Study of parameters influencing the response of HPGe-detectors

The SCK•CEN, the JRC Geel and the University of Hasselt make use of High Purity Germanium detectors (HPGe) for gamma-ray spectrometry. These detectors have a superior resolution compared to other gamma-ray detectors. However, these detectors still need many corrections for quantitative analysis of radioactivity, nuclide identification or the characterisation of unknown samples. Anno 2018 those corrections are mostly calculated by advanced algorithms involving Monte Carlo simulations. Such simulations require a detailed digital model of the detector. In this thesis EGSnrc software was used to make these simulations. Three topics were investigated. First, the creation of a model for the detector of UHasselt was done. This resulted in an irregular deadlayer with a crater in the middle. Second, a new model for detector T7 was created with the aim to investigate the influence of the parameters in the model. All parameters were changed separately and their individual influence was measured by comparing the relative difference in counting efficiency compared to experimental data. Third, a comparison of two deadlayer thickness calculation methods was done. A first method was based on a method described by Budjas et al. [1] and the second method is based on the differences in attenuation coefficients. The results of this comparison showed that both methods gave a good indication of the deadlayer thickness given that a non-collimated point source of 241Am is used.