CsI(Tl)晶体的APD前端读出特性研究

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。

Characteristics study on the APD-based front-end readout for CsI(Tl) detector

Background:The avalanche photodiode (APD) has the advantages of small size, high detection efficiency, internal gain and insensitivity to magnet fields. But the internal gain and the signal-noise ratio(SNR) of the output signal of pulse are affected by bias voltage and temperature. Purpose:This study aims to test the effect of bias voltage and temperature on the APD-based front-end readout of scintillation detector.Methods:The avalanche photodiode is employed as the photodetector for CsI(Tl) scintillation, and equiped a charge sensitive preamplifier of low noise to form a probe. The energy resolution of scintillation detector with this probe was tested on a137Cs radiation source under different bias voltage and temperature.Results: The experimental results show that the energy resolution of the detection system is affected by both the bias voltage and the temperature. When the bias voltage at both ends of the APD is 370 V, the energy resolution is 4.98% for the gamma ray with the energy of 662 keV at the room temperature.Conclusion:The energy resolution will increase with the decrease of temperature within the range of?20 oC to 40 oC.