MSc Thesis Presentation: Investigation of High-Lying (alpha,gamma) Resonances in 22Ne through One-Neutron Transfer in Inverse Kinematics at TIGRESS

MSc Candidate

Beau Greaves

Abstract

Our knowledge of astrophysical processes is dependent on our understanding of the nuclei involved in these reactions. By studying the structure of such nuclei, the information measured can be directly applied to reaction rate calculations, and by defining these rates, we are able to gain information on the isotopic abundances not only specific to these stellar environments, but the universe as a whole. An example of one of these key nuclei is ²²Ne. Involved in both the production of ¹⁹F and as a neutron source in the s-process in both AGB and massive stars, probing the properties of the resonance states for the ¹⁸O(alpha,gamma)²²Ne reaction allows for a unique opportunity to limit the uncertainty in this reaction rate, as well as the resultant isotopic abundance for the fed and competing reactions.

In November of 2018, a 165 MeV beam of ²¹Ne was delivered to a thin deuterated foil target (CD₂) in order to study the ²¹Ne(d,p)²²Ne reaction in the ISAC II subfacility at TRIUMF, located in Vancouver, British Colombia. This was accomplished using the high-purity, segmented germanium clover array, TIGRESS, alongside the complementary segmented silicon array for measurement of recoil particles, SHARC. From this transfer reaction, twenty four states were populated, including four of the six ¹⁸O(alpha,gamma)²²Ne resonance states. The measurement of these resonance states allowed for the determination of the spin of the 9.841 MeV resonance using the gamma-coincident proton angular distribution, the main source of reaction rate uncertainty present for the ¹⁸O(alpha,gamma)²²Ne reaction below 0.1 GK. Further information gained on these resonance states, as well as the methods used, are discussed in further detail throughout this work.

Examination Committee

• Dr. Xiaorong Qin, Chair
• Dr. Dennis Mücher, Advisor
• Dr. Paul Garrett
• Dr. Joanne O’Meara