Influence of geometric factor on detection efficiency in low-background α/βradioactivity measurement
Objective To study the influence of the radius of the active zone of the plane source and the horizontal dis-tance between the source center and the center of the detection window on the detection efficiency of low-background α/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 R1=9 mm,the G value was greatest;and when the horizontal dis-tance a=0 mm,the G value was greatest.According to the calculation formula of the verification regulation,for the 90Sr-90Y 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 dis-tance 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,meas-ures should be taken to ensure that the plane source is always centrally located in the sample tray.
α/β radioactivitySolid angleGeometric factorDetection efficiencyRelative standard uncertainty
NETL
NSTL
万方数据
