Photon Strength Functions for nuclear astrophysics
Thibault Laplace, Research Scientist
Nuclear Engineering
Open. Apprentices needed for the Fall semester. Enter your application online beginning August 22nd. The deadline to apply is Tuesday, September 2nd, 4pm.
Photon strength functions (PSFs) quantify the probability of γ‐ray emission and absorption in atomic nuclei as a function of energy, and they play a critical role in determining radiative neutron‐capture rates that drive the production of elements in stars. In particular, low‐lying resonances in PSFs can significantly enhance capture cross sections, thereby altering the predicted abundances of heavy isotopes produced in various nucleosynthesis processes. Despite their importance, the detailed structure and strength of these resonances remain poorly constrained for many nuclei. This project will explore the strength of low‐lying PSF resonances by comparing theoretical model predictions with existing experimental data, with the ultimate goal of providing refined inputs for nucleosynthesis calculations.
Role: The work will involve sourcing data from nuclear data repositories. In parallel, data from two theoretical approaches will provide model estimates. Once validated, the models will be used to generate predicted γ‐strength curves in the energy regions where the resonances of interest are located. In the data‐model comparison phase, least‐squares fitting routines will be employed to adjust model parameters so that the theoretical curves match the experimental data in the resonance region. From these fits, resonance energies, widths, and strengths will be extracted. These refined resonance strengths will then be incorporated into calculations to compute updated neutron‐capture rates at a later stage.
By the end of the semester, this project is expected to deliver a set of low‐lying PSF resonance strengths for key nuclei, complete with quantified uncertainties. Such results will enhance the reliability of theoretical abundance predictions in astrophysical models.
Qualifications: Qualifications: Required: Lower Division Physics (7 Series) and math through Math 54; Programming fundamentals Desired skills (or what you'll learn): Upper division standing; Proficiency in C++ or python programming; Familiarity with a Linux/Unix environment; Completion of NE101 Nuclear Reactions and Radiation (or equivalent); Proficiency in nuclear data analysis
Hours: 9-11 hrs
Off-Campus Research Site: Remote or in-person options at Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720
Related website: https://www-nds.iaea.org/PSFdatabase/
Related website: https://nucleardata.berkeley.edu/research/PSF_NLD.html