CSNS/RCS次级准直器吸收体的冷却设计

作为CSNS/RCS横向束流准直系统的关键部件,次级准直器用于吸收经主准直器散射后不在预定轨道的束晕粒子,其工作原理决定了该设备要求满足强辐射环境下的稳定性、超高真空及高定位精度等要求。基于主准直器的设计及研制经验,对次级准直器结构方案及控制系统进行详细设计。针对关键部件吸收体,结合辐射防护分析结果,考虑水冷降温的方式,设计了控制程序,通过有限元分析软件ANSYS对其进行瞬态热分析,保证吸收体设计的可行性。     

Longitudinal RF capture and acceleration simulation in CSNS RCS

China Spallation Neutron Source (CSNS) is a high power proton accelerator-based facility. Uncontrolled beam loss is a major concern in designing the CSNS to control the radioactivation level. For the Rapid Cycling Synchrotron (RCS) of the CSNS, the repetition frequency is too high for the longitudinal motion to be fully adiabatic. Significant beam loss happens during the RF capture and initial acceleration of the injection period. To reduce the longitudinal beam loss, beam chopping and momentum offset painting methods are used in the RCS injection. This paper presents detailed studies on the longitudinal motion in the RCS by using the ORBIT simulations, which include different beam chopping factors, momentum offsets and RF voltage optimization. With a trade-off between the longitudinal beam loss and transverse incoherent tune shift that will also result in beam losses, optimized longitudinal painting schemes are obtained.     

Study on the effects of chromaticity and magnetic field tracking errors at CSNS/RCS

The Rapid Cycling Synchrotron (RCS) is a key component of the China Spallation Neutron Source (CSNS). For this type of high intensity proton synchrotron, the chromaticity, space charge effects, and magnetic field tracking errors between the quadrupoles and the dipoles can induce beta function distortion and tune shift, and induce resonances. In this paper, the combined effects of chromaticity, magnetic field tracking errors and space charge on beam dynamics at CSNS/RCS are studied systemically. 3-D simulations with different magnetic field tracking errors are performed by using the code ORBIT, and the simulation results are compared with the case without tracking errors.     

Beam collimation for CSNS/RCS

The current design of the CSNS/RCS beam collimation system consists of a two-stage betatron collimation and a single momentum collimator. This paper summarizes various aspects of collimator design, including collimation principle and layout, material choice and collimator mechanical structure, etc. At last, radiation and thermal analysis are carried out to illustrate the feasibility of the current beam collimation scheme.     

Beam collimation for CSNS/RCS

The current design of the CSNS/RCS beam collimation system consists of a two-stage betatron collimation and a single momentum collimator. This paper summarizes various aspects of collimator design, including collimation principle and layout, material choice and collimator mechanical structure, etc. At last,radiation and thermal analysis are carried out to illustrate the feasibility of the current beam collimation scheme.     

中国散裂中子源快循环同步加速器主准直器的设计与研究

为满足强流加速器对准直器高散热性能、高抗辐射性能、超高真空、高定位精度、高稳定性和在线实时调整等特殊要求,在CSNS/RCS主准直器设计时针对结构方案和控制方案进行了详细设计和研究,针对关键部件:刮束器、真空盒、驱动装置和远程快速拆卸装置等设计难点进行了阐述,在设计中使用ANSYS完成了刮束器的热分析及支架强度和变形校核,用FLUKA程序对辐射屏蔽进行了分析和设计,确保主准直器设计的可靠性。     

Experiments and analysis of thin tungsten slice and W/Cu brazing for primary collimator scraper in CSNS/RCS

According to the requirements for the beam collimation system of the rapid cycling synchrotron(RCS)of China Spallation Neutron Source(CSNS),the main structure of a scraper of primary collimator is made by W/Cu brazing,in which the thickness of tungsten slice is 0.17 mm.In order to get the best mechanical properties,the brazing temperature is suggested to be controlled under the recrystallization temperature of tungsten,while the recrystallization temperature is affected directly by the thickness of tungsten.Because of little research and application on the brazing of thin tungsten slice of 0.17 mm and copper,tensile tests are done to get the mechanical properties of tungsten slices which experience different brazing temperatures.In keeping the inner relationships between the mechanical properties and temperature,another experiment is done by using SEM to scan the microstructures including the size and distribution of crystals.Finally we determine the recrystallization temperature of tungsten slice of 0.17 mm,and get the best parameters of W/Cu brazing for scrapers of primary collimator in CSNS/RCS.     

Study on space charge effects of the CSNS/RCS

The Rapid Cycling Synchrotron (RCS) is a key component of the China Spallation Neutron Source (CSNS). The space charge effect is one of the most important issues in the CSNS/RCS, which limits the maximum beam intensity, as well as the maximum beam power. Space charge effects are the main source of emittance growth and beam loss in the RCS. Space charge effects have been studied by simulation for the CSNS/RCS. By optimizing the painting orbit, the optimized painting distribution was obtained. The space charge effects during the acceleration are studied and dangerous resonances, which may induce emittance growth and beam loss, are investigated. The results are an important reference for the design and commissioning of the CSNS/RCS.     

CSNS反角白光中子源束线控制系统研制

中国散裂中子源(CSNS)反角白光中子源束线主要由中子束窗、中子开关、中子准直器和真空管道等组成。为了保证CSNS反角白光中子源束线安全、稳定、可靠地运行,研制了基于EPICS(Experimental Physics and Industrial Control System)软件架构的控制系统。该系统主要由中子束窗、中子开关及中子准直器的运动控制系统、真空控制系统和控制室三部分组成,实现了对反角白光中子源束线主要设备的远程监测和控制。测试结果表明,该系统具有稳定可靠性高、人机交互友好的特点,很好地满足了反角白光中子源束线运行的需要。     

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。     

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.     

A prototype RF power source for CSNS/RCS

A prototype RF power source has been built to supply high RF power to a ferrite-loaded cavity, which is a part of R&D of the Rapid Cycling Synchrotron of China Spallation Neutron Source (CSNS/RCS). A direct fast RF feedback amplifier, a 4:1 impedance transformer and auto tuning grid were locally located to compensate the heavy beam loading of CSNS/RCS. Design and commissioning of the RF power source is discussed here, also with some advice on system improvement.     

CSNS\RCS引出系统快脉冲冲击磁铁样机的设计

 设计了中国散裂中子源(CSNS)快循环同步加速器(RCS)引出系统快脉冲冲击磁铁样机。为降低磁铁和其电源的研制难度,保证运行的可靠性,决定采用美国散裂中子源(SNS)的Single-turn结构。根据磁铁的设计指标,给出了磁铁设计要求铁芯材料选择方法、整体的结构设计以及如何对磁铁进行定位和准直,并采用Opera程序进行模拟计算,结果表明：当铁芯长度为220 mm时,磁有效长度大约为302 mm;磁感应密度最大的地方在4个内角上,约为0.215 T;在133 mm×200 mm的平面范围内,磁场均匀性优于±0.8%。理论分析和Opera程序模拟均验证了磁铁结构方案的可行性。     

CSNS RCS注入涂抹凸轨磁铁脉冲电源设计

中国散裂中子源(CSNS)快循环同步加速器(RCS)是一台高束流功率质子加速器, RCS注入系统是将直线加速器预加速的负氢离子束流通过剥离的方式注入到RCS环中, 注入系统采用凸轨方案和相空间涂抹技术并要求涂抹凸轨磁铁脉冲电源输出脉冲电流的下降沿能够被程序控制, 电源采用IGBT功率放大的方式产生脉冲电流, 用程序控制电源的给定波形, 通过电源反馈控制系统, 使电源的输出波形跟随电源的给定波形, 达到控制电源输出脉冲电流下降沿的目的. 电源输出脉冲电流的跟踪误差是涂抹凸轨磁铁脉冲电源的重要指标, 为了满足跟踪误差小于2%的指标, 要求IGBT拓扑频率大于400kHz. IGBT拓扑采用IGBTH桥串并联错相工作的方式达到分压、分流和提高频率的作用. 高功率、高频率、快速的响应时间和最佳的反馈控制策略是涂抹凸轨磁铁脉冲电源具有良好性能的关键.     

Introduction to the overall physics design of CSNS accelerators

The China Spallation Neutron Source (CSNS) is an accelerator-based facility. The     

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。     

中国散裂中子源快循环同步加速器主剥离膜设计

设计了中国散裂中子源(CSNS)快循环同步加速器(RCS)注入区的主剥离膜装置。为降低研制难度和成本，提高运行可靠性，选择了回转体式的结构。根据在线可调性、高稳定性、高定位精度和超高真空等技术难点，给出了CSNS/RCS主剥离膜的具体结构方案和控制方案。利用ANSYS有限元分析软件和材料力学原理，对设备的核心部件不锈钢同步带进行了模拟计算和理论分析。     

CSNS/RCS环射频腔用铁氧体环测试系统研制

为测试环射频铁氧体加载同轴谐振腔中铁氧体环的性能和批量筛选铁氧体环,研制了铁氧体双环测量系统。与国内外同类设备相比,该系统采用了扫频测量的闭环控制,可以模拟射频腔的运行工况、实现对铁氧体环性能的动态测量。扫频范围测量结果表明:该测试系统满足在0~3 000 A偏流调谐范围内的1.02~2.44 MHz频率覆盖要求,固定频率点的高功率测量结果和材料性能参数与日本J-PARC测量数据吻合。     

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.     

Longitudinal RF capture and acceleration simulation in CSNS RCS

China Spallation Neutron Source (CSNS) is a high power proton accelerator-based facility. Uncontrolled beam loss is a major concern in designing the CSNS to control the radioactivation level. For the Rapid Cycling Synchrotron (RCS) of the CSNS, the repetition frequency is too high for the longitudinal motion to be fully adiabatic. Significant beam loss happens during the RF capture and initial acceleration of the injection period. To reduce the longitudinal beam loss, beam chopping and momentum offset painting methods are used in the RCS injection. This paper presents detailed studies on the longitudinal motion in the RCS by using the ORBIT simulations, which include different beam chopping factors, momentum offsets and RF voltage optimization. With a trade-off between the longitudinal beam loss and transverse incoherent tune shift that will also result in beam losses, optimized longitudinal painting schemes are obtained.