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内容記述 |
Coaxial high-purity germanium (HPGe) detectors are widely used in applications requiring high-resolution gamma-ray spectroscopy. However, the internal structure of HPGe detectors, particularly the geometry of the inactive volumes inside the core of the detector, can significantly influence their performance in beam detection configurations. In this work, we investigate the impact of detector structure on the spectral response to pencil-like gamma-ray beams by comparing gamma-ray spectra measured with two coaxial HPGe detectors with similar active volumes but distinct internal geometries. Experimental measurements were conducted at the UVSOR synchrotron facility using collimated laser Compton scattered (LCS) gamma-ray beams with an energy of 5.53 MeV. Monte Carlo simulations using Geant4 toolkit have been performed to refine the detector models and replicate experimental results. The results reveal that the front layer thickness and the presence of structural elements such as the cold finger strongly affect the spectral features, particularly the appearance of coincidence sum peak of the annihilation radiation at 1.022 MeV. Off-axis irradiation significantly improves the detection efficiency and reduces the undesired induced interactions with inactive volumes. Additionally, we validate the observed pair production signatures through the available theoretical cross section, confirming the dominant role of internal structures in shaping the detector response under beam geometry. These findings are essential for optimizing detector configurations in precision gamma-ray beam experiments. |
