The Plasma Dynamics Computational Laboratory performs cutting-edge plasma physics research in a variety of areas ranging from laboratory-to-astrophysical applications, fluid-to-kinetic regimes, and basic-to-applied research.  Select representative applications from our group are included here to provide some insight into the work that we do.  Contact us for further details on these topics.

In a plasma, ions are much heavier than electrons. This results in higher electron mobility and higher thermal flux even if the species have the same temperature. Therefore, when a plasma comes into contact with a solid surface acting as a sink, electrons quickly leave the domain and quasineutrality no longer holds. This non-quasineutral region near the wall is called a sheath. Inside a sheath, the electric field arises self-consistently and equalizes the fluxes by accelerating ions and retarding electrons. Even though the sheath is a very small region near the wall, it can have global effects on a plasma.  A study of sheaths is important for any bounded plasma.

  • Plasma-wall interactions occurring in the sheath can play a significant role in affecting material lifetimes as well as plasma dynamics.  For example, Hall thruster lifetimes are limited by plasma-wall interactions and electrode erosion. 
  • Secondary electron emission (SEE) from a solid surface can drastically influence plasma behavior.  Some recent works suggest that SEE can even reverse the gradient of the electrostatic potential in the plasma sheath. Therefore, a self-consistent SEE model based on real material parameters needs to be included in numerical models.  
  • While this study is fundamental and is generally applicable to plasma-material interactions, our focus is on plasma thrusters with electrodes (such as Hall thrusters) and magnetic confinement fusion (tokamaks). 

For additional information on this topic, check out our recent poster on

Studies of plasma sheaths with secondary electron emission using continuum kinetic model

Funding acknowledgements: Air Force Office of Scientific Research & US Department of Energy Office of Science

Weibel-type instabilities, which grow in plasmas with an anisotropic velocity distribution, have been studied for many years and have drawn recent interest due to their broad applicability spanning from laboratory laser plasmas to origins of intergalactic magnetic fields in astrophysical plasmas. Magnetic particle trapping has been considered the main mechanism of the nonlinear saturation of these instabilities.

A novel continuum kinetic algorithm is used to study the Weibel instability and is benchmarked to previous work that studies magnetic trapping. However, in our work, we also show the significant role of electrostatic trapping in cold counter-streaming beams. This electrostatic trapping works together with magnetic trapping and alters the nonlinear saturation of the instability. The role of the electrostatic field is negligible when the populations are at higher temperatures.

For additional information on this topic, check out our recent poster on

Nonlinear saturation of Weibel-type instabilities

Funding acknowledgements: Air Force Office of Scientific Research

Inertial Confinement Fusion (ICF) relies on imploding targets that contain deuterium-tritium fuel to conditions that can produce fusion.  This includes laser-driven implosion experiments such as those at the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory and pulsed-power driven experiments such as the Magnetized Liner Inertial Fusion (MagLIF) experiments at Sandia National Laboratory.  Hydrodynamic and magnetohydrodynamic instabilities such as the Rayleigh-Taylor and magneto-Rayleigh-Taylor instabilities that occur in these fusion concepts are detrimental to achieving fusion igniton. This study aims to mitigate hydrodynamic mix and instabilities that occur in high-energy-density imploding fusion concepts. We study multiple ICF concepts in this group and will discuss one of them here. 

MagLIF involves imploding an initially solid cylindrical metal liner (Aluminum or Beryllium) on to a pre-magnetized Deuterium-Tritium (D-T) fuel target. The most detrimental instability toward achieving net gain is the magneto Rayleigh-Taylor instability (MRT) that occurs at the accelerating liner-vacuum interface during implosion. As the current from the pulse ionizes the solid liner the resulting process produces an exterior coronal region where the configuration is MRT unstable.  Recent work at Sandia National Laboratory suggests that the electro thermal instability (ETI), which occurs early-in-time as the solid melts, seeds the MRT instability that occurs later in time. This project seeks to find more insight in the transition of the ETI to the MRT.

For additional information on this topic, check out our recent poster on

Enhancing understanding of magnetized high-energy-density plasmas from solic liner implosions using fluid modeling

Funding acknowledgements: US Department of Energy Office of Science

This work aims to study ionospheric instabilities that may develop significant growth under the conditions of the August 21, 2017 solar eclipse. Evaluating the time-scales of several plasma instabilities, it is hypothesized that the gradient-drift (GDI) instability is likely to develop significant growth during the timespan of a solar eclipse given the relevant gradients that may arise.  The plasma instabilities that exist can transition to turbulence and could lead to GPS scintillation.  While one aspect of this study aims to better understand plasma dynamics during a solar eclipse, there is broad applicability of this work to ionospheric plasma physics and communication. Numerical growth rates are derived for the set of plasma equations being solved to better understand ionospheric instabilities and theory is compared to two-fluid plasma simulations, the two fluids being ions and electrons, as well as to previously published theoretical growth rates. 

For additional information on this topic, check out our recent poster on

Modeling the gradient-drift instability with temperature gradient effects as applied to the August 21, 2017 solar eclipse using two-fluid plasma equations

Funding acknowledgements: NSF CEDAR

The discontinuous Galerkin (DG) method is employed in this work to study plasma instabilities using high-order accurate numerical solvers for problems in a variety of plasma regimes. The DG method has the advantage of resolving shocks and sharp gradients that occur in neutral fluids and plasmas. An unstructured DG code that uses triangles to set up a grid for an arbitrarily shaped domain has been developed to study plasma instabilities in general geometries.  The two-fluid plasma model is used, the two fluids being ions and electrons. Carefully constructed unstructured meshes are known to produce small and randomized grid errors for general geometries compared to traditional structured meshes.  

For additional information on this topic, check out our recent poster on

Studies of plasma instabilities using unstructured discontinuous Galerkin method