Efficiency curves of the Ghana Research reactor-1(GHARR-1) spectrometry system at near and far geometries

Abstract

The efficiency curves of the HPGe detector at different geometries were measured in a wide energy range of 53.16 to 1408keV. In this study emphasis was laid on the effects of the source energy and the source-to-detector distance. Due to the variation of the activity levels of various samples in gamma-ray spectroscopy, the source-to-detector distance is not fixed at a constant value. This means that the measurements of the absolute detector efficiency must be carried out for each geometrical arrangement used in gamma-ray measurements. The full energy peak efficiency in terms of the gamma-ray energy and the vertical distance from the detector surface has been obtained for an N-type high purity germanium (HPGe) detector using point-like calibrated sources at four different distances from the detector. Comparison of the calculated and the experimentally measured efficiency values for the energy range of 26.345-1408 keV and a source to detector distances of 36, 49, 62, and 75 mm showed that the calculated values agree with that of the experiment within the limits of uncertainty. The standard deviations of the calculated efficiency values from the experimental at the respective source-to-detector height were as follows: 0.05% for 36 mm, 0.08% for 49 mm, 0.03% for 62 mm and 0.01% for 75 mm. © Maxwell Scientific Organization, 2011.