Gamma ray registration efficiency simulation of a HPGe detector with PHITS

Simulation of the detector response to determine the detection efficiency as a function of gamma-ray energies makes it possible to avoid the efficiency calibration when this process is difficult for some reasons. In this study, full energy peak efficiencies of gamma-rays for a high-purity germanium (HPGe) detector have been calculated. A geometry consisted of the HPGe detector and a volume source was constructed by using PHITS. The energy deposition to the HPGe was calculated for γ rays generated in the source. The full energy peak efficiency was estimated from counts of the full energy peak on the deposition distribution. The results obtained by PHITS simulations were validated by comparing with measured efficiencies (88–1836 keV) obtained from actual measurements of a nine-nuclide mix-standard source. The overall discrepancy between the simulated and measured data showed a maximum of 3.7% difference, which means with this method, the efficiency of gamma-ray detection by HPGe detector could be determined with a certain degree of certainty even in the absence of a standard sample.