Abstract
This thesis describes a study of geometry effects in beta-ray thickness gauging which was performed in order to facilitate the design and improve the performance of such gauges. The work carried out included the formulation of some mathematical models to describe two of the major geometry effects known as passline effects and d[2]-effects. These models were not developed to a very high degree of sophistication because suitable data on the multiple scattering of beta-particles was not available. A review of the literature on electron interactions revealed the complexity of scattering by thick absorbers and the inadequacy of present theories in describing it. An experimental approach to obtaining the desired data was therefore adopted and a beta spectrometry system based on a Si(Li) detector was developed. This system was found to be satisfactory and a set of results for aluminium absorbers was obtained for incorporation into the models described.