摘要
目的针对^60Coγ射线空气比释动能基准建立的需求,对球-圆柱形石墨空腔电离室壁修正因子Kvall进行Monte Carlo模型研究。方法通过对EGSnrc软件包的子程序$HOWFAR、$HOWNEAR以及相应的抽样程序进行改写,实现对球-圆柱形石墨空腔电离室壁修正因子Kwall的Monte Carlo模拟计算,并将计算结果与实验测量进行比对。结果对于10cm^3NIM球-圆柱形石墨空腔电离室,Monte Carlo模拟结果与采用“等效平均厚度”实验外推得到的结果在0.02%内吻合,与法国国家BNMI-LNHB基准实验室计算结果在0.01%内吻合,比传统的线性外推方法得到的结果高0.47%。结论NIM球-圆柱形空腔石墨电离室Kwall因子值为Kvall=1.0166±0.0004。
Objective In order to establish the criterion of air-kerma of 10 cm^3 NIM sphere-cylindrical graphite ion chamber in a ^60Co beam, the wall correction factor Kwall was calculated by the Monte Carlo simulation. Methods Several subroutines, such as SHOWFAR, SHOWNEAR, and some others related in EGSnrc, were rewritten to make the user codes applicable for any sphere-cylindrical geometry. Results The wall correction factor Kwall of 10 cm^3 NIM sphere-cylindrical graphite ion chamber in a ^60Co beam was calculated by Monte Carlo simulation, and the result compared was with the experimental data. The comparison shows that the present result of Monte Carlo simulation accords with the BNMI-LNHB's and the "mean equivalent thickness" values in a precision of 0.01% and 0.02%, respectively, higher than the value obtained by the traditional linear extrapolation by 0.47%. Conclusions The value for Kwall of 10 cm^3 NIM sphere-cylindrical graphite ion chamber in a ^60 Co beam from Monte Carlo simulation 1.0166( standard uncertainty 0.0004)
出处
《中华放射医学与防护杂志》
CAS
CSCD
北大核心
2007年第6期577-581,共5页
Chinese Journal of Radiological Medicine and Protection
基金
国家自然科学基金资助项目(10275058)