Darren Bleuel | 18-ERD-061
Electron-mediated nuclear-plasma interactions (NPIs) have the potential to change nuclear reaction rates in high-energy-density plasma (HEDP) environments, such as National Ignition Facility (NIF) experiments, astrophysical phenomenon, or nuclear detonations, relative to conventional laboratory measurements on room-temperature targets. Two Discovery Science (DS) shots to detect these interactions at NIF were conducted in January and September 2017 at the conclusion of a campaign to develop the indirect-drive exploding pusher experimental platform and diagnostics. The shots were designed to measure the differential population of a high-spin isomer of 133 Xe of an in-plasma versus a control sample, where a non-zero differential would indicate a measurable influence of the plasma on 134 Xe(n,2n) reactions.
Our project sought to complete analysis of the DS data. Preliminary observations from the shots were consistent with a small NPI effect, but improved theoretical understanding coupled with refined data analysis were needed to definitively establish the discovery or lack thereof. Achieving both of these, a statistically-credible NPI was indeed observed at a level predicted by an adapted Monte Carlo gamma-cascade model, a significant lowering of the isomer-to-ground state activity ratio in 133 Xe.
Impact on Mission
Our research leveraged Lawrence Livermore National Laboratory's core competencies in high-energy-density, nuclear, and laser sciences and supports the Laboratory's weapons mission by advancing understanding of nuclear reaction rates in HEDP environments.