基于^(90)Sr源β射线的外推电离室入射窗修正因子

Extrapolation Chamber Entrance Window Correction Factor on ^(90)Sr β Ray Radiation Field

为实现外推电离室对β辐射吸收剂量的准确测量,对影响外推电离室入射窗修正因子k_(wi)的主要量进行了研究。实验测量了外推电离室不同极间距和不同源-探距(源到外推电离室入射窗表面的距离)下的k_(wi)。研究结果表明,在源-探距不变的条件下,k_(wi)随电离室极间距的增大而减小;在电离室极间距为3 mm的条件下,k_(wi)随源-探距的增大而减小。利用蒙特卡罗模拟计算出不带展平过滤器、源-探距为30 cm、电离室极间距为3 mm时,k_(wi)为1.084 5,与实验测量结果比较,其相对偏差为0.11%。因此,在给出k_(wi)的同时,应提供相应的源-探距和电离室极间距。

In order to achieve accurate measurement of the absorbed dose of beta radiation,the main influence factors of the extrapolation chamber entrance window correction factor k wi were studied. k wi at different cavity lengths and different source-detection distances was measured by experiments.The results show that the correction factor k wi with the same source-detection distance decreases with the increase of the cavity length.And k wi decreases with the increase of the source-detection distance when the cavity length is 3 mm.The calculated k wi without flattened filter at source-detection distance of 30 cm and cavity length of 3 mm was simulated using Monte Carlo method.The simulation result is 1.084 5,which differs from the experiment result by 0.11%.Therefore,in addition to the correction factor k wi,corresponding source-detection distance and cavity length should be supplied.