Charged particle transport coefficient challenges in high energy density plasmas

We compare a variety of models used for the calculation of transport coefficients in dense plasmas, including average-atom models, models based on kinetic theory, structure matching effective potentials, and pair-potential molecular dynamics. In particular, we focus on the parameter space investigated in the second charged-particle transport coefficient code comparison workshop [Stanek et al., Phys. Plasmas 31, 052104 (2024)]. Each model is based on the self-consistent output of our average-atom calculations. Ionic transport properties are generated from implicit electron pair matched molecular dynamics simulations, bypassing the need for either dynamical electron simulations or on-the-fly electronic structure calculations. These matched pair potentials are generated in a nonlinear way using a classical mapping procedure, further avoiding an expensive force-matching procedure. We compare these results with the density functional theory data presented at the workshop, as well as a set of widely used parametric models, which we have modified to enhance accuracy, especially at the low- and high-temperature extremes of the parameter space. We also detail the non-trivial statistical aspect of converging ionic transport coefficients.

Comparison of transport models in dense plasmas

Johnson,

Silvestri,

Petrov

et al. 2024

ETHOS: An automated framework to generate multi-fidelity constitutive data tables and propagate uncertainties to hydrodynamic simulations

Stanek,

Lewis,

Cochrane

et al. 2024

Accurate constitutive data, such as equations of state and plasma transport coefficients, are necessary for reliable hydrodynamic simulations of plasma systems such as fusion targets, planets, and stars. Here, we develop a framework for automatically generating transport-coefficient tables using a parameterized model that incorporates data from both high-fidelity sources (e.g., density functional theory calculations and reference experiments) and lower-fidelity sources (e.g., average-atom and analytic models). The framework incorporates uncertainties from these multi-fidelity sources, generating ensembles of optimally diverse tables that are suitable for uncertainty quantification of hydrodynamic simulations. We illustrate the utility of the framework with magnetohydrodynamic simulations of magnetically launched flyer plates, which are used to measure material properties in pulsed-power experiments. We explore how changes in the uncertainties assigned to the multi-fidelity data sources propagate to changes in simulation outputs and find that our simulations are most sensitive to uncertainties near the melting transition. The presented framework enables computationally efficient uncertainty quantification that readily incorporates new high-fidelity measurements or calculations and identifies plasma regimes where additional data will have high impact.

Charged-particle transport in high energy density plasmas

Hansen,

Stanek,

Haines

et al. 2024

This Special Topic Collection grew out of two gatherings of researchers active in the high energy density (HED) physics community: a mini-conference on charged-particle transport in HED plasma held during the 64th annual meeting of the American Physical Society's Division of Plasma Physics (Spokane, WA, November 2022) and a dedicated charged-particle transport coefficient code comparison workshop (Livermore, CA, July 2023). These gatherings provided opportunities for theoretical, computational, and experimental researchers to discuss the state of the field, including current capabilities and methods, needs of hydrodynamic simulations, and frontiers for future research. This special issue collects a total of 13 research and review articles on charged-particle transport in HED plasmas.