The Compact Pulsed Hadron Source Construction Status-猫眼课题宝

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2010

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Jie Wei;Z. Zeng;Huayi Zhang;W. Guan;J. Stovall;Wenqian Li;Cheng Cheng-Cheng;Q. Feng;Zhe Feng;Hongwei Zhao;Shu-xin Zheng;C. Loong;Dong Xu;B. Zhong;B. Shao;Renkai Li;H. Gong;Yu He;J. Billen;Dongsheng Zhang;Xuewu Wang;Guohua Li;T. Du;Jian Li;Q. Xing;T. Liang;Xiao-Ke Xie;X. Guan;Zhanwen Liu;J. Tao;Tuchen Huang;L. Young;Yaliang Zhao;Liangting Sun;Jinchi Cai;Zhifeng Huang;Yigang Yang;Chuanxiang Tang;Huaibi Chen;Jinghai Li;Xiaoxue Han;Xiaozhang Zhang;Q. Du;Yangli Tian;Z. Xiong;Z.Zheng;Yujie Bai;S. Fu

本文报道了清华大学质子直线加速器紧凑型脉冲强子源（CPHS）的设计和建造现状、技术挑战和未来展望。虽然21世纪在高功率中子源项目方面取得了显著进展，特别是SNS（美国）、J-PARC（日本）、ISIS升级（英国）的实现以及ESS（欧盟）和CSNS（中国）的持续进展，但紧凑型基于加速器的中子源的发展相对缓慢，尽管它们的重要性，特别是在教育方面，用户培训和研发的中子学和仪器，早已得到认可。清华大学的CPHS项目于2009年6月开始建设[1]。最初，CPHS由质子直线加速器（13 MeV，16 kW，峰值电流50 mA，50 Hz脉冲宽度为0.5 ms），中子靶站，小角中子散射仪，中子成像/放射学站和质子辐照站组成。目前，加速器系统的制造已经开始。CPHS的第一阶段建设计划于2012年完成。设施布局CPHS主要设施位于清华大学主校区现有的屏蔽建筑内，紧邻清华汤姆逊反向散射光源[2]（图1）。包括主体及配套设施在内的总建筑面积约1,000平方米。电容为1 MVA。冷却水容量约为2000 l/min。机器和人员保护系统设计用于应对突发故障条件和常规操作。设施边界的辐射剂量限制为2.5 Sv/h，以满足政府规定的2.5 mSv/年的限制。相应地评估了Skyshine和地下水的影响。图1：CPHS主要设施布局。加速器和目标站的建筑空间为6米x22米。阴影区域显示可移动的屏蔽块。技术系统进展离子源和低能束传输质子束由电子回旋共振（ECR）质子源（2. 45 GHz，1. 5 kW）产生，并通过LEBT传输（图2）。H2等离子体受到全永磁体（NdFeB环）设计的源体形成的轴向磁场的限制。用四电极系统引出了50 keV、0.5ms脉冲束流。1.3米长的LEBT由两个螺线管透镜，两组转向磁铁，和一个圆锥配置光学匹配的courant-Snyder参数=1.354和=7.731的courant-Snyder。该设计由Trace-3D [3]和PBGUN [4]模拟辅助，用于以100 mA的电流达到97%空间电荷中和率的束流。中科院百人计划（KJCX 2-YW-N22）、中科院海外杰出青年计划、国家自然科学基金（10628510）。weij@tsinghua.edu.cn日本京都IPAC'10会议录MOPEC 071 04强子加速器A15高强度加速器633峰值电流和0.2 m rms归一化发射度。该离子源目前正在兰州IMP进行测试。射频四极杆（Radio Frequency Quadrupole，缩写为QRF）3 MeV，50 mA峰值电流QRF的物理设计于2009年底完成修订[5]。新的设计方案缩短了束流长度约30%，并消除了中能束流输运（MEBT）。在高能端的横向和纵向聚焦的电子束被定制，以匹配DTL入口提供独立于束流的连续恢复力。腔的横截面和叶片尖端的几何形状是纵向定制的，同时将峰值表面电场限制在1.8基尔帕特里克。PARMTEQM代码[6]给出的传输率为97.2%。当束流到达平行出口时，横向发射度增加~20%。从机械上讲，3米长的金属板分为三个部分，每个部分1米，以便于加工和钎焊。上海科林有限公司已开始试生产（图3）。图2：ECR离子源和LEBT的布局。漂移管直线加速器（DTL）13 MeV，50 mA峰值电流DTL的物理设计也在2009年底进行了修改[7]，以匹配无MEBT方案中的设计。FD晶格中4.4m长的DTL腔由两部分共40个单元组成。永久磁铁四极（PMQ）用于横向聚焦，最大梯度为0.9 T/cm。平均加速场从2.2到3.8 MV/m变化，最大表面场高达1.6 Kilpatrick。目前，清华大学正在进行全面建设（图4）。射频系统DPL和DTL共用一个射频电源，该电源由325 MHz信号发生器、放大器、速调管、高压电源、脉冲调制器、撬棍保护、射频传输以及控制和联锁系统组成。射频传输由1：2的功率分配器、隔离衰减器、隔离移相器和波导组成（图5）。来自速调管的2.1MW峰值功率相应地被分割。隔离衰减器由四端口环行器、Y结、大功率负载和滑动短路组成。它可以在100%到80%的幅度范围内进行调节，以满足0.6 MW的功率需求。对于DTL，移相器的输出可在+/45°范围内调整。图3：1米长的第1段隧道的结构布置图。图4：2.2m长DTL第1段结构布置图。(Fig. 6）、小角中子成像/射线照相仪器、电子探测器和斩波器已重新设计图5：射频传输系统布局。参考文献[8]介绍了中子靶站和仪器在靶-慢化剂-反射层和低温系统散射方面的进展以及在中子研究与发展方面所作的努力。

This paper reports the design and construction status, technical challenges, and future perspectives of the proton-linac based Compact Pulsed Hadron Source (CPHS) at the Tsinghua University, Beijing, China. INTRODUCTION While the 21st century has witnessed outstanding progress in high-power spallation neutron-source projects, noticeably the realization of the SNS (US), J-PARC (Japan), ISIS upgrade (UK) and the ongoing progress of the ESS (EU), and CSNS (China), the development of compact, accelerator-based neutron sources is relatively tardy although their importance, especially in education, user training and R&D of neutronics and instrumentation, has long been recognized. The CPHS project at Tsinghua University started its construction in June 2009 [1]. Initially, CPHS consists of a proton linac (13 MeV, 16 kW, peak current 50 mA, 0.5 ms pulse width at 50 Hz), a neutron target station, a small-angle neutron scattering instrument, a neutron imaging/radiology station, and a proton irradiation station. Currently, fabrication of the accelerator systems has begun. The initial phase of the CPHS construction is scheduled to complete in 2012. FACILITY LAYOUT The CPHS main facility is housed in an existing shielded building immediately adjacent to the Tsinghua Thompson-backscattering light source [2] in the main campus of Tsinghua (Fig. 1). The total building area including the main and supporting facilities is about 1,000 m. The electrical capacity is 1 MVA. The cooling water capacity is ~2000 l/min. Machine and personnel protection systems are designed to act upon both sudden fault conditions and routine operations. Radiation dosage is limited to 2.5 Sv/h at the facility boundary so as to satisfy the 2.5-mSv/yr limit set by the government. Skyshine and ground water impacts are evaluated accordingly. Figure 1: CPHS main facility layout. The building space housing the accelerator and the target station is 6m x 22m. Shaded area shows moveable shielding blocks. TECHNICAL SYSTEM PROGRESS Ion Source and Low Energy Beam Transport The proton beam is produced from the electron cyclotron resonance (ECR) proton source (2.45 GHz, 1.5 kW) and transported through the LEBT (Fig. 2). The H2 plasma is restricted by an axial magnetic field shaped by the source body of an all-permanent-magnet (NdFeB rings) design. The 50 keV pulsed beam of 0.5 ms length is extracted by a four-electrode system. The 1.3 m long LEBT consists of two solenoid lenses, two sets of steering magnets, and a cone configuration optically matches to the RFQ with the Courant-Snyder parameters of =1.354 and =7.731. The design was assisted by Trace-3D [3] and PBGUN [4] simulations for a beam of 97% spacecharge neutralization rate reaching the RFQ with 100 mA ____________________________________________ *Work supported by the “985 Project” of the Ministry of Education of China, CAS Sciences Hundred People Initiative (KJCX2-YW-N22), CAS Overseas Outstanding Youth Program, and the National Natural Science Foundation (10628510). weij@tsinghua.edu.cn Proceedings of IPAC’10, Kyoto, Japan MOPEC071 04 Hadron Accelerators A15 High Intensity Accelerators 633 peak current and 0.2 m rms normalized emittance. This ion source is currently under tests at IMP in Lanzhou. Radio Frequency Quadrupole (RFQ) The physical design of the 3 MeV, 50 mA peak-current RFQ was completed revised in late 2009 [5]. With the new design, the length of the RFQ was shortened by about 30%, and the medium-energy-beam-transport (MEBT) was eliminated. The transverse and longitudinal focusing at the high energy end of the RFQ are tailored to match the DTL entry providing continuous restoring forces independent of the beam current. The cavity cross section and vane-tip geometry are tailored longitudinally while limiting the peak surface electric field to 1.8 Kilpatrick. The transmission rate given by the PARMTEQM codes [6] is 97.2%. The transverse emittance increases by ~20% when the beam reaches the RFQ exit. Mechanically, the 3-m long RFQ is separated into three sections of 1 m each to facilitate machining and brazing. Trial fabrication has started at the Kelin Co. Ltd. in Shanghai (Fig. 3). cross-section prototype is un Figure 2: Layout of the ECR ion source and the LEBT. Drift-tube Linac (DTL) The physical design of the 13 MeV, 50 mA peakcurrent DTL was also revised in late 2009 [7] to match the RFQ in the no-MEBT scheme. The 4.4-m long DTL cavity in a FD lattice consists of two sections of totally 40 cells. Permanent-magnet quadrupoles (PMQs) are used for the transverse focusing at the maximum gradient of 0.9 T/cm. The average accelerating field varies from 2.2 to 3.8 MV/m with the maximum surface field up to 1.6 Kilpatrick. Presently, the full der construction at the Tsinghua University (Fig. 4). Radio-frequency System Both RFQ and DTL share a single RF power source that consists of the signal generator at 325 MHz, amplifier, klystron, high voltage power supply, pulsed modulator, crowbar protection, RF transmission, and control and interlock systems. The RF transmission consists of a power divider with a ratio of 1:2, an isolating attenuator, an isolating phase shifter, and waveguides (Fig. 5). The 2.1 MW peak power from the klystron is split accordingly. The isolating attenuator consists of a 4-port circulator, a Y-junction, a high power load and a sliding short. It can be adjustable for amplitudes from 100 to 80% to meet the 0.6 MW power need of the RFQ. The output of the phase shifter can be adjusted for a range of +/45° for the DTL. Figure 3: Structure layout of the 1-m long RFQ section 1. Figure 4: Structure layout of the 2.2m long DTL section 1. (Fig. 6), the small-angle neutron imaging/radiography instruments, the tron detectors and choppers have been re Figure 5: Layout of the RF transmission system. Neutron Target Station and Instruments Progresses in the target-moderator-reflector and the cryogenic systems scattering and the R&D efforts in neu ported in Ref. [8].

The Compact Pulsed Hadron Source Construction Status

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