强γ抑制的^(6)Li F/ZnS(Ag)中子探测器研制及性能测试

Development and Characteristic of ^(6)Li F/ZnS(Ag)Neutron Detector with StrongγSuppression

在慢热中子探测领域,为应对3He气体资源的日益短缺,迫切需要研究新型中子探测器以替代3He气体探测器。基于^(6)Li F/ZnS(Ag)的闪烁体材料由于具有中子截面大、探测效率高、γ抑制强等特点,是较为理想的中子探测材料。本文采用蒙特卡罗程序MCNP5构建闪烁体结构模型,在不同质量比、厚度参数条件下计算了中子探测效率,并对闪烁体结构参数进行了优化设计。利用纯国产的^(6)Li F和ZnS(Ag)材料研制了不同质量比和不同厚度的^(6)Li F/ZnS(Ag)闪烁体。通过252 Cf源和60 Co源测试了不同厚度和不同质量比条件下^(6)Li F/ZnS(Ag)闪烁体的探测效率及γ灵敏度。测试结果表明,^(6)Li F和ZnS(Ag)质量比1∶3、厚度400μm是较为理想的中子探测参数。新研制的^(6)Li F/ZnS(Ag)闪烁体的热中子探测效率达到30%以上,对γ具有较强的抑制能力,在45 mV阈值设置条件下γ灵敏度可达10-7。

Due to the shortage of 3He gas and the rapidly increasing price,it is urgent to seek a new neutron detector to replace 3He gas detector.Scintillator based on ^(6)Li F/ZnS(Ag)is an ideal material for thermal neutron detection because of its large neutron cross section,high detection efficiency and strongγsuppression.The neutron detector model was established using Monte Carlo procedure MCNP5 in this work.The neutron detection efficiency was calculated under different mass ratio and thickness parameters.The simulation results show that the thermal neutron detection efficiency improves with the increase of detector thickness.This means that one can use laminated construction to increase neutron efficiency in subsequent detector design.The simulation results also show that the thermal neutron detection efficiency improves with the increase of the mass ratio of ^(6)Li F and ZnS(Ag)(the value increases from 1∶6 to 1∶2 in this work).^(6)Li F/ZnS(Ag)detectors in five different thicknesses(100,200,250,300,400μm)and two mass ratios with 1∶3 and 1∶4 were manufactured.A 252 Cf neutron source and a 60 Coγsource were used to measure the performance of detectors.Detection efficiency measured results show that the detectors with mass ratio of 1∶3 and 1∶4 have higher detection efficiency of thermal neutrons.They both can reach 30%or more.However,the detector with mass ratio of 1∶3 is better than that of 1∶4.The detector with 400μm thickness has higher thermal neutron detection efficiency.γsensitivity measured results show that the detector has a strong ability to inhibitγsignal.In certain threshold voltage condition,theγsensitivity can reach 1×10-7.There is no significant difference inγsensitivity of detectors with two mass ratios of 1∶3 and 1∶4.To consider neutron detection efficiency andγsensitivity comprehensively,the threshold voltage setting in 45 mV was appropriate under the current detector conditions.In general,the detector developed in this paper has a good property and it is equivalent to the international level of similar products.