外推电离室内部电场模拟研究  

Simulation of the electric field in extrapolation ionization chamber

作　　者：刘川凤 宋明哲[1] 高飞[1] 倪宁[1] 徐阳 张曦[1] 刘蕴韬[1] LIU Chuanfeng;SONG Mingzhe;GAO Fei;NI Ning;XU Yang;ZHANG Xi;LIU Yuntao(National Key Laboratory for Metrology and Calibration Techniques,China Institue of Atomic Energy,Beijing 102488,China)

机构地区：[1]中国原子能科学研究院计量与校准技术重点实验室

出　　处：《中国测试》2020年第1期147-153,共7页China Measurement & Test

摘　　要：目前国际上将空气比释动能强度作为近距离治疗125I粒子源剂量计算及评价粒子源强度的物理量。测量粒子源空气比释动能强度的标准装置拟采用外推电离室,外推电离室结构设计会影响内部电场,内部电场的均匀性对电离电荷有效收集产生一定的影响。该文利用Maxwell软件建立电离室结构,研究有无保护电极以及栅极个数和栅极尺寸对内部电场均匀性的影响,对模拟得到的电场图进行分析,得到结论为当保护电极半径大于收集极半径时,增加栅极的个数,并且当栅极中心间距小于保护电极环宽的1/10时,有利于增加电离室内部电场的均匀性,对外推电离室的设计提供一定的参考。At present,the quality air-kerma strength is used to calculate the dose of 125I seed and evaluate the strength of brachytherapy source in the world.Extrapolation ionization chamber is used as primary standard to measure the quantity air-kerma strength.The structure of the ionization has an effect of the electric field distribution.And it is important to have uniformity electric field for collecting the ionization charges.This paper adopted Maxwell program to create the structure of chamber.It studied the effect of guard electrode and structure of grid electrode on electric field of extrapolation ionization chamber.By analysis the figure of electric field,the ionization chamber has more uniformity electric field with the radius of guard electrode larger than that of collecting electrode,more potential rings,and the distance of two potential rings less than 1/10 of the width of guard electrode.That provides certain reference to related types of extrapolation ionization chamber optimization design of the structure.

关 键 词：外推电离室 电场 Anosft Maxwell 

分 类 号：TB98[一般工业技术—计量学] TL8111[机械工程—测试计量技术及仪器]