Neutron energy spectrum measurement imposes requirements for single-bunch selection and acceleration on the CiADS (China Initiative Accelerator Driven System) superconducting linear accelerator, which operates at a fundamental frequency of 162.5 MHz. Existing chopper power supplies have rise/fall times approaching 20 ns, making them unable to achieve the required 6.15ns bunch selection via a...
The rational use of multipole magnets in a beam line is an effective method of transverse beam profile uniformization. This paper introduces an octupole magnet uniformization design of an about 2.1 MeV proton beam accelerated by a RFQ accelerator and the design is based on TraceWin. This design contains two octupole magnets, which are dedicated to uniformization of x and y directions...
Ultra-high dose rate (FLASH) radiotherapy is emerging as a novel cancer treatment due to its tumor-killing efficacy and superior normal tissue protection compared to conventional therapy. However, in compact synchrotrons, achieving the required FLASH dose rates is challenging, since conventional RF-KO extraction struggles to achieve the short (tens of milliseconds) extraction times needed. To...
The integration of machine learning (ML) techniques into beam commissioning and operations at CSNS has shown promising potential for improving beam quality, operational efficiency. This work presents a comprehensive overview of recent ML applications across multiple stages of CSNS operations. A key foundation of these efforts is the development of an AI-ready dataset generation platform, which...
Longer bunch spacing is essential for precise product detection in certain nuclear physics experiments. At LEAF, a 10.156 MHz pre-buncher has been successfully commissioned, producing a 98.4 ns main-bunch spacing with a measured FWHM of 1.7 ns using a fast Faraday cup. Residual satellite bunches at the 12.3 ns linac micro-pulse period necessitate a dedicated RF deflector to remove unwanted...
To enable the compact design of an accelerator-driven neutron source, this study developed a beamline scheme that combines a double Einzel-lens focusing system with a compact RFQ accelerator. A double Einzel-lens configuration is employed in the low-energy beam transport section, successfully reducing its length to less than 0.2 m. The accelerator section utilizes a 325 MHz four-vane Radio...
A superconducting radio-frequency quadrupole (SRFQ) is proposed for the future upgrade of the China Initiative Accelerator Driven System (CiADS). The SRFQ is de-signed to accelerate a 10 mA proton beam to 2.5 MeV within a compact length of 2.9 m. This design achieves 100% transmission efficiency and a carefully controlled output longitudinal emittance, ensuring minimal beam loss in the...
Beam loss is a critical challenge in the physics design of high power superconducting proton linacs. The challenge is even more acute in linacs that feature high peak intensity and low energy, which has strong space charge effect and RF nonlinear force. In this paper, we study how to achieve a high transmission rate for beam halo particles, commonly a major source of beam loss, via beam halo...
To make ion accelerators in applications more compact, the Institute of Modern Physics, Chinese Academy of Sciences is dedicated to researching the radio frequency quadrupole (RFQ) operating at a frequency as high as 1 GHz. While high frequency can effectively enhance the acceleration gradient of RFQ, it also leads to low transverse focusing force, reduced acceptance and decreased transmission...
Beam loss is the most critical topic in the high power accelerator community. During high power proton beam commissioning of Chinese ADS Front end (CAFe), unexpected irradiation dose was detected opposite to the proton beam deflection direction. This indicates there are parasitic negative hydrogen particles inside the proton beam, which is first observed in the linac facility. In the paper,...
In the 3-GeV RCS of J-PARC, we have already achieved user operation at the designed 1 MW beam power. The beam loss and the corresponding machine activation have been sufficiently minimized to obtain a stable operation. To cope with user demands, the beam power of the RCS has to be increased far beyond the designed 1 MW. For that purpose, we have performed numerical simulation and beam studies...
Laser-driven proton sources produce ultra-short, high-current pulses ideal for FLASH radiotherapy but lack therapeutic energy levels. Bridging this energy gap via RF linac post-acceleration faces critical beam transport challenges due to wide angular divergence and broad energy spreads intrinsic to laser protons. This work analyzes how large energy spreads constrain RF bunching and capture...
Accurate setting and readback of radio frequency (RF) cavity voltage is critical for precise beam control in accelerator systems. To address potential discrepancies between set and actual voltages, this study presents an in-situ calibration of the MEBT Buncher1 cavity using a Time-of-Flight (ToF) method. The phase of the cavity was systematically swept while measuring the resulting energy...
A residual gas Ionization Profile Monitor (IPM) was designed and installed in CSNS-Linac for horizontal beam profile measurement. In the design of the IPM, the use of equipotential electrodes was abandoned. Instead, a honeycomb structure is incorporated at the openings of the anode plate to suppress the horizontal component of the electric field. The shadowing introduced by the honeycomb...
Resonance crossing, jointly determined by a large space-charge tune spread and magnetic field errors, is the main cause of beam loss and emittance growth in HIAF-BRing. For weak beams, the classical theory based on the resonance driving terms (RDTs) allows a perfect resonance compensation through precisely pre-known nominal TWISS parameters. As the space-charge gets intensified, however, the...
CiADS (China initiative Accelerator Driven sub-critical System) is an experiment facility to demonstrate the ADS concept with high energy proton beam hitting the LBE (Liquid Lead-bismuth Eutectic) target, generating high-flux neutrons to boost the reacotor to transmutate nuclear waste. BLR (Beam Line to Reactor) is one of the key part in CiADS program, which is to transport and match the 2.5...
The CSNS RCS (Rapid Cycling Synchrotron) is a proton accelerator designed to achieve a target beam energy of 1.6 GeV, with a typical operating intensity of 140 kW, which is expected to increase to 500 kW after the CSNS II upgrade. However, a significant current instability has been observed during the 100 kW beam operation. To mitigate this instability, techniques such as operational tuning...
The muon collider is a promising candidate for exploring new physics at the energy frontier, offering the advantages of lepton collisions at multi-TeV scales. Achieving high luminosity requires reducing the six-dimensional (6D) emittance of the muon beam by several orders of magnitude within the muons’ limited lifetime. This is accomplished through ionization cooling, which involves two main...
For multi-unit RF amplifier systems, a 2300 W solid-state RF power amplifier module with integrated EtherCAT and USB interface has been developed. The RF amplifier section is constructed from the latest LDMOS from Ampleon with a power of 2300 W at an efficiency of 72 % and is fully shielded and offers space for adding a driver amplifier or phase shifter circuit. The module is equipped with a...
After the success of 80 MeV negative hydrogen beam profile measurement based on laser wire monitor, in order to further realize the beam emissivity measurement, an emissivity measurement system combining the laser wire monitor and LGAD (low-Gain Avalanche Diode) sensor is designed in this paper. The main idea is to use the LGAD sensor to reconstruct the H0 distribution, combined with the laser...
The upgrade of linac in China Spallation Neutron Source (CSNS-II) requires a robust Differential Beam Current Measurement (DBCM) system to ensure safe operation of superconducting cavities within the Fast Protection System (FPS). This paper presents a practical design for a DBCM system tailored for the chopped-beam operation. The system integrates a Bergoz Fast Current Transformer (FCT) with a...
The Beam Loss Monitor (BLM) system for the High-Intensity heavy-ion Accelerator Facility (HIAF) has been constructed and deployed. This system features ultra-fast response (≤20 μs, measured down to 4.5 μs) and employs 196 plastic scintillator detectors coupled to photomultiplier tubes (PMTs), strategically positioned in critical areas. It achieves a wide dynamic range of 6 orders of magnitude,...
At the ISIS Neutron and Muon Source, accelerator tuning has traditionally been a manual process, relying on expert operators to adjust control system parameters to achieve optimal beam efficiency and intensity. With the recent migration of the control system to EPICS and the availability of optimization frameworks such as Xopt, we have initiated the first efforts to automate tuning of the Low...
Target Multi-Wire Scanner is a beam diagnostics device in the CSNS-II accelerator, designed to measure the pre-target beam profile. This paper details the hardware composition, software architecture, and beam-target interaction test results of the CSNS-II front-end multi-wire scanner readout system. In contrast to the CSNS predecessor, the upgraded system employs a hybrid software architecture...
Dynamic aperture tracking is an widely employed and effective method in the design of circular accelerators. However, in high-intensity proton accelerators, the pronounced space charge effect induces substantial tune shifts, which can severely compromise the accuracy of nonlinear dynamics analysis. In this study, we present a novel dynamic aperture tracking code tailored for high-intensity...
In the case of “linear RF system” the longitudinal Schottky noise of bunched beam is presented as a set of synchrotron lines around each revolution harmonics or, in the case of transverse Schottky noise, around each betatron sideband. In a typical accelerator or storage ring the RF system generates harmonic RF which makes the synchrotron motion non-linear resulting in a dependence of...
Beam tuning in particle accelerators is a complex task, especially when physical modeling is impractical due to the lack of complete beam diagnostics. Manual, iterative adjustment by operators is time-consuming and often fails to converge rapidly on optimal settings.
We propose a reinforcement learning (RL) approach accelerated by a surrogate model trained on limited online data, enabling...
The intra-beam scattering in high charge state intense heavy ion beams is a problem worth considering. By controlling the longitudinal distribution of the ion beam, it may be possible to alleviate the ion beam loss and improve the lifetime of the ion beam caused by intra-beam scattering. Unlike the traditional cooling process of direct current electron beams or longitudinal uniform...
For high-intensity hadron synchrotrons, the longitudinal manipulation (rf gymnastic) is of practical importance to customize the parameters and status of the hadron beams to fulfill various scientific and industrial goals. For the recently-built China Spallation Neutron Source (CSNS), a high-intensity single-bunch operation mode based on longitudinal bunch merging has been proposed to enhance...
The China Accelerator Facility for superheavy Elements (CAFE2) stands as a world-leading dedicated facility for superheavy element synthesis research, boasting the highest beam intensity among international counterparts of its kind. It provides advanced experimental conditions for synthesizing new superheavy elements, investigating their chemical properties, and generating neutron-rich...
This paper presents a thermionic cathode electron gun with a compact structure for generating continuous-wave electron beams by introducing 650MHz microwave power into the cathode-grid assembly.
A study campaign to identify potential limitations at highest intensities has been performed in the Proton Synchrotron (PS) in view of future requirements for fixed-target beams at CERN. Previous explorations of the maximum intensity date back more than two decades, and they required two injections from the PS Booster (PSB) with a long flat-bottom in the PS. This scheme resulted in...
HIAF is a high-intensity particle accelerator that will perform injection, acceleration, and extraction at a repetition rate of 3 Hz. The beam will be affected by a variety of high-intensity effects. In order to increase the beam intensity, we hope to fully and accurately simulate the impact of those effects so that we can take appropriate suppression measures. For this purpose, we are...
To mitigate beam loss during RCS injection and in the transport line from the linac to the ring, a novel transverse beam halo collimation system was developed for the CSNS LRBT beamline. The system employs three sets of stripping foils arranged with a 60° phase shift, using twelve carbon foils to convert peripheral H⁻ ions with beam power below 2 kW into protons. Experimental results...
updating
Beam feedback systems are crucial in high-energy circular accelerators to suppress undesired bunch oscillations and prevent beam quality degradation. In the longitudinal plane, the CERN Super Proton Synchrotron (SPS) is equipped with beam phase and synchronization loops. The phase loop locks the RF phase of the accelerating voltage to the one of the bunches detected by a pickup, while the...
The delivery of a high-brightness muon beam through ionisation cooling is essential to produce sufficient luminosity in a muon collider. The ionisation cooling technique has been demonstrated in principle by the Muon Ionisation Cooling Experiment (MICE) but the potential detrimental impacts of collective effects still need to be carefully investigated. Using the same formalism as the one...
To meet the stringent requirements of the downstream superconducting accelerating section for beam matching conditions and intensity specifications, it is necessary to maximize the beam intensity while maintaining the transverse emittance performance at the exit of the normal-conducting front-end. Systematic measurements were conducted of the emittance at the exit of the Low Energy Beam...
Resonant slow extraction is widely utilized in hadron synchrotron accelerators. This paper proposes a longitudinal localized excitation method for slow extraction, in which transverse excitation is applied only within a limited phase interval located at the edge of the longitudinal phase space. As a result, only particles situated in this region are excited and subsequently extracted. This...
Obtaining complete high-dimensional phase space distributions is essential for predicting and controlling intense beam evolution. Building on our prior tomography algorithm that reconstructs four-dimensional (4D) transverse phase space distributions from 2D measurements, applicable under both linear and nonlinear beam transport, this work extends the framework to incorporate frozen space...
Dipole magnet vacuum chambers are among the critical and costly components of rapid-cycling accelerator facilities. Alternative
approaches to traditional ceramic chambers have been explored for the implementation of fast-ramping dipole-magnet vacuum chambers,
including thin-wall metallic beam pipe chambers strengthened with transverse ribs. Here, we report a novel 3D-printed titanium alloy...
ISIS is the pulsed muon and neutron source at RAL in the UK. Its operation centres on an 800 MeV RCS cycling at 50 Hz and providing up to 3E13 protons per pulse corresponding to 0.2 MW mean beam power to the user targets.
Work is presently underway to improve the measurement, modelling, and control of the ISIS ring beam dynamics in order optimise operational setup as well as allow...
In the study of plasma properties of an Electron Cyclotron Resonance Ion Source (ECRIS), it is essential to accurately model the critical features of ECRIS within a numerical framework, particularly for third-generation ECRIS systems that operate at microwave frequencies exceeding 20 GHz. The three-dimensional particle-in-cell model, NAM-ECRIS, has been updated to investigate the response of...
This research presents a new numerical method of the beam envelope equations in the presence of acceleration. By using a scanning technique, a matched solution set with acceleration has been obtained. With focusing cases as constant wave number per unit length, it is found that the conventional adiabatic approximation theory fails when dealing with high acceleration gradients. Moreo-ver, for...
In absence of direct space charge, the indirect electromagnetic self-interaction of particle beams via surrounding materials is typically described by wakefields. Beam stability can then readily be assessed in terms of absolute stability of the dipole moment density using linear stability analysis via eigenfunctions, where small density perturbations either decay (stable regime) or...
Online monitoring of beam phase and energy gain within accelerating cavities is crucial for the stable operation of accelerators, especially in high-power scenarios. As cavities are typically calibrated with a low-current, short-pulse beam for safety purposes, the beam behavior may deviate from the calibrated case when running high-current beams, due to strong space charge effects and other...
The Heavy Ion Research Facility in Lanzhou (HIRFL) is a globally significant full-ion acceleration system. Its Cooler Storage Ring (CSR) facility demonstrates versatile capabilities in beam accumulation, cooling, and acceleration. During operational cycles, periodic beam losses have been observed, prompting an investigation into their root causes.Our study focused on analyzing analog dipole...
As prerequisites for automatic phase setting and fault compensation, precise longitudinal alignment and RF phase calibration are critical for high-intensity superconducting hadron linacs. While multiple facilities have successfully aligned or synchronized their linacs with time-of-flight (TOF) beam-based methods, existing error analyses typically assume uncorrelated position and phase...
Abstract
With the advancement of high-intensity proton linacs, compact neutron sources with a limited footprint have become feasible. Such a neutron source, consisting of a radio frequency (RF) ion source, a radio frequency quadrupole (RFQ), and a rotating Li target, operating in continuous wave (CW) mode, has been proposed. In this paper, we present the overall system design and...
In the China Spallation Neutron Source II (CSNS-II), the H⁻ beam will be accelerated in the Linac to 300 MeV. Subsequently, the electrons are stripped from the H⁻ ions through a stripping foil during injection into the Accumulator Ring, converting them into a proton beam. Wire scanners are employed to measure the transverse beam profile and emittance in the injection area. This paper presents...
High-current or low-energy slow extraction from proton synchrotron suffers from strong space charge effect. Longitudinal localized excitation slow extraction method is proposed in this paper to reduce the spill energy spread while mitigating space charge effects. This method applies transverse excitation within a limited phase interval which locate at the edge of the longitudinal phase...
To enhance the accelerating efficiency of the high-current accelerator for a neutron source, a 100-mA, 162.5-MHz, CW compact hybrid accelerating cavity incorporating inductively coupled four-vane RFQ and CH DTL structures is designed. The dynamics design, the RF structure design, and water-cooling design of the hybrid cavity have been accomplished. The proton beam is accelerated from 80 keV to...
Proton linear accelerators are crucial in spallation neutron sources, CANS, proton therapy, etc. DTL, especially Alvarez-type, is used for intense pulsed proton beams at several to tens of MeV. High-intensity neutron sources characterized by superior temporal resolution, unprecedented peak brightness demand higher pulse current intensity proton linear accelerator. With the in-depth research on...
High reliability is a major challenge of high-current linear accelerators. This is particularly problematic for Accelerator Driven Systems (ADS) such as the China initiative Accelerator Driven System (CiADS). In order to achieve rapid beam recovery, it is necessary to adjust and compensate the superconducting solenoids and cavities adjacent to the failed components in superconducting linear...
The transverse coupled-bunch instability (TCBI) has been observed in the rapid cycling synchrotron (RCS) of the China Spallation Neutron Source. Subsequent measurements indicated that the RF shield of the ceramic chambers exhibits a resonant impedance in the low-frequency range, preliminarily suggesting it is responsible for the instability. The RF shield has been carefully simulated to...
High-intensity hadron accelerators demand precise modeling of collective effects to ensure beam quality preservation and beam loss mitigation. RF-Track is a versatile, computationally efficient 6D particle tracking code developed to simulate the dynamics of beams under the influence of space charge, wakefields, and scattering effects in complex accelerator layouts, including RFQs, LEBT and...
The China Spallation Neutron Source (CSNS) is a large multidisciplinary experimental facility that generates neutrons by targeting a strong current proton accelerator. Its linear accelerator consists of a front-end accelerator, a 3 MeV RFQ accelerator, and an 80 MeV DTL accelerator. The second phase of the project will upgrade the linear accelerator by installing superconducting cavities after...
In high-intensity beam transport systems, the interaction between resonance and instability significantly impacts beam quality and transmission efficiency. This study aims to investigate the intrinsic link between resonance excitation and instability growth in mismatched high-intensity beams propagating through periodic focusing channels.
Based on envelope oscillation theory, this paper...
The Rapid Cycling Synchrotron (RCS) of the China Spallation Neutron Source (CSNS) is a key part of the accelerator chain. It accelerates the 80 MeV low-energy beam from the linac to 1.6 GeV and extracts it to hit the target for neutron production. As an important optics parameter, the precise measurement of the transverse emittance is vital for understanding the space charge evolution in the...
In the J-PARC Main Ring (MR), an upgrade project involving a total of 24 Trim-S units is in progress to further suppress beam loss caused by off-momentum particles. This effort targets key resonances, including the third-order resonance 3νx=64 and νx+2νy=64, and a fourth-order resonance 4νx=85, which are produced by the combination of vx=21 and 3vx=64. Four additional Trim-S units have been...
For accumulating high-intensity beam, the H- stripping injection is adopted in the rapid cycling synchrotron (RCS) of the China Spallation Neutron Source (CSNS). For the CSNS-II, the painting injection is a key solution, which is performed in a straight section of RCS by the bump magnets, including four BCH magnets for horizontal painting, four BV magnets for the vertical painting and one LRBD...
Exotic nuclei far away from the valley of β-stability are characterized by tiny production cross-sections and short half-lives, therefore highly efficient and fast mass measurement techniques are required. The Spectrometer Ring (SRing) at the HIAF provides such conditions for accurate mass and unique half-life measurements of exotic nuclei. The SRing is designed as a multi-function...
The slow extraction feedback system is built at HIRFL-CSR, Lanzhou. It is an auto adjusted feedback system based on the predicted value from DCCT at CSRm. The TMIC with the ability of online monitoring spill structure and beam profile is equipped at the terminal. The 10 kHz intensity signal is fed into the electronics of RFKO with a 1 kW power amplifier. The system is operated at July, 2025....
In accelerator-based spallation neutron sources, which include a rapid cycling synchrotron (RCS), the energy spread at the end of the linac is a crucial parameter that significantly impacts the operational efficiency of the downstream RCS ring. However, in recent years, the energy spread at the linac of the Chinese Spallation Neutron Source has been inadequately measured due to limited methods...
Beam loss reduction is essential to achieve higher beam intensity in the main ring synchrotron (MR) of the Japan Proton Accelerator Research Complex (J-PARC). We have observed the effect of the third order non-structure resonances of 3νx=64 and νx+2νy=64. The resonance driving terms were measured with the current settings of the trim coils of the sextupole magnets. Both resonances have been...
High-intensity ion beams are inherently subject to significant space charge effects, which lead to complex beam dynamics and emittance growth, particularly in the Low Energy Beam Transport (LEBT) region. In this study, the dynamics and optimization of space charge compensation (SCC) of a high-perveance proton beam are investigated through a combination of 3D numerical modeling and...
The characterization of particle distribution in phase space and its evolution along the beamline is fundamental for accelerator beam commissioning and analysis. While numerical simulations enable straightforward tracking in phase space, experimental reconstruction of phase space distributions remains challenging, particularly for hadron beams where space-charge effects are unavoidable. This...
Based on the beam commissioning of CSNS-I RCS, the current tune above the half-integer resonance exhibits extremely narrow parameter margins and severe instabilities. Therefore, to further increase the beam power in Phase II, significant optimization of the tune is required.
First, we conducted a series of simulations. A total of 97 tunes were selected on the resonance diagram, and the beam...
The Institute of Modern Physics (IMP) has independently developed a conduction-cooled superconducting electron linac prototype without liquid helium. The prototype, based on a 650 MHz (β = 0.82) SRF cavity, successfully accelerated 200 mA, 60 keV, 2 µs pulsed beam to 4.6 MeV with stable operation, demonstrating the feasibility of high-current acceleration.
Building on this achievement, an...
Accurate simulation of high‑brightness, high‑intensity hadron beams is essential for the design, commissioning, and optimization of modern accelerators such as the LHC injector complex, the LHC, and future high‑energy machines. Beam dynamics is governed by complex multiparticle effects, including space charge, impedance‑driven instabilities, intrabeam scattering, beam–beam interactions, and...
