Downstream power flow study of microsecond conduction time plasma opening switches on ACE 4

A coaxial plasma opening switch (POS) was mounted on the 4 MJ ACE 4 pulsed power generator, and the effects of downstream geometry on POS performance were measured. Typical POS parameters were conduction times of about 1 microsecond, conduction currents up to 2 MA, and POS opening voltages ranging from a low of 200 kV to over 1 MV. Three configurations were studied: a large volume immediately downstream of the POS injection region, a solid; "stove pipe" transition region between the POS injection region and the load; and an extended transparent anode followed by a coaxial feed and load. Each configuration used a large volume inductive short circuit as the load, and operated in the "switch limited" regime. Results in all cases indicated plasma motion downstream of the injection region at densities above 5/spl times/10/sup 14/ electrons/cm. Opening in all cases occurred inside the load inductor. The evolution of downstream plasma depended strongly on the downstream geometry.