4πγ电离室活度标准装置测量系统的建立及性能测试

Establishment and Performance Testing of Measurement System for 4πγ Ionization Chamber Radioactivity Standard

基于汤姆逊平衡法原理建立了4πγ电离室活度标准装置的测量系统，该系统由高压电源、电压测量及补偿电路、测控软件组成。利用汤姆逊平衡法原理测量微弱电流，可以有效减小系统的漏流，减小本底电流对测量结果的影响，经测试该系统的本底电流小于3×10-14A。通过对测量系统的重复性、稳定性、线性和角响应等性能测试，结果表明，该测量系统能够满足4πγ电离室活度标准装置的要求。

A measuring system based on Townsend induction balance method for 4πγ ionization chamber radioactivity standard is developed. The measuring system consists of high voltage source, voltage measurement, compensation circuit and control software. During Townsend balance process, the leakage currents and offset current are small in comparison with the current to be measured. The leakage and background current obtained with the measuring system is less than 3 × 10-14A. Measurements are performed to check the repeatability, stability, linearity and angle response of the system. The testing result shows that the measuring system meets the requirement of 4πγ ionization chamber radioactivity standard.