X射线石墨空腔电离室壁修正因子的蒙特卡罗模拟

X-rays Graphite Cavity Ionization Chamber Wall Correction Factor Monte Carlo Simulation

在250～600 kV X射线宽谱系列辐射质下,运用EGSnrc蒙特卡罗程序模拟计算3种不同结构石墨空腔电离室的壁修正因子.根据辐射质和光机参数使用BEAMnrc程序包模拟8组规范下辐射质的X射线注量谱,将模拟得到的相空间文件作为X射线源,运用EGSnrcMP程序包中的cavity程序代码模拟计算得到石墨空腔电离室的壁修正因子.模拟结果表明:对于相同体积的球型电离室,收集极长的电离室其壁修正因子更大;对于收集极长度相同电离室,球柱球型电离室比球型电离室的壁修正因子数值大.并且当X射线能量增加时,电离室的壁修正因子都有减小的趋势.

The wall correction factor of three kinds of graphite cavity ionization chamber in 250 ～ 600 kV X-rays wide spectrum radiation quality is simulated by using EGSnrc Monte Carlo program.According to the radiation quality and X-rays tube parameters,8 standard X-rays spectrum are simulated by BEAMnrc program package.The phase space files that simulated by BEAMnrc is used as X-rays source of user code cavity,then the phase space files is used to calculate correction factors of graphite cavity ionization chamber.The simulation results show that the spherical ionization chamber of the same volume,the longer collector electrode is with larger wall correction factor;for the same length of collector electrode,the wall correction factor of the sphere-cylindrical ionization chamber is larger than the spherical ionization chamber.And when the X-rays energy is increased,the wall correction factor of the ionization chamber is tend to decrease.