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The full energy peak efficiency (FEPE) determined by experimental or Monte Carlo (MC) simulation methods is a very important parameter in HPGe detectors. Since FEPE depends on the detector's geometric parameters, the parameters provided by the manufacturer are of great importance in modeling the detector with the MC method. The most important reason for the discrepancy between MC and experimental calculations is the lack of accurate information about the detector's geometric properties. The thickness of the copper contact pin in the middle of the detector hole is not given by the manufacturer. In this study, the effect of copper contact pin thickness on detector efficiency was investigated by using the PHITS 3.24 MC simulation program both at different copper contact pin radii and at different detector-source distances. The efficiency values were calculated for photons in the energy range of 59.5 keV-1408 keV, at 4 different distances, namely 5 cm, 13.25 cm, 15 cm, and 20 cm and for the radii of copper contact pins increased from 1 mm to 3.5 mm at 0.5 mm intervals. According to the results, it has been determined that the presence of copper contact pins causes a change in detector efficiency up to 1.9%, especially in the high energy region, and has no effect on the detector efficiency in the low energy region. In addition, it has been observed that the effect of copper contact pin thickness on detector efficiency is almost independent of the source-detector distance.

Using the gamma spectroscopy system, it can be determined whether environmental samples or standard radioactive sources are radioactive, and from which elements their radioactivity originates. The purpose of Monte Carlo (MC) simulation is to model a real-life system with its inputs and evaluate the outputs with real results. This study calculates the experimental efficiency of a p-type HPGe detector using a 0.5 g/cc Epoxy Matrix Marinelli beaker and compares these results with GESPECOR and PHITS MC Simulation programs. Thus, the thickness of the dead layer, which thickens over time and affects the detector efficiency, was determined from the most compatible result of the MC calculations made repeatedly at various alternative thicknesses to the experimental results. For 1.5 mm dead layer thickness, less than 2 % error was found between the test and MC results, especially at energies above 165 keV. As a result, it was determined that the dead layer thickness of the detector reached 1.5 mm with an increase of 114 % after its production. The current value of the dead layer thickness of each detector should be checked, as the efficiency affects the determination of the activity.

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It is clear that humans are exposed to ionizing radiation both of internally or externally in radiotherapy. The determination of ionizing radiation dose in human blood has been previously performed by us using optically stimulated luminescence technique. OSL technique is based on measuring the luminescence intensity from a sample that has been exposed to ionizing radiation. In this study, the detrapping constants for human blood samples were investigated using Curve-Fitting, Active OSL-Approximation and Linear Modulation techniques. The Active OSL-Approximation was based on the radioactive decay law of successive disintegration. It allows obtaining the peak forms of luminescence signal. It has been observed that the decay rates for blood sample exposed to different radiation doses were changed with dose. AOSL-Approximation is appropriate for separating the peaks that correspond to decay rates.