多丝正比计数器工作气体压强变化对α、β表面粒子发射率测量的影响

为了研究工作气体气压变化对α和β源表面发射率绝对测量的影响,在α、β表面粒子发射率基准装置上,通过改变多丝正比计数器工作气体压强,对大面积α平面源241Am、β平面源204Tl和90Sr/90Y的表面粒子发射率进行了绝对测量,并通过阈值外推方法对低能信号引起的漏计数率进行修正。结果表明,当工作气体压强在50～180kPa气压范围内变化时,不同气压条件下的α、β表面粒子发射率测量结果在实验不确定度范围内相一致。基于Geant4程序包对探测器结构进行建模,Monte Carlo方法给出的模拟结果得出的结论与实验结果相符。

Study of Gas Pressure Dependence in the Multi-wire Proportional Counter on the Absolute Measurement for Alpha and Beta Sources Surface Emission Rates

In order to the investigation of the absolute measurements for α and β surface emission rates due to the working gas pressure variations in China NIM by using α and β multi-wire proportional counter. The surface emission rates measurement of plane sources 241Am、204Tl and 90Sr/90Y is measured respectively by changing working gas pressure in multi-wire proportional counter. The counting rate loss of small pules is corrected by the threshold extrapolation method. The results show that by taking in to account the counting loss of small pules, there is no significant difference observed and all of the measured emission rates are consistent in the range of the evaluated uncertainty within the range of 50 kPa to 180 kPa atmosphere. Monte Carlo simulations based on Geant4 code were also carried out to support our results. The results obtained by the Monte Carlo method are in agreement with the experimental results.