Investigation of centimeter-scale shock structures observed during plasma jet collisions

Bow shock structures are observed in collisions of high velocity (∼10 km/s), low density (∼10²² m^-3) plasma jets. Plasma jets are accelerated by a small gas-fed linear railgun featuring a 0.50 x 0.32 cm rectangular bore and 10.2 cm long rails powered by an LC pulse-forming network delivering ∼100 kA pulses of 15 microsecond duration. Chord-integrated electron number densities of ∼10²⁰ m^-2 were estimated in several-centimeter diameter jets 10 cm downstream of the gun muzzle by a Mach-Zehnder heterodyne interferometer, jet velocities of ∼10 km/s were estimated with a photodiode array, a 750 mm imaging spectrograph and scanning monochromator was used to estimate plasma temperature, Rogowski coils were used to estimate current pulse width and amplitude delivered to the accelerator, and short-exposure images of shock phenomena were captured with an image-intensified CCD camera. A campaign is underway to study the spatial distribution of multiple ion species within the shock front and to infer the role of diffusive phenomena in the observed shock structures.