基于蒙特卡罗模拟研究锗死层对高纯锗探测效率的影响  

Effect of Germanium Dead Layer on Detection Efficiency of High-Purity Germanium Based on Monte Carlo Simulations

作　　者：宋海声[1] 庞荣妮 蔡啸[2] Song Haisheng;Pang Rongni;Cai Xiao(School of Physics and Electronic Engineering,Northwest Normal University,Lanzhou 730070,Gansu,China;State Key Laboratory of Nuclear Detectors and Nuclear Electronics,Institute of High Energy Physics,Chinese Academy of Sciences,Beijing 100043,China)

机构地区：[1]西北师范大学物理与电子工程学院,甘肃兰州730070 [2]中国科学院高能物理研究所核探测器与核电子学国家重点实验室,北京100043

出　　处：《激光与光电子学进展》2023年第23期78-82,共5页Laser & Optoelectronics Progress

摘　　要：为了更精确方便地分析测量样品的放射性含量,本文提出了利用蒙特卡罗应用软件工具(Geant4)获取高纯度锗(HPGe)探测器的全能峰效率曲线,进行放射性样品测量中全能峰效率的模拟及修正。测量距离高纯锗探头25 cm处探测器对点源中不同特征能量γ射线的实验探测效率,与模拟探测效率进行对比,采用Geant4模拟方式研究了高纯锗晶体表面死层对探测器效率的影响。通过修正上、下死层厚度依次分段对模型探测效率进行校正,优化探测器蒙特卡罗几何模型参数。将优化模型的模拟计算效率与点源的实测效率进行比较,得到了高纯锗探测器在59.54~1406 keV范围内的全能峰效率曲线。实验结果表明,蒙特卡罗模拟结果与实验测量结果有很好的一致性,相对误差在5%之内,并证实高纯锗晶体表面死层厚度随探测器的老化而发生变化,在7年后死层厚度从0.5 mm增加到约为1.40 mm±0.05 mm。In order to analyze and measure the radioactive content of samples more accurately and conveniently,a Monte Carlo application software tool(Geant4)is used to obtain the full energy peak efficiency curve of high-purity germanium(HPGe)detectors and thus to simulate and correct it in the measurement of radioactive samples.In particular,the different characteristic energies of a detector are measured in response to a point source 25 cm away from the HPGe probe.The experimental detection efficiency ofγ-rays is compared with the simulation detection efficiency,and the influence of the dead layer on the detector efficiency of the HPGe crystal surface is studied by means of Geant4 simulations.The detection efficiency of the model is corrected by modifying the thickness of the upper and lower dead layers in turn,and the parameters of the Monte Carlo geometric model of the detector are optimized.Thereafter,the simulated efficiency of the optimized model is again compared with the measured efficiency of the point source,and the full energy peak efficiency curve of the HPGe detector in the range of 59.54‒1406 keV is obtained.The experimental measurement results show good agreement with the Monte Carlo simulations,exhibiting a relative error within 5%.The experimental results also demonstrate that the thickness of the dead layer on the surface of the HPGe crystal changes with the aging of the detector.After 7 years,the thickness of the dead layer increases from 0.5 mm to approximately 140 mm±0.05 mm.

关 键 词：探测器 放射性 高纯锗探测器 能量刻度 蒙特卡罗模拟 死层厚度 

分 类 号：TL84[核科学技术—核技术及应用] TL814TL817.2