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雪崩光电二极管(Avalanche photodiode,APD)体积小、探测效率高、内置增益、对磁场不敏感,但其内置增益、输出脉冲信号的信噪比受偏置电压与温度影响明显。将APD作为Cs I(Tl)闪烁晶体的光电读出器件,并配以低噪声的电荷灵敏前置放大器,组成闪烁探测器的探头。在不同的偏置电压与温度下,测试了该探头组成的闪烁探测器的能量分辨率。实测表明,偏置电压、温度将影响探测系统的能量分辨率,在室温且APD两端的偏置电压为370 V时,对能量为662 ke V的γ射线能量分辨率为4.98%;在-20-40oC内,能量分辨率随温度的降低而提高。
Avalanche photodiode (APD) is small in size, high in detection efficiency, and has built-in gain and is insensitive to magnetic field. However, its built-in gain and signal-to-noise ratio of output pulse signal are greatly affected by bias voltage and temperature. The APD is used as a photo-sensing device for CsI (Tl) scintillation crystal with a low-noise, charge-sensitive preamplifier to form a scintillation detector probe. At different bias voltages and temperatures, the energy resolution of the scintillation detector consisting of the probe was tested. The measured results show that the bias voltage and temperature will affect the energy resolution of the detection system. The energy resolution of γ ray with energy of 662 keV is 4.98% at room temperature and the bias voltage of APD is 370 V. At -20 Within -40oC, the energy resolution increases with decreasing temperature.