大尺寸BGO晶体的温度特性研究

Study of Temperature Sensitivity of Large BGO Crystal

锦屏深地核天体物理(JUNA)实验项目将在中国锦屏深地实验室开展恒星平稳氦燃烧阶段关键的(α,γ)和(α,n)反应以及恒星平稳氢燃烧阶段关键的(p,γ)和(p,α)反应的直接测量。该项目计划研制一套锗酸铋(BGO)探测器阵列用于(α,γ)和(p,γ)反应的γ射线探测。由于BGO晶体的光产额对温度敏感,温度的变化会导致γ能谱峰位的漂移和能量分辨率的变化。本文使用制冷系统对尺寸为6cm×8cm×25cm的BGO晶体进行降温,利用^(137)Cs源测量了其γ能谱峰位和能量分辨率,对BGO探测器性能随温度的变化关系进行了研究。结果表明:在-20~22.1℃温度区间内,BGO探测器的γ能谱峰位与温度呈良好的线性关系,能量分辨率随温度的降低而提高。

JUNA(Jinping Underground Nuclear Astrophysics)project has planned several direct measurements of key(α,γ)and(α,n)reactions in stellar hydrostatic helium burning stage and(p,γ)and(p,α)reactions in stellar hydrostatic hydrogen burning stage in China Jinping Underground Laboratory.A BGO detector array will be constructed to detectγ-rays emitted in(α,γ)and(p,γ)reactions.Due to the temperature sensitivity of the light yield of BGO crystal,the variation of temperature will lead to peak drift when BGO detector is used to detectγ-ray.To study this effect,a 6 cm×8 cm×25 cm BGO crystal was cooled down to-20℃.A 137 Cs source was used to study the influence of temperature on peak drift of theγspectrum and the change of energy resolution.The result shows that the peak position ofγspectrum is linearly correlated with temperature within the range of-20-22.1℃and the energy resolution of BGO detector improves with the decrease of temperature.