井型高纯锗探测器体源样品无源效率刻度

摘要

采用蒙特卡罗程序MCNP建立物理模型,对井型高纯锗探测器的效率进行虚拟刻度.模拟计算在密度为0.4,1.2 g·cm-3的6种不同成分环境样品中,探测器对γ射线的探测效率,当能量高于0.10 MeV时,体源样品的探测效率主要与样品密度、γ射线能量相关.以土壤、水和植物油样品为代表,结合所选取的函数模型,确定了密度范围0.1—1.6 g·cm-3的固体源、密度1.0 g·cm-3的水溶液和密度0.92 g·cm-3的油溶液体源的效率函数及参数.实验采用标准源,对探测效率模拟结果进行了验证,探测效率的模拟值与实验值符合较好,二者误差均在3％以内.说明MCNP程序可以较为准确地模拟计算井型高纯锗探测器对γ射线的探测效率,验证了该无源效率刻度方法的准确性和可行性.%Efficiency calibration of high purity germanium detector is accurately completed,which is related with accuracy of quantitative analysis for radioactive isotope.The physical model of a well-type high purity germanium detector is constructed by Monte Carlo software MCNP and efficiencies of this detector are determined by sourceless efficiency calibration.For samples with densities of 0.4 g·cm-3 and 1.2 g·cm-3,efficiencies of gamma rays are simulated by MCNP.When gamma ray's energy is larger than 0.10MeV,detection efficiency is mainly related with sample's density and gamma ray energy.For samples of soil (density from 0.1 g·cm-3 to 1.6 g·cm-3),aqueous solution (density is 1.0 g·cm-3) and oil solution (density is 0.92 g·cm-3),combined with the function models,the functions and parameters are determined.Combined with four standard sources,simulations of efficiency are verified,whose efficiencies are in agreement with the experimental values and errors of them are all lower than 3％.It is proved that MCNP code can be used to calculate efficiency of gamma ray for well-type high-purity germanium detector.