基于数字化多道谱仪的能谱计数率修正方法  

Counting rate correcting method of gamma spectrum based on Digital Multichannel Analyzer

作　　者：陈宸 吴桓 CHEN Chen;WU Huan(Technology Center,Chongqing Jianan Instrument Co.Ltd.,Chongqing 400060)

机构地区：[1]重庆建安仪器有限责任公司技术中心,重庆400060

出　　处：《辐射防护》2023年第1期31-37,共7页Radiation Protection

摘　　要：受死时间影响,数字化多道谱仪(DMCA)γ能谱会发生一定程度的计数率损失,给后续的γ能谱分析带来一定的误差,因此必须对产生计数率损失的γ能谱进行修正。在数字化多道谱仪死时间模型的基础上利用Lambert W函数建立真实计数率关于实测计数率的闭式解;给出DMCA系统计数率限值的定义与快成形通道死时间最优阈值的理论计算,并结合快成形通道检测出的有用脉冲信号作为计数率修正的依据;在此基础上,提出了一种γ能谱计数率修正方法。实验结果表明该方法可有效克服因高计数率造成γ能谱计数率损失的不利影响;在输入DMCA系统(采用LaBr 3(Ce)探测器)的计数率小于1.8 Mcps的范围内使修正后的特征峰净计数率的相对固有误差控制在9%以内,并且特征峰净计数率与剂量率的线性相关系数在0.995以上,拓宽了数字化多道谱仪的应用范围。Affected by the dead-time,the Digital Multichannel Analyzer(DMCA)which receives gamma spectrum will occur counting rate loss.This effect will bring some errors toγspectrum analysis.Therefore it is necessary to correct the gamma spectrum with counting rate loss.Based on the dead-time model of Digital Multichannel Analyzer,Lambert W function is used to establish the closed form solution of real counting rate relative to the measured counting rate.Then the definition of counting rate limit of DMCA and the theoretical calculation of the optimal threshold of the dead time of the fast channel are proposed,and the pulse signal detected by fast channel is used as the basis of counting rate correction.Based on this basis,a method for correcting the counting rate of gamma spectrum is proposed.Experimental results show that this method can correct the counting rate loss effectively;Within the range of counting rate less than 1.8 Mcps of DMCA[using LaBr 3(Ce)detector],the relative inherent error of the net counting rate at the corrected characteristic peak is less than 9%,and the linear correlation coefficient between the net counting rate at the characteristic peak and the doserate was above 0.995,which broadens the application range of Digital Multichannel Analyzer.

关 键 词：数字化多道谱仪 死时间 Lambert W函数 能谱修正 

分 类 号：TL817.2[核科学技术—核技术及应用]