代表点法体源探测效率刻度研究

Efficiency Calibration of Volume Source with the Representative Point Method

代表点法能在不受探测器内部结构和尺寸的影响下,实现高纯锗(HPGe)γ谱仪的快速效率刻度,简化传统地质和环境放射性样品核素分析过程。通过实验测量和蒙特卡罗模拟两种手段,对比研究其代表点位置求取的准确性,以证明代表点法在体源探测效率刻度工作中的可行性。结果表明,蒙特卡罗方法相较于传统的实验测量方法,代表点求取过程更加迅速,且同实验法计算的代表点位置基本接近。在不同测量高度下,代表点法计算出的土壤圆柱体源探测效率理论值与实验值的相对误差在5%之内,满足土壤圆柱体源探测效率刻度时不确定度的要求。

The representative point method can satisfy the rapid demanding for efficiency calibration of HPGe without influence of the detector structure and size,which simplify the nuclide analysis process of geological and environmental samples.However,this method is severally affected by the position accuracy and efficiency of representative point.The mathematical method was used to estimate the representative point position,which avoids the influence of radioactive source and detector.The accuracy and feasibility of the Monto Carlo method were analysed by comparing the representative point position between experimental results and Monto Carlo output.The practicable of the representative point method in body source detection efficiency calibration was analysed by comparing the detection efficiency of soil cylinder source and soil calibration source at different measuring heights.The Monto Carlo method is easier to calculate the representative points and approximate to the experimental results.At different measuring heights,the relative error of detection efficiency for the soil source between the representative point method results and the experiment conclusion is within 5%,which meets the requirement of uncertainty in soil source calibration.The internal size and structure of the detector have no influence on the location of the representative point.Therefore,the representative point method can realize the efficiency calibration for various body source,improve radionuclide analysis efficiency of geological and environmental samples.