the irradiation section, was carried out. Especially, we designed a 10 MeV, 50 mA high-current beam accelerator by using a new Nb3Sn superconducting cavity. We estimated how compact the accelerator can be and how much the operating electrical power can be suppressed.
Hadron therapy is established as a method of choice for a number of cancerous diseases, and its advantages are well-established for specific malignancies. Modern medical particle accelerators still struggle to fulfil critical features required by advanced treatment modalities, such as variable energy beams, high repetition rate, and pulse-by-pulse intensity modulation. Fixed Field Accelerators (FFAs) are suited to tackle these challenges as they can accelerate particles over a wide energy range with fixed magnetic fields. Vertical orbit excursion FFAs feature constant tunes and a small horizontal footprint, making them excellent candidates for medical applications. We propose a conceptual design of a medical vFFA. Its linear and nonlinear beam dynamics is presented in-depth. This study demonstrates the vFFA potential to provide a new direction for the study and design of medical FFAs suitable for next-generation particle therapy systems.
Experiments requiring the use of plasma sources often have trouble getting time on large plasma sources to perform their experiments despite needing only a few centimeters of high density plasma. It is significantly more convenient to have a short, high density plasma source that is available on demand for immediate experimentation. A capillary discharge plasma source was built at UCLA for this exact reason and is due to enter experimental service soon. Using argon gas and a spontaneous breakdown approach to plasma formation, this capillary is capable of generating plasmas up to 10^14 cm^-3 with a repetition rate of about 10 seconds without requiring excessive laboratory space. This compact plasma source will be used in experiments involving the SAMURAI and AWA facilities, whose results will be evaluated against the MHD code FLASH. This paper will discuss the theory behind and construction of a capillary discharge plasma source and interferometric diagnostic system, and present experimental results that utilized this plasma source.
Particle therapy has advantages over conventional radiotherapy, but is not so widespread because of significant facility costs. In this work, we developed a compact, low-cost, expandable and high-performance beamline for a multi-room particle therapy facility. The accelerator is located at a lower level (underground) and the beamline guides the particles to treatment rooms located on the upper level of the floor. Such a compact beamline can rotate 360o about the vertical axis to deliver beams to the treatment delivery rooms, which are then designed in a circular arrangement. The rotating beamline can then deliver beam to each treatment room, where the patient is treated in an upright position and rotated in front of a static treatment beam. The beamline characteristics have been calculated with BDSIM Monte Carlo simulations code. Simulation indicates that our beamline can transport full momentum spread (±5%) up to patient location allowing to have broadened Bragg peaks and ultra-high dose rates (>1000 Gy/s) to limit the field delivery time within a single breath-hold (5 second field delivery) even for large tumors. With this design, we can fit a single-room proton facility within an existing LINAC vault and a four-room facility within the area of a tennis court. We believe that such a high throughput and low investment cost facility could eventually allow to treat patients with particles at costs approaching that of conventional radiation therapy.
The electrons, which passed the undulators in a linac-driven Free Electron Lasers, could be utilized for additional radiation generation in an Inverse Compton Scattering process (ICS). The PolFEL, facility, currently in preparatory phase in NCBJ, is planned to be equipped with ICS system, to generate continuous (10kHz repetition rate) pulses train of hard X-ray radiation, in addition to THz-, VUV- and IR-light produced in FEL process. Taking into account the principles of Compton scattering, we designed the interaction chamber to assure head-on collision of electrons and optical photons and an X-ray detection system. To simplify the setup, we designed to use similar type of laser source for ICS system, as for photocathode excitation. The energy of generated X-rays, calculated on the basis of laser and linac parameters are in range between 115 keV and 1.9 MeV. The maximum number of X-ray photons is estimated to reach about 3x106 photons per mrad2 per second. In the paper, the design of ICS interaction chamber, detectors, and also calculated X-ray photon characteristics will be presented.
The Flash Therapy is a revolution in the cancer cure, since it spares healthy tissue from the damage of the ionization radiations without decreasing its effectiveness in the tumor control. To allow the implementation of the FLASH therapy concept into actual clinical use and treat deep tumors, Very High Electron Energy (VHEE) should be achieved in range of 50-150 MeV. In the framework of VHEE project carried out at Sapienza University, in collaboration with INFN, we investigate the main issues in the design of a compact C band (5.712 GHz) electron linac for FLASH Radiotherapy. In this paper we describe the design strategy,
the electromagnetic properties and the first prototype of the RF structure to be tested at Sapienza University.
Wuhan Advanced Light Source (WALS) is a fourth-generation synchrotron radiation facility with 1.5 GeV designed energy and 500 mA beam current. The high-heat-load absorber is designed to protect downstream ultrahigh-vacuum chambers from overheating. It is the only heat mask component to absorb large amount of synchrotron radiation (bending magnet) in the storage ring. This presentation is focused on the design and thermal-mechanical calculations of the absorber. Thus, the Synrad software which is developed by CERN is used to investigate the distribution of the synchrotron radiation and the power density on the designed absorber. And the Finite Elements Analysis (FEA) calculation will show the distribution of the thermal and the stress on the absorber body. The calculation results indicate that the designed absorber is suitable the absorption of the synchrotron radiation generated by the WALS.
High power particle producing target components in research facilities often consist of refractory metals. They experience challenging thermo-mechanical conditions and therefore require dedicated cooling systems. Employing water-cooling in direct contact with the target materials, especially tungsten (W), induces erosion and corrosion. Cladding the target blocks with erosion/corrosion-compliant materials is also a solution for a reliable heat transfer from the core materials to the coolant. Tantalum (Ta) is used in various facilities as cladding due to its corrosion resistance, outstanding thermo-mechanical properties, and diffusion bonding compatibility.
The Beam Dump Facility (BDF) - a new proposed fixed target experiment at CERN – explored at first Ta2.5W cladding for molybdenum-based alloy TZM and pure W blocks. However, Ta presents non-negligible decay heat and high price. In this study, niobium-based materials – pure Nb, Nb1Zr, and Nb10Hf1Ti (C-103 alloy) – are evaluated as an alternative for cladding. The niobium alloys are assessed by their diffusion bonding via Hot Isostatic Pressing (HIP) and by thermo-mechanical characterization of the interfaces. Simulations of the impact with a high-power proton beam complement the study.
The Drift Tube Linac (DTL) of the European Spallation Source (ESS) is composed of 5 independent Tanks, each of which of 8 t in weight and 8 m in length, is made of 4 modules and is positioned and aligned to the Nominal Beam Line with 2 mechanical supports. The supports are designed to perform the iso-statical alignment of the tank, and to allow its longitudinal displacement for the installation and maintenance of the Intertanks.
Presently, 4 of 5 Tanks have been successfully installed and aligned with respect to the Nominal Beam Line, using a Laser Tracker to monitor the position with a tolerance of 0.1 mm.
This paper details the chosen kinematic configuration, the supports design, the calculation and simulations for design validation, the procedures for regulation and alignment and the achieved results.
A pulsed septum magnet (SMH40) is used for heavy ion extraction from the Low Energy Ion Ring (LEIR). A non-conformity on the coil cooling circuit made it necessary to consolidate the design of the septum blade and related manufacturing process. A stringent failure analysis, including structural analysis and computational fluid dynamics, combined with destructive and non-destructive testing, has allowed to identify a design weakness. Subsequently, a new manufacturing process has been proposed, fully validated by numerical computation and after production of a 1:1 prototype. The achieved leak-tightness and cooling performance as well as optimization of the manufacturing process shall significantly increase the operational life cycle. This paper describes results from the initial root cause analysis and summarizes the design iterations and final results.
ZAP-X is an innovative radiosurgery platform that is self-shielded, using gyroscopic motion to allow precision neurosurgical treatment. It requires a compact linac with lower than typical energy for medical applications. A 3 MeV S-band linac is designed and fabricated for this purpose. Thorough, clinical style testing was performed to verify the performance. The characteristics of photon beam, which is generated by the linac, are compared with the design goal, as well as Monte Carlo simulations.
Based on an initial proof-of-concept, a full-size single-piece pure-copper Radio Frequency Quadrupole (RFQ) prototype module was for the first time designed and additively manufactured (AM), as a result of a multi-disciplinary collaborative effort and of the deployment of state-of-art AM technology. The 39-cm long prototype with modulated electrodes replicates, with several improvements allowed by AM, the design of the CERN high-frequency (750 MHz) RFQ that has already found applications in proton therapy of cancer and ion beam analysis.
Thanks to its unique features, AM technology is unlocking great potential for the optimisation of a complex accelerating cavity like the RFQ. The RFQ geometry can be improved based only on accelerator physics and functional requirements without considering limiting factors (e.g. tolerances, shape, size and configuration) imposed by the conventional manufacturing techniques. Additionally, cooling channels and connection flanges can be integrated in the overall structure, with a gain in installation and operation flexibility.
In-depth geometrical accuracy and surface roughness measurements were performed on the proof-of-concept prior and after the surface treatment operations. The results are fully in line with the standard RFQ requirements. Vacuum, RF and water tightness tests are being performed on the full prototype. The paper will discuss in detail the technological process, the measurements and the test results.
A Low Energy Branch is being built at Micro Analytical Centre * that will allow us to produce a variety of high current (up to 50 µA) ion beams, ranging from light (i.e. H, He, C, B, 15N), mid-mass (i.e. Si) to heavy (Ag, W, Pb, Bi) ion beams in the energy range of 100 eV up to 30 keV. Ions will be produced with the use of ion sources that are currently available at the facility.
The branch will provide beams: a) for implantation of gases into solid targets, b) for the creation of Nitrogen-Vacancy centres in diamond ** needed for quantum computing research, c) for simulation of the effects of solar wind on the lunar surface, d) for studies of ion-gas reactions at low energies and e) for commissioning of ion optics and testing of machine learning algorithms for automatic beam control.
The branch will employ electrostatic steerers for beam position control, Einzel lenses for minimising beam size, a magnetic dipole to purify the ion beam and a Wien filter to produce ion beams with the highest possible monochromaticity.
The poster will present the progress and development of the ion optics, experimental stations and beam profile monitors designed for the above branch.
The J-PARC main ring is being upgraded to a beam intensity of 1.3 MW. The capacity of the beam dump used for beam tuning is planned to be increased from 7.5 kW to 30 kW. The current beam dump has a vacuum that extends from the accelerator tunnel to 4.5 m inside the wall, keeping the radiation back scattered from the dump at a sufficiently low level. The new beam dump design requires to have a beam window to break the vacuum in the accelerator tunnel. The beam window is a new beam loss spot and radiation from it needs to be shielded, but we would rather consider actively using it as a low-dose neutron and meson source. In the J-PARC main ring, a test bench has already been set up downstream of the beam collimator for irradiation tests in a high-dose composite particle environment, but access to the test bench requires opening and closing the steel shielding wall each time, and the residual radiation dose is high. By preparing a test bench that can be used for tests that do not necessarily require high doses, it will be possible to perform various irradiation tests more easily. The neutron and meson distributions obtained from the beam window are predicted and the availability of irradiation test bench is outlined in this report.
The electron beam at CERN Linear Accelerator for Research (CLEAR) has been intensively used to study the potential use of Very High Energy Electrons (VHEE) for radiotherapy, including the so-called FLASH regime. An important part of these studies revolves around the development of reliable dosimetry methods, given that generally accepted standards are partly lacking for electron beams in the 100 MeV range and even more so in the ultra-high dose rates (UHDR) conditions needed for FLASH. Passive dosimetry methods, such as radiochromic films and alanine pellets are presumed to be energy- and dose-rate independent and constitute an indispensable tool for VHEE studies. Furthermore, the development and testing of new modalities for active UHDR dosimetry relies heavily on them for validation and cross-calibration. In this context, efforts have been made to establish reliable and systematic approaches for passive dosimetry at CLEAR. This paper describes studies related to the processing of radiochromic films, the energy dependence of the dose measurements and comparisons with alanine pellets and other media.
The synchrotron-based ELSA facility delivers up to 3.2 GeV electrons to external experimental stations. In a new setup the irradiation of tumor cells with doses of up to 50 Gy by ultra-high energy electrons (UHEE) in time windows of microseconds up to milliseconds (FLASH) is currently investigated. This technique may enable highly efficient treatment of deep-seated tumors alongside optimal sparing and protection of healthy tissue. In a preliminary setting electrons with an energy of 1.2 GeV are used to irradiate cell samples which are located inside a water volume, representing the human body. The relative biological effectiveness (RBE) can be determined by assessing the cell survival of healthy and tumor tissues. For precise dose determination, simulations by Geant4 reproduce the electromagnetic shower process, taking the extracted electron pulse properties into account. The water volume consists of voxels of different sizes for precise investigation in the volume of interest. Various properties such as particle types, deposited energy and the energy spectra of the particle shower can be extracted. The method and first results in comparison to measured data will be presented.
The CLEAR facility at CERN allows users to receive an electron beam with energy up to 200 MeV, allowing flexibility in intensity, beam size and bunch structures. Separate from the main CERN accelerator complex, it is capable of hosting numerous experiments with rapid installations at two test stands.
It would be highly desirable for many applications, but particularly those of a medical nature, to be able to provide a ‘flat’ beam at CLEAR, with a uniform intensity distribution over a significant component of its transverse dimensions.
Over the winter shutdown 2022-2023, a dual-scattering system has been installed in the CLEAR beamline to generate such a beam distribution. It was placed several metres upstream of the beamline end to reduce X-ray contamination in the flattened beam and increase total transmission of the beam. Studies on the flattened beam composition in terms of structure and dose were carried out, utilising a dipole directly upstream of the in-air test stand to separate the electron and X-ray components for analysis.
Polycrystalline SiC wafers were implanted with 300 keV strontium ions at room temperature to a fluence of 2×10^16 cm^−2. Silicon dioxide (SiO2) layers of about 100 nm thick were deposited onto the surface of implanted SiC via magnetron sputtering of a SiO2 target in argon-oxygen atmosphere. The as-deposited (i.e., SiO2/implanted SiC) samples were subjected to sequential isochronal annealing, under vacuum, at temperatures ranging from 1100 to 1400 ˚C in steps of 100 ˚C for 5 h. The effect of annealing on the surface topography and migration of strontium in SiC and SiO2 layers were investigated by scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM) and Rutherford backscattering spectrometry (RBS), respectively. RBS and STEM results showed that annealing at 1100 and 1200 ˚C, caused strong strontium segregation toward both SiO2/SiC interface region and SiO2 surface. The migration of strontium from SiC to the SiO2 layer at 1100 and 1200 ˚C enhanced the sublimation of SiO2 in an ultrahigh vacuum chamber, where the pure SiO2 layer (i.e., without impurities) showed no sublimation after annealing under the same conditions. However, further annealing, at 1300 and 1400 ˚C, showed strong sublimation of the pure SiO2 layer. This indicates that SiO2 is not suitable for use as an additional diffusion barrier for SiC since temperatures in a nuclear reactor can reach 1600 ˚C during accidence conditions.
The APAM Laboratory of the ENEA Frascati Research Centre hosts two electron beam S-Band standing wave linacs. The older one, named REX, produces a 5 MeV, 150 mA electron beam with maximum PRF of 20 Hz. The second one, named TECHEA, was recently commissioned within a Research and Development program focused on breast radiotherapy applications: it produces a 3 MeV, 130 mA electron beam with maximum PRF of 100 Hz. Both plants can produce either electrons or X-rays through a conversion target with photon energies peaked at 2.5 and 1 MeV, respectively. In this contribution we report qualification activities on the electron beam properties in air (flux, uniformity and energy spectrum) at different target from source distances and at different extraction energies to assess the applicability of these facilities for multiple applications, such as sterilization, conservation of cultural heritage artifacts, material degradation, space components testing.
In everyday the lighting environments is increasingly replacing incandescent and fluorescent bulbs with light-emitting diodes (LEDs), which offer superior electricity-to-light conversion efficiency. In accelerator facilities, too, the time has come to replace conventional lighting with LEDs and other high-efficiency, green lighting. In order to promote the replacement of lighting in an accelerator tunnel, we investigated the process of the radiation damage for commercially available LED lightings in an X-ray radiation environment such as in the electron storage ring SPring-8. It was found that metal-oxide-semiconductor field-effect transistors (MOSFETs) to be supply power for the LED lighting were damaged by X-ray irradiation with the total dose effect greater than several hundred Gy (air kerma). In situ measurements of the MOSFET under an irradiation by an X-ray tube clearly showed a sudden increase of the off-state drain current accompanying with a sharp increase of MOSFET temperature as a function of radiation dose, which eventually caused the device failure. This presentation shows two effective countermeasures for the longer lifetime of LED and application examples.
Beam lines magnets for high rigidity particles can have a large power dissipation. In presence of a high duty cycle, this translates in a considerable amount of energy waste. The call for sustainability of large research infrastructures, like particle accelerator centers, and also the recent increase of the cost of energy, requires to take measures to reduce the energy consumption, even if at cost of moderate investment. A project called ESABLIM (Energy SAving Beam LIne Magnets) has been launched at the LASA lab of University and INFN Milano, aimed at revamping existing normal-conducting magnets for beam lines in order to cut by a factor 10 to 20 the peak power and reducing the energy consumption by factor 3 to 5. The idea is to re-use the iron yoke-pole assembly of a magnet and replace the water cooled coils with new superconducting coils cooled at 10-20 K by means of a cryocooler. We envisage use of MgB2. For its moderate cost. However, we are also considering HTS (REBCO) conductor. We present the first advanced design for revamping of a large bending dipole in a hadron therapy center (CNAO), and the conceptual design for magnets in a nuclear physics laboratory and we try to define the domain where this transformation of normal-conducting into super-ferric magnets can be technically and economically advantageous.
After 25 years of successful research in the nuclear and radiation physics domain, the KVI-CART research center in Groningen is upgraded and re-established as the PARticle Therapy REsearch Center (PARTREC). Using the superconducting cyclotron AGOR and being embedded within the University Medical Center Groningen, it operates in close collaboration with the Groningen Proton Therapy Center. PARTREC uniquely combines radiation physics, medical physics, biology and radiotherapy research with an R&D program to improve hadron therapy technology and advanced radiation therapy for cancer. A number of further upgrades, scheduled for completion in 2023, will establish a wide range of irradiation modalities, such as pencil beam scanning, shoot-through with high energy protons and SOBP for protons, helium and carbon ions. Delivery of spatial fractionation (GRID) and dose rates over 300 Gy/s (FLASH) are envisioned. In addition, PARTREC delivers a variety of ion beams and infrastructure for radiation hardness experiments conducted by scientific and commercial communities, and nuclear science research in collaboration with the Faculty of Science and Engineering of the University of Groningen.
In EUV lithography, high volume manufacturing already started using a laser-produced plasma (LPP) source of 250-W power at 13.5 nm. However, development of a high-power EUV light source is still very important to overcome the stochastic effects for a higher throughput and higher numerical aperture (NA) in future. The required EUV power for the 3-nm node and beyond at the maximum throughput of future scanners is estimated to be more than 1 kW. We have designed and studied an EUV-FEL light source based on ERL for future lithography [1,2]. This light source offers many advantages such as high EUV power (> 10 kW), upgradability to a Beyond EUV (BEUV) FEL for finer patterning, polarization controllability for high-NA lithography, low electricity consumption and cost per scanner, as compared to the LPP source. Excellent high-power performance of the EUV-FEL light source was newly demonstrated by a start-to-end simulation with new optimization and more accurate calculation and conceptual schemes of upgrade to a BEUV-FEL, polarization control of the FEL light and an optical beamline to the scanners were proposed. Proof of concept (PoC) of the EUV-FEL light source using an IR-FEL constructed in the Compact ERL (cERL) at KEK is also in progress. In this presentation, we will present the EUV-FEL light source for future lithography including the PoC using the cERL IR-FEL.
Additive Manufacturing (AM) offers different benefits such as efficient material usage, reduced production time and design freedom. Moreover, with continuous technological developments, AM expands in versatility and different material usage capabilities. Recently new energy sources have been developed for AM – green wavelength lasers, which provide better energy absorption for pure copper. Due to high thermal and electrical conductivity of copper, this novel AM technology is highly promising for various industries, particularly, there is a huge interest to use it for accelerator applications. In particular, these AM produced accelerator components should reach the associated Ultra High Vacuum (UHV) requirements. In this study, vacuum membranes of pure copper were produced by AM using a green laser source, in different thicknesses and built angles. Furthermore, a vacuum membrane helium leak tightness test was performed at room temperature by using a high-sensitivity mass spectrometer. Comparison of these test results was performed with previously established results. Through this study, novel knowledge and initial results are provided for green laser source AM technology usage for applications for UHV accelerator components.
The NHa C400 is the first compact superconducting cyclotron used for carbon therapy in the world. Carbon therapy is particularly effective for treating radiation-resistant tumors, as compared to more conventional radiotherapy techniques.
In this work, a 3D finite element model of the Nb-Ti coil has been developed using the open-source solver GetDP. First, an accurate representation of the DC magnetic fields, required for beam dynamics computation, is obtained. Second, analytical models of increasing complexity for hysteresis losses in the superconducting filaments are investigated. For discussing their accuracy, a single filament model has been developed. Third, the heat loss in the Nb-Ti coils during energization of the cyclotron is evaluated based on a multi-scale approach involving the single filament model.
Ultrafast electron microscopy (UEM) can be used to probe
ultrasmall (nm scale) and ultrafast (fs scale) world. At the
fundamental level, atomic potentials determine the elastic
electron scattering in UEMs. Here we calculate the first
correction term analytically for elastic scattering of electrons
by atoms in the weak phase object approximation. Its effect
varies with atom types and electron energies and may be
non-negligible for electron microscopy images.
Recently presented RF cavity prototypes printed entirely from pure copper illustrate the potential of additive manufacturing (AM), and particularly laser powder bed fusion (L-PBF), for accelerator technology. Thereby, the design freedom of L-PBF is only limited by overhanging geometries, which have to be printed with supporting structures to ensure sufficient accuracy. However, subsequent removal of these support structures is a major challenge for cm-sized GHz cavities. Therefore, our approach is to design self-supporting geometries. In this contribution we present a DTL cavity geometry as used in e.g. proton therapy linac systems that can be fabricated by L-PBF without support structures. A 5-cell prototype was manufactured from high-purity copper using L-PBF. It is shown that the developed geometry allows a print accuracy sufficient to reach the defined resonance frequency. A chemical, as well as dynamic electrochemical finishing process, was applied to optimize the prototypes surface quality. Thus, the CST simulated figures of merit (e.g., $Q_0$, ${Z_{eff}}$) were obtained for the first time with a printed cavity.
CEPC can also work as a powerful and excellent synchrotron light source, which can generate high-quality synchrotron radiation. This synchrotron radiation has potential advantages in the medical field, with a broad spectrum, with energies ranging from visible light to X-rays used in conventional radiotherapy, up to several MeV. FLASH radiotherapy is one of the most advanced radiotherapy modalities. It is a radiotherapy method that uses ultra-high dose rate irradiation to achieve the therapeutic dose in an instant; the ultra-high dose rate used is generally greater than 40 Gy/s, and this type of radiotherapy can protect normal tissues well. In this paper, we evaluated the therapeutic effect of CEPC synchrotron radiation for FLASH radiotherapy by simulation. First, we established a physicochemical model of radiotherapy response kinetics, and comprehensively used a large number of radiotherapy experimental data to fit and determine the functional relationship between the treatment effect and the dose rate. Then, we use Geant4 simulation to build a synchrotron radiation radiotherapy beamline station, and then calculate the dose rate that CEPC can produce. Finally, we predicted the macroscopic therapeutic effect of FLASH radiotherapy using CEPC synchrotron radiation light through this dose rate and the above-mentioned functional relationship. The results show that CEPC synchrotron radiation beam is one of the best beams for FLASH radiotherapy.
The two dominant radiotherapy methods are either simplified in terms of beam generation and handling, which compromises the energy deposition curve in tissues (photon therapy) or require extensive accelerator facilities and complex beam delivery systems to provide a favourable shape of the energy deposition curve (hadron therapy). The advantages of both of these methods, such as the low cost of the apparatus, ease of beam generation and a suitable shape of the energy deposition curve in tissues, can potentially be achieved by using a high-energy electron beam (beam energy in the order of a few hundreds of MeV) focused on the area of the tumour lesion. However, focusing of the beam is usually done with the use of quadrupole magnets which makes the beam delivery system complex and challenging from the engineering point of view. In this paper, we explore the feasibility of an alternative solution, where focusing is performed by a bent silicon crystal with an appropriate shape of its exit face. Such a crystal lens can be a very light object (mass in the order of grams), allowing for much simpler beam delivery systems of radiotherapy facilities.
Proton therapy provides significant advantages over classic radiotherapy for specific cancerous diseases, notably by limiting the delivered dose to organs at risk (OARs). Novel treatment modalities such as flash and arc therapy require changing the energy delivered at the isocenter while providing a high dose rate. Fixed-field achromatic transport lattices satisfy both constraints, allowing ultra-fast energy modulation and excellent transmission efficiency while providing a compact footprint. Prior studies [1] have shown that lattices using scaling fixed field magnets allow the achromatic transport of energies between 70 and 230 MeV. We investigate the use of straight scaling FFAG line that uses nonlinear fields, fulfilling the straight scaling conditions for achromatic transport, to be used as a matching section for the CASPRO ("Compact Achromatic System for Proton Therapy") project.
Laser Compton Scattering Gamma-ray beam (F-LCS), which has a flat distribution in the energy spectrum and the special distribution, has been developed to study an isotope selective CT Imaging application in the beamline BL1U in UVSOR. The generation of F-LCS beam has been demonstrated by using the Apple-II undulator installed in BL1U in UVSOR*. The principle of F-LCS generation, EGS5 simulation which takes into account the distribution of the laser-electron interaction region and detailed measurement results will be presented at the conference. In addition, the application of F-LCS beam to Nuclear Resonance Fluorescence (NRF) experiment has been performed in UVSOR and the result will be discussed.
The CHIMERA (up to December 2022) and HEARTS (as of January 2023) projects aim to facilitate radiation effects testing of electronics components using heavy ion beams before deployment in harsh radiation environments such as space or high energy accelerators. The required (micro-) electronics reliability assurance testing conditions can be met by using 100 MeV/n - 5 GeV/n Pb ion beams extracted from CERN’s Proton Synchrotron (PS) which have a surface Linear Energy Transfer (LET) range of 10-40 MeV cm2/mg, >1 mm penetration depth in silicon and several cm FWHM beam size. This paper gathers the results from Monte Carlo simulations in FLUKA which were used to understand the transport of ions through the T08 transfer line in the PS East Area, focusing on key effects such as energy straggling, loss of transmission (e.g. through scattering and nuclear fragmentation) and beam size. These calculations served as input for machine development activities and allow us to characterize the radiation field at the testing location, in present and future experimental configurations. The simulation results are compared to instrumentation data obtained during an experimental campaign in November 2022. Potential future upgrades and developments are also discussed.?
A center for ion beam therapy and research is under development in Waco, TX with site preparation and construction underway. The center incorporates state-of-the-art accelerator technologies including the capability to perform ultra-high dose irradiation (FLASH) research with ions. The ion source and beam capture system will be comprised of an Electron-Cyclotron-Resonance (ECR) source coupled to a Radio-Frequency Quadrupole linac (RFQ) through a conventional Low-Energy Beam Transport (LEBT) section. An RFQ linac, which uses electrical RF focusing, has the noted advantage of capturing, auto-bunching and efficiently accelerating DC (constant current) ion beams directly from the source. A test stand is being designed and implemented using an existing CW, variable-frequency, ion RFQ with the capability to accelerate ions with a charge to mass ratio of 1/8 up to 1/2 to a maximum output energy of 0.4 MeV/nucleon. The ion RFQ, originally used as an injector to the HZB cyclotron, has been transferred to the Waco center for ion therapy and research. This paper documents source, the LEBT design and optimization to match to the RFQ capabilities. This multi-ion RFQ frontend will serve as the pre-accelerator and ion selector for injection into higher energy ion cyclotrons.
We present design of a normal conducting, high efficiency linac that would provide a CW beam of 1 MW electrons at 1 MeV energy for various environmental applications. When a flowing sheet of wastewater is exposed to such a beam, various radiation-induced reactants are generated that lead to water purification by decomposing the chemical and biological pollutants therein. Such a linac could treat about 20 million gallons of wastewater per day with an ample dose of 1 kGy. Our linac comprises of three optimized accelerating rf cavities operating at 476 MHz. A compact rf distribution manifold splits the rf power from a 1-MW klystron in the appropriate ratio and phase for each accelerating cavity. The beam capture efficiency is 82% and the rf-to-beam efficiency is 94.5%. The total length of our accelerator is 2 m, which includes the 30 keV gun, the buncher cavity, and the accelerating cavities. In this paper, we present the corresponding beam dynamics, the implementation of rf couplers and feeding manifold, and the steady-state thermal analysis.
The strong penetrating ability of relativestic electron beam with energy as high as several tens of MeV prohabits the possibility forming an image based on absorption by material. However, we demonstrate that it can make a shadowgraphy based on scattering. The demand for electron beam is analyzed and simulations are conducted, experiments carried out at the 120 MeV linear accelerator proves the feasiblity, and preliminary diagnosing magnetic field of a customized dipole shows this method has great reliability.
Tetrode-based amplifiers are well-established, and now have a revitalized supply chain after their demise looked imminent. High power tetrodes have been to show a greater power density and frequency range than solid state amplification, making them a robust choice for future accelerators and fusion devices. Recently, the MIT PSFC spearheaded an effort to source new pyrolytic graphite grids, to re-establish the supply chain for the Communication and Power Industries (CPI) high power 4CM2500KG tetrode. This allows Vacuum Electron Device (VED) amplification methods to be seriously considered for the next generation accelerators [2].
Development and experimental validation [1] of a 120 MHZ, 2.5 MW tetrode is described. The tetrode Final Power Amplifier (FPA) was excited with both a (1) tetrode-based Driver, and (2) Solid-State-Amplifier (SSA), utilizing a cavity power system, and protective circuitry developed at DTI. The experimental electrical schematic, setup, and measured results of the Driver and FPA output power, gain, bandwidth, efficiency, and frequency range are discussed and differences in performance between Driver- and SSA-excitation of the FPA are shown.
Superconducting curved magnets are able to reduce accelerator footprints by producing strong fields (>3T) for applications such as carbon ion therapy, however the effect of strongly curved magnetic multipoles and fringe fields on accelerator beam dynamics is not fully understood. This is especially important in compact synchrotrons, where fringe fields can significantly affect beam quality and long-term beam stability. To establish tolerances on these higher order harmonic errors, an electromagnetic model of a superconducting, strongly curved canted-cosine-theta (CCT) combined-function dipole is analysed. The CCT magnet is studied as a potential option for the main dipole of a 27m circumference carbon ion therapy synchrotron within the Next Ion Medical Machine Study (NIMMS) at CERN and the European project HITRIplus. Curved magnetic multipoles are modelled in MAD-X and PTC; results are presented and compared with particle tracking through the magnet’s 3D fieldmap in Zgoubi for additional investigation of non-linear effects. Preliminary assessment of the performance of the synchrotron subject to the tolerances on the harmonic errors is given with discussion for the suitability of the synchrotron for clinical applications.
The IBA ProteusOne (P1) system is suitable to treat ocular tumors and achieves efficient dose conformality using state-of-the-art pencil beam scanning. Nevertheless, with the limited cyclotron current of the P1 system, clinically relevant (> 15 Gy/min) dose rates can barely be achieved in eye tumors treatment cases with the baseline configuration of the system due to the significantly high energy degradation required (from 230 to 70 MeV). One way to improve this dose rate is to modify the degrader to use a material causing a smaller emittance increase. In this work, we compare the performances of the P1 system in the context of eye tumors treatment when using Beryllium degrader on the one hand and Diamond degrader on the other. For the latter case, the optics is modified to reduce the losses along the beamline and ultimately increase the dose rate of the system while maintaining a symmetrical spot at the isocenter. Using Beam Delivery SIMulation, the dosimetric properties of the system are assessed and compared for the two configurations, and the differences in dose rate are quantified and discussed in detail.
Additive Machining (AM) technology is already used in many manufacturing domains and provides many benefits such as design freedom, cooling, and performance improvements as well as significant manufacturing time reduction. AM is also being considered for the manufacture of a Radio Frequency Quadrupole, where an important unknown is the voltage holding capability of AM surfaces. To address this question a series of high electrical field tests was performed on additively manufactured (AM) pure copper electrodes using the CERN pulsed dc high-voltage system. The tests were carried out with different test surface conditions such as “rough”, as built by AM, post-processed and machined. During each test, an ultra-high vacuum was maintained, and the breakdown rate monitored by changing the electric field level and pulse structure. The initial results provide the first reference values for AM built pure copper electrodes performance under vacuum arc breakdown test. According to test results, AM process and material powder characterisation as well as post-processing will be improved in preparation for RF power and beam tests on a full RFQ prototype.
Modern hadron-therapy accelerators have to provide high intensity beams for innovative dose-delivery modalities such as FLASH, pencil beams for 3D scanning, as well as multiple ions with radio-biological complementarity. They need to be compact, cheap and have a reduced energy footprint. At the same time, they need to be reliable, safe and simple to operate. Cyclotrons and compact synchrotrons are nowadays the standard for proton therapy. For heavier ions such as carbon, synchrotrons remain the most viable option, while alternative solutions based on linacs, FFAs or cyclotrons are being proposed. In this context, the European project HITRIplus studies the feasibility of an innovative super-conducting magnets synchrotron for carbon ions, with state-of-the-art multi-turn injection from a specially designed linac and advanced extraction modalities. A compact synchrotron optimized for helium ions, making use of proven normal-conducting technology, is also being designed.
Neutron scattering experiments have undergone significant technological development through large area detectors with concurrent enhancements in neutron transport and electronic functionality. Data collected for neutron events include detector pixel location in 3D, time and associated metadata, such as, sample orientation, neutron wavelength, and environmental conditions. RadiaSoft and Oak Ridge National Laboratory personnel are considering single-crystal diffraction data from the TOPAZ instrument. We are leveraging a new method for rapid, interactive analysis of neutron data using NVIDIA’s IndeX 3D volumetric visualization framework. We have implemented machine learning techniques to automatically identify Bragg peaks and separate them from diffuse backgrounds and analyze the crystalline lattice parameters for further analysis. The implementation of automatic peak identification into IndeX allows scientists to visualize and analyze data in real-time. Our methods include a robust comparison with current analysis techniques which show improvement in a variety of aspects. These improvements will be incorporated into IndeX for visualization to allow scientists an interactive tool for crystal analysis.
The Italian Minister for University and Research has recently funded a large program for an Innovative Research infrastructure on applied Superconductivity in Italy. Based on the LASA lab in Milan it is a partnership among: INFN (leader, participating with 4 labs: Frascati, Genoa, Milan, Salerno); CNR (SPIN institute in Genoa, Naples and Salerno); five Universities: Genoa, Milan, Naples, Salento and Salerno. The infrastructure will expand and coordinate existing infrastructures, with new state of the art instruments for: 1) characterization of new superconducting wires/tapes and cables at high field and large current; 2) for implementing the construction of innovative small scale superconducting magnets or accelerator, beam lines and detectors; 3) developing advanced instrumentation and measurements for magnets and accelerators; 4) for testing large superconducting magnets and high power transmission superconducting lines; 5) for characterization of new superconducting materials and magnetism in matter. IRIS will be a key feature for participation to future projects requiring advanced superconducting technology, like FCC or the Mun-Collider, and also for developing societal applications, especially in the energy domain and the medical sector, of technologies pursued for high-energy accelerators. The paper will illustrate the IRIS project, its 3-year development and the idea to make it an open-access infrastructure.
Jacobs remote leak sealing service seals holes of up to 10mm effective diameter within inaccessible pipes where access is either dangerous, impractical, or not cost effective. Many complex research facilities such as particle accelerators contain large amounts of remote pipework in inaccessible areas. This inaccessibility can be caused by being:
• Buried post construction in concrete
• Situated in high hazard environments (radiation, magnetic flux, high temperature)
• In physically challenging areas (height or confined space)
Cooling water systems associated with these facilities often suffer from minor leaks in inaccessible areas. Such leaks can interfere with vacuums, electronics or reduce cooling efficiency. Replacement of these pipes may result in extensive programme downtime and increased financial costs. The poster describes a unique technique to permanently repair such leaks remotely by injecting a water-based sealant into the pipe. The sealants used are compatible with the vast majority of pipework, valves, and instrumentation. The internals of the pipe are not coated in any way; hence the heat transfer properties of the cooling system are unaffected. The poster describes how this technology has been successfully applied to cooling systems within research facilities, such as at ISIS, Rutherford Appleton Laboratories (UK). A variety of components associated with the LINAC at Los Alamos Neutron Science Centre (USA) were sealed during a demonstration of the technique.
Copper and copper alloys are widely used in the Nuclear Fusion field for their outstanding characteristics, especially in terms of thermal and electrical conductivities. CuCrZr is peculiarly suitable and well-known in High Energy applications because it combines good conductivity and good mechanical properties. Moreover, the material properties can be tuned with thermal treatments to fit the application requirements even more. Additive manufacturing is then a revolutionizing process that permits the creation of geometrically optimized components. This near-net-shape process allows to produce seamless parts reducing material waste and saving time. We investigate the application of the Laser Powder Bed Fusion technology to produce the acceleration grids of a Neutral Beam Injector.
In this work, the authors analyzed different CuCrZr powders and investigated the material properties obtained after the printing parameters optimization, in as-built conditions and after several heat treatments. The high density and high mechanical and thermal properties allowed us to proceed with the creation of the first prototypes of the acceleration components.
Niobium is particularly appreciated for its superconductive properties. One of the main applications of this metal in Nuclear Physics is the production of superconducting radiofrequency (SRF) cavities for particle accelerators. Additive Manufacturing (AM) gives the chance to fabricate objects with very complex shapes; also, high melting temperature and hard-to-machine materials can be easily processed. However, AM is not free from challenges, and the creation of devices such as the SRF cavities is not trivial. In this work, the characterization of pure niobium produced by Laser Powder Bed Fusion (LPBF) and a fine-tuning of the printing parameters have been carried out. Much emphasis was put on the development of innovative contactless supporting structures for improving the quality of downward-facing surfaces with very small inclination angles. A relative density higher than 99.8% was achieved and the efficiency of such innovative supports was demonstrated, as they made the fabrication of seamless SRF cavities possible. Smoothing surface treatments and performance tests on AMed cavities were also performed.
LhARA*, the ‘Laser-hybrid Accelerator for Radiobiological Applications’, will be a novel, uniquely flexible, facility dedicated to the study of radiobiology. LhARA will use a high-power pulsed laser to generate a short burst of protons or light ions. These will be captured using strong-focusing electron-plasma (Gabor) lenses. Acceleration using a fixed-field alternating-gradient accelerator will deliver proton beams with energies up to 127 MeV and ion beams, such as C^6+, with energies up to 33.4 MeV/nucleon. The laser-hybrid source allows high instantaneous dose rates of up to 10^9 Gy/s to be delivered in short (10–40 ns) pulses.
The laser-hybrid approach will allow the exploration of the vast “terra incognita” of the mechanisms by which the biological response to radiation is modulated by the beam’s characteristics. The technologies to be demonstrated in LhARA have the potential to allow particle-beam therapy to be delivered in completely new regimens, providing a variety of ion species in a range of spatial configurations and exploiting ultra-high dose rates**.
This contribution describes the status of the LhARA project in the context of the Ion Therapy Research Facility***.
Longitudinal phase space (LPS), referring as the current profile and the energy spread, is among the most important parameters to be known in many accelerators that require high quality electron beams, such as an Ultrafast Electron Diffraction (UED) or a Free Electron Laser (FEL). For a UED or a long wavelength FEL, the beam energy is usually on the level of several MeV or a few tens MeV. In this situation, the beam measurement has to be done at a short distance to avoid space charge induced quality deterioration. This paper will present a systematical design of an LPS measurement system consisting mainly of a rectangular type RF deflector and a magnetic bend. The system is particularly developed for low energy electron beams, so the deflector structure and the optical lattice are carefully optimized. Particle tracking of the LPS measurement system is performed with the PARMELA code. It is shown that the time resolution and energy spread resolution of the designed system are 500 fs and 0.05%, respectively. Enhancing the time resolution to less than 100 fs is also discussed.
Various initiatives in Europe have bene launched to study superconducting magnets for a rotatable gantry suitable for delivery up to 440 MeV/A carbon ions for hadron therapy. One initiative is led by INFN inside an agreement with CERN, CNAO and MedAustron aiming at designing and manufacturing a strongly curved costheta dipole (Rbending = 1.6 m) rated for 4 T central field and a ramp rate of 0.15-0.4 T/s. Here we explore the suitability of dipole technology derived from HEP collider (use of Nb-Ti Rutherford cable, classical shell type for the coils, use of collar/yoke for force containment, etc…) for a rotatable gantry that poses severe conditions on the thermal design (conduction cooled coils). A second one, is in the frame of the European program H2020-HITRIplus-WP8, aimed at exploring the feasibility of using the novel Canted Cosine Theta (CCT) concept to produce a superconducting dipole with similar characteristics. The scope is to design and built one or two prototypes with Nb-Ti rope, to see if this route could be a viable alternative. Finally in the European collaboration H2020-I.FAST-WP8 we are exploring both CCT in combined function design (dipole + quadrupole, in Nb-Ti) and the use of HTS (REBCO tapes) with CCT dipole layout, pursuing the design manufacture of a small prototypes with European Industry. If HTS will be found successful, it will be a great benefit for the cryogenic design of the magnet system.
In 2021 there were 36 particle therapy facilities under construction world wide of which 5 are planned to be able to deliver Carbon. One in Caen France and four in Asia. In May 2022 Mayo Clinic Florida (MCF) broke ground to build a Proton and Carbon Ion treatment center in Jacksonville Florida. The MCF facility is comprised of a hybrid synchrotron 56.8 m in circumference with twelve dipoles and two injectors. One 7 MeV AccSys proton injector and a 4 MeV SHI Carbon injector which is also capable to deliver Helium. Beam is delivered using a feedback controlled one third resonant extraction using the RF Knock Out method and includes multi energy extraction. There will be initially three treatment rooms: a Fixed Beam room with one horizontal beam line that delivers up to 430 MeV/u Carbon as well as all other ions extracted from the hybrid synchrotron and two treatment rooms each equipped with a 360 proton gantry to deliver 70 to 230 MeV protons to isocenter. Provision was made in control system design to deliver to five treatment rooms which could include two Carbon gantries in the future. Accelerator and dosimetry control system advancements include more stored charge, advanced imaging, real time adaptive treatments, and high intensity delivery capabilities with clinically optimized safety systems. The facility was shielded to allow the system to deliver with maximum efficiency.
This paper reports the results of the first measurements of the differential cross section of the 80Se(γ,n)79Se reaction with a linearly polarized gamma-ray (γ-ray) beam. The cross section was measured at three incident γ-ray beam energies: 15.6, 15.8, and 16.0 MeV, with a beam energy spread of 3.0% full width at half-maximum (FWHM). The differential cross section for the excitation spectrum in 79Se was measured at two scattering angles in the plane of the beam polarization: θ=90∘ and 135∘, and at one angle in the plane perpendicular to the plane of polarization: θ=90∘. The total photoneutron cross sections determined from these data are between 0.8 and 1.3 standard deviations smaller than previously published results. The excitation spectra measured in this work were fit with a Hauser-Feshbach model. Better fits to the data were obtained with a constant-temperature formulation of the nuclear level density (NLD) than with a Fermi-gas NLD model. The parameters for the constant-temperature NLD model obtained in this work are consistent with those obtained for medium-mass nuclei in previous studies.
Measurements of the extracted beam current (BC) for a Clinical Hitachi carbon therapy synchrotron and a Hitachi compact proton therapy synchrotron are reported for a nominal extracted beam current (BC0) of $\approx$ 10 $\frac{MU}{sec}$ and a sample rate of 5 usec (Carbon) and 8 usec (proton). A noise power spectrum analysis identifies the source of variation to be beam or power supply related. The rise time in the BC has been modelled and estimates of its effect on beam delivery time simulations. Two quantities minMoveT and minMoveMU are defined as the time and dose delivered between spots. Increasing scanning magnet (SCM) speeds of the last decade have implications for these quantities and a model is proposed for the variation in BC from BC0 during the delivery of the spill and compared to measurements. The impact of the variation in BC from BC0 is shown to cause potentially significant dosimetric uncertainties in treatment delivery for modern particle therapy accelerators using fast SCM if plans are not simply beam current moderated or robustly optimized. The variation in beam current is shown to be inconsequential for medical physics quality assurance and commissioning measurements using properly biased ion chambers. Analogous measurements were previously reported for the NIRS/QST synchrotron (1). Comparable results are found for the Hitachi synchrotron when using only the moderated beam current approach instead of the robust optimization approach.
The Beam Position Monitor (BPM) is one of the crucial components for Sirius, and they were manufactured in the Materials Group – CNPEM, through the vacuum brazing process. The mechanical strength characterization of the brazed interface is extremely important to protect the storage ring from unwanted leaks in case of breakage of these sensors. The objective of this work is to report the tests used to determine the maximum load resisted by the brazed sensor before leaking. During the tests, the sensors were subjected to load in axial and perpendicular directions, so that brazing was tested under tension and shear loads. During the tests, the sensors were subjected to a vacuum atmosphere, attached to a leak detector and a continuous flow of He gas until leakage was detected. For all cases in axial load, a plastic deformation at the tip of the electrode is visually noticed and brittle fracture in the ceramic was observed. The mechanical strength of brazing interface was superior to that of the ceramic itself. The samples submitted to the brazing shear test showed continuous bending of the electrode until the end of course of the machine, with no leaks. Summarizing, the values of the tensile tests are in the same order of magnitude as data in the literature, although here we also considered the tightness under vacuum, which was maintained until the collapse of the test specimens.
Commercial Nuclear Reactors have been licensed for construction and operation by the US Nuclear Regulatory Commission based on ensuring that criticality accidents and accidental releases of radioactive isotopes are acceptably unlikely. The process to get these licenses is long and expensive, involving extensive calculations and demonstrations, with explicit requirements on all reactor components that cannot be changed for the several decades that the reactor operates. The process can be replaced by 1) using accelerator-driven subcritical reactors that never contain a critical mass and 2) continuously removing volatile fission products from the molten salt reactors so that any accidental releases are insignificant. Mu*STAR Nuclear Power plants, composed of upgradable modular accelerators and reactors, can then be continuously improved using Deming’s principles of Total Quality Management.
The fast cyclic synchrotron (IS) using the principle of induced acceleration was demonstrated at KEK in 2013 and is now being studied for application to a compact hadron therapy driver (ESCORT) capable of energy swept beam extraction. The ESCORT has the feature of avoiding instability caused by synchro-beta coupling by accelerating ions using a true variable amplitude pulse voltage that is extracted from the time varying DC voltage, rather than an equivalent variable voltage pulse system using a pulse density modulation method as used in the existing IS (KEK-DA). Furthermore, the accelerator cell driver is designed to be more compact by generating pulses at several MHz, whereas in the past, the upper frequency limit of the accelerator cell driver was set at about 1 MHz**, and multiple accelerator cells were used adapted for higher orbital frequencies. These innovations are made possible by the latest advances in power device and power electronics technology. This paper describes the development of an inductive acceleration cell driver for application to ESCORT.
During the Long Shutdown 2 (LS2) at CERN, the new Linac4 (L4) accelerator has been
successfully connected to the PS Booster (PSB) to inject 160 MeV H− beam into the 4
superposed PSB rings. The horizontal displacement of the circulating beam during injection
relies on 4 pulsed dipole magnets. During the initial run of the new magnet system, non-
conformities have been observed. These could be traced back mainly to early fatigue effects,
some of which were in brazed joints on the coil cooling circuit. An extensive program has been
launched to improve the brazing technology for the spare coil manufacturing. This effort has
been combined with numerical computations as well as destructive and non-destructive
testing of brazed joints, allowing to identify critical stress domains resulting in fatigue sensitive
areas. This paper describes the applied methodology and implements measures to increase
the robustness of the magnet coils. The achieved improvements have been validated by
testing based on an instrumented coil, allowing to correlate stress-strain measurements with
results from the structural and transient numerical computation.
An R&D platform for electron FLASH radiation therapy and radiation biology is being prepared at the Photo Injector Test facility at DESY in Zeuthen (FLASHlab@PITZ). This platform is based on the unique beam parameters available at PITZ: ps scale electron bunches of up to 22 MeV with up to 5 nC bunch charge at MHz bunch repetition rate in bunch trains of up to 1 ms in length repeating at 1 to 10 Hz. These beams allow to study an uniquely wide parameter range for radiation biology and FLASH radiation therapy, which is a new treatment modality against cancer.
A startup beamline has been installed to allow dosimetry studies and irradiation experiments on chemical, biochemical and biological samples and cell cultures after a 60-degree dispersive arm. The measured dose and dose rates under different beam conditions and first experimental results will be reported in this paper.
In addition, a dedicated beamline for FLASHlab@PITZ has been designed for better control of the electron beams. This includes a dogleg to translate the beam and a 2D kicker system to scan the tiny beam focused by quadrupoles across the samples within less than 1 ms. Simulation studies will be presented to demonstrate the extremely flexible dose parameters with various irradiation options for FLASH radiation therapy and radiation biology studies.
In an Ultrafast Electron Diffraction (UED), high-brightness ultrafast electron beams are indispensable to capture critical ultrafast events on an atomic/molecular scale. For space-charge effects (SCE) dominated electron beams, the beam emittance increases significantly during propagation. Understanding the beam emittance evolution during its passage is critical for further improving the UED performance. To diagnose the in situ emittance of the beam at several certain positions, we use a multi-slit device with a low sampling rate to eliminate the SCE influence. Due to the fabrication technology limitation, only a few slits can be made, leading to a severe undersampling rate, creating challenges in reconstructing the original beam information. This paper introduces a method to reproduce beam from severely under-sampled data.
To achieve the vacuum quality required for the operation of particle accelerators, the surface of the vacuum vessels must be clean and free of hydrocarbons. This is usually done by wet chemistry processes, e.g. degreasing chemical baths that, in case of radioactive vessels, must be disposed accordingly. An alternative way to perform the removal of hydrocarbons exploits the oxygen plasma produced by a downstream RF plasma source. This technique offers the possibility of operating in-situ, which is an advantageous option in the case of voluminous and/or fragile components and a more sustainable alternative to large volume disposable baths. In this work, we test a commercial plasma source in a dedicated vacuum system equipped with a residual gas analyser (RGA) and quartz crystal microbalances (QCMs). The evolution of the hydrocarbon RGA peaks and the removal rates of amorphous carbon (a-C) thin films deposited on the QCMs to mimic contamination are studied. The plasma cleaning efficiency is evaluated as a function of various operational parameters and for chambers of different geometries and volumes. The studies are complemented by finite element simulations and by X-ray photoelectron spectroscopy (XPS) surface analysis. We present the results of the plasma cleaning process applied to the real case of a hydrocarbons-contaminated large vacuum vessel. The evaluation of the vessel cleanliness, based on CERN's outgassing acceptance criteria, is compared to the simulations results.
Recently, Metal Additive Manufacturing technology enables the possibility to realize cooling systems in accelerator components during the manufacturing process phase, obtaining extremely high density, high thermal, and mechanical properties in metals. In the Neutral Beam Injection for the Divertor Tokamak Test facility, the beam acceleration components are submitted to extremely high-power loads. A tailored cooling channel shape for the acceleration grids is proposed and tested. However, the roughness issue in MAM manufacturing is a problem that can strongly affect the pressure drop in long and small-section channels. CFD is a valid tool that, if properly calibrated, predicts the pressure drop and efficiency of the cooling system. In this work, different single-channel samples have been manufactured via MAM and they have been tested to characterize the pressure drop behaviour. The single-channel samples have been internally smoothed via a chemical process to reduce the pressure drop and tested again. CFD models, using Ansys Fluent software, have been calibrated to properly predict the pressure drop of the single-channel samples. The CFD models have been implemented to optimize the channel design of the Extraction Grid cooling system. The optimized shape of the EG channels has been adopted to produce different scaled AM prototypes and tested with a thermal power map, which is similar to the nominal one.
Linear accelerators for medical applications present the possibility to reduce costs compared to cyclotrons or synchrotrons while offering higher beam stability and flexibility. In the framework of NIMMS, the Next Ion Medical Machine Study, the design of a linear accelerator for carbon ion therapy has been completed at CERN. The pre-injector is composed of a fully stripped ${}^{12}\mathrm{C}^{6+}$ carbon ion source and a 750$\,$MHz Radio Frequency Quadrupole (RFQ) accelerating the beam to 5$\,$MeV/u. The Carbon RFQ is based on a compact, successfully commissioned 750$\,$MHz RFQ presently operating for the commercial proton therapy Linac facility LIGHT. The RFQ is divided in two independent RF cavities of 2$\,$m length. The first RFQ cavity, accelerating the ions to 2.5$\,$MeV/u, is currently being built by CIEMAT and its delivery to CERN is planned for 2023. It will be commissioned initially with a proton and then a helium beam. Beam characterization is crucial to validate the transmission to the next sections of the Linac. In this paper, we describe the diagnostic test bench and highlight the necessary measurements for the acceptance of the second RFQ cavity.
Hadron therapy with light ion beams is gaining momentum due to the possibility to treat tumors that are resistant to chemotherapy and radiotherapy. In addition, hadron therapy is the preferred choice of treatment for tumors that are inoperable due to their vicinity to vital organs.
The main advantages of charge particle therapy compared to conventional X-ray radiotherapy are related to the possibility to target the tumor site with higher precision, both longitudinally and radially.
The high precision of the dose deposition requires also a high accuracy that is presently hindered by limited dose monitoring capabilities.
One of the approaches towards improving dose monitoring involves the use of radioactive ion beams that expose the dose distribution by the decay radiation after stopping in the tissue.
Another advantage of using specific short-lived isotopes, such as Li-8 and He-8, is the beta delayed alpha emission that is expected to increase even further the dose delivery at the tumor. He-8 has an additional feature of a single gamma emission in 84% of the decays.
There are different production schemes for radioactive ion beams based on either isotope separation on-line (ISOL), or on In-flight production and separation, or combinations of the two. The main advantages and disadvantages of the production in various scenarios will be discussed in detail. A kinematic advantage originating from the In-flight production and separation of neutron-rich beams will be presented.
Department of Accelerator Science at Korea University, Sejong was established in 2014 to promote accelerator science research and train accelerator scientists and engineers for the growth of domestic accelerator projects in Korea. In addition, Accelerator Research Center and Small Accelerator Application Core Facility Research Center under the department hood were also organized to foster in-depth research on accelerators. Since 2017, several small accelerators have been introduced on our campus. These accelerators include a 14GHz ECR Ion Source for heavy ion accelerator research, a 7 MeV microtron with an undulator for terahertz radiation application research, a 150 keV proton accelerator for ion implantation applications, a 50 MeV microtron for a variety of low energy electron applications, and 60 MeV electron linac with an RF photoinjector gun for electron injector linac research. This work presents the results of recent progress in construction and commissioning of these accelerators, as well as educational programs for graduate students in our own department and users in various fields.
Superconducting radio frequency (SRF) cavities performances strongly depend on the surface preparation. Conventional protocol of SRF surface preparation includes electropolishing (EP) as the main treatment achieving low roughness, clean surface, both for Nb and Cu substrates. Harsh and corrosive solutions are typically used: concentrated HF and H2SO4 acids for Nb, and H3PO4 with Butanol mixtures for Cu. The application of PEP can be not only used for conventional elliptical resonators, but also for normal conducting cavities and other components of accelerators where polishing is normally applied, such as couplers. PEP is an evolution of EP with a list of advantages. Only diluted salt solutions are used, unlike EP. PEP can in principle substitute, or eliminate, intermediate steps, like mechanical and/or (electro) chemical polishing, thanks to superior removing rate in the field (up to 3.5 μm/min of Nb, and 10 μm/min of Cu). A ≤100 nm roughness achieved both for Nb and Cu substrates. A higher smoothing/polishing effect respect to an EP was obtained. PEP application onto the SRF substrates is shown. Defects evaluation of the substrate has been analysed.
LhARA, the Laser-hybrid Accelerator for Radiobiological Applications, is a proposed novel facility capable of delivering high intensity beams of protons and ions that will enable radiobiological research to be carried out in completely new regimes. A two-stage facility, the first stage utilizes laser-target acceleration to produce proton bunches of energies up to 15 MeV. A series of Gabor plasma lenses will efficiently capture the beam which will be delivered to an in-vitro end station. The second stage will accelerate protons in a fixed-field alternating-gradient ring up to 127 MeV, and ions up to 33.4 MeV/nucleon. The beams will subsequently be deliverable to either an in-vivo end station or a second in-vitro end station. The technologies demonstrated in LhARA have the potential to underpin the future of hadron therapy accelerators and will be capable of delivering a wide variety of time structures and spatial configurations at instantaneous dose rates up to and significantly beyond the ultra-high dose rate FLASH regime. We present here recent progress and the current status of the LhARA accelerator as we work towards a full conceptual design.
TURBO – Technology for Ultra Rapid Beam Operation – is a novel beam delivery system (BDS) in development at the University of Melbourne. The BDS determines several aspects of treatment delivery, where a bottleneck is the deadtime associated with beam energy variation. Beamlines at treatment facilities have a ±1% momentum acceptance range, requiring all the magnetic fields to adjust to deliver beams of different energies at multiple depths along the tumour volume. A BDS using Fixed Field Alternating Gradient optics could reduce the energy layer switching time by enabling the transport of a large range of beam energies within the same fixed fields. We present recent progress and ongoing developments with TURBO, a proof-of-concept demonstrator adapted for low energy protons. Characterisation measurements were performed to determine realistic parameters for beam transport and particle tracking modelling. Initial simulation and design studies are shown for an energy degrader, prototype magnets constructed using 3D-printed holders and considerations of canted-cosine-theta magnets for a scaled-up BDS. Future plans further explore the clinical feasibility of TURBO for charged particle therapy.
The HZB cyclotron continues to provide protons for eye tumor treatment in collaboration with the Charité – Universitätsmedizin Berlin after 24 years and more than 4400 patients so far. With the perspective of broadening its research capabilities in the field of radiation therapy, intensive effort has been dedicated towards proton FLASH irradiation, which requires ultra-high dose rates or beam intensities.
By combining a fast and reliable switch-off mechanism, accurate dosimetry, and a double-scattering beam nozzle with a static 3D-printed range modulator, HZB is now able to deliver a dose rate above 150 Gy/s within a flat circular irradiation field of 18 mm diameter and a 27 mm spread-out Bragg peak with a distal fall-off of 1 mm in water. The reproducibility of the delivered dose meets the clinical acceptance criteria for a total irradiation time as low as 2.5 ms.
The first experiments with this setup were used on fibroblastic and sarcoma organoids. By adapting the design to a 35 mm lateral field and using optimal accelerator tuning to increase beam transmission, similar or even higher dose rates are expected, satisfying thus the FLASH conditions for eye-tumor treatment with protons.
A 4th generation storage ring based light source is being developed in Korea since 2021. The storage ring based on the multi-bend achromat lattice concept may be able to surpass the brightness and coherence. It features about 800 m circumference with 28 cells, 4 GeV e-beam energy. The storage ring girders consist of 140 girders and each cell of girder is composed of five pieces. We have designed prototype girder using new schemes to achieve long-term mechanical stability, vibration suppression and precision adjusting system. Each girder have vertical, transverse and longitudinal adjusting mechanism with ball screw jack. The alignment error between girders should be less than 50 μm. In this report, the conceptual design of the 4GSR girder and support systems are reported.
Additive manufacturing ("AM") has become a powerful tool for rapid prototyping and manufacturing of complex geometries. A 433 MHz IH-DTL cavity has been constructed to act as a proof of concept for direct additive manufacturing of linac components. In this case, the internal drift tube structure has been produced from 1.4404 stainless steel, as well as pure copper using AM. The Prototype cavity, as well as stainless steel AM parts have been copper plated. We present results from low level rf measurements of the cavity with and without copper plating, as well as the status of preparations for high power rf tests with a 30 kW pulsed power amplifier.
The availability of modern accelerators has become a key performance indicator. This is especially the case for accelerator-driven-systems (ADS), such as MYRRHA, which need to deliver beam with very few interruptions longer than a few seconds over a period of several months.
Quantification of such beam interruptions at other accelerators such as LINAC4 at CERN and SNS at ORNL show that their fault count would need to be reduced by more than two orders of magnitude to comply with ADS requirements. Redundancy of systems is one viable strategy to achieve this. For MYRRHA, the use of redundant low-energy injectors, modular-redundant RF power amplifiers and serial-redundant RF cavities is presently proposed. The resulting gain in the accelerator availability using these redundant systems has been quantified by simulating the operation of the MYRRHA accelerator with AvailSim4, an availability-modelling tool developed at CERN. The study results highlight the importance to focus on optimizing system design and repair strategies to maximize the effectiveness of such redundancy schemes as well as the value of powerful availability simulation tools.
Particle accelerators are complex and energy-intensive facilities that require extensive and intertwined connections with the public electrical grid. Furthermore, accelerator facilities are well known for their low power demand flexibility, which depends only on experimental operations, and it must be accommodated independently from the grid. So, it is necessary to develop and test new energy solutions for an energy-efficient and stable operation of particle accelerators. However, validating novel solutions at a research facility is difficult, because technical problems can disrupt the operation and research process.
In the project ACCESS (ACCelerator Energy System Stability), an energy system-informed digital twin of the Karlsruhe Research Accelerator (KARA) will be realized at the Energy Lab 2.0 in a real-time simulation environment. The goal is to validate energy solutions that can be applied to accelerators in a safe and flexible environment (simulation) without interfering with experiments performed at KARA, while retaining high accuracy (digital twinning).
This contribution will provide a look at the first results of the project ACCESS and will highlight the need for fast measurement systems in particle accelerators.
Funding: The authors acknowledge funding by the BMBF ErUM-Pro project ACCESS (FKZ 05K22CKA).
Researchers at the National Synchrotron Radiation Re-search Center should use respiratory protective equip-ment to prevent respiratory damage caused by gases, steam, solvents, chemicals, materials containing toxic substances, and oxygen-deficient environments. Those working with organic matter and certain chemical sub-stances and those exposed to occupation dust should use respiratory protective gear to ensure their health. This study conducted qualitative and quantitative fit tests for various mask brands and sizes, namely 3M-9042, N95-9211, P95-8576, and 3M-6200 masks. The gear worn by all 18 participants in the qualitative fit test passed. By contrast, the gear worn by 12 of the 15 participants in the quantitative test passed; the failure of the remaining gear was due to differences in face shape. The N95-9211 mask can be used in three-piece protective gear because it exhibited a tight fit. Additionally, the 3M-6200 negative-pressure half-face mask exhibited the most satisfactory fit and can be used in protective gear.
The aims of this work are to measure the energy consumption performance of compressed air systems, determine the weak points, implement the economic assessments and execute energy saving improvements in NSRRC. The compressed air discharge pressure is regulated in 6.0±0.5 kg/cm2. The specific energy requirement (SER) of those compressors is 7.74 ~ 20.05 kW/m3/min. Based on the performance results, we have to make a decision to repair or replace the inefficient compressors. Next, we decided three phases implements, stop leaks in phase I, replace compressor with VFD and heat-regeneration desiccant drier in phase II, connect TLS and TPS compressed air pipelines in phase III. Finally, we got great energy saving of 543,754 kWh/yr and 4.3 years pay-back time in capital investment.
The upgrade program for AREAL accelerator includes beam energy increase from 5 MeV up to 50 MeV. For this purpose, two 43 cells, and 1.6 m long, S-band accelerating structures are foreseen. The design and fabrication of cells are already carried out in CANDLE. For effective acceleration the tuning of phase advance and frequency of the structure is necessary. The precise geometrical dimension measurements to pick the proper sequence of cells are necessary to minimize accelerator structure tuning routine after brazing.
In this paper, a method for cell geometry precise measurements is presented. The method based on TM resonance frequencies measurement for radius and length variation evaluation in µm range. The µm variation driving resonance frequency shift by few tens’ kHz, which is measurable by conventional VNA. The theoretical basis and experimental results for AREAL 50 MeV upgrade accelerator structures cells are presented.
FLASH Radiotherapy is a revolutionary new technique in the cancer cure. Several pre-clinical studies have demonstrated that treatment with electron radiation delivered with mean dose rates above 100Gy/s, an ultra-high instantaneous dose rate > 106Gy/s, and total irradiation time < 100ms, significantly decreases the toxicity in the healthy tissue while keeping the same efficacy in cancer treatment.
Although recent studies shed some light on the biological mechanisms and on the effects of FLASH electron beams on tissues and organs of small animals, more research investigation is necessary before the FLASH technique can be translated into clinical applications. Researchers also aim to explore the radio-therapeutic effects of high-dose beams delivered at Very High Electron Energy (VHEE), in the range 50-250 MeV, suitable for treating deep-seated tumors.
We describe the project SAFEST, carried out at La Sapienza University in collaboration with INFN for the realization of a compact C-band electron linac VHEE at the energy of 60-150 MeV, able to deliver the high current up to 200mA and the very high dose rates required by the FLASH regime, and suitable for a hospital environment.
BDSIM is a Monte Carlo simulation program for start-to-end particle tracking through 3D models of particles accelerators. Based on the Geant4 toolkit, BDSIM provides a holistic approach to accelerator modelling by using Geant4’s particle-matter interaction physics with dedicated accelerator tracking routines for beam vacuum transport. Subsequently, the ability to model the hits, losses, & energy deposition throughout a machine makes BDSIM highly suited for modelling medical accelerators where beam transmission, target dosimetry, and shielding requirements often need to be considered simultaneously. This has already been demonstrated by BDSIM’s adoption in modelling proton therapy beam lines. The growing recognition of ions as a treatment modality that offers a potentially significant improvement in relative biological effectiveness is driving an increase in the number of planned carbon ion therapy centres. The technology to deliver ion beams, however, is prohibitively expensive and remains a challenging research topic. Here, we show the first demonstrations of therapeutic ion tracking in BDSIM in an example model developed for showcasing BDSIM’s medical accelerators simulation capabilities.
NHa and IBA are collaborating to develop a new cyclotron dedicated to hadron therapy. The manufacturing of the magnet is in an advanced stage. In parallel, extensive studies are carried out to develop an accurate field mapping system. It is required to perform the high precision magnetic field measurement (75 ppm) that will provide the final isochronous field after the well-known shimming procedure.
Due to the wide pole diameter (1.8 m), the large magnetic field amplitude and the numerous shims, a technology based solely on Hall probe would request too much time of operation and a mismatch to perform a full mapping of the magnetic field in what is considered a reasonable time.
For this reason, a new system based on a dual search coil is under design. The two coil geometries will enable to match the different gradient regimes and granularity requirements present over the pole surfaces. In addition to the moving coils, an NMR probe will be included to provide the reference absolute measurement together with a Hall probe to confirm the data recorded through the search coils.
In this report, the status of the new mechanical system providing the probe motion will be presented but the article focuses on the modelling of the search coil response as a function of its geometrical form factor. The aim is to evaluate and control the potential errors induced by the measurement of such averaged flux over the coil inner volume in case of very inhomogeneous fields.
The Slotted Waveguide Elliptical (SWELL) cavity is an elliptical accelerating cavity with an innovative design, proposed by CERN and developed in the scope of the FCC-ee study. The SWELL design is composed of four quadrants, separated by radial slots in order to improve higher order modes (HOM) transverse damping, while minimizing impact on the longitudinal accelerating mode. The quadrants for the SWELL cavity prototype were manufactured in CERN main mechanical workshop from the bulk Oxygen-Free Electronic (OFE) copper rods. Specific fabrication strategy and R&D have been implemented, to optimise fabrication yield with respect to RF performance. The fabrication approach was created based on the experience gained with Radio Frequency Quadrupole (RFQ) production. The introduced process relay on thermal treatment cycle and close synergy between high precision milling operations and metrological CMM measurements. In parallel with this fabrication, CERN lunches studies for optimization of machining parameters with regard to radio frequency performance.
Radiation resistance of materials is an important area of research, relevant to nuclear reactor technology. Various challenges are associated with this research; one of which is the selection of radiation resistant material for the plasma facing wall of the reactor due to its harsh operating environment. Recent studies reveal that WC has the potential to be developed as radiation resistant material.* To explore this possibility, WC thin films synthesized using RF Magnetron sputtering at a substrate temperature of 700 K have been irradiated with 100 MeV Ag8+ ions from 15 MV Pelletron accelerator at three different fluence. Glancing angle X-ray diffraction (GAXRD), Atomic Force Microscopy (AFM), Field Emission Scanning Electron Microscopy (FE-SEM) and Raman spectroscopy of the films have been performed to determine structural and morphological changes due to ion irradiation. GAXRD of the pristine and irradiated thin films reveal the reduction in grain size and loss of crystallinity with ion irradiation. FESEM images of the thin films showed no significant change in surface morphology and the thin film continuity is maintained even after ion irradiation of higher fluence. Raman spectroscopy of the WC thin films shows the decrease in intensity of peaks corresponding to Raman shift resulting in the decrease in polycrystalline nature of WC upon ion irradiation. Further, thermal spike calculations are also done to estimate the evolution of lattice temperature with ion irradiation.
In ion beam therapy most cancer patients are treated using the raster-scanning dose delivery method of heavy ion pencil beams, with the penetration depth determined by the ion beam energy. The beams are provided by synchrotrons, which currently have to start a new cycle to change the beam energy. The number of particles available in one cycle typically exceeds the required amount for a single energy. Thus changing the beam energy by reacceleration of the stored beam could significantly reduce the overall treatment duration.
Within the HITRIplus project a novel accelerator control system will be designed, which will enable multiple reaccelerations within one synchrotron cycle. As this drastically increases the amount of parameter combinations, it is no longer feasible to use pre-calculated control data for each cycle. Instead the data will be calculated on-the-fly by the device controllers when a new energy is requested.
Here, we will present the current status of the data generation strategy and the architectural model of the new accelerator control system.
The HZB cyclotron provides protons for eye-tumor treatment in collaboration with the Charité – Universitätsmedizin Berlin. So far, more than 4300 patients have been treated. Parallel to therapy, there is an on-going R & D program for beam dosimetry and beam delivery. Furthermore, beam time is used for external users, e.g. the irradiation of geological samples or radiation hardness tests.
For the irradiation of geological samples, a new experimental setup was designed and implemented.
For radiation hardness tests, the set-up has been equipped with a new camera for measuring the spatial beam distribution. The use of this camera facilitates the area determination of irregularly formed beam shapes. For the measurements of degradation of solar cells their response is monitored on-line in parallel with the incoming proton beam.
In response of requests of our users, a new target station for the irradiation of solar cells is planned. This target station will be equipped with in-situ luminescence measurements.
Furthermore, a study for a cyclotron being able to deliver He and protons with an energy of 70 MeV/u has been started.
Given the current availability of high-gradient accelerator technology for cost effective and compact electron LINACs in the 100-200 MeV energy range, using Very High Energy Electron (VHEE) radiotherapy (RT) for cancer treatment recently gained a lot of interest. The Ultra High Dose Rate (UHDR) or FLASH dose regime, in which cancerous cells are damaged while healthy tissues are largely spared is one of the main topics studied. VHEE beams are especially adapted for FLASH RT, given their penetration depth and the high beam current, needed to treat large deep-seated tumors. In the CERN Linear Accelerator for Research (CLEAR) facility, numerous unique experiments have been initiated on VHEE and FLASH RT issues, in collaboration with several multidisciplinary user groups, including dosimetric, chemical and biological studies. The dedicated systems, techniques and methods used for VHEE/UHDR RT studies, locally developed by members of the CLEAR operation team, are presented in this paper together with a summary of the main results obtained in collaboration with the user groups.
A systematic comparison of experimental data with 2-dimensional semi-analytical modelling of beam collective effects at the FERMI free-electron laser has led to the first evidence of intrabeam scattering in a single pass electron accelerator, and of its contribution to beam quality for the production of longitudinally coherent seeded FELs. A quantistic evaluation of FEL coherence is proposed then, and a conceptual experiment illustrated for a confirmation of theoretical expectations.
Superconducting Energy Recovery Linacs (ERLs) promise a step change in the capabilities, and sustainability, of accelerator based facilities. This was highlighted in the 2022 ECFA/CERN European Strategy for Particle Physics Accelerator R&D Roadmap. Potential beneficiary fields include high energy particle physics, free-electron laser light sources for physical and life sciences and industry, and inverse Compton based gamma sources for nuclear science and industry. This talk will explore contemporary theoretical and experimental progress in ERLs, discuss the ongoing technical challenges, and present the community roadmaps toward deployment of ERLs in facilities globally.
From the initial success of LCLS, the world has seen a lot of progress in the X_FEL facilities in Europe and Asia. With the successful implementation of cw operation such as LCLS-II, X-FEL is now able to significantly step up its average brilliance as well as user capabilities. This presentation is expected to share with the accelerator community the decadal operation experiences of existing X-FEL facilities, and the outlook of what the next generation of X-FEL shall look like as well as key challenges towards it.
Medipix and Timepix are pixel-based technology detectors that can be employed to measure charged particles, photons (visible through gammas), and neutrons. Their readout chips are used at synchrotron light sources, and as mixed field radiation monitors on the International Space Station. Furthermore, clinical trials have started in the domain of medical spectroscopic X-ray radiology. The devices are used at CERN in experiments studying transition radiation, as detectors of anti-matter and as beam monitoring devices. This talk will provide an overview of the Medipix and Timepix devices and describe some applications. The last generation of Timepix 4, just made available, offers a time resolution of up to 200 picosec, space resolution of 55 micrometers and is can be tiled seamlessly to cover large areas.
The SPIRAL2 linac is now successfully commissioned; H+, 4He2+, D+ have been accelerated up to nominal parameters and 18O6+,7+ and 40Ar14+ beams have been also accelerated up to 7 MeV/A.The main steps with 5 mA H+, D+ beams and with 0.8 mA 18O6+ are described. The general results of the commissioning of the RF, cryogenic and diagnostics systems, as well as the preliminary results of the first experiments on NFS are presented. In addition of an improvement of the matching to the linac, the tuning procedures of the 3 Medium Energy Beam Transport (MEBT) rebunchers and 26 linac SC cavities were progressively improved to reach the nominal parameters in operation, starting from the classical “signature matching method”. The different cavity tuning methods developed to take into account our particular situation (very low energy and large phase extension) are described. The tools developed for an efficient linac tuning in operation, e.g. beam energy and intensity changes, choice of the optics to obtain the requested beam parameters on target… are also discussed.
The successful development of a quantum computers, quantum sensing and communication is dependent, amongst other aspects, on the capability of extending the coherence time of qubits - the limit on how long a qubit can retain its quantum state before that state is destroyed by noise. Ultra-high Q radio frequency superconducting cavities, initially developed for particle accelerators, have allowed this coherence time of qubits to be extended by several orders of magnitude. After an introduction to the present challenges of quantum computing and sensing, an overview of how accelerator technology has contributed and continues to contribute to the significant progress in these domains will be given. Future developments will also be outlined.
[session-stream] https://www.youtube.com/watch?v=eUvQOcCVU3M [/session-stream]
The European Spallation Source (ESS) linear accelerator, one the largest scientific equipment under realisation in Europe, is now in the beam commissioning stage. The project is implemented thanks to the collaboration of several European countries, mostly following the scheme of the in-kind contribution, with the involvement of scientists from many European laboratories and Universities in all phases, from design to beam commissioning. The most recent achievements are described in detail.
The in-kind contributions are vast and differentiated, including delivery of normal conductive and superconducting accelerating structures, ion sources, magnets, power converters, RF systems, controls, diagnostics as well as the participation to design, installation, and commissioning of the linac. Results of this collaborative effort will be shown in details.
One of the greatest challenges for nuclear energy is how to properly manage the highly radioactive waste generated during irradiation in nuclear reactors. Accelerator Driven Systems (ADSs) is one methods of addressing the transmutation of such high level nuclear waste. ADS or accelerator driven transmutation of waste (ATW) consists of a high power proton accelerator, a heavy metal spallation target that produces neutrons when bombarded by the high power beam, and a sub-critical core that is neutronically coupled to the spallation target. This talk presents the world overview of nuclear energy that has proven to assist in dee-carbonization of energy sectors since the mid-1970s as well as the approaches to ADS being explored around the globe
Particle physics has been a major innovation driver and user of accelerators over the last century. Some past highlights are quickly presented and the future directions in particle physics are discussed. Future options for accelerators are reviewed, also discussing major constraints in beam energy, luminosity and practical details, like power consumption.
[session-stream] https://www.youtube.com/watch?v=eUvQOcCVU3M [/session-stream]