This paper will use avalanche photodiode as a photo detector for LaBr3 ( Ce) scintillation of small vol-ume, and design a low noise charge sensitive preamplifier which can match with avalanche photodiode to form a probe that can be used in portable small volume energy spectrometer. The gain, dark current and junction ca-pacitance of the avalanche photodiode are affected by the bias voltage at both ends of the avalanche photodiode, and the changes of these characteristics will affect the readout effect of the energy spectrum. Therefore under different bias voltages, the energy resolutions of the scintillator detector composed of this probe are tested. The best energy resolution of the 662 keV gamma ray is 3. 97% when the bias voltage is 380 V.%本文以雪崩光电二极管为小体积Labr3( Ce)闪烁体的光电读出器件，并设计低噪声电荷灵敏前置放大器与雪崩光电二极管进行匹配组成完整前端探头，可应用于便携式小体积能谱仪中。雪崩光电二极管的增益、暗电流和结电容易受两端偏置电压影响，而这些特性的变化将影响能谱的读出效果。为此在不同的偏置电压下，测试了该探头组成的闪烁探测器的能量分辨率。当偏置电压为380 V时，对能量为662 keV的γ射线的最佳能量分辨为3.97%。
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