Understanding the evolution of transverse beam profiles in high-intensity proton synchrotrons is crucial for stable, high-power operation. A residual gas ionization profile monitor (IPM) has been developed and commissioned for the Rapid Cycling Synchrotron (RCS) at the China Spallation Neutron Source (CSNS) to enable non-invasive, bunch-by-bunch horizontal beam profile measurements. During commissioning, key challenges such as electromagnetic interference (EMI) from the high-intensity proton beam and accelerator components, insufficient microchannel plate (MCP) gain due to power supply limitations, and elevated vacuum pressure were addressed through RF shielding and an enhanced Faraday cage for EMI suppression, a pull-down resistor for optimal MCP gain, and an additional vacuum pump for pressure reduction. These improvements enabled successful commissioning, with a peak-finding algorithm and RF-synchronized window technique developed to identify individual bunches and reconstruct profiles. Measurements were performed in both ion and electron collection modes, revealing beam position and horizontal size distributions during the injection painting process. This paper details the IPM’s design, commissioning strategies, and data analysis methods for achieving bunch-by-bunch non-invasive beam profile observations.

Accurately measuring and controlling the transverse position of the particle beam in a high energy particle accelerator is crucial for its efficient and safe operation. The China Spallation Neutron Source (CSNS) is a major facility for neutron science in China, and it uses an accelerator complex to generate high-intensity pulsed neutron beams for a wide range of scientific and industrial applications. This paper discusses the design, implementation, and evaluation of the Beam Position Monitor (BPM) system for the CSNS H-injector LINAC. The BPM system is used to measure the beam transverse position precisely along the injector LINAC, with the aim of improving the beam stability and quality. This study outlines the BPM system design strategy, emphasizing the stripline-type BPM selection for its structural rigidity and signal-to-noise ratio. The various parameters of the BPM geometry have been optimized to meet the mechanical and electrical requirements along different sections of the LINAC. Furthermore, we present the numerical simulation studies and the mechanical design of the BPM system, along with the beam tests.

A pulsed muon facility (the so‐called EMuS) at the China Spallation Neutron Source (CSNS) has been studied since 2007. It aims for multidisciplinary applications but with a focus on those based on muon spin rotation/relaxation/resonance techniques. As a standalone facility, EMuS will take about 5% or 25 kW of the total beam power (500 kW) from the CSNS‐II accelerator complex. Two schemes have been designed: the baseline scheme is based on an inner conical target in graphite and superconducting solenoids for the capture and transport of pions and muons; the simplified scheme is based on a conventional thick target and room‐temperature magnets for transport. With the former, multiple kinds of muon beams can be provided, from surface muons, decay muons, negative muons, to low‐energy muons. Mainly surface muons are available with the simplified scheme. With a number of novel design concepts such as forward capture of pions/muons from a target station based on superconducting solenoids and triple spatial beam splitting of a muon beam, the design aspects of EMuS are presented here. The wide application potential and the R&D progress are also included.

中国散裂中子源的强流质子加速器采用剥离注入的方式,碳膜将H?剥离两个电子后变成质子,多圈涂抹注入到快循环同步环加速中,并加速至1.6 GeV.为了精确测量剥离膜的剥离效率并研究不同厚度剥离膜的使用寿命,在I-Dump束线上新研发并安装了一套束流流强探测器(H0CT),用于测量未完全剥离的H?和H0(H?被剥离一个电子)粒子.为了测量μA级束流,H0CT弱流强测量系统的研制考虑了外部干扰,配合探头、线缆及电子学低噪声的抗干扰设计,将环境噪声及干扰的影响降至最低,提高信噪比,实现了μA级脉冲电流的测量.

The Associated Proton beam Experiment Platform (APEP) beam line that is under construction at the China Spallation Neutron Source (CSNS) linear accelerator (linac) will begin commissioning in 2022, eventually providing nearly 4800 h of proton beam time every year. It will be the first proton irradiation facility to use naturally-stripped protons – H− beams from the linac are stripped by the residual gas in the beampipe. A number of APEP applications have been proposed, including proton irradiation experiments. We completed the design of the beam line – including proton beam transport, collimation, energy degradation, and shielding – based on the requirements developed in test experiments. Both the proton beam spot sizes and the proton energy can be adjusted continuously across a broad range. The background and residual radiation dose rates around the beam line are maintained at a low level.

The China Spallation Neutron Source project Phase-II aims to deliver 500 kW beam power to the spallation target. To meet the beam power requirement, an RF-driven negative hydrogen ion source with an external-antenna has been developed. In order to optimize the beam transmission through the radio frequency quadrupole and the downstream linac, the low energy beam transport line needs to be carefully studied and the transverse emittance is focused in this paper. With computational simulation and experimental verification, the emittance growth caused by nonlinear magnetic fields of the solenoid and the residual magnetic fields at the measuring position has been carefully analyzed. The measurement uncertainty of the double-slit scanner has also been quantitatively estimated. Using the same plasma-beam boundary setting, the beam extraction system is also optimized with particle tracking simulation in CST PARTICLE STUDIO.

Hadron monitor (HM) plays an important role in inferring or estimating the properties of a neutrino beam by measuring the secondary hadrons in the beam. The HM is also used for the alignment of the primary beam on the production target and for the beam status monitoring during operation. Since HM is permanently placed in the beam line, it has to be robust enough to endure high-level radiation when beam is on. Considering very large dynamic ranges for the beam size and current in different machine modes at the Long Baseline Neutrino Facility (LBNF), an HM in multi-strip secondary electron emission (SEM) type was proposed to meet all the requirements. This paper presents a simulation study of several key issues related to the multi-strip HM, such as energy deposition, signal level estimation and vacuum in a long pipe. A test stand has been setup for measuring the sag in the strips at different temperature that imitates the energy deposition of beam in the strips. The measurements show that with appropriate tension applied, the sag can be easily controlled within a few micrometers.

The back-streaming white neutron source (Back-n) is a comprehensive neutron experimental platform for nuclear data measurement, nuclear astrophysics, neutron irradiation, detector calibration, etc. In order to meet a variety of experimental requirements, an attempt of various combinations of collimators has been made for the current collimation system. The basic parameters such as beam flux and beam spot characteristics under different beam operation modes have been studied. According to the change of the CSNS proton beam operation mode, the influence of different proton beam spots on the Back-n beam is also studied. The study finds that some beam modes with new collimator combinations can meet the experimental requirements and greatly shorten the experimental time. In addition, we have found a parameterized formula for the uniform beam spot of the high-power proton beam based on the beam monitor data, which provides a more accurate proton-beam source term for future white neutron beam physics and application researches.

Faraday cup is used to absorb and stop the beam during the two phases of beam commissioning, such as the front end (FE) system and the temporary line after the drift tube linac (DTL) at the Chinese Spallation Neutron Source (CSNS). According to the beam physical parameters, graphite is selected to stop the beam directly, and oxygenfree copper which is just behind the graphite as the thermal conductive material. By the analysis and comparison of the target type and cooling efficiency, the single slant target is adopted. The incident angle between the target surface and the beam is set as 10°, meanwhile a new waterfall type water-cooling structure with parallel tunnels is designed to improve the cooling efficiency. The finite element software ANSYS is used for thermal analysis of the model, by which the diameter and interval of water cooling tunnels are optimized. The faraday cup discussed in this paper is finally successfully installed in the beam commissioning line and went well.

Beam loss detection is essential for the machine protection and the fine-tuning of the accelerator to reduce the induced radioactivity. Monte Carlo simulations are also vital for the choice of beam loss monitor (BLM) type, for predicting and understanding the BLM response to beam losses. At the China Spallation Neutron Source (CSNS), the cylindrical ionization chamber (IC) filled with $\mathrm{Ar}/{\mathrm{N}}_{2}$ gas mixture is the main type of the BLM to detect the beam losses. This paper presents the detailed beam loss experiments and fluka simulations for the CSNS BLM system. It includes the response functions of the BLM detectors by taking into account the contributions of different secondary particles to the energy deposition in the sensitive volume of the BLM. Dedicated experiments were compared with fluka simulations. It was found that in the low energy section of the linac the usual ion chamber based BLMs are not sensitive enough. A BLM based on ${\mathrm{BF}}_{3}$ enclosed by a high-density polyethylene (PE) moderator is effective to detect the beam losses through detecting thermal neutrons. Its signal is about 3 orders of magnitude higher than that of $\mathrm{Ar}/{\mathrm{N}}_{2}$ BLM for a beam energy of 15 MeV. The simulations provide the results of the intrinsic delay time for the ${\mathrm{BF}}_{3}$ monitor and the thickness optimization for PE to reduce the delay. Finally, the simulated spatial resolution of loss location by detection of neutrons is also evaluated for a beam energy of 15 MeV, which presents a resolution of $\ensuremath{\sim}2\text{ }\text{ }\mathrm{m}$ in our experimental configuration.

The beam windows of high-energy beam lines are important, and it is sometimes difficult to design because it is necessary to ensure particle propagation with minimum disturbance and fulfill mechanical requirements at the same time. The upstream decay pipe window of the long baseline neutrino facility at Fermilab has an extremely large diameter (1.8 m), with a thickness of only 1.5 mm to separate the helium atmosphere in the decay pipe and the nitrogen atmosphere on the other side. Furthermore, the center of this dish-shaped window is expected to be a 200-mm-diameter beryllium dish welded to the outside aluminum alloy A6061, and this welded combination must withstand extreme conditions of a 2.4-MW, high-energy proton beam without leakage. These severe conditions make the design of this window an unprecedented challenge. This paper describes the static thermal-structural analyses based on which the structure has been optimized, as well as dynamic analyses for understanding the shockwave effects originating in the beam. After optimization, the maximum von Mises stresses in the window decreased significantly in both normal operation and accident cases, making our design very reasonable.

The China Spallation Neutron Source (CSNS) has been passed the national acceptance in 2018 and opening for users for several months. Some beam study experiments with wire scanner and beam loss monitor were performed at the CSNS-LINAC during the machine study time. Quite amount of positive ions were found by wire scanner at the Middle Energy Beam Transport line (MEBT), but no more exist at LINAC to Ring Beam Transport line (LRBT). Meantime, the sensitivity of the Beam Loss Monitor (BLM) was verified by the wire scanner through these experiments.

The measurement of beam profile by hadron monitor is in fact the measurement of the positive current after the secondary electrons escaped. According to the situation that the number of beam particles (10 11 /s) is small and the current signal is weak, the material titanium with high secondary electron generation rate is select by material comparison, and the foil strip type is used to increase the cross section area to obtain lager current level. On account of dead weight itself, as well as thermal expansion and contraction, the foil strip shall be loose. The loosen strip will deviate from its theoretical position, and cause the measuring error. Therefore, the deformation-stress of Ti foil strip (1000*50*0.1) was simulated under the pretension (10~90N) with the finite element software ANSYS. A set of experiment device with pretension adjustment and heating for the foil strip was designed, and then the deformation-stress was tested by a high precision 3-D imaging measurement system. Compared with the simulation results, the pretension would better set at about 50N.

China Spallation Neutron Source(CSNS), the biggest platform for neutron scattering research in China, will be finished built and run in the end of 2017. It mainly consists of a 80MeV H⁻ linac and a 80MeV to 1.6GeV Rapid Cycling Synchrotron, two beam transport lines, one target station and relative ancillary facilities. The Linac beam commissioning with beam loss monitors, current transformers, BPMs, beam profile monitors and beam emission measurement has been the main task since last year. Beam instrumentations, commissioning of the temperary 60 MeV linac will be discussed in this paper.

A double-slit type monitor will be used in the emittance measurements at the exit of the first tank of the drift tube linac in the China Spallation Neutron Source where the H-ion energy is 21.67 MeV. The rapid energy deposition in the first slit may generate a rapid temperature rise and high thermal stress, which may damage the slit plate. This article presents detailed thermo-mechanical studies for the slit by Monte Carlo program and finite element analysis. The existence of Bragg peak of the stopping power introduces a thermal spike and stress peak in the slit plate, and both the peak values reach a quasi-steady-state after several beam pulses, moreover, they show different variation trends with changing the beam repetition rate and pulse width. The equilibrium peak temperature and stress are about 1605 K and 78 MPa, respectively, at beam pulse width of 100 mu s and repetition rate of 5 Hz when the beam centered at the edge of slit, which does not exceed the corresponding threshold value of graphite, however, high cycling stress may bring about fatigue damage, so the beam parameters should be selected at suitable values according to the demands of actual measurements.

The first section DTL commissioning of China Spallation Neutron Source (CSNS) project has been successful finished in January, 2016. The H⁻ beam can be accelerated to 21.6 MeV at peak current 18 mA, achieved the design point. Different elements of the beam instrumentation system have been tested during the commissioning, including BPM, CT, FCT, WS, EM, BLM, and corresponding electronics and control systems. High accuracy phase measurement (precision @ ±1°) system has been started into operation. Beam loss monitor (BLM) for low energy, 3 MeV to 21.6 MeV, has been tested too, and got very positive results. For the LRBT, RCS and RTBT, different type wire scanner, BPM, WCM, CT were designed. The monitors fit for the high-radiation environments were considered. All the physical design work has been finished, and being manufactured. Lab test will be started in June and the LINAC commissioning (beam energy up to 80 MeV) will be started in August.

An accelerator-driven subcritical system (ADS) program was launched in China in 2011, which aims to design and build an ADS demonstration facility with the capability of more than 1000 MW thermal power in multiple phases lasting about 20 years. The driver linac is defined to be 1.5 GeV in energy, 10 mA in current and in cw operation mode. To meet the extremely high reliability and availability, the linac is designed with much installed margin and fault tolerance, including hot-spare injectors and local compensation method for key element failures. The accelerator complex consists of two parallel 10-MeV injectors, a joint medium-energy beam transport line, a main linac, and a high-energy beam transport line. The superconducting acceleration structures are employed except for the radio frequency quadrupole accelerators (RFQs) which are at room temperature. The general design considerations and the beam dynamics design of the driver linac complex are presented here.

从973-RFQ束流传输线上束流位置(BPM)测试需求出发,开发了一套完整的束流位置读出系统,其将移植到CSNS工程的京流位置测量系统中.该系统由信号采集、处理和显示模块组成.BPM读出系统采用EPICS作为软件开发平台,并选用Motorola公司的MVME5100作为IOC；硬件采用Hytec公司的ADC8411U卡实现对束流位置信号100 kHz的同步触发采样.信号处理模块对采集到的信号进行数值平均滤波,并实现到束流位置的转换.信号显示模块选用EPICS客户端软件EDM实现对束流位置信息2种不同方式的显示.经测试,整个系统最终读出的束流位置分辨率远好于0.2 mm,符合设计要求.