CSNS带宽限制中子斩波器系统的设计方法
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摘要
带宽限制中子斩波器是中国散裂中子源上飞行时间中子散射谱仪不可缺少的关键设备之一,谱仪获得的中子能谱波段范围由带宽斩波器决定,其主要原理是通过转盘的机械式阻挡来对中子束流进行斩波,选择到达样品的中子波长范围,从而起到降低背底、提高信噪比的作用。本文介绍了带宽限制中子斩波器的基本原理及其设计要求,重点阐述了带宽限制中子斩波器系统的设计方法,提出了斩波器系统配置布局的基本原则,并给出了带宽斩波器各物理参数的计算公式。带宽斩波器的配置数量应满足谱仪背底要求,去除背底的斩波器应放置在束线前端并使谱仪所需波段的中子无损失通过,带宽选取的斩波器则尽可能放置在束线后端。另外,满足同相位、同转速、同开口角和转动方向相反等条件的双盘斩波器可以在一定程度上提高中子通量。本文的工作可为中国散裂中子源二十台中子散射谱仪斩波器系统的物理设计提供指导和参考。
[Background] Bandwidth-limited neutron chopper(BWL choppers) is one of the indispensable key equipments in the time-of-flight neutron scatter of China spallation neutron source(CSNS), which decide the neutron energy spectrum obtained by detectors. The main principle is to chop the neutron beam to limit the neutron wavelength bandwidth at the neutron detector, so as to reduce the background and improve the signal-to-noise ratio. [Purpose] This study aims to design BWL chopper system reasonably and reduce faults. [Methods] The basis principle of BWL chopper was reviewed, Design method, basis configuration principle of BWL chopper and system layout were put forward. The formulas for calculating the physical parameters of BWL chopper were given. [Results] The configuration numbers of bandwidth chopper should meet the requirement of neutron scatter. The background removing chopper should be inserted in the front end of the beam line so that the neutrons in the required band of the spectrometer could pass through without loss, while the bandwidth selecting chopper should be placed at the back end as far as possible. In addition, the flux can be increased by double disk chopper that satisfies same phase, same speed, same slit angle but counter-rotating. [Conclusion] The work can guide the physical design of twenty neutron instruments of CSNS.
[Background] Bandwidth-limited neutron chopper(BWL choppers) is one of the indispensable key equipments in the time-of-flight neutron scatter of China spallation neutron source(CSNS), which decide the neutron energy spectrum obtained by detectors. The main principle is to chop the neutron beam to limit the neutron wavelength bandwidth at the neutron detector, so as to reduce the background and improve the signal-to-noise ratio. [Purpose] This study aims to design BWL chopper system reasonably and reduce faults. [Methods] The basis principle of BWL chopper was reviewed, Design method, basis configuration principle of BWL chopper and system layout were put forward. The formulas for calculating the physical parameters of BWL chopper were given. [Results] The configuration numbers of bandwidth chopper should meet the requirement of neutron scatter. The background removing chopper should be inserted in the front end of the beam line so that the neutrons in the required band of the spectrometer could pass through without loss, while the bandwidth selecting chopper should be placed at the back end as far as possible. In addition, the flux can be increased by double disk chopper that satisfies same phase, same speed, same slit angle but counter-rotating. [Conclusion] The work can guide the physical design of twenty neutron instruments of CSNS.
引文
1张杰.中国散裂中子源(CSNS)--多学科应用的大科学平台[J].中国科学院院刊,2006,21(05):415-417.DOI:10.3969/j.issn.1000-3045.2006.05.017.ZHANG Jie.CSNS:a large scientific facility for multidisciplinary purposes[J].Bulletin of Chinese Academy of Sciences,2006,21(05):415-417.DOI:10.3969/j.issn.1000-3045.2006.05.017.
2王芳卫,贾学军,梁天骄,等.散裂中子源靶站谱仪的物理设计[J].物理,2008,37(6):449-453.DOI:10.3321/j.issn:0379-4148.2008.06.016.WANG Fangwei,JIA Xuejun,LIANG Tianjiao,et al.Physical design of target station and neutron scattering spectrometers for the Chinese spallation neutron source[J].Physics,2008,37(6):449-453.DOI:10.3321/j.issn:0379-4148.2008.06.016.
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4李新喜,黄朝强,王燕,等.双盘斩波器的设计与优化[J].核技术,2008,31(5):392-395.LI Xinxi,HUANG Chaoqiang,WANG Yan,et al.Design and optimization of a double-disk chopper[J].Nuclear Techniques,2008,31(5):392-395.
5李新喜,黄朝强,王燕,等.水平散射几何中子反射谱仪的三盘斩波器设计[J].核技术,2009,32(7):510-514.LI Xinxi,HUANG Chaoqiang,WANG Yan,et al.Triple-disk chopper design of horizontal neutron scattering reflectometer[J].Nuclear Techniques,2009,32(7):510-514.
6李新喜,王燕,黄朝强,等.盘间距可调斩波器设计及模拟[J].核技术,2010,33(3):192-196.LI Xinxi,WANG Yan,HUANG Chaoqiang,et al.Design and simulation of a space-adjustable chopper[J].Nuclear Techniques,2010,33(3):192-196.
7杨博,王平,王芳卫.CSNS中子带宽限制斩波器样机控制系统的设计与实现[J].核技术,2012,35(4):305-308.YANG Bo,WANG Ping,WANG Fangwei.Development of the bandwidth-limiting neutron chopper prototype control system for CSNS[J].Nuclear Techniques,2012,35(4):305-308.
8 Jaksch S.Considerations about chopper configuration at a time-of-flight SANS instrument at a spallation source[J].Nuclear Instruments and Methods in Physics Research A,2016,835:61-65.DOI:10.1016/j.nima.2016.07.041.
9 Bewley R I,Taylor J W,Bennington S M.LET,a cold neutron multi-disk chopper spectrometer at ISIS[J].Nuclear Instruments&Methods in Physics Research A,2011,637(1):128-134.DOI:10.1016/j.nima.2011.01.173.
10 Ehlers G,Podlesnyak A A,Niedziela J L,et al.The new cold neutron chopper spectrometer at the spallation neutron source:design and performance[J].Review of Scientific Instruments,2011,82(8):085108.DOI:10.1063/1.3626935.
11 Wang P,Yang B,Cai W L.Development of a bandwidth limiting neutron chopper for CSNS[J].Nuclear Instruments and Methods in Physics A,2015,792:56-60.DOI:10.1016/j.nima.2015.04.047.
12 Mezei F,Russina M.Multiplexing chopper systems for pulsed neutron source instruments[J].Advances in Neutron Scattering Instrumentation,2002,4785:24-33.
13 Mezei F.Multiplexing chopper systems for pulsed neutron sources:practical basics[J].Journal of the Physical Society of Japan,2013,82:1-25.DOI:10.7566/JPSJS.82SA.SA025.
2王芳卫,贾学军,梁天骄,等.散裂中子源靶站谱仪的物理设计[J].物理,2008,37(6):449-453.DOI:10.3321/j.issn:0379-4148.2008.06.016.WANG Fangwei,JIA Xuejun,LIANG Tianjiao,et al.Physical design of target station and neutron scattering spectrometers for the Chinese spallation neutron source[J].Physics,2008,37(6):449-453.DOI:10.3321/j.issn:0379-4148.2008.06.016.
3陈和生.中国散裂中子源[J].现代物理知识,2016,28(01):3-10.DOI:10.13405/j.cnki.xdwz.2016.01.001.CHEN Hesheng.China spallation neutron source[J].Modern Physics,2016,28(01):3-10.DOI:10.13405/j.cnki.xdwz.2016.01.001.
4李新喜,黄朝强,王燕,等.双盘斩波器的设计与优化[J].核技术,2008,31(5):392-395.LI Xinxi,HUANG Chaoqiang,WANG Yan,et al.Design and optimization of a double-disk chopper[J].Nuclear Techniques,2008,31(5):392-395.
5李新喜,黄朝强,王燕,等.水平散射几何中子反射谱仪的三盘斩波器设计[J].核技术,2009,32(7):510-514.LI Xinxi,HUANG Chaoqiang,WANG Yan,et al.Triple-disk chopper design of horizontal neutron scattering reflectometer[J].Nuclear Techniques,2009,32(7):510-514.
6李新喜,王燕,黄朝强,等.盘间距可调斩波器设计及模拟[J].核技术,2010,33(3):192-196.LI Xinxi,WANG Yan,HUANG Chaoqiang,et al.Design and simulation of a space-adjustable chopper[J].Nuclear Techniques,2010,33(3):192-196.
7杨博,王平,王芳卫.CSNS中子带宽限制斩波器样机控制系统的设计与实现[J].核技术,2012,35(4):305-308.YANG Bo,WANG Ping,WANG Fangwei.Development of the bandwidth-limiting neutron chopper prototype control system for CSNS[J].Nuclear Techniques,2012,35(4):305-308.
8 Jaksch S.Considerations about chopper configuration at a time-of-flight SANS instrument at a spallation source[J].Nuclear Instruments and Methods in Physics Research A,2016,835:61-65.DOI:10.1016/j.nima.2016.07.041.
9 Bewley R I,Taylor J W,Bennington S M.LET,a cold neutron multi-disk chopper spectrometer at ISIS[J].Nuclear Instruments&Methods in Physics Research A,2011,637(1):128-134.DOI:10.1016/j.nima.2011.01.173.
10 Ehlers G,Podlesnyak A A,Niedziela J L,et al.The new cold neutron chopper spectrometer at the spallation neutron source:design and performance[J].Review of Scientific Instruments,2011,82(8):085108.DOI:10.1063/1.3626935.
11 Wang P,Yang B,Cai W L.Development of a bandwidth limiting neutron chopper for CSNS[J].Nuclear Instruments and Methods in Physics A,2015,792:56-60.DOI:10.1016/j.nima.2015.04.047.
12 Mezei F,Russina M.Multiplexing chopper systems for pulsed neutron source instruments[J].Advances in Neutron Scattering Instrumentation,2002,4785:24-33.
13 Mezei F.Multiplexing chopper systems for pulsed neutron sources:practical basics[J].Journal of the Physical Society of Japan,2013,82:1-25.DOI:10.7566/JPSJS.82SA.SA025.