Evidence of Ion Stratification in Strong Collisional Multi-Ion Shocks on OMEGA

Plasma shocks are thought to be important in a variety of plasma phenomena, such as cosmic ray acceleration and solar wind interactions. In the lab, they feature themselves in high energy density environments, particularly in the ICF shock phase. These shocks are usually multi-ion shocks with ion mean free paths comparable to the length scale of the plasma. Theory and simulations predict that in this regime of ICF plasmas, multi-ion shocks will exhibit separation of different ion species and other kinetic effects. Such effects would indicate a marked deviation from single fluid description of the ICF shock phase that is usually employed in hydrodynamic simulations to study yield and design experiments. We present here the results of experimental observation of strong collisional multi-ion shocks. Shocks were driven by a pusher in a H2-He plasma on the OMEGA facility and their structure was analyzed by using a probe beam to obtain Thomson Scattered light. Our analysis shows highly resolved features in the shock front, including evidence of ion species separation in terms of both ion temperature and ion concentrations.