圆饼电离室空气比释动能物理参量的蒙特卡洛模拟

为建立基于圆饼电离室系统的~(60)Coγ射线空气比释动能基准装置,对辐射场及场中电离室的相关物理参量进行了蒙特卡洛模拟研究。通过BEAMnrc程序建立辐照器模型计算测量点处能谱和注量分布,使用EGSnrc计算圆饼电离室在辐射场中各物理参量。~(60)Coγ射线空气比释动能绝对测量装置通过蒙特卡洛模拟得到的相关物理参数合成不确定度为0.20%,该结果与澳大利亚计量院同结构电离室的结果在不确定度范围内一致,与国家基准球-圆柱形电离室及球形电离室相比在不确定范围内符合。

Monte CarIo SimuIation of PhysicaI Parameters for Air Kerma Measurement by Graphite Pancake Ionization Chamber

In order to establish the air kerma primary standard based on a graphite pancake ionization chamber for 60 Co gamma rays,the radiation field and related physical parameters of the chamber are calculated by the Monte Carlo simulation method. The γ-ray energy spectra and fluence distributions are calculated by the model built by BEAMnrc code,the parameters of the graphite pancake ionization chamber in 60 Co γ-ray radiation filed are calculated by EGSnrc code. The combined standard uncertainty of the parameters of the chamber calculated by Monte Carlo method is 0. 20%,the results of simulation are accord with results of the same structural chamber from the ARPANSA in the region of the uncertainty. And the change of the values with the primary standard based on a sphere-cylindrical graphite ionization chamber is under expected.