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

TL;DR

This study measures ion heating in collisional plasma shocks and supersonic plasma flows, revealing how ion temperatures vary with different conditions and comparing results with plasma simulations.

Contribution

It provides the first detailed time-resolved measurements of ion heating in plasma shocks and interpenetrating flows across multiple gas species.

Findings

Ion temperature peaks align with shock theory in low interpenetration cases.

Ion temperatures are elevated above electron temperatures in all conditions.

Results agree with multi-fluid plasma simulations in shock scenarios.

Abstract

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 was repeated using four jet species: N, Ar, Kr, and Xe. In conditions with small interpenetration between jets, the observed peak ion temperature Ti is consistent with the predictions of collisional plasma-shock theory, showing a substantial elevation of Ti above the electron temperature Te and also the subsequent decrease of Ti on the classical ion-electron temperature-equilibration time scale. In conditions of significant interpenetration between jets, such that shocks do not apparently form, the observed peak Ti is still appreciable and greater than Te, but much lower than that predicted by collisional plasma-shock theory. Experimental results are compared with multi-fluid plasma simulations.