This CAREER award supports exploration of some of the most extreme states of matter we know to exist in the universe and can probe in a laboratory setting. All visible matter is made up of two components, heavy nuclei surrounded by much lighter electrons. The slow-moving nuclei are often assumed to respond weakly to the electrons hurtling around them. This premise is the cornerstone of modern simulation techniques in both physics and chemistry. However, extreme environments, such as in the center of planets and stars, create incredibly hot dense matter. This results in fast-moving electrons that begin to strongly interact with the slow-moving nuclei, challenging previous assumptions. This award supports experimental work at some of the world's largest lasers, including the National Ignition Facility - the world's most energetic laser. The harsh astrophysical conditions will be recreated on Earth to measure the nuclei dynamics in regimes where data is scarce. Measurements of fundamental quantities, including particle diffusion and sound speed, will be used to validate state-of-the-art quantum mechanical simulations. The project will help train the next generation of scientists by offering education and research opportunities to the global plasma community. The education and outreach will focus on providing underrepresented students access to and training in high-performance computing techniques.
Simulations of dense plasmas typically employ the adiabatic approximation, usually justified through the disparate energy scales of the electron and ion motion. The electrons are assumed to instantaneously adjust to the ion fields, while the ions are confined to a single adiabatic surface. Recent approaches that go beyond this approximation have led to significant differences in the predictions of plasma properties, with a dearth of experimental measurements preventing discrimination between competing models. This research program will employ a new experimental platform, developed for the Omega and NIF laser facilities, to perform the first measurement of diffusion in the warm dense matter regime. This platform will employ Fresnel Diffractive Radiography, a novel diagnostic technique for laser-driven X-rays that measures the slow, diffusion-driven changes in density gradients with exceptional spatial resolution. The experimental work is supported by predictions of the diffusion coefficient using new advanced simulations that incorporate the electron dynamics within a complex, quantum-mechanical framework. These simulations will be conducted by undergraduate students and performed with support from the University of Nevada, Reno High-Performance Computing team. The primary research goal is to clearly discriminate between plasma models with fundamentally different approaches to non-adiabaticity. This project is jointly funded by the Division of Physics and the Established Program to Stimulate Competitive Research (EPSCoR).
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
