Measurements of the 16C + 12C and 16C + 13C Fusion Cross Sections with Implications for Astrophysics

Author

Ashley Ann HoodFollow

Degree

Doctor of Philosophy (PhD)

Department

Physics and Astronomy

Document Type

Dissertation

Abstract

The fusion of neutron-rich nuclei is of interest to nuclear astrophysics and nuclear structure. X-ray superbursts are powered by runaway thermonuclear burning deep inside of a neutron star, where heating from the pycnonuclear fusion of neutron-rich isotopes is an important heat source. Experimental measurements of fusion cross sections of neutron-rich isotopes have provided insights regarding nucleon transfer and nuclear structure properties affecting fusion. Recently, the ¹⁵C + ¹²C total fusion cross section was measured using a ¹⁵C beam produced by the in-flight beam production facility, which is part of the Argonne Tandem LINAC Accelerator System (ATLAS) at Argonne National Laboratory (ANL). As an extension of that study to more neutron-rich systems, the ¹⁶C + ¹²C and ¹⁶C + ¹³C total fusion cross sections were measured. This dissertation presents the first fusion cross section measurements made with a ¹⁶C radioactive beam. The beam was produced using the newly upgraded RAdioactive Ion SeparatOR (RAISOR) facility at ANL. The total fusion cross sections were measured with ¹²C and ¹³C targets in the active target MUlti-Sampling Ionization Chamber (MUSIC) detector filled with natural methane gas and 99.9% enriched ¹³C methane gas, respectively. This is the most neutron-rich carbon fusion system that has been studied experimentally to date. The ¹⁶C + ¹²C and ¹⁶C + ¹³C cross sections were measured for E_C.M. = 8 - 22 MeV. The measured cross sections show good agreement with theoretical models developed using the barrier-penetration formalism with the Sao Paulo potential and theoretical models using the selective resonant tunneling model and a complex square-well nuclear potential. Despite the significantly larger RMS radius of ¹⁶C, the ¹⁶C + ^{12, 13}C cross sections are measured to be smaller than the ¹⁵C + ¹²C cross section. This indicates that an enhanced s-wave ¹⁵C wave function might be increasing the ¹⁵C fusion cross section or that neutron pairing effects in ¹⁶C may reduce the ¹⁶C cross sections.

Date

11-15-2019

Recommended Citation

Hood, Ashley Ann, "Measurements of the 16C + 12C and 16C + 13C Fusion Cross Sections with Implications for Astrophysics" (2019). LSU Doctoral Dissertations. 5109.
https://repository.lsu.edu/gradschool_dissertations/5109

Committee Chair

Blackmon, Jeffrey

DOI

10.31390/gradschool_dissertations.5109