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研制了一套大面积超低本底α表面发射率测量装置,该装置主要由大面积电离室、高压电源、前置放大器、数字化波形采集卡、数据分析软件、气路系统等组成。正常工作时大面积电离室中充入1个大气压的高纯氮气,由于对宇宙射线和γ射线不灵敏,其主要的本底来自电离室内表面发射的α粒子。利用脉冲形状分析、增加保护极等技术实现了电离室位置灵敏,从而可以分辨出α粒子来自于电离室内表面或样品,最终甄别掉电离室内表面发射的α本底达到超低本底的目的。
A large area ultra-low background α-surface emissivity measurement device has been developed. The device mainly consists of a large-area ionization chamber, a high-voltage power supply, a preamplifier, a digital waveform acquisition card, data analysis software and a pneumatic system. In normal operation, a large area of ionization chamber filled with 1 atmosphere of high-purity nitrogen gas, due to cosmic rays and γ-ray insensitivity, the main background from the ionization chamber surface emission of α particles. The pulse shape analysis and the technique of increasing the guarding pole are used to realize the ionization chamber position sensitivity, so that the α particle can be distinguished from the ionization chamber surface or the sample. Finally, the α background emitted by the ionization chamber surface can reach the ultra-low background.