A measurement system for alpha and beta surface emissionrate using MWPC

We have developed a large area multi-wire proportional counter (MWPC) as a standard for the measurement of alpha and beta surface emission rate at the Shanghai Institute of Measurement and Testing Technology (SIMT). To shorten the preparation time for chamber gas refilling, a self-designed gas control unit was adopted. Various characteristics of the system have been studied. The uncertainties were analysed. Three certified alpha plane sources (Am-241) and six certified beta plane sources (Tl-204 and Sr-90/Y-90) were measured by this system. The results show excellent agreement with the surface emission rate reported by the National Institute of Measuring, China (NIM) that E_n values of all measured sources are within ±1.