@article{oai:repo.qst.go.jp:00086291,
 author = {M.Omer and Toshiyuki, Shizuma and Ryoichi, Hajima and M.Koizumi and Toshiyuki, Shizuma and Ryoichi, Hajima},
 journal = {Radiation Physics and Chemistry},
 month = {Jun},
 note = {In beam geometries where a directed γ-ray beam hits the surface of a coaxial high purity germanium detector (HPGe), the detector efficiency is sensitive to the position where γ-rays initially hit the detector surface because the structure of the detector is nonuniform. This may cause inaccuracy of the detector efficiency when measured using standard sources that are point-like sources emitting γ-rays isotropically. Obtaining a precise estimation of the full energy peak efficiency of the coaxial HPGe detector in the beam geometry for on-axis and off-axis measurements requires a Monte Carlo simulation. We performed Monte Carlo simulations that calculate the detector efficiency in the beam geometry. The effects of the off-axis distance and γ-ray beam size on the efficiency are quantitatively analyzed. We found that the intrinsic efficiency in the beam geometry is maximized when the beam hits the detector at specific off-axis distances. Our Monte Carlo calculations have been supported by nuclear resonance fluorescence experiments using laser Compton scattering γ-ray beams.},
 title = {Calculating off-axis efficiency of coaxial HPGe detectors by Monte Carlo simulation},
 volume = {198},
 year = {2022}
}