No abstract

In this work, a system for the characterization of materials using transmission and scattering of gamma rays is described and used to assess the attenuation properties of some liquid materials. The apparatus consists of a 45 mCi point source of 124Am and thin NaI (Tl) detector. Measurements are presented for sucrose solutions with densities ranging from 1 to 1.86 g/cm3. For the absorbance, the solution Z (0.66 g/cm3) with the lowest density has higher absorption with chances to attenuate more than some higher density absorber solution like the sucrose (1.37 g/cm3) while sucrose (1.86 g/cm3) solution with the highest density possessing highest absorption and attenuation capabilities. This however did not fully accord to the conformity with the theory in low-density absorber which will give rise to less attenuation than a high-density absorber since the chances of an interaction between the radiation and the atoms of the absorber are relatively lower. Consequently, the variation of the ratio of scattered and transmitted intensity against the density of the solutions display some arbitrary dependence with energy of the photons interacting with the density of the absorber solution with some little deviation to the exact ideal scattering and transmission case. With gamma rays, most likely the scattering is in the forward direction and that the probability of scattering backwards or in larger angles is relatively constant as the angle approaches 90.

Operation of gamma spectrometry requires intensive monitoring of gamma ray fluxes. When a radioactive intense source is placed close to a crystal detector, it becomes saturated as a result of detector dead time. On the contrary, when placed far away, there is loss of count statistics. For this reason, optimal position for placing the source has to be investigated. With the improvement in the instrumentation of radiation detection applications over the years, high count rate measurement accuracy is more crucial than ever. This is due to periodic measurement and new correction models for dead time. The aim of this study is to examine the performance of two gamma spectroscopic systems. The source detector distance dependence on dead time, peak-to-compton ratio, overall amplifier gain, FWHM, and voltage variation were investigated using American standard procedures (ANSI/IEE -325). Measurements were performed at five (5) different distances of detector cap for four (4) point sources (Co-60, Eu-152, Cs-137 and Ba-133). Source-to-detector distance at 25 cm was improved to avoid summing coincidence and dead time correction. The results obtained at 25 cm showed that the dead time was found less than 1% as compared to 4 cm. This will describe the stability of dead time. It also indicated that for both detectors the rise in biased voltage will yield a good resolution at 1332.5 KeV. This study is significant as it provides information to ensure that detectors are kept at optimal distance to achieve good dead time.

The study aimed at comparing the resolution and effectiveness of three-electrode arrays (Wenner-α, Wenner-β, and Wenner-γ) in the 2D Electrical resistivity method using Numerical analysis of geological models. Three synthetic geological models that simulate block-one dyke and water layer were generated using RES2DMOD software. The inversion used for the geological models was based on smoothness-constrained least-square inversion which was carried out with RES2DINV. The inversion results were imputed into surfer11 software to examine the image resolution, thereafter absolute percentage error (APE) was calculated to measure the effectiveness of the arrays. The result for the block-one model shows that the Wenner-β array has an APE of 14.45%, the Wenner-α array has an APE of 32.67%, and the Wenner-γ array with an APE of 29.15%. Similarly, for the dyke model, the Wenner-α array, Wenner-β array, and Wenner-γ array have an APE of 69.61%, 57.43%, and 45.49% respectively. However, the results for the water layer model show that the Wenner-α array has an APE of 17.11%, the Wenner-β array has an APE of 12.16%, and that the Wenner-γ array has an APE of 16.21%.  Wenner-α is expected to produce an image with the best resolution having the highest APE, henceforth APE suggests the resolution capacity of an array.