Cross-talk elimination in determination of gross α and gross β activities using a low-background α/β gas-flow proportional counter / 中国辐射卫生

Objective To explore cross-talk elimination method in the determination of gross α and gross β activities using a low-background α/β gas-flow proportional counter. Methods A CLB-104 low-background α/β gas-flow proportional counter was used in this study. First, the α threshold was increased to eliminate the cross-talk counting caused by β particles in the α channel. Then, the α-β anticoincidence threshold was reduced to eliminate the cross-talk counting induced by low-energy α particles in the β channel, and β counts were corrected to eliminate the counts induced by internal convention electrons in the β channel. Finally, gross α and gross β activities of non-saline water samples with different activity levels were determined and compared with gross α and gross β activities of the same samples determined on a BH1227 low-background α/β solid scintillation counter, in order to verify effectiveness of the cross-talk elimination method. Results By eliminating the cross-talk counts of β particles in the α channel and the cross-talk counts of α particles in the β channel, and deducting the counts of internal convention electrons in the β channel, the gross α and gross β activities of the same samples determined by CLB-104 were consistent with the values determined by BH1227. Conclusion Cross-talk counts induced by low-energy α particles or β particles can be eliminated by threshold adjustment, and the counts caused by internal convention electrons in the β channel can be eliminated by correction.

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

@#<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.