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Omer, M.; 静間 俊行*; 羽島 良一*; 小泉 光生
Radiation Physics and Chemistry, 198, p.110241_1 - 110241_7, 2022/09
被引用回数：2 パーセンタイル：50.96(Chemistry, Physical)In beam geometries where a directed 
-ray beam hits the surface of a coaxial high purity germanium detector (HPGe), the detector efficiency is sensitive to the position where -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 -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 a Monte Carlo simulation that calculates the detector efficiency in the beam geometry. The effects of the off-axis distance and -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 a nuclear resonance fluorescence experiment using laser Compton scattering -ray beam.
Omer, M.; 静間 俊行*; 羽島 良一*; 小泉 光生; 平 義隆*
no journal, ,
High-resolution -ray spectroscopy involving beam geometry may be measured with higher efficiency if -ray beam hits out of the axis of the coaxial HPGe detector. Hitting off-axis makes -rays avoid travelling through the contact hole, which is an inactive axial portion of the detector. We performed Monte Carlo simulations to study the effects of contact hole dimensions and off-axis distance on the coaxial HPGe detector efficiency. The simulation considered -ray energy up to 10 MeV. In general, the simulation results reveal that the off-axis efficiency is higher than on-axis efficiency for a wide range of -ray energies and beams sizes. Our simulations results are validated by experimental measurements of -ray beams generated from laser Compton scattering at UVSOR III facility.
-ray beamOmer, M.; 静間 俊行*; 小泉 光生; 羽島 良一*; Zen, H.*; 平 義隆*
no journal, ,
Coaxial high-purity germanium detectors are essential components of high-resolution -ray spectrometers. Indeed, these detectors come in various dimensions with different internal structures. Particularly when the measured -rays are in the form of a directed beam, the detector internal structure may affect the measured -ray spectra significantly. Here we investigate the effect of the internal structure of two different coaxial HPGe detectors using 5.54 MeV -rays generated by laser Compton scattering at the UVSOR III facility. The -ray beam hit the detectors in two configurations, axial and nonaxial. We found that the nonaxial configuration provides higher efficiency and lower background than the axial configuration, which was confirmed using Monte Carlo simulations. Our results provide improvements in the measurement of -ray beams. This work is a contribution of the Japan Atomic Energy Agency (JAEA) to the International Atomic Energy Agency (IAEA) under the agreement of the coordinated research program (CRP), J02015 (Facilitation of Safe and Secure Trade Using Nuclear Detection Technology - Detection of RN and Other Contraband).
