Progress in Medical Physics (한국의학물리학회지:의학물리)

Korean Society of Medical Physics (한국의학물리학회)
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Dead Layer Thickness and Geometry Optimization of HPGe Detector Based on Monte Carlo Simulation

  • Suah Yu (Research Team of Medical Physics, Korea Institute of Radiological & Medical Sciences) ;
  • Na Hye Kwon (Department of Radiation Oncology, Yonsei Cancer Center, Yonsei University College of Medicine) ;
  • Young Jae Jang (Research Team of Medical Physics, Korea Institute of Radiological & Medical Sciences) ;
  • Byungchae Lee (R&D Institute, Sae-An Enertech Corp) ;
  • Jihyun Yu (R&D Institute, Sae-An Enertech Corp) ;
  • Dong-Wook Kim (Department of Radiation Oncology, Yonsei Cancer Center, Yonsei University College of Medicine) ;
  • Gyu-Seok Cho (Research Team of Medical Physics, Korea Institute of Radiological & Medical Sciences) ;
  • Kum-Bae Kim (Research Team of Medical Physics, Korea Institute of Radiological & Medical Sciences) ;
  • Geun Beom Kim (Research Team of Medical Physics, Korea Institute of Radiological & Medical Sciences) ;
  • Cheol Ha Baek (Department of Radiological Science, Kangwon National University) ;
  • Sang Hyoun Choi (Research Team of Medical Physics, Korea Institute of Radiological & Medical Sciences)
  • Received : 2022.11.18
  • Accepted : 2022.12.07
  • Published : 2022.12.31
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Abstract

Purpose: A full-energy-peak (FEP) efficiency correction is required through a Monte Carlo simulation for accurate radioactivity measurement, considering the geometrical characteristics of the detector and the sample. However, a relative deviation (RD) occurs between the measurement and calculation efficiencies when modeling using the data provided by the manufacturers due to the randomly generated dead layer. This study aims to optimize the structure of the detector by determining the dead layer thickness based on Monte Carlo simulation. Methods: The high-purity germanium (HPGe) detector used in this study was a coaxial p-type GC2518 model, and a certified reference material (CRM) was used to measure the FEP efficiency. Using the MC N-Particle Transport Code (MCNP) code, the FEP efficiency was calculated by increasing the thickness of the outer and inner dead layer in proportion to the thickness of the electrode. Results: As the thickness of the outer and inner dead layer increased by 0.1 mm and 0.1 ㎛, the efficiency difference decreased by 2.43% on average up to 1.0 mm and 1.0 ㎛ and increased by 1.86% thereafter. Therefore, the structure of the detector was optimized by determining 1.0 mm and 1.0 ㎛ as thickness of the dead layer. Conclusions: The effect of the dead layer on the FEP efficiency was evaluated, and an excellent agreement between the measured and calculated efficiencies was confirmed with RDs of less than 4%. It suggests that the optimized HPGe detector can be used to measure the accurate radioactivity using in dismantling and disposing medical linear accelerators.

Keywords

Acknowledgement

This research was supported by the National Research Foundation of Korea (NRF) grant (No. 2020M2D9A309417021) and the Nuclear Safety Research Program through the Korea Foundation of Nuclear Safety (KoFONS) using the financial resource granted by the Nuclear Safety and Security Commission (NSSC) of the Republic of Korea (No.2003013&2205013).

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