Experimental Measurements of Ion Heating in Collisional Plasma Shocks and Interpenetrating Supersonic Plasma Flows

We present time-resolved measurements of ion heating due to collisional plasma shocks and interpenetrating supersonic plasma flows, which are formed by the oblique merging of two coaxial-gun-formed plasma jets. Our study is repeated using four jet species: N, Ar, Kr, and Xe. In conditions with small interpenetration between jets, the observed peak ion temperature T_{i} is consistent with the predictions of collisional plasma-shock theory showing a substantial elevation of T_{i} above the electron temperature T_{e} and also the subsequent decrease of T_{i} on the classical ion-electron temperature-equilibration timescale. In conditions of significant interpenetration between jets, such that shocks do not apparently form, the observed peak T_{i} is still appreciable and greater than T_{e} but much lower than that predicted by collisional plasma-shock theory. Experimental results are compared with multifluid plasma simulations.