Experimental characterization of railgun-driven supersonic plasma jets motivated by high energy density physics applications

TL;DR

This paper presents experimental data on high-Mach-number argon plasma jets generated by a railgun, providing insights into their parameters, structure, and evolution relevant for high energy density physics applications.

Contribution

It offers the first detailed experimental characterization of railgun-driven supersonic plasma jets, including their parameters and evolution, relevant for forming plasma liners.

Findings

Jet parameters approach those needed for the Plasma Liner Experiment

Density drops by an order of magnitude over 40 cm, less than ideal hydrodynamic predictions

High ionization fraction and supersonic velocities achieved

Abstract

We report experimental results on the parameters, structure, and evolution of high-Mach-number (M) argon plasma jets formed and launched by a pulsed-power-driven railgun. The nominal initial average jet parameters in the data set analyzed are density \approx 2 x 10^(16) cm^(-3), electron temperature \approx 1.4 eV, velocity \approx 30 km/s, M \approx 14, ionization fraction \approx 0.96, diameter \approx 5 cm, and length \approx 20 cm. These values approach the range needed by the Plasma Liner Experiment (PLX), which is designed to use merging plasma jets to form imploding spherical plasma liners that can reach peak pressures of 0.1-1 Mbar at stagnation. As these jets propagate a distance of approximately 40 cm, the average density drops by one order of magnitude, which is at the very low end of the 8-160 times drop predicted by ideal hydrodynamic theory of a constant-M jet.