Date of Award
Doctor of Philosophy
Kate Jones, Steven Pain, Thomas Papenbrock, Anthony Mezzacappa, Jason Hayward
The 30P(p,γ)31S reaction acts as a bottleneck for classical nova nucleosynthesis beyond A=30 in ONe novae, due in part to the long lifetime of 30P (∼2.5 minutes) with respect to the timescale of a nova outburst. Also, the 30P(p,γ)31S reaction rate directly affects the isotopic ratio of 30Si/28Si, which is an important nova identifier in the analysis of pre-solar grains. O/S, S/Al, O/P, and P/Al elemental abundance ratios can be used as nuclear thermometers for classical novae by constraining the 30P(p,γ)31S reaction rate.
However, direct measurement of the 30P(p,γ)31S reaction is not feasible because proton capture reactions at astrophysical energies have very low cross sections as the proton has to tunnel through the Coulomb barrier and due to experimental challenges in producing an intense 30P beam at relevant astrophysical energies. An indirect method was used which measured the 30P(d,pγ)31P transfer reaction with a radioactive 30P beam at 8 MeV/A at Argonne National Laboratory using the GODDESS (GRETINA-ORRUBA: Dual Detectors for Experimental Structure Studies) system, which is a coupling of position-sensitive silicon detectors array ORRUBA, with the γ-ray tracking array GRETINA.
The angular distributions and the single-neutron spectroscopic structure of 31P were studied. The single-proton spectroscopic structure, resonance structure, and reaction rate of the astrophysically important resonances in 31S were constrained via mirror symmetry. Details of the experiment, data analysis process, and results from this work will be presented.
Ghimire, Rajesh, "Constraining the 30P(p,γ)31S reaction using 30P(d,pγ)31P with GODDESS. " PhD diss., University of Tennessee, 2022.
Available for download on Friday, December 15, 2023