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根据CSNS加速器束流调试经验,由于相关和反相关涂抹各具特点,如果在初始设计阶段只选择单一固定的涂抹方式,那么所选择的涂抹方式并不一定能满足未来机器的真实束流状态,进而影响加速器运行,甚至可能造成无法达到验收指标。因而,我们需要寻找同时实现相关和反相关涂抹的新注入方案,这样就可以按照建成之后加速器真实束流状态切换涂抹方式,避免由于初始设计时选择不合适的涂抹方式造成诸多故障,进而以最快的方式达到加速器各项设计指标。
经过深入研究,参考了美国散裂中子源现用涂抹方案(相关涂抹)[2]和上小节提到的在反相关涂抹机械结构基础上实现相关涂抹的方法[25],我们提出了一种同时实现相关和反相关涂抹的新注入方案。该注入方案以相关涂抹方法为设计基础,兼顾反相关涂抹方法。对于相关涂抹,在水平和垂直方向上均采用脉冲电流下降曲线进行涂抹;对于反相关涂抹,在水平方向上采用脉冲电流下降曲线进行涂抹,在垂直方向上采用脉冲电流上升曲线进行涂抹。图10给出了RCS接收度椭圆和注入束流的关系示意图。从图中可以看出:对于相关涂抹,在注入开始时,RCS循环束流轨道在水平和垂直方向都是与注入点重合,与正常循环束流轨道中心的偏离最大,涂抹在相空间接收度的中心区域;在注入接近完成时,RCS循环束流轨道在水平和垂直方向都是远离注入点,涂抹在相空间接收度的外围区域。对于反相关涂抹,在注入开始时,RCS循环束流轨道在水平方向是与注入点近似重合,与正常循环束流轨道中心的偏离最大,而在垂直方向上远离注入点,水平方向涂抹在相空间接收度的中心区域,而垂直方向涂抹在相空间接收度的外围区域;在注入接近完成时,循环束流轨道在水平方向是远离注入点,但在垂直方向上与注入点重合,水平方向涂抹在相空间接收度外围区域,而垂直方向涂抹在相空间接收度的中心区域。因而,对于相关涂抹,在水平和垂直方向上都是从中心往边缘涂抹;对于反相关涂抹,在水平和垂直方向上分别是从中心往边缘涂抹和从边缘往中心涂抹。
对于相关涂抹,涂抹束流中心相对于循环束流闭合轨道的水平和垂直偏移可以分别表示为
$$ x = {x}_{\mathrm{m}\mathrm{a}\mathrm{x}}-\left({x}_{\mathrm{m}\mathrm{a}\mathrm{x}}-{x}_{\mathrm{m}\mathrm{i}\mathrm{n}}\right)\times \sqrt{\frac{t}{{T}_{\mathrm{i}\mathrm{n}\mathrm{j}}}},\;{x}' = 0 , $$ (1) $$ y = {y}_{\mathrm{m}\mathrm{a}\mathrm{x}}\times \left[1-\sqrt{\frac{t}{{T}_{\mathrm{i}\mathrm{n}\mathrm{j}}}}\right], \;{y}' = 0 , $$ (2) 其中:
$ {x}_{\mathrm{m}\mathrm{a}\mathrm{x}}-{x}_{\mathrm{m}\mathrm{i}\mathrm{n}} $ 是水平涂抹范围;$ {y}_{\mathrm{m}\mathrm{a}\mathrm{x}} $ 是垂直涂抹范围;$ {T}_{\mathrm{i}\mathrm{n}\mathrm{j}} $ 是注入时间。对于反相关涂抹,涂抹束流中心相对于循环束流闭合轨道的水平和垂直偏移位置可以表示为$$ x = {x}_{\mathrm{m}\mathrm{a}\mathrm{x}}-\left({x}_{\mathrm{m}\mathrm{a}\mathrm{x}}-{x}_{\mathrm{m}\mathrm{i}\mathrm{n}}\right)\times \sqrt{\frac{t}{{T}_{\mathrm{i}\mathrm{n}\mathrm{j}}}}\text{,}{x}' = 0 , $$ (3) $$ y = {y}_{\mathrm{m}\mathrm{a}\mathrm{x}}\times \left[1-\sqrt{1-\frac{t}{{T}_{\mathrm{i}\mathrm{n}\mathrm{j}}}}\right]\text{,}{y}' = 0\mathrm{。} $$ (4) 不管相关涂抹还是反相关涂抹,直线加速器束流的注入点都设置在 (
$ {x}_{\mathrm{m}\mathrm{a}\mathrm{x}} $ ,$ {y}_{\mathrm{m}\mathrm{a}\mathrm{x}} $ ),而且其在注入过程中保持不变。Py-ORBIT为国际上通用的强流质子同步加速器多粒子模拟跟踪程序,模拟结果被多个实验室所验证[26-27]。以CSNS-II加速器注入束流参数为基础,如表1所列,利用Py-ORBIT对新注入方案的相关和反相关涂抹过程进行详细模拟。结果表明,相关和反相关涂抹的发射度、束流损失和束流分布均符合加速器稳定运行要求。表2给出了相关和反相关涂抹的发射度和束流损失模拟结果。图11和12分别给出相关和反相关涂抹注入完成后束流分布图。因而,新注入方案可以同时实现相关和反相关涂抹注入。
表 1 CSNS-II加速器注入束流参数
注入束流参数 值 注入能量/GeV 0.3 平均束流流强/μA 312.5 每个脉冲粒子数 7.8×1013 重复频率/Hz 25 注入束流功率/kW 94 注入束流脉宽/μs 500 切束率/% 50 表 2 相关和反相关涂抹的发射度和束流损失模拟结果
涂抹方式 水平/垂直
涂抹范围(mm/mm)涂抹后水平/垂直99.9%
发射度/(π·mm·mrad)1 000圈后水平/垂直99.9%
发射度/(π·mm·mrad)束流损失% 相关涂抹 30/30 249/233 260/272 0.0 反相关涂抹 30/30 220/267 247/305 0.02 根据模拟结果,新的注入方案可以同时实现相关和反相关涂抹,加速器可以按照建成之后真实束流状态切换涂抹方式,避免由于初始设计时选择不合适的涂抹方式造成的诸多故障。新的注入方案作为中国散裂中子源二期工程新注入系统的预选方案之一,将在工程技术实现方面进行更加深入研究和验证。
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摘要: 空间电荷效应是强流质子加速器的核心问题之一,在注入和初始加速阶段其影响最大。采用相空间涂抹方法并优化其涂抹过程,可以有效地减少空间电荷效应对束流注入和加速效率及发射度增长的影响。横向相空间涂抹方法可分为相关涂抹和反相关涂抹。首先,本工作对强流质子同步加速器的横向相空间涂抹方法进行深入研究,包括不同的涂抹方法和实现方式。其次,基于中国散裂中子源(CSNS)注入系统,对束流注入过程和反相关涂抹设计方案进行详细研究,深入探索实际垂直涂抹范围变小的原因和凸轨磁铁边缘聚焦效应对涂抹效果和束流动力学的影响。同时,简单介绍了在反相关涂抹机械结构基础上实现相关涂抹的方法及其对实现CSNS设计指标起到的关键作用。最后,根据未来加速器对不同涂抹注入方法在线切换的需求,我们提出了一种同时实现相关和反相关涂抹的新注入方案,并对其进行详细的论证、模拟和优化。Abstract: The space charge effect is the core problem of high intensity proton accelerator, especially at injection and initial acceleration stages. Using the phase space painting with optimized process, will effectively reduce the influence of space charge effect on injection and acceleration efficiency, and emittance increase. Transverse phase space painting methods can be divided into correlated painting and anti-correlated painting. In this paper, firstly, the transverse phase space paintings for the high intensity proton synchrotron are discussed in detail, including different painting methods and different implementation methods. Secondly, based on the injection system of the China Spallation Neutron Source (CSNS), the beam injection process and anti-correlated painting design scheme are studied in detail. The reasons for the reduction of the actual vertical painting range and the influence of edge focusing effects of the bump magnets on the painting and beam dynamics are deeply explored. In addition, the method to perform the correlated painting based on the mechanical structure of the anti-correlated painting scheme and its key role in realizing the CSNS design goal are briefly introduced. Finally, according to the requirement of switching between different painting methods online in future accelerators, a new injection scheme that can realize correlated and anti-correlated painting simultaneously has been proposed. The new painting injection scheme has been demonstrated, simulated and optimized in detail.
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Key words:
- proton synchrotron /
- injection /
- painting /
- space charge effect
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表 1 CSNS-II加速器注入束流参数
注入束流参数 值 注入能量/GeV 0.3 平均束流流强/μA 312.5 每个脉冲粒子数 7.8×1013 重复频率/Hz 25 注入束流功率/kW 94 注入束流脉宽/μs 500 切束率/% 50 表 2 相关和反相关涂抹的发射度和束流损失模拟结果
涂抹方式 水平/垂直
涂抹范围(mm/mm)涂抹后水平/垂直99.9%
发射度/(π·mm·mrad)1 000圈后水平/垂直99.9%
发射度/(π·mm·mrad)束流损失% 相关涂抹 30/30 249/233 260/272 0.0 反相关涂抹 30/30 220/267 247/305 0.02 -
[1] WEI Jie. Rev Mod Phys, 2003, 75: 1383. doi: 10.1103/RevModPhys.75.1383 [2] HENDERSON S, ABRAHAM W, ALEKSANDROV A, et al. Nucl Instr and Meth A, 2014, 763: 610. doi: 10.1016/j.nima.2014.03.067 [3] GALAMBOS J D, HOLMES J A, LEE Y Y, et al. Status of the SNS Injection System[C]//Proceedings of the 6th European Particle Accelerator Conference. Stockholm, Sweden: EPS-AG, 1998: 341. [4] High-Intensity Proton Accelerator Project Team. Accelerator Technical Design Report for High-intensity Proton Accelerator Facility Project[R]. Ibarakiken: JAERI Report No. JAERITech2003-044, 2003. [5] NAITO F. Nuclear and Particle Physics Proceedings, 2016, 273: 181. doi: 10.1016/j.nuclphysbps.2015.09.023 [6] BOARDMAN B. Spallation Neutron Source: Description of Accelerator and Target [R]. Oxford: Rutherford Appleton Laboratory Report No. RL-82-006, 1982. [7] FINDLAY D J S, ADAMS D J, BROOME T A, et al. ISIS Upgrades-A Status Report[C]//Proceedings of the 10th European Particle Accelerator Conference. Edinburgh, Scotland: EPS-AG, 2006: 935. [8] 陈和生, 马力, 奚基伟, 等. 散裂中子源可行性研究报告[R]. 北京: 中国科学院, 2009. CHEN Hesheng, MA Li, XI Jiwei, et al. China Spallation Neutron Source Feasibility Research Report[R]. Beijing: Chinese Academy of Sciences, 2009 (in Chinese). [9] WEI Jie, FU Shinian, TANG Jingyu, et al. Chin Phys C, 2009, 33(11): 1033. doi: 10.1088/1674-1137/33/11/021 [10] WEI Jie, CHEN Hesheng, CHEN Yanwei, et al. Nucl Instr and Meth, 2009, 600: 10. doi: 10.1016/j.nima.2008.11.017 [11] WANG Sheng, FANG Shouxian, FU Shinian, et al. Chin Phys C, 2009, 33(S2): 1. doi: 10.1088/1674-1137/33/S2/001 [12] HUANG Mingyang, WANG Sheng, XU Shouyan. Preliminary Study on the Injection System Upgrade for CSNS-II[C]//Proceedings of the 10th International Particle Accelerator Conference. Geneva: JACOW, 2019: 2037. doi:10.18429/JACoW-IPAC2019-TUPTS048 [13] HOLMES J A, DANILOV V V, GALAMBOS J D, et al. Phys Rev ST Accel Beams, 1999, 2: 114202. doi: 10.1103/PhysRevSTAB.2.114202 [14] COUSINEAU S, LEE S Y, HOLMES J A, et al. Phys Rev ST Accel Beams, 2003, 6: 034205. doi: 10.1103/PhysRevSTAB.6.034205 [15] WEI Jie, BEEBE-WANG J, BLASKIEWICZ M, et al. Injection Choice for Spallation Neutron Source Ring[C]//Proceedings of the 2001 Particle Accelerator Conference. New York: IEEE, 2001: 2560. [16] BEEBE-WANG J, LEE Y Y, RAPARIA D, et al. Transverse Phase Space Painting for SNS Accumulator Ring Injection[C]//Proceedings of the 1999 Particle Accelerator Conference. New York: IEEE, 1999: 1743. [17] TAIT N R S, TOLFREE D W L, ARMITAGE B H, et al. Nucl Instr and Meth, 1979, 167: 21. doi: 10.1016/0029-554X(79)90469-5 [18] TAIT N R S, TOLFREE D W L, WHITMELL D S, et al. Nucl Instr and Meth, 1979, 163: 1. doi: 10.1016/0029-554X(79)90027-2 [19] 黄明阳, 许守彦, 卢晓含, 等. 原子能科学技术, 2012, 46(S1): 530. doi: 10.7538/yzk.2019.53.09.1708 HUANG Mingyang, XU Shouyan, LU Xiaohan, et al. Atom Energy Sci Technol, 2012, 46(S1): 530. (in Chinese) doi: 10.7538/yzk.2019.53.09.1708 [20] TANG Jingyu, QIU Jing, WANG Sheng, et al. Chin Phys C, 2006, 30(12): 1184. doi: 10.1007/s10714-006-0346-6 [21] QIU Jing, TANG Jingyu, WANG Sheng, et al. Chin Phys C, 2007, 31(10): 942. doi: 10.1016/S1872-2040(07)60079-6 [22] HUANG Mingyang, WANG Sheng, QIU Jing, et al. Chin Phys C, 2013, 37(6): 067001. doi: 10.1088/1674-1137/37/6/067001 [23] HUANG Mingyang, XU Shouyan, AN Yuwen, et al. Nucl Instr and Meth A, 2021, 1007: 165408. doi: 10.1016/j.nima.2021.165408 [24] LU Xiaohan, HUANG Mingyang, WANG Sheng. Phys Rev Accel Beams, 2018, 21: 062802. doi: 10.1103/PhysRevAccelBeams.21.062802 [25] HUANG Mingyang, IRIE Y, XU Shouyan, et al. Phys Rev Accel Beams, 2022, 25: 110401. doi: 10.1103/PhysRevAccelBeams.25.110401 [26] OSTIGUY J F, HOLMES J. PyORBIT: A Python Shell for ORBIT[C]//Proceedings of the 2003 Particle Accelerator Conference. New York: IEEE, 2003: 3503. [27] SHISHLO A, COUSINEAU S, HOLMES J, et al. Procedia Comput Sci, 2015, 51: 1272. doi: 10.1016/j.procs.2015.05.312