高气压充氙电离室电极结构对能谱分辨率影响的模拟研究

Effect of Electrode Structure of High-Pressure Xenon Chambers on Energy Spectrum Resolution

高气压充氙电离室对能量为几百keV的γ射线有较高的探测效率。本文首先从理论上分析了采用共面栅极阳极技术高气压充氙电离室的信号产生机理,得到该电离室输出信号和电场分布的关系式;然后使用Maxwell3D软件和Geant4程序分别建立该电离室电场计算模型及蒙特卡罗模型,模拟得到其灵敏体积内电场分布及粒子能量沉积信息;最后利用上述模拟结果分析确定该电离室的输出信号受极丝数目、极丝直径和极丝距中轴的距离等的影响情况。结果表明,电离室的极丝数目越多,直径越小,距中轴越近,其对137Cs的测量谱能量分辨率将越好。本研究将对该电离室谱仪的优化设计提供参考,同时也可用于其它类型谱仪能量分辨特性的研究。

The mechanism of signal induction in the high-pressure xenon chamber with coplanar grid anode was theoretically analyzed first in this paper. The relationship between its output signal and electric field distribution inside that chamber were gained. Then the electric field calculation model and Monte-Carlo simulation model of a high-pressure xenon chamber were set up with Maxwell3D software and Geant4 toolkit respectively. Using these models the electric field distribution and energy deposited for every incident particle in the chamber and eventually the output signals of the chamber were obtained. Finally, the effect on output signal of the wire number, diameter and distance from the axis are analyzed and determined by using the forgoing-mentioned both models. The results indicated that the more wire number, smaller diameter and nearer distance the chamber has, the better the energy resolution of 137 Cs is becoming. This study provides a method to optimize these detectors, and this method can be also used for other kinds of spectrometer resolution study.