The BEPCII-Upgrade project has been completed to achieve a higher luminosity and higher energy, which can improve the collision efficiency and extend physics range. Two more superconducting RF (SRF) cavities and two more high-power sources are installed in the storage rings and in Linac, respectively. In order to improve short-term jitter and long-term phase stability of the whole facility, the phase reference line was upgraded not only on the master oscillator (MO) but also on the phase-stabilized signal transmission. The two oscillators of storage rings and Linac are integrated together and driven by one single frequency standard. Four self-developed high-precision optical fiber-based RF signal transmission links are established to distribute RF reference to Linac microwave system (571.2 MHz), east SRF system (499.8 MHz), west SRF system (499.8 MHz) and a new PWFA facility (571.2 MHz), which requires 50 fs-level synchronization with Linac beam. The long-term phase stability between the MO and received RF signals after 150–400 m transmission is better than ± 0.02 degree peak to peak over 3 weeks. The jitters of 2856 MHz and 499.8 MHz for the Linac and SRF system are 40.7 fs and 58.9 fs (10 Hz–10 MHz), respectively. The phase reference line system provides monitorable and automatically feedback control of RF phase, which improved the long-term stability of the collider and satisfied the requirements of PWFA experiments.

Accelerator-based boron neutron capture therapy (AB-BNCT) necessitates highly reliable timing and rapid protection systems with minimal latency to ensure safe and synchronized operation. Conventional clinical accelerator control architectures; however, are often characterized by fragmented subsystems, excessive signal delays, and insufficient integration of timing, protection, and device control functions. To address these challenges, we introduce a unified hardware architecture specifically designed for AB-BNCT. This system integrates device control, timing, and fast protection into a single standardized platform using a custom reverse backplane that provides direct, low-latency data paths. Such a centralized design eliminates redundant interconnections, reduces end-to-end propagation delay, and enhances real-time responsiveness. Precise measurements indicate that the core protection logic responds in under 500 ns, excluding interlock-communication latency, thereby establishing a new benchmark for medical accelerator safety systems. Additionally, an intelligent beam-operation and shutdown mechanism is complemented to dynamically optimize beam delivery while ensuring fail-safe termination under fault conditions. This work offers three key contributions: First, it introduces the first integrated hardware platform tailored for AB-BNCT; second, it demonstrates record-low protection latency validated by metrology-grade testing; and last, it presents a safety-aware beam-control strategy that integrates real-time protection with clinical workflow stability. The proposed architecture significantly enhances the reliability, efficiency, and clinical feasibility of next-generation AB-BNCT facilities.

This paper describes the design and implementation of the control system for the BEPCII upgrade project, which was undertaken to meet the enhanced performance requirements of the accelerator complex. Based on the EPICS framework, the original control system—which had been operating reliably since 2005 but was considered obsolete in both hardware and software—was completely redesigned and rebuilt to support higher colliding beam currents, increased RF cavity voltages, and improved data acquisition efficiency. The new control system was completed and commissioned in November 2024 and is currently operating normally. It successfully supports the BEPCII upgrade goal of tripling the peak luminosity in the high-energy region. The EPICS-based control system redesign effectively addresses the obsolescence of the original system and fulfills the new operational requirements, providing a reliable foundation for the upgraded performance of BEPCII.

The Circular Electron Positron Collider (CEPC) distributes a reference clock distributed to 192 control nodes along its 100 km underground tunnel. The required synchronization precision is 30 ps (standard deviation). We present an enhanced White Rabbit (WR)-based clock synchronization system designed to meet this requirement. A noise-budget analysis of the standard WR slave loop identifies the analog actuation chain (DAC + VCXO + multiplier PLL) and restart-induced timing uncertainty as the dominant limitations. In our redesigned node, the DAC+VCXO chain is replaced by a Si5345A DSPLL clock generator with DCO-based phase control, removing the board-level analog tuning stage. GTX transceiver phase alignment and manual byte-alignment fixing reduce restart uncertainty from 88.8 ps to 12 ps peak-to-peak. For multi-node operation, we introduce a cascaded global-control architecture with PC-side PID auto-tuned by TD3 reinforcement learning, on-chip-temperature feed-forward calibrated to -0.76 ps/^∘C. The measured point-to-point synchronization precision is 3.38 ps over 1 m fiber and 3.92 ps over 50 km. In a 12-level cascade, the end-node precision reaches 6.66 ps at constant temperature and 7.30 ps under a 13^∘C temperature swing. Synchronized-clock TIE jitter stays below 1 ps regardless of cascade depth. Restart uncertainty is 2.82 ps (std. dev.). A 4-level cascade operated stably for 25 hours of continuous monitoring. All measured metrics fall well within the CEPC 30 ps budget.

The BEPCII upgrade targets improved collision energy and data-taking performance via full-scale retrofi tting of RF,cryogenic, vacuum and power subsystems. Serving as the core safeguard for accelerator facilities and staff, theoriginal central safety interlock system suff ers from component ageing, poor compatibility with newly upgradedequipment and insuffi cient expandable interfaces after long-term in-service operation. This work is intended toelaborate the overall architecture of the renovated interlock system and verify the practicability of its core functionalmodules. System design follows the updated BEPCII upgrading technical specifi cations; modularized hardware layout andstandardized communication frameworks are adopted for subsystem docking, while targeted development andoffl ine bench tests are completed for pivotal functional units before site integration and accelerator joint debugging. All core functional components successfully pass factory inspection and on-site joint debugging. The upgradedcentral safety interlock system completed formal online commissioning in early 2025 and has been running offi ciallyever since. In practical application, it provides stable safety guarantee for BEPCII beam commissioning and dailyroutine operation, eliminates the inherent defects of the old-generation system, and fully meets the safety controlrequirements of the collider upgrade project.

The Circular Electron-Positron Collider (CEPC), a pivotal platform led by Chinese scientists for producing high-purity, high-energy Higgs bosons, requires back-end readout electronics in its vertex detector to achieve high-data-rate transmission and high-precision clock synchronization while minimizing material mass. To address this requirement, this study proposes a multi-channel free-space optical (FSO) communication system based on wavelength division multiplexing (WDM). The performance of the proposed system has been experimentally validated in a laboratory environment. Experimental results demonstrate a maximum data transmission rate of 118 Gbps over 1.5 meters, with multi-channel clock synchronization achieving sub-nanosecond accuracy and synchronization precision of within 20 picoseconds.

The China Spallation Neutron Source (CSNS) is designed and constructed by the Institute of High Energy Physics, Chinese Academy of Sciences. The construction of CSNS includes an 80-MeV Linac, a 1.6-GeV Rapid Cycling Synchrotron (RCS), two beam transport lines, a solid target station of 100 kW, three initial neutron instruments and other utility facilities. Based on limited funding and lack of experience in the high-power proton accelerator and the spallation target, the CSNS design was optimized to an advanced user faculty to fulfill the urgent user demand, with a high performance/cost ratio, and to have the capability for the CSNS phase two project (CSNS-II) to increase the beam power to 500 kW with less investment. The CSNS construction started in October 2011, and finished in March 2018 on schedule, and reached the acceptance parameters. Since then, CSNS has been operating efficiently and stably. In March 2024, the proton beam power on the target was increased to 160 kW. More than 1700 user experiments have been carried out so far, indicating a strong user demand. The design, construction and commissioning of CSNS are presented in this paper.

China Spallation Neutron Source II (CSNS-II) plans to upgrade its linear accelerator to increase the beam energy from 80 to 300 MeV. The upgrade will utilize 324 MHz double-spoke superconducting cavities and 648 MHz elliptical superconducting cavities. In order to minimize and shorten the future commissioning duration of the superconducting cavities with beam functionality, the management department of CSNS-II has decided to conduct validation of superconducting cavity beam tuning software and methods at the Chinese Accelerator Driven Sub-critical System (C-ADS) Injector I facility. As an experimental device, the C-ADS Injector I facility has been shut down for almost six years. To restore the operation of this machine, it is essential to effectively improve and upgrade the original control system of C-ADS Injector I facility. To ensure high availability and reliability for the reactivation of the C-ADS Injector I facility, both the hardware and software of the original control system have been improved and enhanced. For example, the global timing was upgraded from continuous mode to pulsed mode, providing the operational sequence for the ECR (electron cyclotron resonance), chopper, RFQ (radio frequency quadrupole), and beam instruments. The beam interlock system, which includes MPS and FPS, has been redesigned to ensure the safe operation of all equipment, particularly the critical accelerator components. Proxmox VE was selected as the virtualization software to implement the private cloud platform. Throughout the improvements and optimizations to the control system, it is evident that the availability and reliability of the control system have been substantially and effectively enhanced, which is crucial for the successful validation of the beam tuning methods and software for CSNS-II superconducting cavity at the C-ADS injector I facility.

The CEPC clock issue is related with the RF frequency coordination between the various accelerator systems and may affect the operation modes of both the accelerator and the detector. The timing structure of CEPC has been restudied with the collaboration of the accelerator team and the detector team. After discussions between two sides, the CEPC bunch structure is set such that the spacings between adjacent bunches in any CEPC operation mode are integer numbers of 23.08 ns. The master CEPC clock will be provided by the accelerator to the detector systems with a frequency of 43.33 MHz, synchronous to the beam. The CEPC detector system relies on the clock to sample physics signal at the right time. It was found that if the circumference of CEPC is slightly changed to 99955.418 m, not only is the orbit length closer to 100 km, but also the detector would benefit more for the first 10-year operation.

The Circular Electron Positron Collider (CEPC) is a large scientific project initiated and hosted by China, fostered through extensive collaboration with international partners. The complex comprises four accelerators: a 30 GeV Linac, a 1.1 GeV Damping Ring, a Booster capable of achieving energies up to 180 GeV, and a Collider operating at varying energy modes (Z, W, H, and ttbar). The Linac and Damping Ring are situated on the surface, while the Booster and Collider are housed in a 100 km circumference underground tunnel, strategically accommodating future expansion with provisions for a Super Proton Proton Collider (SPPC). The CEPC primarily serves as a Higgs factory. In its baseline design with synchrotron radiation (SR) power of 30 MW per beam, it can achieve a luminosity of 5e34 /cm^2/s^1, resulting in an integrated luminosity of 13 /ab for two interaction points over a decade, producing 2.6 million Higgs bosons. Increasing the SR power to 50 MW per beam expands the CEPC's capability to generate 4.3 million Higgs bosons, facilitating precise measurements of Higgs coupling at sub-percent levels, exceeding the precision expected from the HL-LHC by an order of magnitude. This Technical Design Report (TDR) follows the Preliminary Conceptual Design Report (Pre-CDR, 2015) and the Conceptual Design Report (CDR, 2018), comprehensively detailing the machine's layout and performance, physical design and analysis, technical systems design, R&D and prototyping efforts, and associated civil engineering aspects. Additionally, it includes a cost estimate and a preliminary construction timeline, establishing a framework for forthcoming engineering design phase and site selection procedures. Construction is anticipated to begin around 2027-2028, pending government approval, with an estimated duration of 8 years. The commencement of experiments could potentially initiate in the mid-2030s.

PurposeAs a fourth-generation light source, High Energy Photon Source (HEPS) has much more stringent requirements to the beam orbit stability in both horizontal and vertical directions than the previous sources due to the much smaller beam sizes.MethodsA Fast Orbit FeedBack (FOFB) system, with the closed-loop bandwidth around 500 Hz, is needed to meet the critical requirements. The latency of the FOFB system is the key to achieve these requirements.ResultsProper design and implementation of the feedback logic to have low latency is illustrated in the paper. Calculation accuracy is kept in the whole operation except for the last-minute data translation into 32-bit floating point number.

High Energy Photon Source(HEPS),as a 4th generation synchrotron radiation light source,has stringent requirement for beam orbit stability:the orbit fluctuations should be below 10％of the beam RMS sizes in both horizontal and vertical directions with a bandwidth around 500 Hz.Overall,the latency of the Fast Orbit FeedBack(FOFB)system is the key factor to achieve the requirement.Data transmission of the beam positions from the beam position monitor(BPM)electronics to all of the FOFB sub-stations is the key to achieve very low latency,as which contributes the largest part of the total FOFB system latency.Preliminary test results of prototype showed that the total latency of data transmission is less than 10 μs with no bit errors during data transmission,satisfying the requirements on the FOFB system of HEPS.

One of the radiation hotspots induced by beam losses is the component of debuncher in the beamline when China Spallation Neutron Source (CSNS) linac regularly operates. The beam loss of negative hydrogen ions at the entrance of the debuncher is simulated by FLUKA. The resultant mixed radiation field is composed of charged and neutral hadrons (protons and neutrons), photons, and electrons over a range of energies. This radiation field is suitable for the Single Event Effect (SEE) tests of electronic components operating in the mixed radiation environment, especially for the electronic components used in the accelerator tunnel. Based on simulated mixed radiation, a SEE cross section for a 65 nm Static Random-Access Memory (SRAM) is employed to evaluate the complicated mixed field. The results show that the radiation of neutrons plays an important role in causing SEEs in a complicated radiation environment.

BackgroundVery small angle neutron scattering (VSANS) instrument is a powerful tool for structure calibration.PurposeThis study aims to ensure the repeat positioning accuracy is better than ±2 μm for the moving parts of VSANS instrument at China spallation neutron source (CSNS).MethodsA prototype motion control system based on experimental physics and industrial control system (EPICS) software architecture was designed. The stepper motor was used to drive the movement of the displacement platform, the absolute optical encoder was applied to feedback of the real-time position of the displacement platform, and the Beckhoff embedded controller was employed to implement the full closed loop control of the position of the displacement platform.Results & ConclusionsThe test results show that the repeat positioning accuracy of this prototype motion control system is better than ±2 μm with high stability and high reliability, satisfying the needs of the VSANS instrument at CSNS.

中国散裂中子源(CSNS)是基于强流质子加速器的大科学装置,通过高功率质子束流轰击重金属靶产生高通量中子用于开展中子散射研究,CSNS是世界上第四台、发展中国家第一台脉冲型散裂中子源.CSNS包括高功率强流质子加速器、中子靶站和中子谱仪以及相应的配套设施等.加速器由80 MeV负氢直线加速器、1.6 GeV快循环同步加速器及相应的束流输运线组成.CSNS加速器是我国第一台中高能强流高功率质子加速器,本文将介绍CSNS加速器的设计、关键技术、设备研制以及束流调试过程和其中关键问题.

介绍了国内外大气中子单粒子效应的现状和最新研究进展,主要包括单粒子效应的物理机制研究、新型半导体器件的抗大气中子辐照研究及当前国内外仿真大气中子辐照实验装置等.对未来大气中子引起的单粒子效应研究趋势做了展望.

对加速器运行过程中出现的故障进行准确分析,可有效提升加速器的可靠性及运行效率.而对于一些快速故障过程,必须依赖故障发生时刻存储的高度时间相关和高分辨率的数据,才能进行准确分析.设计了一种用于加速器的故障分析软件,可用于对快速故障进行可靠分析.在中国散裂中子源加速器中进行了应用,该系统非常准确地分析了此前无法定位的大部分束流丢失过程.该故障分析具有一定的通用性,可应用到其它加速器装置.