A Determination of the 27Si(P,y) Reaction Rate Using its Mirror and its Importance in X-Ray Burst Nucleosynthesis

Abstract

X-ray bursts are the most frequent thermonuclear explosions occurring in the universe and represent one of the sources of heavier element nucleosynthesis. In order to determine how much X-ray bursts influence the abundances of these heavier nuclei there is a need for critical nuclear information such as: nuclear masses, ß-decay rates and reaction rates.

Due to this need, the field of experimental nuclear physics has been focusing on developing unstable beams and new or improved indirect methods of studying nuclei and reactions, as well as detection systems of higher capability.

In light of this perspective, the focus of this dissertation was twofold. One part involved performing a low-cost, low-modification upgrade to the Oxford focal plane detector using Micromegas technology. The upgrade was very successful in improving the total energy loss resolution by as high as a factor of 3 and thus improving the particle identification ability of the detector. This leads to an increase in the mass range of nuclei possible to study from A=16 to A=32.

The other part of this dissertation project was aimed at studying the proton-capture reaction ^27Si(p, γ)^28P using an experimental indirect method called the Asymptotic Normalization Coefficient method. This reaction is part of the thermonuclear runaway network of an X-ray burst suggested by the theoretical models. The spectroscopic factor of ^28P was evaluated for the first time in literature at Sv2s½= 1:11±0:56. The direct capture reaction rate was found to be in agreement with the theoretical predictions, and it was confirmed experimentally that at astrophysical energies, the non-resonant component is overwhelmed by the contributions of the resonances.