2πα、2πβ粒子发射率的绝对测量

The Absolute Measurement for 2πα and 2πβ Particle Emission Rate

基于大面积流气正比计数器建立了2πα、2πβ粒子发射率测量系统。对该系统进行了性能测试,结果表明其对α平面源的坪长为600～800V,最优平均坪斜为0.2%/100V;对β平面源的坪长为350～400V,最优平均坪斜为0.23%/100V;用点状239Pu α源测得100mm×150mm中心区域的计数均匀性为0.45%。通过对粒子发射率测量结果进行本底、死时间、甄别阈修正,实现了α、β平面源的2π粒子发射率绝对测量,其中对α源发射率测量结果的扩展不确定度优于0.9%（k=2）,对β源发射率测量结果的扩展不确定度优于1.1%（k=2）。与2πα、2πβ粒子发射率基准比对测量了233U、241Am等9枚进口的α、β标准平面源,测量结果均在不确定度范围内一致。

Based on a large-area gas flow proportional counter, a 2π alpha and 2π beta particle emission rate measurement system is established. Performance test is executed and the results show that the plateau length of 600～800V, the optimal average plateau incline of 0.2%/100V for alpha plane sources, and the plateau length of 350～400V, the optimal average plateau incline of 0.23%/100V for beta plane sources are achieved. Uniformity for counting is measured by 239Pu alpha point source to be 0.45% in the central region of 100mm×150mm. Corrections including the background, dead time and the discrimination threshold are executed, and the absolute measurement of particle emission rate for the alpha and beta plane sources are realized. The expanded uncertainty of measurement result are better than 0.9% （k=2） for alpha sources and better than 1.1% （k=2） for beta sources. Comparisons of emission rate of 9 importing sources including 233U and 241Am etc. are executed between 2πα、2πβ primary standard equipment and new built emission rate measurement system, and the measurement results are equivalent in expanded uncertainties limits.