Counting loss correction in ³⁷Ar activity measurement based on Geant4 simulation / 中国辐射卫生

ABSTRACT

@#<b>Objective</b> To correct the counting loss of ³⁷Ar below the activity threshold during the measurement of the absolute activity of the inert radioactive gas ³⁷Ar using the proportional counter filled with gas. <b>Methods</b> Monte Carlo simulation with Geant4 was performed to establish a proportional counter model and output the energy deposition spectrum of ³⁷Ar, which were used to simulate and analyze the causes and correction of counting loss. <b>Results</b> The photon detection efficiency was only 38.7% at 60 kPa. The counting loss was mainly caused by the wall effect produced by the photons, which could be reduced by increasing the gas pressure and corrected by extrapolation. The influence of wall effect at 100 kPa was 4.4%, and the deviation between simulation and experiment was < 0.6%. <b>Conclusion</b> A factor could be calculated by Geant4 simulation for the correction of counting loss, thus achieving the accurate measurement of ³⁷Ar activity by proportional counter.