Measurements of photon beam intensity at the High Intensity Gamma-Ray Source (HIGS) facility for astrophysically relevant photodisintegration reaction cross section

Author

Evan G. Meekins, James Madison UniversityFollow

Creative Commons License

This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

Date of Graduation

Spring 2016

Document Type

Thesis

Degree Name

Bachelor of Science (BS)

Department

Department of Physics and Astronomy

Advisor(s)

Adriana Banu

Abstract

How nuclear reactions in stars and stellar explosions such as supernovae have forged the elements out of hydrogen and helium leftover from the Big Bang is a longstanding, still timely research topic in nuclear astrophysics. Although there is a fairly complete understanding of the production of the chemical elements and their isotopes up to iron by nuclear fusion in stars, important details concerning the production of the elements from iron to uranium remain puzzling. Current knowledge is that the nucleosynthesis beyond iron proceeds mainly via neutron capture reactions and subsequent electron decays to stability. However, some 35 proton-rich stable isotopes, between ⁷⁴Se and ¹⁹⁶Hg, cannot be synthesized by neutron-capture processes, since they are located on the neutron-deficient side of the region of stable isotopes. These proton-rich nuclides are generally referred to as p-Nuclei. Among them, ⁹⁴Mo is the most abundant. Our interest is to constrain the origin of p-Nuclei through nuclear physics by studying the cross section of ⁹⁴Mo(γ,n)⁹³Mo, a key photodisintegration reaction for the nucleosynthesis of p-Nuclei occurring in Type Ia supernovae. An experiment measuring this reaction cross section was performed at the High Intensity Gamma-Ray Source (HIγS) Facility in the spring of 2014. A crucial role in measuring the ⁹⁴Mo(γ,n)⁹³Mo cross section is the determination of the photon intensity. In this thesis the two experimental methods that were employed for the photon intensity determination are presented: photoactivation of ¹⁹⁷Au and photodisintegration of deuterium. The photon flux was determined range from ± 5% photons per second.

Recommended Citation

Meekins, Evan G., "Measurements of photon beam intensity at the High Intensity Gamma-Ray Source (HIGS) facility for astrophysically relevant photodisintegration reaction cross section" (2016). Senior Honors Projects, 2010-2019. 214.
https://commons.lib.jmu.edu/honors201019/214