Long conduction time plasma opening switch experiments

This paper includes results of two experiments, one in which the characteristics of a flash board plasma source were determined as a function of space and time using spectroscopic techniques, and the other in which a long conduction time plasma opening switch plasma has been studied before, during and after opening, mainly with the use of optical photography and magnetic probes. The 6cm × 10cm carbon coated flashboard generates a few 10¹³ ions/cm³, 3-4eV mostly C⁺ and C⁺⁺ plasma with a directed velocity away from the flash-board of about 10cm/ /μsec and a transverse spread rate of only 1.5cm/ /μs. When the plasma impinges upon a metal plate placed 10cm away, a substantial build-up of cooler plasma occurs within 2-3cm of the surface. In the opening switch experiment, 5ns optical photographs taken from the side showed a narrow (1-2cm) band of light connecting the anode to the cathode (separated by 9mm) during the conduction phase. The band moved from the current source end of the switch to the load end, where the channel width decreased and the light substantially decreased in the middle of the gap. The maximum dI/ dt into a short circuit load occurred when the light decreased midgap, after which plasma was ejected nonuniformly several cm downstream of the switch region.