低本底α、β放射性测量中几何因子对探测效率的影响分析  

Influence of geometric factor on detection efficiency in low-backgroundα/βradioactivity measurement

作　　者：李小双 刘佳煜 LI Xiaoshuang;LIU Jiayu(Shanghai Insitution of Measurement and Testing Technology,Shanghai 201203 China)

机构地区：[1]上海市计量测试技术研究院,上海201203

出　　处：《中国辐射卫生》2024年第2期183-188,202,共7页Chinese Journal of Radiological Health

摘　　要：目的研究对低本底α、β放射性测量仪计量时平面源活性区半径以及其中心与探测窗中心位置水平间距的变化对探测效率的影响。方法基于MATLAB对不同条件下的几何因子的数值计算,采用经溯源的平面源对常用的测量仪器进行实验分析。结果保持其他参数不变,活性区半径R_(1)=9 mm时,G值最大;间距a=0 mm时,G值最大;按照检定规程计算公式,对于^(90)Sr-^(90)Y平面源,a最大时,FYFS-400X探测效率偏小1.2%,MPC-9604探测效率偏小3.2%;对于^(241)Am平面源,a最大时MPC-9604探测效率偏小1.9%。结论几何因子随着活性区半径、间距的增大而减小。在居中位置,几何因子对探测效率相对标准不确定度的影响更小。建议使用标准平面源对仪器计量时应该采取有效措施确保平面源始终处于样品盘的正中央位置。Objective To study the influence of the radius of the active zone of the plane source and the horizontal distance between the source center and the center of the detection window on the detection efficiency of low-backgroundα/βmeasuring instruments.Methods The geometric factor was calculated under different conditions in MATLAB,and a traceable plane source was used to test and analyze two commonly used measuring instruments.Results With the other parameters unchanged,when the radius of the active zone R_(1)=9 mm,the G value was greatest;and when the horizontal distance a=0 mm,the G value was greatest.According to the calculation formula of the verification regulation,for the ^(90)Sr-^(90)Y planar source,at the maximum value of a,the detection efficiency of FYFS-400X was 1.2%lower,and that of MPC-9604 was 3.2%lower;for the ^(241)Am planar source,the detection efficiency of MPC-9604 was 1.9%lower at the maximum value of a.Conclusion The geometric factor decreases with the increase in the radius of the active zone and the horizontal distance between the source center and the center of the detection window.At the central position,the geometric factor has less influence on the relative standard uncertainty of detection efficiency.When using a standard plane source for counting,measures should be taken to ensure that the plane source is always centrally located in the sample tray.

关 键 词：α、β放射性 立体角 几何因子 探测效率 相对标准不确定度 

分 类 号：TL81[核科学技术—核技术及应用]