Thesis (Ph.D.) - Cairo University - Faculty of Science - Department of Physics

This work aims mainly at development and improvement of the performance of the cylindrical (standard nuclear material -SNM) and point sources (radioactive 137Cs) assay. New geometries and arrays of detectors were installed and investigated to reduce the unwanted noises and interactions. Two different detectors arrays design are optimized and presented with respect to the analyzed nuclear material samples. The arrays consist of three Sodium Iodide (NaI) detectors; one of them is in annular perpendicular position and the others are guards surrounding the main Hyper Pure Germanium Detector (HPGe). An enhanced Peak-Compton (P/C) ratios were obtained and discussed. Calculations were performed using a The Monte Carlo code (MCNP5) for estimating the optimum conditions to the design at which the systematic error is being as low as possible. The calculations required the knowledge and data of the internal dimensions of the used detectors and samples and the distances between them. The results calculated by MCNP5 at different angles proved that the optimum position for the array is when the guard detectors (NaI) is positioned at zero angle from the x-axis of the main HpGe detector (the array of detectors design number 2)

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