Study of Temperature Sensitivity of Large BGO Crystal

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 detect γ-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 detect γ-ray. To study this effect, a 6 cm×8 cm×25 cm BGO crystal was cooled down to -20 ℃. A ¹³⁷Cs source was used to study the influence of temperature on peak drift of the γ spectrum and the change of energy resolution. The result shows that the peak position of γ spectrum 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.