Introduction to the overall physics design of CSNS accelerators

The China Spallation Neutron Source (CSNS) is an accelerator-based facility. The accelerator of CSNS consists of a low energy linac, a Rapid Cycling Synchrotron (RCS) and two beam transport lines. The overall physics design of CSNS accelerator is described, including the design principle, the choice of the main parameters and design of each part of accelerators. The key problems of the physics design, such as beam loss and control, are also discussed. The interface between the different parts of accelerator, as well as between accelerator and target, are introduced.     

基于深度学习的CSNS加速器预警系统样机

为了能在中国散裂中子源（CSNS）加速器的部分故障发生前发出预警信息,利用深度学习建立了基于CSNS加速器真空度和漂移管直线加速器（DTL）温度的特征模型,开发了一套CSNS加速器预警系统样机。该样机基于实验物理及工业控制系统（EPICS）架构搭建,主要由训练、识别和信息发布3部分组成,采用Python进行程序设计开发,实现了训练样本获取、深度学习网络设计和训练、在线识别和信息发布等功能。测试结果表明,该样机对基于CSNS加速器真空度和DTL温度历史数据生成的测试集的准确率达98.4%,且能根据实时数据识别出CSNS加速器真空度和DTL温度的异常,并能发出预警信息,证明了其可行性和有效性。     

中国散裂中子源直线加速器束流流强测量系统

介绍了中国散裂中子源(CSNS)直线加速器(Linac)采用的自主研制的束流变压器(BCT)系统。根据CSNS Linac的束流参数、加速器管道的横向孔径和纵向空间,专门设计了BCT进行束流宏脉冲流强的测量。在CSNS Linac试运行阶段成功地测量到了负氢粒子束流的宏脉冲信息,给调束运行提供了有利的保障和支撑。     

强流质子加速器ns级快沿切束电源系统

详细分析了中国散裂中子源(CSNS)直线加速器低能端预切束电源工作原理。切束束团上升沿和下降沿的快慢是衡量切束电源性能好坏的重要指标,经过研究,研制了一台脉冲幅值6 kV,前后沿纳秒级的切束腔电源,应用纯硬件电路代替软件的方法实现高频和低频定时信号的同步和与处理,使该电源输出稳定可靠的高压脉冲。该电源基于直流高压加快速高压开关的设计方案来实现高压、高重复频率及纳秒级快沿的脉冲输出,具有多脉冲和单脉冲两种工作模式,满足了直线加速器单束团和多束团注入到快循环质子同步加速器(RCS)的要求。CSNS直线加速器切束实验的结果表明,切束电源满足各项设计指标要求。     

Vibration research of the AC dipole-girder system for CSNS/RCS

The China Spallation Neutron Source (CSNS) is a high intensity proton accelerator based facility. Its accelerator complex includes two main parts: an H^- linac and a rapid cycling synchrotron (RCS). The RCS accumulates the 80 MeV proton beam and accelerates it to 1.6 GeV, with a repetition rate of 25 Hz. The AC dipole of the CSNS/RCS is operated at a 25 Hz sinusoidal alternating current which causes severe vibration. The vibration will influence the long-term safety and reliable operation of the magnet. The dipole magnet of CSNS/RCS is an active vibration equipment, which is different from the ground vibration accelerator. It is very important to design and study the dynamic characteristics of the dipole-girder system. This paper takes the AC dipole and girder as a specific model system. A method for studying the dynamic characteristics of the system is put forward by combining theoretical calculation with experimental testing. The ANSYS simulation method plays a very important role in the girder structure design stage. With this method, the mechanical resonance phenomenon was avoided in the girder design time. At the same time the dipole vibratory force will influence the other equipment through the girder. Since it is necessary to isolate and decrease the dipole vibration, a new isolator was designed to isolate the vibratory force and decrease the vibration amplitude of the magnet.     

中国散裂中子源直线输运线束流位置测量系统

介绍了针对中国散裂中子源(CSNS)的直线到环输运线(LRBT)所设计的条带式束流位置测量(BPM)系统,探头方案以条带式电极为基础进行物理设计及参数优化,并通过机械标定减少机械加工误差,电子学选用商用数据处理方案。此系统在加速器实际运行中有效提供位置信息,对在线测量数据采用奇异值分解(SVD)进行分析,根据分析结果,对束流轨道测量的精度达到预期设计目的,满足物理调束需求。     

环-靶站输运线末端准直器的研究

环-靶站输运线(RTBT)末端的准直器是中国散裂中子源(CSNS)工程中的关键部件之一,因其靠近靶站,辐射剂量大,维护困难,故设计可靠性极为重要。根据准直器的工作原理,及CSNS物理设计要求,对比国外同类加速器的设计经验,设计完成准直器设备。在设计过程中兼顾了热沉积、功率损耗和材料性能等方面的严格要求,并逐一阐述了具体方案。利用Bethe-Bloch公式计算与SRIM软件模拟的结果比较,确定了模拟工具和模拟方法的可靠性,根据ANSYS有限元软件模拟的结果,验证了准直器结构设计的可靠性。     

Simulation on buildup of electron cloud in a proton circular accelerator

Electron cloud interaction with high energy positive beams are believed responsible for various undesirable effects such as vacuum degradation, collective beam instability and even beam loss in high power proton circular accelerators. An important uncertainty in predicting electron cloud instability lies in the detailed processes of the generation and accumulation of the electron cloud. The simulation on the build-up of electron cloud is necessary to further studies on beam instability caused by electron clouds. The China Spallation Neutron Source(CSNS) is an intense proton accelerator facility now being built, whose accelerator complex includes two main parts: an H-linac and a rapid cycling synchrotron(RCS). The RCS accumulates the 80 Me V proton beam and accelerates it to 1.6 Ge V with a repetition rate of 25 Hz. During beam injection with lower energy, the emerging electron cloud may cause serious instability and beam loss on the vacuum pipe. A simulation code has been developed to simulate the build-up,distribution and density of electron cloud in CSNS/RCS.     

中国散裂中子源直线射频功率源系统的研制

中国散裂中子源加速器质子束流加速能量为1.6 GeV,重复频率为25 Hz,撞击固体金属靶产生散射中子,一期工程的打靶束流功率为100 kW。直线加速器的设计束流流强为15 mA,输出能量为81 MeV。射频加速和聚束系统包括一台射频四极场加速器、中能束流传输线的两个聚束器、四节漂移管直线加速器加速腔和直线-环束流传输线的一个散束器,与之相对应,共有8个单元在线运行的射频功率源为其提供所需的射频功率。目前,直线射频功率源系统预研项目已全部完成,各项性能参数均已达到设计指标,当前正处在批产安装调试阶段。151013     

CSNS束流损失测量系统设计

介绍了束流损失测量系统探测器的选型、前置放大电子学的功能、数据采集系统的硬件配置及本地站显示界面,着重介绍了本系统在加速器不同能量段的束流调试中的应用。DTL低能段成功观测到了束流损失,针对RCS段脉冲高功率设备,对本系统的干扰提出了解决方案,便于加速器调束时区分干扰与束损,针对RTBT微脉冲大信号的束损进行了积分展宽,满足数据采集系统带宽需求。     

An overview of design for CSNS/RCS and beam transport

The China Spallation Neutron Source (CSNS) is the first accelerator-based pulsed neutron source in China. Its accelerators are made up of an 80 MeV H⁻ linac, a Rapid Cycling Synchrotron (RCS) and two beam transport lines. RCS accumulates and accelerates protons to the design energy of 1.6 GeV, and extracts high energy beam to strike the target. The overview of RCS is presented, and the key problems of the physics design are discussed. The two beam transport lines, from linac to RCS and from RCS to the target, are also introduced.

     

中国散裂中子源二期双spoke超导腔设计

中国散裂中子源是中国第一台、世界第四台脉冲型散裂中子源,其已于2020年2月达到100 kW功率的设计指标,运行稳定高效,供束效率位于国际前列。中国散裂中子源二期升级方案中总束流功率将升级到500 kW,其中直线加速器段将采用超导加速腔结构,束流能量由80 MeV提高到300 MeV。其中在80～165 MeV能量段采用324 MHz双spoke超导腔,在165～300 MeV能量段采用648 MHz 6-cell椭球超导腔。采用CST、COMSOL等仿真软件完成324 MHz双spoke超导腔的电磁、机械设计及优化,达到实际运行指标要求。为了提高腔运行的稳定性,在腔的设计中对E_P/E_acc着重进行了优化,使其尽量降低。     

中国散裂中子源注入系统电切割磁铁物理设计

利用OPERA/TOSCA大型有限元分析软件对中国散裂中子源/快循环同步环（CSNS/RCS）注入系统的直流C型特种电切割磁铁进行了2维/3维磁场计算和设计,通过放置1 mm厚的DT4铁磁性屏蔽板,可将循环束流轨道上的边缘漏场比降低至2.610-4,大大减小了切割板外侧的边缘漏场对循环束流动力学的影响。另外,对该类型切割磁铁的线圈做了详细的水冷计算,以保证磁铁能在适当的温度下运行。结果表明,无论从物理上还是工程上,该类型磁铁完全可以满足CSNS/RCS注入系统物理设计以及长期稳定运行的要求。     

Study of accelerator neutrino detection at a spallation source

We study the detection of accelerator neutrinos produced at the China Spallation Neutron Source(CSNS).Using the code FLUKA,we have simulated the production of neutrinos in a proton beam on a tungsten target and obtained the yield efficiency,numerical flux,and average energy of different flavors of neutrinos.Furthermore,detection of these accelerator neutrinos is investigated in two reaction channels:neutrino-electron reactions and neutrino-carbon reactions.The expected numbers of different flavors of neutrinos have also been calculated.     

散裂中子源高气压二维位置灵敏3He探测器的实验研究

为满足中国散裂中子源多功能反射谱仪中子探测器的基本物理要求:有效面积达到200 mm×200 mm、探测效率大于50%（2Å）、位置分辨好于2 mm等,中国科学院高能物理研究所研制了3He高气压二维多丝正比室位置灵敏中子探测器。该探测器采用二维多丝室结构,腔体内充3He/C₃H₈（6 atm/2.5 atm）的组合气体。本文首先利用Am/Be中子源完成对探测器全面积均匀性测试,均匀性指标达到了95.1%;探测器在中国散裂中子源的20号束流线站安装后,对其进行了在束测量,通过飞行时间选取波长2.8Å的慢中子,测量了探测器二维位置分辨和二维成像性能。在X方向（垂直于阳极丝的方向）的位置分辨为0.99 mm,Y方向（平行于阳极丝的方向）的位置分辨为1.36 mm,探测器具有很好的二维位置分辨和二维成像能力。测量结果表明探测器满足反射谱仪的研制要求。     

CSNS加速器真空控制系统的设计与实现

中国散裂中子源(CSNS)加速器真空控制系统负责真空数据采集、设备监控和闸板阀控制与联锁,是设备运行和故障诊断以及超高真空保持的重要保障。本文介绍了加速器真空需求,基于实验物理及工业控制系统EPICS软件框架的真空控制系统设计与实现,使用横河可编程逻辑控制器PLC控制与联锁设备,摩莎MOXA工控机监测真空状态,EPICS PV数据直接进入声音报警系统和历史数据库系统,为工作人员及时发现和处理问题、进行后续数据分析和机器研究等提供了便捷途径和可靠保障。目前,该系统已完成现场安装和调试,并已正式投入运行。运行结果表明,该系统具有稳定性好、可靠性高、人机交互友好的特点,很好地满足了加速器真空控制系统运行的需要。     

快循环同步加速器射频加速电压幅度的数字化控制

 中国散裂中子源(CSNS)快循环同步加速器（RCS）中的射频低电平控制系统是基于FPGA的全数字控制系统,旨在完成对射频频率、加速电压和同步加速相位的控制。介绍了CSNS/RCS射频系统的低电平数字化控制设计方案,并着重对射频加速电压幅度控制回路进行了分析与讨论。电压幅度控制环路通过射频电压幅度信号与电压幅度设定值的比较,得到误差信号。误差信号经过控制器来控制输入到射频腔的功率,以达到稳定和改变腔压的目的。通过对控制对象的分析和建模,得到了满足系统要求的控制器。详细介绍了数字系统的实现,尤其是信号的解调和控制算法的实现。用ALTERA公司的DSP builder进行数字控制系统开发,系统仿真结果表明,环路误差信号大约于10 μs（400个系统时钟）后归于0,整个电压幅度控制环路能稳定运行。     

中国散裂中子源旋转线圈测量系统研制

中国散裂中子源(CSNS)加速器主要由一台直线加速器、一台快循环加速器以及低能、高能输运线组成。针对CSNS加速器部分直流磁铁研制了一套旋转线圈测量系统。对系统的研制方案、功能、精度、完成的磁铁类型以及部分测量结果进行介绍。该系统解决了CSNS批量磁铁之间的不同中心高度、质量、有效长度、磁场强度的兼容性难题。经过测试运行,积分场测量重复性误差好于±0.02%,空间谐波重复性误差好于0.005%,磁中心测量重复性误差好于±0.03 mm,顺利完成了中国散裂中子源工程150台多种类型磁铁的检测任务。     

Dragon-I Linear Induction Electron Accelerator

Dragon-Ⅰ is a linear induction electron accelerator. This facility consists in a 3.6MeV injector, 38 meter beam transport line and 16MeV induction accelerator powered by high voltage generators, including 8 Marx generators and 48 Blumlein lines. This paper describes the physics design, development and experimental results of Dragon- Ⅰ. The key technology is analyzed in the accelerator development, and the design requirements and operation of the major subsystems are presented. The experimental results show Dragon-Ⅰ generates an 18—20MeV, 2.5kA, 70ns electron beam. The X-ray spot size is about 1.2mm and dose level about 0.103 C/kg at 1 meter.     

CSNS LINAC低电平射频控制系统软件设计

低电平射频控制系统主要用于对加速腔的高频场和谐振频率的控制,保证加速器的稳定运行并输出高品质的束流.低电平控制系统软件提供可视化操作界面,实现数据显示和存储、自动化算法等功能,提高了低电平系统的可操作性,减少了人工作业量和故障率.软件开发具有灵活性强、开发周期短的特点,适合控制速度要求相对不高而逻辑较为复杂的功能开发....