Nuclear data activities for medium mass and heavy nuclei at Los Alamos

TL;DR

This paper discusses Los Alamos's nuclear data efforts for medium to heavy nuclei, emphasizing the NEXUS framework, Bayesian model optimization, and applications in astrophysics and nuclear data evaluation.

Contribution

It introduces the NEXUS framework's module for Bayesian model parameter optimization and demonstrates its application to nuclear data evaluation and astrophysical simulations.

Findings

Successful optimization of 239-Pu cross section

Effective data assimilation with Bayesian techniques

Enhanced astrophysical modeling accuracy

Abstract

Nuclear data is critical for many modern applications from stockpile stewardship to cutting edge scientific research. Central to these pursuits is a robust pipeline for nuclear modeling as well as data assimilation and dissemination. We summarize a small portion of the ongoing nuclear data efforts at Los Alamos for medium mass to heavy nuclei. We begin with an overview of the NEXUS framework and show how one of its modules can be used for model parameter optimization using Bayesian techniques. The mathematical framework affords the combination of different measured data in determining model parameters and their associated correlations. It also has the advantage of being able to quantify outliers in data. We exemplify the power of this procedure by highlighting the recently evaluated 239-Pu cross section. We further showcase the success of our tools and pipeline by covering the insight gained from incorporating the latest nuclear modeling and data in astrophysical simulations as part of the Fission In R-process Elements (FIRE) collaboration.