This paper discusses crystal growth and characterization of 1.0-inch LiI:Ag scintillators for thermal and epithermal neutron detection on the lunar surface as part of the Lunar Vehicle Radiation Dosimeter project. Zone purification method was employed to purify the raw material of LiI, and the crystals were grown using the Bridgman method. X-ray luminescence spectrum was measured to confirm the presence of Ag in the crystal lattice of LiI. The feasibility of neutron detection under Cf fast neutron irradiation was investigated. A hydrogen-rich paraffin wax moderator was used to slow down fast neutrons to obtain thermal and epithermal neutrons. The charge comparison method was used to perform pulse shape discrimination. The maximum value of the Figure of Merit was obtained to be 1.3, which demonstrates the capability of using LiI:Ag crystal scintillators in high neutron and gamma mixed fields. The energy resolution of the thermal neutron peak varied with the thickness of scintillators, achieving 12.0 % for the 0.5 cm thick samples. The potential for further improvement of the scintillation performance of LiI:Ag crystal relies on reducing impurities and color centers.

中文翻译：

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用于月球表面热中子和超热中子探测的 6LiI:Ag 晶体闪烁体的生长和表征

本文讨论了用于月球表面热中子和超热中子探测的 1.0 英寸 LiI:Ag 闪烁体的晶体生长和表征，作为月球车辆辐射剂量计项目的一部分。采用区域纯化法对LiI原料进行纯化，并采用布里奇曼法生长晶体。测量 X 射线发光光谱以确认 LiI 晶格中存在 Ag。研究了Cf快中子辐照下中子探测的可行性。使用富氢石蜡慢化剂来减慢快中子以获得热中子和超热中子。采用电荷比较法进行脉冲形状判别。获得的品质因数最大值为 1.3，这证明了在高中子和伽马混合场中使用 LiI:Ag 晶体闪烁体的能力。热中子峰的能量分辨率随闪烁体厚度的变化而变化，0.5 cm 厚的样品达到 12.0%。进一步提高 LiI:Ag 晶体闪烁性能的潜力取决于杂质和色心的减少。