溴化镧探测器探测效率刻度及影响因素分析  

Efficiency calibration of lanthanum bromide scintillation detector and analysis of influencing factors of the detection efficiency

作　　者：杨体波 王敏[1] 代光明 曹彧 廖光辉 范新洋 YANG Tibo;WANG Min;DAI Guangming;CAO Yu;LIAO Guanghui;FAN Xinyang(College of Nuclear Technology and Automation Engineering,Chengdu University of Technology,Chengdu 610059,China)

机构地区：[1]成都理工大学核技术与自动化工程学院,成都610059

出　　处：《核技术》2021年第10期23-29,共7页Nuclear Techniques

基　　金：国家自然科学基金(No.11975060);国家重点研发计划课题(No.2018YFC060334);四川省科技计划(No.2021JDRC0028)资助。

摘　　要：有源效率刻度需要使用多种能量不同的源,并且要求样品源与标准源的测量条件一致,对于一般的实验室,由于实验条件的限制,并不能有效地对探测器进行效率刻度。为了解决此类问题,针对地层元素测井中使用的溴化镧探测器(LaBr3:Ce晶体,ø3.18 cm×10.16 cm),首先用蒙特卡罗软件MCNP(Monte Carlo N Particle Transport Code)研究了影响探测效率的因素,主要包括探测器Al壳厚度、MgO反射层厚度、晶体尺寸大小;其次,进行了无源全能峰效率刻度,并与理论计算结果和实测结果进行了对比。结果表明:端面Al壳和MgO反射层厚度的增加都会降低全能峰探测效率,侧面Al壳厚度变化对全能峰探测效率的影响较小;晶体长度、半径的增加会提高全能峰探测效率,且半径的变化对全能峰效率的影响较大。全能峰效率的模拟结果与理论计算结果和实测结果之间的误差分别在7%和6%以内,这表明模拟结果是准确的,为实验室进行无源效率刻度提供了一定的参考。[Background]Active efficiency calibration of radiation detector requires the multiple standard radioactive sources with different energies,and the measurement condition of the standard sources need to be consistent with sample sources.Due to the limitation of these experimental conditions,it is difficult to achieve efficiency calibration of detectors effectively in ordinary laboratories.[Purpose]This study aims to solve the above problems by simulation and experimental test.[Methods]First of all,Monte Carlo software MCNP(Monte Carlo N Particle Transport Code)was used to explore the influences of detection efficiency for a lanthanum bromide scintillation detector corresponding to the simulated energy of 0.662 MeV of 137Cs source.Influencing factors such as Al shell thickness,MgO reflector thickness and crystal size of LaBr3:Ce(ø3.18 cm×10.16 cm)detector on full-energy peak efficiency were calculated.Then,passive full-energy peak efficiency calibration of the detector was carried out by the MCNP,and the simulation results were compared with the ones of theoretical calculation and measurement.[Results]The full-energy peak efficiency decreases with the increase of thicknesses of the Al shell in end-face and the MgO reflector,and thickness of the cylindrical Al shell has little effect on that.The full energy peak efficiency raises with the increase of the crystal length and radius of the detector,and the effect of the radius on the full-energy peak efficiency is more obvious than that of the length.The errors between the simulation and the theoretical calculation as well as the measurement results are within 7%and 6%,respectively.[Conclusions]The accurate of simulation results proves the correctness of efficiency calibration in this study which provides reference for the laboratory to perform passive efficiency calibration.

关 键 词：MCNP模拟 影响因素 全能峰效率 效率刻度 

分 类 号：TL812.1[核科学技术—核技术及应用]