THE DESIGN OF BEAM COLLIMATION SYSTEM FOR CSNS / RCS *
THE DESIGN OF BEAM COLLIMATION SYSTEM FOR CSNS / RCS *
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发表时间：
2010
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通讯作者：
Na Wang
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作者：
Na Wang
中国空间中子源（CSNS）加速器由一台80 MeV的直线加速器和一台1.6 GeV的快速循环同步加速器（RCS）组成，其设计输出功率为100 kW，重复频率为25 Hz。对于这样一个高强度的RCS，光束损失和控制是主要关注的问题。设计了两级准直系统，使光束损失集中在一个限制区域内，而在另一部分RCS处，不受控制的光束损失小于1 W/m。对光束准直系统进行了详细的设计，并对各种方案进行了比较。分析了影响准直效率的关键因素，并利用ORBIT软件对准直效率和光束损失分布进行了研究。CSNS [1]需要1.56×10 ~（-10）个质子，靶束功率为100 kW。在设计RCS时，主要关注的问题之一是由不受控制的射束损失引起的机器部件放射性激活[2]。为了便于维护，机器周围的光束损失不应超过每米1 W。另一个重要的问题是在单匝提取过程中的光束损失。提取时较小的射束发射度允许提取时较小的紧急冲击强度和较小的射束损失。为了实现环周围的低损耗要求和良好约束的提取光束扩展，设计了两级准直系统以将光束损耗定位在机器的良好屏蔽区域中[3]。表1：CSNS环参数符号的主要参数，单位值注入/分机能量Einj/Eext，GeV 0.08/1.6周长C，m 228束流布居数Np，×10 1.56
China Spallation Neutron Source (CSNS) accelerator consists of a 80 MeV linac and a 1.6 GeV Rapid Cycling Synchrotron (RCS), which is designed to produce beam power of 100 kW with a repetition rate of 25 Hz. For such a high intensity RCS, beam loss and control are of primary concern. A two-stage collimation system is designed to localize the beam losses in a restricted area, and keep the uncontrolled losses less than 1 W/m at the other part of RCS. The detailed design of the beam collimation system is presented, including the compare among different schemes. Key issues which affect the collimation efficiency are analyzed, and the collimation efficiency and beam loss distribution are studied by using the code ORBIT. INTRODUCTION The CSNS [1] requires a total number of 1.56×10 protons for the target beam power of 100 kW. In designing the RCS, one of the primary concerns is machine component radioactivation caused by uncontrolled beam losses [2]. To allow hands on maintenance, beam loss around the machine should not exceed 1 W per meter. Another important concern is the beam loss during the single turn extraction. Smaller beam emittance at extraction allows less exigent kicker strength and small beam loss at extraction. In order to achieve the low loss requirement around the ring and well constrained extraction beam extension, a two stage collimation system is designed to localize the beam losses in well shielded regions of the machine [3]. Table 1: The Main Parameters of the CSNS Ring Parameters Symbol, unit Value Inj./Ext. energy Einj/Eext, GeV 0.08/1.6 Circumference C, m 228 Beam population Np, ×10 1.56