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

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 ≈2×1016 cm−3, electron temperature ≈1.4 eV, velocity ≈30 km/s, M≈14, ionization fraction ≈0.96, diameter ≈5 cm, and length ≈20 cm. These values approach the range needed by the Plasma Liner Experiment, 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.