Monte Carlo uncertainty analysis of germanium detector response to gamma-rays with energies below 1 MeV

Monte Carlo method was used to simulate the pulse-height response function of high-precision germanium (HPGe) detector for photon energies below 1 MeV. The calculations address the uncertainty estimation due to inadequate specifications of source positioning and to variations in the detector's physical components: dead layer thickness, spectrometer angular positioning and the presence/absence of aluminium holder. A detailed Monte Carlo model was developed using the MCNP4C code. The simulation results indicate that the uncertainty due to the dead layer thickness has larger effect on photons energies below 100 keV, where for 15 keV incident photon energy the total counts are by a factor of 7 times higher when the thickness is 50% larger. Small variations in source position and angular spectrometer have minimum effect on the photon energies modelled. The absence of A1-holder in the Monte Carlo model reduces the Compton region information for higher energy regions. This analysis has indicated that Monte Carlo methods can represent a valuable tool for the quantitative uncertainty analysis of radiation spectrometers. They can furthermore be instrumental in the gamma-ray detector quantitative calibration and benchmarking processes, thus minimizing the need for deployment of radioactive sources. (C) 2004 Elsevier B.V. All rights reserved.