Efficiency simulation and coincidence-summing correction for HPGe detector
张瑞芹 1李奇 1樊元庆 1赵允刚 1张新军 1贾怀茂 1牛亚洲 1李芮莹 1王世联1
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作者信息
1. 禁核试北京国家数据中心和北京放射性核素实验室 北京 100085
折叠
摘要
为提高高纯锗(HPGe)探测器测量低水平放射性核素活度的探测灵敏度,通常将样品置于距探测器较近的位置以提高探测效率,但近距离测量不可避免地会带来较严重的符合相加效应,影响活度测量的准确度.本文利用Geant4对HPGe探测器进行了峰效率模拟,并与混合标准刻度源的实验结果对比,表征了探测器内部几何结构;基于表征的探测器几何结构对探测器总效率进行了模拟,进而从物理机制上计算得到了符合相加效应校正因子,并将其用于全面禁止核试验条约(Comprehensive Nuclear Test Ban Treaty,CTBT)筹委会临时技术秘书处(Provisional Technical Secretariat,PTS)组织的2021年度放射性核素滤材样品能力验证,符合相加校正后的核素活度与参考值相对偏差小于3%,验证了计算的符合相加校正因子的准确性,解决了实验测量总效率刻度点受限、实验成本高等问题,为准确测量样品中的核素活度奠定了基础.
Abstract
[Background]In order to enhance the detection sensitivity of HPGe detectors for measuring the low-level activity of radionuclides,samples are usually measured as close to the detector as possible to improve the detection efficiency,which inevitably leads to serious coincidence-summing effects in return and affects the accuracy of measured activity.[Purpose]This study aims to conduct efficiency simulation and coincidence-summing correction for HPGe detectors.[Methods]First of all,the peak efficiency of the HPGe detector was simulated by Geant4 and the internal geometry of the HPGe detector was optimized by comparing the simulated results with the experimental results of the mixed standard calibration source.Then,the total efficiency of the detector with various dead layer thickness was calibrated and the coincidence-summing correction factors were calculated.Finally,"Proficiency Test Exercise(PTE)2021"conducted by the Provisional Technical Secretariat(PTS)of Comprehensive Nuclear Test Ban Treaty(CTBT)was applied to the correction of the measured activity.[Results]Measurement results show that the relative deviation between the corrected activity and the reference result is less than 3%.[Conclusions]Results of this study demonstrate that the efficiency simulation and coincidence-summing correction for HPGe detector solves problems of limited calibration point source and high experimental cost,lays a foundation for measuring activities of nuclides in the sample accurately.
关键词
HPGe探测器/效率刻度/蒙特卡罗模拟/符合相加效应
Key words
HPGe detector/Detection efficiency/Monte Carlo simulation/Coincidence-summing effect
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