Determination of absorption parameters and crystal thickness for HPGe detectors

HPGe detectors are an important part of spectroscopy systems which are used in the qualitative and quantitative analyses of radioisotopes in samples and in nuclear implementations. The accuracy of measurements made with these systems is strongly related to the experimental setup and the performance of the detectors. In order to this, in the first part of the thesis the effect of the diameter of the collimator and of the measurement area on the surface of the detector in the experimental measurement of mass attenuation coefficient was investigated. With the increase in the diameter of the collimator a systematic decrease was observed in the mass attenuation coefficients. It was seen that the results of the mass attenuation coefficient measurements experiments differed according to the areas on the surface of the detector. In addition to this part of the thesis, the effect of the bias voltage in HPGe detectors on some peak parameters was examined. In the last part, a semi-empirical model was employed to determine the thickness of the effective crystal thickness affecting the photopeak efficiency of HPGe detectors used in the measurement of gamma rays. The obtained thickness data was inconsistent with those given by manufacturing firm in some areas. However, to provide the validity of the obtained data the efficiency curve of the detector was comprised experimentally and using the Monte Carlo method. As a result, it was seen that the semi-empirical model used in the Monte Carlo method was more compatible with the experimental results than the model comprised with the catalogue data.