Gamma-ray spectrometry is a very powerful tool for radioactivity measurements. The gamma-ray spectrometer laboratory in Centre for Energy Research and Training (CERT), Ahmadu Bello University, Zaria, Nigeria is accredited to perform measurements of radioactive content of samples collected from the environment, food chain or industrial products with the aid of a high resolution HPGe detector. For accurate gamma-ray spectrometry, certain measurements were considered;the efficiency of the detector was performed experimentally against energies within the range of 59.50 keV (241Am) to 2204.50 keV (226Ra) for the respective geometries of 1 - 6 cm. The sustained solid angle relations with respect to the inverse square of sample geometries from 1 - 6 cm were evaluated. Another main point of this work was focused on the efficiency at geometry of 5 cm with respect to the three selected energies: 661.60 keV (137Cs), 1173.2 keV (60Co) and 1332 keV (60Co) for the main axis, ten degree off main axis, forty five degree off main axis and ninety degree off the detector main axis. In order to verify optimum geometries in our laboratory for both short lived and long lived radionuclides analyses, the evaluation of efficiencies for the respective energies: 1173.2 keV (60Co), 1332.5 keV (60Co), 1764 keV (226Ra) and 2294 keV (226Ra) were plotted against geometries of 1 to 6 cm from the detector end cap along the main axis.
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