Thesis & Dissertations

With the start of using radioactive sources in a variety of different fields such as health physics, industry, energy, and environmental application, nuclear radiation detectors have become the most fundamental instruments, as radiation is hazardous for health. In a radiation measurement, an accurate knowledge of the detector spectral performance is required. As the radiation can travel large distances between the interactions in the detector material before detection is possible, the detectors do not have 100% efficiency. In the radiation measurement, one of the most important characteristics of a detector is its efficiency. Gamma spectrometry is one of the most widely used detector systems in this field and its performance directly depends on the knowledge of the detection efficiency. The detection efficiency is a measure of the percentage of radiation that a given detector detects from the overall yield emitted from the source. It can vary with the volume and shape of the detector material, absorption cross-section in the material, attenuation layers in front of the detector, distance and position from the source to the detector. In this work, we introduce a direct analytical mathematical method for calculating the solid angle, subtended at a point by closed elliptical cylinder. The solid angle is required in many areas of optical and nuclear physics to estimate the flux of particle beam of radiation and to determine the activity of a radioactive source. The validity of the derived analytical expressions was successfully confirmed by the comparison with some published data (Numerical Method). In addition to this work, a direct analytical method is presented for calculating the absolute efficiency of an elliptical cylindrical detector in the case of an arbitrarily positioned point source. The total efficiency is required to determine the activity of an unknown radioactive source, taking into account the attenuation of the gamma-ray photons. The validity of the derived analytical expressions was successfully confirmed by comparing them with published data.