塑料闪烁体探测器成形堆积判别与校正方法

Identification and Correction Method of Plastic Scintillator Detector Forming Pile-up

塑料闪烁体探测器是一种常用的闪烁体探测器。塑料闪烁体探测器接受射线后输出信号常被滤波成形为高斯波形。高斯成形具有良好的时间、响应和信噪比(SNR)。由于其实现简单、综合性能良好,目前广泛应用于核信号处理中。在高计数率环境下工作时,探测器输出脉冲信号常出现堆积现象,导致核能谱测量系统无法准确提取脉冲幅值,进而能谱测量错误。针对该问题,提出了一种脉冲堆积判别与校正方法,首先通过塑料闪烁体脉冲信号到达时间判断脉冲堆积,然后基于脉冲标准模型进行脉冲校正。设计了由信号发生器、被测电路、通讯电路及示波器组成的测试系统,向被测电路输入模拟光电倍增管(PMT)脉冲堆积、非堆积信号,研究校正效果。实验及计算表明,相对于传统直接舍弃堆积脉冲的方法,该方法不仅能准确判断堆积,实现堆积校正,还原被堆积脉冲的峰值,并能提高塑料闪烁体探测器计数率3%~30%。

Plastic scintillation detector is a common scintillation detector.The output signal is usually filtered into Gaussian waveform when plastic scintillator detector receives radiation.Gaussian shaping has good time/response and signal-to-noise ratio(SNR).Because of its simple implementation and good comprehensive performance,it is widely used in nuclear signal processing.In high counting rate environment,the output pulse signal of detector often appears accumulation phenomenon,which leads to the nuclear spectrum measurement system is wrong and can not accurately extract the pulse amplitude.To solve this problem,a method of pulse pile-up identification and correction is proposed.Firstly,the arrival time of the plastic scintillator pulse signals is used to judge the pulse pile-up,and then the pulse correction is carried out based on the pulse standard model.A test system composed of signal generator,communication circuit and oscilloscope is designed to input analog photomultiplier(PMT)pulse pile-up,non-pile-up signal into the circuit under test to study the correction effect.Compared with the traditional method of directly discarding pile-up pulse,Experiments and calculations show that this method can accurately judge the pile-up,realize the pile-up correction,restore the peak value of deposited pulse,improve the counting rate of plastic scintillator detector by 3%~30%.