CAREER: Impact of Plasma Species, Mixing and Ionization Fraction on Drift-Wave Turbulence and Transport

College Of William And Mary, Williamsburg VA

Investigators

Abstract

This award is funded in part under the American Rescue Plan Act of 2021 (Public Law 117-2). This CAREER award supports a study of plasma turbulence using a combination of experimental and computational approaches. 99% of all visible matter in the universe is a plasma, a state of matter commonly created when a gas is heated to high enough temperatures to strip electrons away from the atoms, creating a cloud of electrically charged particles. Experiments and observations have shown that plasmas can be turbulent, demonstrating similar dynamics to that observed in fluids. When studying the turbulence in plasmas, it is often assumed that plasmas only consist of electrons and one ion species, and these clouds are 100% ionized. However, in reality, plasmas are not fully ionized and the presence of neutral particles can influence the dynamics of turbulence. Moreover, plasmas often contain multiple ion species, which means that the individual ions can have a different mass and charge. Even small concentrations of multiple ion species can have non-linear effects on turbulence and these aspects are often neglected in current models and experiments. Better understanding of the role of mixed-ion species plasmas as well as the influence of neutral particles can provide insights into space weather and the design of nuclear fusion power plants. In addition to the scientific scope, this award supports creation of a sustainable K5 program built to introduce topics related to plasmas and turbulence. This project will use the LArge Plasma Device (LAPD), a linear magnetized plasma device within the Basic Plasma Science Facility at the University of California - Los Angeles, to study drift-wave plasma turbulence. LAPD has the possibility to change the neutral pressure as well as the plasma density and temperature, thus effectively allowing alteration of the ionization ratio and the neutral to plasma fraction. Through dedicated scans of electron temperature, density and neutral density, the experiments will measure the changes in turbulence and plasma flows. These scans will be repeated for different plasma species and eventually mixed plasma species. To better interpret experiments, a fluid plasma code HERMES will be used to self-consistently calculate turbulence and plasma profiles in the presence of neutral species. The combination of modeling and experiments will allow a better understanding of whether the models can capture the dynamics of various (mixed) plasma species and neutrals, or whether the models need to be further developed. 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.