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介绍了脉冲中子在ST401塑料闪烁体上的相对光产额评估方法.采用Geant4蒙特卡罗软件模拟X射线和中子在闪烁体中的输运行为，记录产生的全部带电粒子类型和能量，由公式计算得到相对光产额.给出了不同能量的单个中子和单个X射线入射到1 mm，3 mm，5 mm，1 cm，2 cm，3 cm，5 cm厚ST401的平均相对光产额.在0.3 MeV脉冲X射线源和14 MeV脉冲中子源上开展验证实验，采用相同的图像测量系统记录相对光产额，给出了单个中子与X射线的平均相对光产额比值.模拟结果与实验结果相对误差小于10%.结果可以为宽能谱脉冲中子束图像测量系统的量程安排提供依据.
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关键词:
- 脉冲射线测量 /
- ST401塑料闪烁体 /
- 相对光产额 /
- Geant4
High speed imaging technique is an effective method to test the information about pulsed neutron source. Imaging system is usually composed of a pinhole, a scintillator, an image intensifier and a charge-coupled device (CCD) camera. ST401 plastic scintillator is widely used to convert the neutron image into visible light image since it has features of high conversion efficiency and fast time response. When testing a pulsed neutron source of wide energy spectrum, we should evaluate the light yields of ST401 irradiated by neutrons with different energies and make the CCD camera exposed to the light appropriately. A 0.3 MeV pulsed X-ray source is often used to calibrate the imaging system because of its low cost than the D-T fusion neutron source. In this work, a method of evaluating the relative light yield of ST401 irradiated by 0.1-16 MeV neutron to 0.3 MeV X-ray is proposed.Geant4 Monte Carlo software is used to simulate the transport performances of neutrons and X-rays. The software package can simulate the transport process of photons. But the conversion factor of ray energy deposition into photons is unknown. It is difficult to calculate the number of photons generated in ST401 accurately. In this article, we calculate the relative light yield according to the energy of charged particles produced in ST401. Firstly, all information about the particle type, energy deposition, kinetic energy is monitored on event-by-event basis in GEANT4. Secondly, the complete history of the tracks is then used to calculate the light output from the scintillator according to the neutron response functions. Thirdly, the light output caused by charged particles going out of ST401 is deducted. Ratios of average light yield of 1 mm, 3 mm, 5 mm, 1 cm, 2 cm, 3 cm, 5 cm thick ST401 irradiated by 0.1-16 MeV neutron to 0.3 MeV X-ray are given. To confirm the correctness of the simulated result, validation experiment is carried out on IVA pulsed X-ray source and SGIII pulsed neutron source. The simulated ratio of average light yield of ST401 irradiated by one single 14 MeV neutron to 0.3 MeV X-ray has a discrepancy of less than 10% compared with the measured value. Compared with the results of experiment conducted on a constant current source, the simulated results have a maximum discrepancy of less than 44%. If CCD camera exposure 10%-90% of the full scale, the image will have high contrast and information loss can be avoided. According to the simulated results and the neutron yield, exposure can be easily set to be 60% of the full scale by adjusting the gain of the image intensifier. Assume that the simulated results have a 44% discrepancy, the actual exposure will be in a range of 34%-86% of the full scale. Underexposure and overexposure can be avoided by presetting the imaging system sensitivity appropriately based on the simulated results. It implies that the method proposed is effective in predicting the imaging system response to pulsed neutron with wide energy spectrum.-
Keywords:
- pulsed ray detection /
- ST401 plastic scintillator /
- relative light yield /
- Geant4
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[1] Li B J, Zhu X B, Wang L Z, Tang Z K 2014 Nucl. Electron. Detect. Technol. 34 1520 (in Chinese) [李波均, 朱学彬, 王立宗, 唐章奎 2014 核电子学与探测技术 34 1520]
[2] Liu Q Z 1994 Pulsed Radiation Field Diagnostic Technique (Beijing: Science Press) pp553-559 (in Chinese) [刘庆兆 1994 脉冲辐射场诊断技术(北京: 科学出版社) 第553559页]
[3] Xie H W, Zhang J H, Zhang F Q, Li L B, Qi J M, Chen J C, Chen D Y 2013 Process Report on China Nuclear Science Technology Harbin September 2013 p46 (in Chinese) [谢红卫, 张建华, 章法强, 李林波, 祁建敏, 陈进川, 陈定阳 2013 中国核科学技术进展报告 哈尔滨 2013年9月 第46页]
[4] Song G Z, Xie H W, Wang K L, Zhu H Q, Zhang Z H 2007 Exp. Res. 30 33 (in Chinese) [宋顾周, 谢红卫, 王奎禄, 朱宏权, 张占宏 2007 试验与研究 30 33]
[5] Song G Z, Xie H W, Wang K L, Zhu H Q 2008 Nucl. Electron. Detect. Technol. 28 845 (in Chinese) [宋顾周, 谢红卫, 王奎禄, 朱宏权 2008 核电子学与探测技术 28 845]
[6] Zheng W G, Wei X F, Zhu Q H 2016 High Power Laser and Particle Beams 28 019901 (in Chinese) [郑万国, 魏晓峰, 朱启华 2016 强激光与粒子束 28 019901]
[7] Gohil M, Banerjee K, Bhattacharya S 2012 Nucl. Instrum. Meth. Phys. Res. A 664 304
[8] Su Z F, Yang H L, Zhang P F, Lai D G, Guo J M, Ren S Q, Wang Q 2014 Acta Phys. Sin. 63 106801 (in Chinese) [苏兆锋, 杨海亮, 张鹏飞, 来定国, 郭建明, 任书庆, 王强 2014 物理学报 63 106801]
[9] Song Z F, Tang Q, Chen J B, Liu Z J, Zhan X Y, Deng C B 2015 High Power Laser and Particle Beams 27 112005 (in Chinese) [宋仔峰, 唐琦, 陈家斌, 刘中杰, 詹夏宇, 邓才波 2015 强激光与粒子束 27 112005]
[10] Cecil R A, Anderson B D, Madey R 1979 Nucl. Instrum. Meth. 161 439
[11] Hu M C, Liu J, Li Z B, Fu Y C, Li R R, Tang P D, Zhang J H, Huang Y, Feng J H, Guo H S 2011 Chin. J. Sci. Instrum. 32 174 (in Chinese) [胡孟春, 刘建, 李忠宝, 甫跃成, 李如荣, 唐登攀, 张建华, 黄雁, 冯璟华, 郭洪生 2011 仪器仪表学报 32 174]
[12] Han H L 2005 Annual Report of China Academy of Engineering Physics Mianyang December 2005 p48 (in Chinese) [韩惠林 2005 中国工程物理研究院科技年报 绵阳 2005年12月 第48页]
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