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 prop