Abstract
Six HPGe detectors with various crystal diameters were investigated for data related to the aspect ratio, energy resolution, peak shape, Peak-to-Compton ratio and efficiencies as they affect nuclear analytical measurements. The germanium crystal diameters ranged from 4.47 cm to 5.88 cm with lengths varying from 3.34 cm to 7.63 cm. These detectors were classified into two main groups- the Low Aspect Ratio (LAR) and High Aspect Ratio (HAR) group. The efficiencies of the HAR and LAR were investigated as functions of energies within the range of 121.78 keV to 1332.5 keV, for various source detector geometries. The Peak-to-Compton ratio and peak shape measurements were investigated with respect to HAR and LAR. The result shows that Peak-to-Compton ratio and peak shape increased proportionately with all the six GEM-series detectors used. These translate to the six detectors having accurate counting statistics of photons/gamma rays. However, detectors D4, D5, and D6 classified as HAR were higher in resolutions.
Highlights
In nuclear analytical measurements, the aspect of instrumentation deals with detection instruments, methods, and experimental techniques for the measurements of radiations
These classes were divided into two categories termed Low Aspect and High Aspect ratios marking reference to the different crystal diameters ranging between 4.47–5.88 cm and lengths 3.34-7.63 cm
High Aspect Ratio (HAR) implies that the crystal diameter is greater than the crystal depth and Low Aspect Ratio (LAR) means crystal depth greater than the crystal diameter
Summary
The aspect of instrumentation deals with detection instruments, methods, and experimental techniques for the measurements of radiations. It plays important role in counting statistic especially in the evaluation of trace elements, activity of either Naturally Occurring Radioactivity in Materials (NORMS) or induced radioactivity from matrices irradiated in a research reactor Another important characteristic of HPGe detectors is the Peak-to-Compton ratio which measures the detector’s ability to distinguish peaks from the background influence as a result of radiation from environment or surrounding and electronic noise (Debertin and Helmer 1988). In the area of biological and environmental analysis of materials this interference of the Compton plateau result in difficulties such as; detection limit of important nuclides, accuracy and precision measurements of elements in food matrices, accurate measurement of elements in human nutrition and elements composition and their role in food consumption Another factor which forms one of the basic parameters that govern HPGe detector characteristics is the peak resolution defined as the measure of the width of the peak at half its height (Knoll, 1989). This is usually specified at either 1332.5 keV photo-peak of 60Co or 122 keV gamma energy line of 57Co (ANSI/IEEE, 1996)
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