An approach to evaluate the efficiency of γ-ray detectors to determine the radioactivity in environmental samples

Abstract

This work provides an approach to determine the efficiency of γ-ray detectors with a good accuracy in order to determine the concentrations of either naturally occurring or artificially prepared radionuclides. This approach is based on the efficiency transfer formula (ET), the effective solid angles, the self-absorptions of the source matrix, the attenuation by the source container and the detector housing materials on the detector efficiency. The experimental calibration process was done using radioactive (Cylindrical & Marinelli) sources, in different dimensions, that contain aqueous 152 Eu radionuclide. The comparison point to a fine agreement between the experimental measured and calculated efficiencies for the (NaI & HPGe) detectors using volumetric radioactive sources.

Direct mathematical method for calculating the photofraction and intrinsic efficiency of 4πNaI(Tl) borehole cylindrical detectors

“…The photofraction is the ratio between the number of photons that are recorded under certain peak and the number of photons that are recorded in the spectrum at the same energy. It is given by (5) Where Ɛ p is the full energy peak efficiency and Ɛ T is the total efficiency [10].…”

“…The detector walls around this bore hole are made of aluminum with a thickness of only 510 -2 cm to reduce γ -ray absorption [1] The present work is mainly concerned with introducing a straight forward theoretical approach to calibrate the upgraded 4πNaI(Tl) gamma-ray detector for isotropic radiating gamma-ray (point, plane and volumetric) sources. This approach is based on the direct mathematical method reported by Selim and Abbas [2][3][4][5][6][7][8][9][10] and has been used successfully before to calibrate point, plane and volumetric sources with cylindrical, well-type, and parallelepiped detectors. The fact that efficiency can be precisely determined by calculation makes the method absolute (or direct).…”