Measurements of Shock-Front Separation in Multi-Ion-Species Plasma Shocks

Collisional plasma shocks generated from supersonic flows are an important feature in astrophysical systems and high-energy-density (HED) experiments. Compared to single-ion species plasma shocks, plasma shock fronts with multiple ion species contain more features, one of which is interspecies ion separation. This phenomenon has been previously investigated both in theory and simulation, however, few experimental studies of the structure inside a shock front have been performed. This work presents direct measurements of shock-front separation in multi-ion-species collisional plasma shocks, produced by head-on merging of two plasma jets composed of inert gas mixtures of varied concentration. Jet collisions are performed both in a free vacuum and a confining shock tube, resulting in different expansion dynamics out of the plane of the shock. A 1D ion-kinetic simulation is also performed, and the simulation results are compared with experimental results.