强流四杆型RFQ加速腔水冷系统的设计和数值模拟

为了研制一个强中子发生器，北京大学重离子物理研究所设计了一台高负载因子、高流强的RFQ加速器. 本文讨论了RFQ加速腔水冷系统的设计，使用有限元软件ANSYS对水冷系统进行了分析. 使用MAFIA模拟计算得到的功率密度，并将其作为ANSYS水冷模型的边界条件. 因为MAFIA程序和ANSYS程序分网方法的不同，使用一个程序来将MAFIA的结果导入到ANSYS模型中，从而建立起了RFQ加速腔的热分析模型. 通过这个热分析模型分析并检验了水冷系统的设计，确定了水冷系统的结构. 模拟计算结果表明：使用目前设计的这套水冷系统，能够使RFQ加速器工作在适宜的温度下以及长时间稳定的运行.     

强流RFQ的稳定性设计研究

对强流RFQ耦合间隙的确定、二极模稳定杆的设计进行了详细的研究和讨论.利用现有的RFQ冷模,进行了本征模频率的测量、场分布的调试和测量、二极模稳定杆的试验.并通过与模拟结果的比较,验证了模拟程序在RFQ腔体设计中的可靠性.同时,对影响RFQ稳定性设计的物理进行了有益的探讨.     

SSC新高频腔设计与分析

简要分析了HIRFL SFC与SSC之间的束流匹配关系, 给出了新高频腔的频率范围。 利用经典三维电磁场数值模拟软件MAFIA对SSC新高频腔体进行了模拟计算, 得出了SSC新高频腔体的相关物理参数, 并对频率范围、Q值、 并联阻抗和电压分布等参数进行了分析。 高频腔体的模拟计算结果完全符合SSC回旋加速器改造的物理设计及空间结构要求。     

医用质子加速器注入器714MHz RFQ的设计研究

结合近几年来RFQ研究的进展,探讨了进一步提高RFQ工作频率上限的可能性.通过讨论得出了一台714MHz—0.8MeV RFQ的设计参数.动力学模拟计算表明,对医用弱流加速器,RFQ在714MHz频率仍能保持传输效率高,发射度增长小等优良性能.     

利用模拟方法研究RFQ加速器中正、负离子束同时加速的动力学问题

在以时间为自变量的PARMTEQ程序的基础上,添加了另一带相反电荷的束流进行动力学计算,同时考虑了正、负离子束加速的空间电荷效应和束团间的作用.并针对特定结构参数的RFQ加速器,给出了双束加速的动力学模拟过程和结果.模拟计算的目的在于研究正、负离子束在RFQ加速结构中同时加速所引起的动力学问题.结果表明,正、负离子束同时加速有助于克服径向空间电荷效应,但在流强较大时,双束加速时,将会在纵向出现明显的异性电荷之间的“捕捉”(trap)现象,从而导致纵向粒子损失数目的增加.因此,为实现双束加速,必须专门重新设计RFQ加速器,使其传输效率高于单束,才能体现出双束加速的优越性     

200MHz质子带窗四翼型射频四极场加速器结构模拟研究

根据束流动力学设计方案,使用电磁场计算软件CST Microwave Studio对带窗四翼型射频四极场(RFQ)结构进行了模拟研究,分析了加速腔结构参数对其物理特性的影响,得到了200MHz质子带窗四翼型RFQ优化结构方案。该结构的比分路阻抗为79.5kΩ·m,模式间隔达25.802MHz。与传统的四翼型RFQ比较结果表明:带窗四翼型RFQ具有较低的工作频率范围、良好的电稳定性以及较高的比分路阻抗。     

RFQ加速器的束流动力学和高频结构

本文描述了RFQ加速器的特点.说明了束流动力学设计研究对于形成这些特点的贡献.给出了它的五个设计极限.综述了近10年来国内外在RFQ束流动力学和高频结构方面的若干主要发展.     

束团压缩用踢波器的模型腔北大核心CSCD

为了提高中子产额,法兰克福强中子源采用Mobley型束团压缩器来增强打靶时质子流的密度,其入口处由射频踢波器实现微脉冲的偏转,踢波器由一对电偏转板和串联电感线圈组成谐振腔体。考虑到高频下寄生电容效应、导体腔壁对线圈电感的影响以及涡流效应对线圈交流电阻的影响,对一台模型腔的射频特性进行了理论预测。对腔体内电磁场分布进行了数值模拟,并利用电容微扰法进行了冷模测量。针对谐振频率、品质因数和并联分路阻抗等参数,分析比较了理论计算、数值模拟及冷模测量的结果,总结得出射频踢波器的有效设计方法。     

束团压缩用踢波器的模型腔

 为了提高中子产额,法兰克福强中子源采用Mobley型束团压缩器来增强打靶时质子流的密度,其入口处由射频踢波器实现微脉冲的偏转,踢波器由一对电偏转板和串联电感线圈组成谐振腔体。考虑到高频下寄生电容效应、导体腔壁对线圈电感的影响以及涡流效应对线圈交流电阻的影响,对一台模型腔的射频特性进行了理论预测。对腔体内电磁场分布进行了数值模拟,并利用电容微扰法进行了冷模测量。针对谐振频率、品质因数和并联分路阻抗等参数,分析比较了理论计算、数值模拟及冷模测量的结果,总结得出射频踢波器的有效设计方法。     

带空间电荷效应的横向发射度测量（英文）

CADS注入器Ⅰ试验装置由中国科学院高能物理研究所承建。其10mA的束流由RFQ结构加速到3.2 MeV,经中能传输段匹配到超导加速结构。为了减小失匹配造成的束流损失,需要测量RFQ出口束流参数,以便调整中能传输段Lattice结构,使束流能匹配进入超导腔。CADS注入器Ⅰ采用丝靶扫四极铁参数的方式测量束流截面并计算RFQ出口Twiss参数。强流加速器在低能段空间电荷力很强,常规的基于矩阵的数据处理方法会带来误差。本文分别用常规的未考虑空间电荷效应的矩阵方法和考虑了空间电荷效应的遗传算法对数据进行处理,得到的结果显示低能强流加速器进行Twiss参数测量时,必须考虑空间电荷效应的影响。     

The Design and Simulation of a Cooling System of High Current 4-rod RFQ Cavity

To develop a high current neutron generator, preliminary studies on a high current, high duty factor 4-rod RFQ accelerator has been carried out in the Institute of Heavy Ion Physics,Peking University. This paper discusses the design of a cooling system of the RFQ cavity. Finite element program ANSYS was used to analyze the cooling system. The power density was simulated by MAFIA and used as the boundary condition of ANSYS. Due to the different meshing methods between MAFIA and ANSYS, a program was written to transfer the result of MAFIA to ANSYS. Then a thermal analysis model of RFQ cavity was built by using ANSYS. The design of the cooling system was analyzed and checked by using this model, and then the structure of cooling system is determined. Simulation results showed that the design of the cooling system makes RFQ accelerator working at proper temperature and long time steadily.     

Power test of the separated function RFQ accelerator

The progress of the Separated Function RFQ (SFRFQ) accelerator, which can raise the field gradient of acceleration while maintaining the transverse focusing power sufficient for high current beam, is presented. In order to demonstrate the feasibilities of the novel accelerator, a prototype cavity was designed and constructed. Correspondingly, a code SFRFQCODEV1.0 was developed specially for cavity design and beam dynamics simulation. The prototype cavity will be verified as a post-accelerator for ISR RFQ-1000 (Integral Split Ring RFQ) and accelerate O+ from 1 MeV to 1.6 MeV. To inject a higher current oxygen beam for the prototype cavity, the beam current of ISR RFQ-1000 was upgraded to 2 mA. The status of high power and beam test preparation for the prototype cavity are presented in this paper.     

Power test of the separated function RFQ accelerator

The progress of the Separated Function RFQ (SFRFQ) accelerator, which can raise the field gradient of acceleration while maintaining the transverse focusing power sufficient for high current beam, is presented. In order to demonstrate the feasibilities of the novel accelerator, a prototype cavity was designed and constructed. Correspondingly, a code SFRFQCODEV1.0 was developed specially for cavity design and beam dynamics simulation. The prototype cavity will be verified as a post-accelerator for ISR RFQ-1000 (Integral Split Ring RFQ) and     

Progress in the beam commissioning of separated function RFQ accelerator

Separated Function RFQ (SFRFQ) was proposed as a post accelerator of RFQ to accelerate heavy ions at low frequency. It introduces gap accelerating in the quadrupole electrodes, and therefore it has higher accelerating efficiency than the conventional RFQ accelerator. The first SFRFQ prototype cavity has been specially designed and constructed as a post accelerator to accelerate O+ beam from 1.03 MeV to 1.64 MeV. Based on accomplishment of low power measurement and high power test, the beam commissioning was carried out to verify its feasibility. The measured energy gain per cell of SFRFQ is 45 keV, which is about 60% higher than that of Peking University Integral Split Ring (ISR) RFQ.     

Design studies of a high-current radiofrequency quadrupole for accelerator-driven systems programme

A 3 MeV, 30 mA radiofrequency quadrupole (RFQ) accelerator has been designed for the low-energy high-intensity proton accelerator (LEHIPA) project at BARC, India. The beam and cavity dynamics studies were performed using the computer codes LIDOS, TOUTATIS, SUPERFISH and CST microwave studio. We have followed the conventional design technique with slight modifications and compared that with the equipartitioned (EP) type of design. The sensitivity of the RFQ to the variation of input beam Twiss-Courant parameters and emittance has also been studied. In this article we discuss both design strategies and the details of the 3D cavity simulation studies.     

Design study of a radio-frequency quadrupole for high-intensity beams

The Rare isotope Accelerator Of Newness(RAON) heavy-ion accelerator has been designed for the Rare Isotope Science Project(RISP) in Korea. The RAON will produce heavy-ion beams from 660-MeV-proton to200-MeV/u-uranium with continuous wave(CW) power of 400 k W to support research in various scientific fields.Its system consists of an ECR ion source, LEBTs with 10 ke V/u, CW RFQ accelerator with 81.25 MHz and 500 ke V/u, a MEBT system, and a SC linac. In detail, the driver linac system consists of a Quarter Wave Resonator(QWR) section with 81.25 MHz and a Half Wave Resonator(HWR) section with 162.5 MHz, Linac-1, and a Spoke Cavity section with 325 MHz, Linac-2. These linacs have been designed to optimize the beam parameters to meet the required design goals. At the same time, a light-heavy ion accelerator with high-intensity beam, such as proton,deuteron, and helium beams, is required for experiments. In this paper, we present the design study of the high intensity RFQ for a deuteron beam with energies from 30 ke V/u to 1.5 MeV/u and currents in the m A range. This system is composed of an Penning Ionization Gauge ion source, short LEBT with a RF deflector, and shared SC Linac. In order to increase acceleration efficiency in a short length with low cost, the 2nd harmonic of 162.5 MHz is applied as the operation frequency in the D~+RFQ design. The D~+RFQ is designed with 4.97 m, 1.52 bravery factor. Since it operates with 2nd harmonic frequency, the beam should be 50% of the duty factor while the cavity should be operated in CW mode, to protect the downstream linac system. We focus on avoiding emittance growth by the space-charge effect and optimizing the RFQ to achieve a high transmission and low emittance growth. Both the RFQ beam dynamics study and RFQ cavity design study for two and three dimensions will be discussed.     

分离作用射频四极场加速器频率调谐和高功率试验

在分离作用射频四极场(SFRFQ)加速腔中加入频率调谐装置,用步进电机驱动调谐杆运动,改变调谐板在腔中的位置来改变调谐板与支撑环之间的分布电容,从而改变SFRFQ腔的工作频率,使其谐振频率为26.07 MHz,实现了RFQ和SFRFQ组合加速系统频率的匹配。在完成两腔频率调谐的基础上进行了SFRFQ腔体1/6占空比高功率试验,轫致辐射谱的测量表明,SFRFQ极间电压在入射峰值功率为28.8 kW时已达到86.2 kV,超过了设计指标的70.0 kV。     

Numerical Modeling of Ion-Optical Systems for Extraction of a Beam of Negative Hydrogen Ions and Its Acceleration and Matching with a Radio-Frequency Quadrupole Accelerator

A source of negative hydrogen ions is constructed at the Institute for High Energy Physics in order to raise the intensity of the U-70 accelerator complex using multiturn charge-exchange injection. The 3D ion-optical IBSimu simulation package was used to model and optimize the system for extraction of an ion beam from plasma, its acceleration to 100 keV, and matching with a radio-frequency quadrupole (RFQ) accelerator. The system of extraction of an ion beam with a current of 50 mA and electron-flow suppression was modeled. The magnetic transport channels with two solenoids and six quadrupole lenses were compared. The end goals of analysis of the matching channel were to obtain the needed Twiss parameters and to minimize the emittance growth at the RFQ input.     

强流质子加速器束流剖面分布及束晕测量系统设计

 针对一台用于加速器驱动洁净核能源系统研究、高占空比的强流质子加速器,开展强流质子直线加速器束晕产生的研究工作,其中的束流剖面分布特别是束晕部分测量的束流诊断系统是研究工作的核心内容。束晕的产生在低能量段尤其重要,且对整个直线加速器的设计有重要影响。介绍了研究束晕增长的束流输运线和测量系统的布局设计,并根据所研究的加速器束流的情况进行束流剖面探测器和束晕测量的设计和预研,包括丝靶材料的模拟计算和选择、机械驱动的控制系统设计和研究、前端模拟电路的设计和仿真模拟、以及整个系统与EPICS和VxWorks的计算机控制接口等。