内充气正比计数管测量放射性气体活度中修正方法的模拟研究

摘要

The internal proportional counter is one of the most widely used method in the measurement of the absolute activity for the gas.Based on the Geometry and Tracking 4 (Geant4) codes,the effects of the correction method for the small pulse and wall effect are discussed.The simulation results show that the noise level is the crucial factor,for a 0.3％ uncertainty,a 0.2 keY and 0.6 keV threshold is need for the 3H and 85Kr respectively.The wall effect for the 3H is smaller,for the 85 Kr is remarkable,but the results can be corrected with the various pressures and the uncertainty can be less than 0.3 ％.%使用内充气正比计数管测量放射性气体活度是放射性气体活度绝对测量的最主要方法之一.基于Geant4(GEometry ANd Tracking 4)的模拟数据,研究了内充气正比计数法测量活度的过程中,壁效应和小脉冲幅度的修正方法本身对最终活度测量的不确定度的影响.根据模拟结果,得到如下结论:为达到0.3％以下的不确定度,3H与85Kr的测量下阈应分别低于0.2 keV和0.6 keV;壁效应对3H的影响较小,对85Kr的影响较大,但其结果可通过改变气体压强的方法修正到0.3％以内的不确定度.