Publications

Experimental Validation of Dense Plasma Transport Models using the Z-Machine

Knapp, Patrick K.; Beckwith, Kristian B.; Cochrane, Kyle C.; Clay III, Raymond C.; Mattsson, Thomas M.

Mixing of cold, higher-Z elements into the fuel region of an inertial confinement fusion target spoils the fusion burn efficiency. This mixing process is driven by both "turbulent" and "atomic" mixing processes, the latter being modeled through transport corrections to the basic hydrodynamic models. Recently, there has been a surge in the development of dense plasma transport modeling and the associated transport coefficients; however, experimental validation remains in its infancy. To address this gap in our knowledge of interfacial mixing, Sandia National Laboratories is developing a new experimental platform at the Z-facility to investigate plasma transport in dense plasmas that span the entire warm dense matter regime. Specifically, this platform is being developed to measure species transport across a V/CH interface, using an x-ray driven hohlraum to drive the sample to [?] 190eV over 5ns. The heated sample is diagnosed using radiography optimized to measure the distribution of Vanadium perpendicular the interface. In order to interpret measurements made using this experimental platform, modeling tools that incorporate transport effects in strongly coupled plasmas are required. To this end, we utilize new advances in multi-species kinetic theory, collision models applicable to strongly coupled plasmas and modeling of degenerate electron plasmas to develop such a capability. The resulting kinetic transport code has been applied, along with state-of-the-art radiation hydrodynamic codes, to model the experiments. Results from this modeling effort highlight the importance of strong electric fields, which are present in the kinetic transport code, but absent in the radiation hydrodynamics code, in driving interfacial mixing. Synthetic radiography generated from all of these models reveals the ability of experimental diagnostics to distinguish interfacial mixing driven by a range of transport effects. We demonstrate that the spatial and temporal resolution of radiography diagnostics currently available at the Z-facility can distinguish between these different transport effects when multiple (3 [?] 4) radiographs, separated in time ( [?] 2 ns ) with accurate timing are captured per experiment.