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Improving Predictive Capability in REHEDS Simulations with Fast, Accurate, and Consistent Non-Equilibrium Material Properties

Hansen, Stephanie B.; Baczewski, Andrew D.; Gomez, Thomas; Hentschel, T.W.; Jennings, Christopher A.; Kononov, Alina K.; Nagayama, Taisuke; Adler, Kelsey; Cangi, A.; Cochrane, Kyle; Foulk, James W.; Schleife, A.

Predictive design of REHEDS experiments with radiation-hydrodynamic simulations requires knowledge of material properties (e.g. equations of state (EOS), transport coefficients, and radiation physics). Interpreting experimental results requires accurate models of diagnostic observables (e.g. detailed emission, absorption, and scattering spectra). In conditions of Local Thermodynamic Equilibrium (LTE), these material properties and observables can be pre-computed with relatively high accuracy and subsequently tabulated on simple temperature-density grids for fast look-up by simulations. When radiation and electron temperatures fall out of equilibrium, however, non-LTE effects can profoundly change material properties and diagnostic signatures. Accurately and efficiently incorporating these non-LTE effects has been a longstanding challenge for simulations. At present, most simulations include non-LTE effects by invoking highly simplified inline models. These inline non-LTE models are both much slower than table look-up and significantly less accurate than the detailed models used to populate LTE tables and diagnose experimental data through post-processing or inversion. Because inline non-LTE models are slow, designers avoid them whenever possible, which leads to known inaccuracies from using tabular LTE. Because inline models are simple, they are inconsistent with tabular data from detailed models, leading to ill-known inaccuracies, and they cannot generate detailed synthetic diagnostics suitable for direct comparisons with experimental data. This project addresses the challenge of generating and utilizing efficient, accurate, and consistent non-equilibrium material data along three complementary but relatively independent research lines. First, we have developed a relatively fast and accurate non-LTE average-atom model based on density functional theory (DFT) that provides a complete set of EOS, transport, and radiative data, and have rigorously tested it against more sophisticated first-principles multi-atom DFT models, including time-dependent DFT. Next, we have developed a tabular scheme and interpolation methods that compactly capture non-LTE effects for use in simulations and have implemented these tables in the GORGON magneto-hydrodynamic (MHD) code. Finally, we have developed post-processing tools that use detailed tabulated non-LTE data to directly predict experimental observables from simulation output.

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TYPE SAND Report YEAR 2022
DOIOSTI

ALEGRA: finite element modeling for shock hydrodynamics and multiphysics

Niederhaus, John H.J.; Powell, Michael J.; Bova, Steven W.; Carleton, James B.; Carpenter, John H.; Cochrane, Kyle; Crockatt, Michael M.; Dong, Wen; Fuller, Timothy J.; Granzow, Brian N.; Ibanez-Granados, Daniel A.; Kennon, Stephen R.; Luchini, Christopher B.; Moral, Ramon J.; Brien, Michael J.'.; Robinson, Allen C.; Rodriguez, Angel E.; Sanchez, Jason J.; Scott, Walter A.; Siefert, Christopher; Stagg, Alan K.; Tezaur, Irina K.; Voth, Thomas E.

Abstract not provided.

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TYPE Conference Poster YEAR 2022
DOIOSTI

Determining the electrical conductivity of metals using the 2 MA Thor pulsed power driver

Review of Scientific Instruments

Porwitzky, Andrew J.; Cochrane, Kyle; Stoltzfus, Brian

We present the development of a pulsed power experimental technique to infer the electrical conductivity of metals from ambient to high energy density conditions. The method is implemented on Thor, a moderate scale (1-2 MA) pulsed power driver. The electrical conductivity of copper at elevated temperature (>4000 K) and pressure (>10 GPa) is determined, and a new tabular material model is developed, guided by density functional theory, which preserves agreement with existing experimental data. Minor modifications (<10%) are found to be necessary to the previous Lee-More-Desjarlais model isotherms in the vicinity of the melt transition in order to account for observed discrepancies with the new experimental data. An analytical model for magnetic direct drive flyer acceleration and Joule heating induced vaporization based on the Tsiolkovsky "rocket equation"is presented to assess sensitivity of the method to minor changes in electrical conductivity.

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TYPE Journal Article YEAR 2021
DOIOSTIScopus
Results 26–50 of 142
Results 26–50 of 142