基于EGSnrc仿真的二维电离室剂量探测器的室壁厚度确定方法

Method on Determination of Wall-thickness of Two-dimensional Ionization Chamber Dose Detector Based on EGSnrc

室壁厚度是二维电离室剂量探测器的重要设计参数。在二维电离室剂量探测器的单元空腔几何参数确定的情况下,利用蒙特卡罗仿真方法建立了探测器室壁仿真计算的简化模型,并利用EGSnrc程序对模型进行了仿真计算,给出了室壁厚度的参考数值。结果表明,当空腔为直径4.5mm、高5mm的圆柱形时,在能量为1.25MeV射线下,为达到1%的测量精度,电离室前壁厚度需达到4.4mm,侧壁厚度需达到1.5mm;在1.25~4 MeV射线能量范围内使用时,为达到1%的测量精度,侧壁厚度需达到5mm。本文研究结果可作为该种探测器的设计依据。

The wall-thickness is an important design parameter for two-dimensional ionization chamber dose detector.Under the given geometric parameters of the cavity unit of two-dimensional ionization chamber dose detector,the simulation model was built by using Monte Carlo method.The wall-thickness was calculated with the simulation model using EGSnrc,and the reference numerical value was given.The result shows that when the cavity is a cylinder with diameter of 4.5 mm and height of 5 mm,under radiation of 1.25 MeV,the front wall-thickness of ionization chamber should be more than 4.4 mm and the side wall-thickness should be 1.5 mm in order to meet the demand of accuracy of 1%.Under the radiation with energy of 1.25-4 MeV,the side wall-thickness should be more than 5 mm in order to meet the demand of accuracy of 1%.The research result can be used as the design basis for the detector.