球形石墨空腔电离室内部电场的研究

Research in electric field of spherical graphite cavity

国际上辐射剂量计量基标准电离室多采用球形或圆柱型空腔电离室,其腔室自身几何对称。不同形状的收集极置于腔室中,会影响腔室内部的几何对称性,进而对其内部电场的均匀性和电荷的收集产生一定的影响,作为绝对测量需要对电离角响应方向性进行修正。该文采用Ansoft Maxwell 2D程序建立一个石墨空腔电离室灵敏体积内的静电场模型,分别计算含有3种不同形状收集杆腔室内的电势分布;并对同系列大体积电离室收集杆是否产生放电现象进行了分析,对同类型电离室相关指标的优化设计提供一定的参考。

Spherical or cylindrical type cavity ionization chamber are often been used in radiation dose measurement as base standard ionization chamber.The chamber itself has a symmetrical structure.Different shape of the collectors in the cavity chamber will affect the ministry of interior space geometry symmetry,the internal electric field uniformity and charge collection.So there need to correct ionization angle response in absolute measurement.This paper adopted Ansoft Maxwell 2D program to create a graphite cavity ionization chamber sensitive volume of electrostatic field model,and calculated the potential distribution contains three kinds of different shapes collect stem respectively.It analyzed series of ionization chamber volume to know whether the collect bar produces discharge phenomenon or not.This study will provide certain reference to related types of ionization chamber optimization design of the relevant indicators.