Modeling and optimization of HPGe detector GC0518 using MCNP5 code

For precise modeling of a high purity germanium (HPGe) detector, detailed knowledge of its geometry is necessary. Unfortunately, some of the detector geometric parameters are often not available. This study suggests simple procedures for determining geometry without the need for radiography. The study considers the HPGe detector GC0518 manufactured by Mirion. The detector data sheet is available, but the uncertainties do not allow the detector to be modeled without additional corrections. The detector was modeled using MCNP5 code and the results were compared with calibration point sources and Marinelli beakers measurements. We also performed measurements to obtain information on the germanium dead layer, crystal holder shape, inner hole shape and radii of the crystal edges. Then the model was optimized according to the measurements. Finally, the full energy peak efficiencies were evaluated. The relative differences between the measured and calculated efficiencies are less than 4.5% for point sources and 5.4% for Marinelli beakers. (authors)