COAXIAL SNOWPLOW DISCHARGE

The development of a coaxial plasma discharge in an initially uniform gas filling has been studied experimentally and theoretically. In the experiment, the usual outer coaxial electrode was replaced by a current return at the rear of the system, permitting unobstructed access to the discharge for the diagnostics. These diagnostics were image converter photography, magnetic probes, and holographic interferometry. The theory consists of two parts: two-dimensional (axisymmetric) time-dependent fluid computations and a supplementary analytic model, both of which assume that the vacuum magnetic field and the plasma are separated by a sharp interface; the experiments and computations are in good agreement on all gross features of the discharge leading up to the formation of a plasma focus and bubblelike structure in the shock front at the outer end of this focus.