Date of Award

12-2009

Degree Name

Doctor of Philosophy

Department

Physics

First Advisor

Malik, Bary

Second Advisor

Byrd, Mark

Abstract

Space radiation contains nuclei from hydrogen to nickel in various proportions. These nuclei collide with the shielding materials of spacecrafts causing the emission of secondary radiation, consisting of fragmentation of nuclei of the shielding materials by the incident nuclei, inside the cabin, which is a serious hazard to occupants as well as micro-electronic devices. The development of protecting devices requires knowledge of the radiation level inside the cabin caused by the secondary radiation. Because of the varied nature of space radiation nuclei and their broad energy spectra, much of the production cross sections are to be determined theoretically. Aside from this, micro-electronic devices, containing quite often silicon and oxygen, are, in some cases, directly exposed to space radiation. The subject matter of this study would provide an understanding of the fragmentation of silicon by alpha-particle in terms of a modified statistical model. The production cross sections are calculated using an average potential, where a broad resonances are assumed. In case resonances are very narrow, and very closed space, one needs to incorporate the resonance effect in the scattering matrix. Starting from a many body Hamiltonian, containing one- and two-body operators, a microscopic theory has been developed to incorporate resonances in the mean field for the scattering theory. It indicates that the structure of the S-matrix obtained differs from some of the empirical ones applied in an ad hoc way to describe elastic scattering. The derived theory has been applied to α-α scattering in the energy range 35-40 MeV (lab), where the phase shift analysis indicates a sudden jump, thereby imply

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