中子测量用慢化体及热中子转换层厚度优化  

Optimization of Moderator and Thermal Neutron Converter's Thickness for Neutron Measurements

作　　者：黄广伟 吴坤 周春芝 张逸韵[2,3] HUANG Guang-wei;WU Kun;ZHOU Chun-zhi;ZHANG Yi-yun(State Key Laboratory of NBC Protection for Civilian,Beijing 102205,China;Research and Development Center for Solid State Lighting,Institute of Semiconductors,Chinese Academy of Sciences,Beijing 100083,China;Center of Materials Science and Optoelectronics Engineering,University of Chinese Academy of Sciences,Beijing 100190,China)

机构地区：[1]国民核生化灾害防护国家重点实验室,北京102205 [2]中国科学院半导体研究所照明研发中心,北京100083 [3]中国科学院大学材料科学与光电技术学院,北京100190

出　　处：《计算机仿真》2023年第9期262-267,共6页Computer Simulation

基　　金：国家自然科学基金(62134006)。

摘　　要：通常利用慢化体及热中子转换材料来实现中子的间接探测。为了最大程度提高探测器对中子的探测效率,建立并仿真计算了包含^(252)Cf中子源、聚乙烯慢化体和碳化硼(B_(4)C)/氟化锂(LiF)热中子转换层的蒙特卡洛粒子输运模型,并通过理论分析验证该模型的准确性。研究结果表明:在所建立模型中聚乙烯慢化体厚度为5.5 cm时热中子份额最大;在此条件下,B_(4)C和LiF热中子转换层厚度分别在2.8μm~3.3μm时和33μm~35μm时探测效率最高;对于单面转换层型热中子探测器,在测量中子时使转换层面朝向中子入射方向可以有效提高探测效率。理论分析得到的结果与粒子输运计算结果基本一致,B_(4)C和LiF厚度分别在2.9μm~3.1μm时和26μm~32μm时探测效率最高,约为4.8%和5.0%。Indirect measurements of neutrons are often performed by moderators and thermal neutron converters.To improve the detection efficiency of the converter-coated neutron detector,a Monte Carlo particle-transporting model involving ^(252)Cf neutron source,polyethylene moderator and boron carbide(B_(4)C)/lithium fluoride(LiF)was established.Moreover,the correctness and accuracy of the present model were verified theoretically.The results show that the thermal neutron reaches the largest share when the thickness of the polyethylene moderator is 5.5 cm in the established model.Under this condition,the detection efficiency reaches its highest when the thickness of the B_(4)C and LiF thermal neutron converter is from 2.8μm to 3.3μm and from 33μm to 35μm,respectively.When measuring neutrons with a thermal neutron detector coated with a single-sided neutron converter,the detection efficiency can be effectively improved,making the converter surface face the neutron incident direction.The theoretical analysis and calculation results are consistent with the Monte Carlo particle-transporting model results.According to the theoretical calculation results,the highest detection efficiency of approximately 4.8%and 5.0 can be obtained by 2.9μm to 3.1μm B_(4)C and 26μm to 32μm LiF.

关 键 词：中子测量 慢化体 热中子转换层 蒙特卡洛方法 探测效率 

分 类 号：TP391.9[自动化与计算机技术—计算机应用技术]