HIRFL-CSR主环加速腔系统设计

正在建设中的兰州重离子加速器冷却储存环 ( HIRFL- CSR)的主环加速腔系统用于将累积的重离子束流进行加速 .其频率范围为 0 .2 5 - 1 .7MHz,峰值电压为 8.0 k V.重点介绍了主环加速腔系统的设计及主要高频参数 ,包括高频腔体的设计及低电平控制部分的设计. An ion cooler storage ring HIRFL CSR is constructing at Institute of Modern Physics(IMP). It consists of two rings--main ring (CSRm) and experimental ring (CSRe). For the CSRm, two RF systems will be employed. One is for RF stacking, and another is for beam accelerating. The designed parameters of CSRm accelerating system and the control block diagram of RF system are described. The RF accelerating system has a specification of lower and wider frequency range from 0.25 to 1.7 MHz...     

A new compact structure for a high intensity low-energy heavy-ion accelerator

A new compact accelerating structure named Hybrid RFQ is proposed to accelerate a high-intensity low-energy heavy ion beam in HISCL （High Intensive heavy ion SuperConducting Linear accelerator）, which is an injector of HIAF （Heavy Ion Advanced Research Facility）. It is combined by an alternative series of acceleration gaps and RFQ sections. The proposed structure has a high accelerating ability compared with a conventional RFQ and is more compact than traditional DTLs. A Hybrid RFQ is designed to accelerate 238U34＋ from 0.38 MeV/u to 1.33 MeV/u. The operation frequency is described to be 81.25 MHz at CW （continuous wave） mode. The design beam current is 1.0 mA. The results of beam dynamics and RF simulation of the Hybrid RFQ show that the structure has a good performance at the energy range for ion acceleration. The emittance growth is less than 5% in both directions and the RF power is less than 150 kW. In this paper, the results of beam dynamics and RF simulation of the Hybrid RFQ are presented.     

Uncoupled achromatic condition of a dog-leg system with the presence of RF cavities

To merge the beam from either of the two injectors to the main linac, a dog-leg system will be employed in the second Medium Energy Beam Transport （MEBT2） line of the China ADS driving accelerator. The achromatic condition has to be guaranteed to avoid beam center excursion against energy jitter. RF cavities were found to be indispensable to control the bunch length growth in the dog-leg system of MEBT2. The full uncoupling between transverse and longitudinal plane is desired to minimize the growth of projected rms emittances. The uncoupled achromatic condition of this dogleg system with the presence of RF bunching cavities will be deduced using the transfer matrices method. It is found that, to fulfill the uncoupling condition, the distance between the bunching cavities is uniquely determined by the maximum energy gain of the RF cavities. The theoretical analysis is verified by the simulation code TraceWin. The space charge effect on the uncoupled achromatic condition and the beam emittance growth will Mso be discussed.     

HIRFL数字化高频低电平控制系统研究

在HIRFL加速器系统中, 需要对射频加速电压的幅度和相位进行精确控制,以实现对重离子的精确俘获、 加速和引出。传统的幅度、相位稳定控制系统采用幅度和相位两个反馈闭合环路来分别稳定腔体电压的幅度和相位。 数字化高频低电平控制系统(LLRF) 基于可编程逻辑门阵列（FPGA）和数字信号处理（DSP）, 采用直接数字频率合成（DDS）与数字正交调制解调（I/Q）技术来实现对高频功率源的控制。 相位控制精度更高, 系统更加稳定。 目前控制系统在假负载上通过了长期稳定性的实验和高功率实验, 幅度偏差小于或等于±1％, 相位偏差小于或等于±0.5°。 In order to ensure that the beam quality is well enough, we need to precisely control the frequency, amplitude and phase of cavity electric field. Traditional control system consists of amplitude loop and phase loop. And these two loops control amplitude and phase stability respectively. The digital low level radio frequency (LLRF) system, which uses advanced digital control technology, needs only one feed back loop to control amplitude and phase stability. The phase control precision and stability of the system are higher than the traditional control system. The LLRF system is based on field programmable gate array (FPGA) and digital signal processing (DSP), and implemented by direct digital frequency synthesis (DDS) and digital orthogonal modulation and demodulation (I/Q) technology. The digital LLRF system has been tested in a long term stability and high power experiments. The amplitude deviation is lower than ±1%, and phase control accuracy is within ±1°.      

Design and performance of the LLRF system for CSNS/RCS

The rapid cycling synchrotron(RCS) is part of the China Spallation Neutron Source(CSNS). The RCS provides 1.6 Ge V protons with a repetition rate of 25 Hz. The RF system in RCS is mainly composed of a ferrite loaded RF cavity, a high power tetrode amplifier, a bias supply of 3300 A and a digital low level RF(LLRF) system based on FPGA. The major challenge of the LLRF system is to solve problems caused by rapid frequency sweeping and the heavy beam loading effect. A total of eight control loops are applied to ensure the normal operation. An effective feedforward scheme is widely used to improve the dynamic performance of the system. The design of the LLRF system and high power integration test results with the prototype RF system are presented.     

Design of the IMP microbeam irradiation system for 100 MeV/u heavy ions

A state-of-the-art high energy heavy ion microbeam irradiation system is constructed at the Institute of Modern Physics of the Chinese Academy of Sciences. This microbeam system operates in both full current intensity mode and single ion mode. It delivers a predefined number of ions to pre-selected targets for research in biology and material science. The characteristic of this microbeam system is high energy and vertical irradiation. A quadrupole focusing system, in combination with a series of slits, has been designed to optimize the spatial resolution. A symmetrically achromatic system leads the beam downwards and serves simultaneously as an energy analyzer. A high gradient quadrupole triplet finally focuses a C^6＋ ion beam to 1 μm in the vacuum chamber within the energy range from 10 MeV/u to 100 MeV/u. In this paper, the IMP microbeam system is described in detail. A systematic investigation of the ion beam optics of this microbeam system is presented together with the associated aberrations. Comparison is made between the IMP microbeam system and the other existing systems to further discuss the performance of this microbeam. Then the optimized initial beam parameters are given for high resolution and high hitting efficiency. At last, the experiment platform is briefly introduced.     

Status of CSNS H- ion source

A new H^- ion source has been installed successfully and will be used to serve the China Spallation Neutron Source (CSNS). In this paper, we report various components of the ion source, including the discharge chamber, temperature, cooling system, extraction electrodes, analyzing magnet, remote control system and so on. Compared to the previous experimental ion source, some improvements have been made to make the ion source more compact and convenient. In the present arrangement, the Penning field is generated by a pair of pole tip extensions on the 90° analyzing magnet instead of by a separate circuit. For the remote control system, F3RP61-2L is applied to the accelerator online control system for the first time. In the running of the ion source, a stable pulse H^- beam with a current of 50 mA at an energy of 50 keV is produced. The extraction frequency and pulse width is 25 Hz and 500 μs, respectively. Furthermore, an emittance scanner has been installed and measurements are in progress.     

RF system design and measurement of HIRF-CSRe

An RF system for the CSRe （cooling storage experimental ring） is designed and manufactured domestically. The present paper mainly describes the RF system design in five main sections： ferrite ring, RF cavity, RF generator, low level system and cavity cooling. The cavity is based on a type of coaxial resonator which is shorted at the end with one gap and loaded with domestic ferrite rings. The RF generator is designed in the push-pull mode and the low level control system is based on a DSP＋FGPA＋DDS＋USB interface and has three feedback loops. Finally we give the results of the measurement on our system.     

基于FPGA的HIMM同步高频信号源设计

针对医用重离子加速器装置(HIMM)同步加速器对于高频系统不同能量波形输出的需求,设计实现可输出不同能量对应腔体电压及偏磁电流波形的同步信号源。该系统以ARTERA公司FPGA作为核心处理元件,接收并处理多组腔体电压及偏磁电流波形文件,同时以DAC作为输出单元,通过接收同步光触发信号实现不同能量对应给定波形信号的无缝切换及同步输出,完成HIMM同步高频信号源的设计。测试结果表明,该信号源工作稳定,可实现各种不同能量对应波形的无缝切换及同步输出,其性能完全满足HIMM系统对碳离子捕获加速的要求。相比于商业任意波形发生器产品,该系统价格低廉,且模块化的设计易于集成,可广泛应用于其他需产生任意波形信号的场合。     

医用加速器装置的离子源进气系统控制

HIMM是国产自主研发的医用加速器装置,作为目前最大的医学放疗装置,整个加速器控制系统的稳定性和可靠性要比工业系统有更高的要求。离子源针阀是离子源产生束流的重要组件,气体流量的大小和混合比直接影响源体真空度、电离效率、离子源稳定性等。本文针对HIMM离子源进气系统设计了基于三菱伺服电机和菲尼克斯PLC的控制系统,从系统结构、硬件设计、软件设计、数据分析等方面进行了介绍。为保证系统稳定性,加入伺服驱动器与相关真空度的硬连锁和远程开关功能。经过实际测试,该系统运行稳定,定位精度可达0.1?,满足设计要求。     

HIMM回旋加速器控制系统中连锁保护功能设计与实现

在HIMM医用重离子加速器（Heavy Ion Medical Machine）中,回旋加速器的连锁保护功能针对离子源、高频、真空、电源、冷却水等子系统的连锁要求,设计实现了设备+PLC+软件三层结构的连锁系统,并保证连锁功能在系统断电、线缆连接故障、数据传输异常等情况下的正常工作。连锁系统可实现硬连锁毫秒级、软连锁次秒级别的反应速度。整体功能在回旋调试过程中得到验证,保障了整个加速器的顺利供束。     

基于AD9854重离子治癌加速器高频控制器设计

介绍了兰州重离子治癌加速器治疗装置的高频控制系统原理、软件设计、硬件配置和布局。提出并实现了对重离子治癌加速器高频控制系统的高频腔体的精确控制。在硬件上,重离子治癌加速器高频控制系统硬件平台由监视控制板和数据分析板两部分构成,采用双FPGA+DSP+DDS+PXI 结构,此结构具有强大的数据处理能力,其核心器件是FPGA和DDS。通过设计编写FPGA VHDL代码实现对DDS芯片的配置,产生的IQ两路信号,分别发送到高频腔、幅度调制器以及偏流电源上,完成幅相同调和频率调制。通过该设计,实现与DAC和ADC操作配合进行高速高效的数据传输,产生高品质束流。     

重离子治癌加速器束诊探测器运动控制系统设计

重离子医疗装置（HIMM）中需要束流诊断探测器来测量加速器束流参数,其中大部分探测器属于拦截式探测器,拦截式探测器在测量束流参数时需要将探测器探头插入束流管道中心,测试完成后将探测器拉出。另外,部分探测器需要联动控制,针对上述需求,设计了基于EtherCAT协议的拦截式探测器的运动控制系统架构,并且开发了基于OPC UA （OLE for Process Control Unified Architecture）协议的客户端/服务器软件系统,所有拦截式探测器已通过CFDA （China Food and Drug Administration）验证,自2017年起在束运行至今。使用结果表明,该系统具有较高的稳定性以及可移植性,控制精度以及控制模式均可完全满足现场应用要求。     

基于射频功率调节的负离子源束流反馈控制研究北大核心CSCD

基于射频负离子源的中性束注入系统是高功率长脉冲(稳态)运行中性束注入系统的最佳选择。负离子源是中性束注入系统的核心部件,需要实现稳定的负离子束引出和加速。在负离子源的运行过程中引出负离子电流会发生变化,尤其在长脉冲、高能量运行条件下会更加明显,因此无法满足稳定运行的要求。为了实现引出束流的稳定引出,开展了束流反馈控制研究,研发了一套基于射频功率调节的束流反馈控制系统,并将束流反馈控制系统应用在射频负离子源测试平台,开展了束流反馈控制测试。测试结果表明束流反馈控制系统能够实现对束流的实时反馈调节以获得束流的稳定引出,验证了基于射频功率调节的束流反馈控制的可行性,为高功率射频负离子源的研制提供支持。     

用于重离子治癌回旋引出的实时流强测量系统北大核心CSCD

为满足重离子治癌加速器装置(HIMM)回旋加速器引出段束流流强的测量需求,设计了新的束流流强测量系统,该系统利用积分电流变换器(ICT)及锁相放大器等配套电子学,能够实现束流流强的非拦截实时测量。文中首先分析了中能束线(MEBT)束流流强的测量需求,并对设计方案进行了实验室系统分析和在线束流强测量。实验室结果表明,锁相放大器的幅度和相位响应一致性满足测量需求。由于ICT对束流流强的测量是相对测量,先使用法拉第筒对ICT进行在线标定;标定前先对法拉第筒(FC)(20μA档位)和ICT系统的流强分辨在线测量,分别为6.45 nA和5.163 nA。由于束流抖动的影响,测量的束流的稳定性约90 nA,其对应的相对测量误差约8%,ICT系统响应时间小于1 ms。测量结果表明,该系统满足物理测量需求。回旋加速器高频系统参数变化引起ICT标定系数变化的工作将在进一步工作中展开。     

31.02 MHz回旋加速器谐振腔Dee电压的标定

中国科学院近代物理研究所医用重离子加速器(HIMM) 高频系统31.02 MHz回旋加速器谐振腔已完成设计加工和腔体的老炼,并投入正常运行。高频腔体的设计峰值Dee 电压要求达到70 kV,但是Dee 电压准确计算比较困难,可以通过CST 仿真软件对腔体进行模拟得到高频腔体的RP=Q0 值,结合输入到腔体的实际功率,计算出腔体的实际电压值。为了验证Dee 电压的准确性,在相同的腔体输入功率条件下,利用韧致辐射法测量腔体电压,测量结果与计算结果误差在0.6% 以内。The 31.02 MHz cyclotron RF system of Heavy Ion Medical Machine (HIMM) in IMP(Institute of Modern Physics, Chinese Academy of Sciences) has completed the design and commssioning,and now has already been put into operation. Its peak voltage requires 70 kV, but the precise calculation of the Dee voltage is still a difficulty problem, we can get the value Rp/Q0 of the cavity by CST simulation, and then combining the actual input power for cavity to calculate the real Dee voltage. In order to verify its accuracy, we use the bremsstrahlung method to test the cavity voltage under the condition of same input power. The error between test results and calculation is less than 0.6%.     

HIRFL-CSRE 脉冲堆积式高频数字低电平系统

为突破传统束流堆积方式瓶颈、提高重离子流强,兰州重离子加速器冷却储存实验环（HIRFL-CSRe）将采用移动式脉冲堆积方案（Moving Barrier Bucket）。该方案要求高频系统能产生高精度的单正弦电压,然而由于Barrier Bucket（BB）电压的宽带特性以及高频系统的非线性,高频腔内的BB电压存在着严重的失真问题。针对此问题,在全面分析了BB电压波形特性以及高频系统的频率响应的基础上,设计了BB电压预失真前馈控制方案,并详细描述了该方案的原理、仿真、软硬件设计以及实际测试结果。研究成果将应用于HIRFL-CSRe的BB束流堆积实验以及十二五强流重离子加速器（HIAF）的BB堆积模式。