Measurements of Strong Shock-Front Structure in Multi-Ion Species Plasmas on OMEGA

Plasma shocks are ubiquitous in the context of astrophysical plasmas, such as supernova blast-waves and planetary ionospheres, as well as in laboratory plasmas such as laser-driven plasma experiments and inertial confinement fusion. In most cases, the shock front is considered to be negligibly thin compared to other scale lengths, simplifying modeling using hydrodynamic techniques. Shock fronts, however, feature a finite structure that is established by the kinetic motion of ions and electrons within several ion mean free paths of the discontinuity. We present the results of experiments to measure the structure of strong collisional shock fronts in two-species plasmas. The OMEGA laser was used to drive a strong shock into a gas with a mixture of ion species (H₂ and He), and Thomson-scattering images were collected from a probe beam incident along the axis of the shock. We present analyses of this dataset measuring the multispecies structure of the collisional shock front. Spatial variations in density, temperature, and flow velocity are obtained for the electrons and multiple ion species, demonstrating the dynamics of a shock propagating through multiple ion species. This material is based upon work supported by the Department of Energy [National Nuclear Security Administration] University of Rochester “National Inertial Confinement Fusion Program” under Award Number DE-NA0004144 and Department of Energy under Award Number DE-SC0020431.