In order to enhance the detection sensitivity of HPGe detectors for measuring the low-level activity of radionuclides, samples are usually measured as close to the detector as possible to improve the detection efficiency, which inevitably leads to serious coincidence-summing effects in return and affects the accuracy of measured activity.

This study aims to conduct efficiency simulation and coincidence-summing correction for HPGe detectors.

First of all, the peak efficiency of the HPGe detector was simulated by Geant4 and the internal geometry of the HPGe detector was optimized by comparing the simulated results with the experimental results of the mixed standard calibration source. Then, the total efficiency of the detector with various dead layer thickness was calibrated and the coincidence-summing correction factors were calculated. Finally, "Proficiency Test Exercise (PTE) 2021" conducted by the Provisional Technical Secretariat (PTS) of Comprehensive Nuclear Test Ban Treaty (CTBT) was applied to the correction of the measured activity.

Measurement results show that the relative deviation between the corrected activity and the reference result is less than 3%.

Results of this study demonstrate that the efficiency simulation and coincidence-summing correction for HPGe detector solves problems of limited calibration point source and high experimental cost, lays a foundation for measuring activities of nuclides in the sample accurately.