An inverse pinch plasma source for opening switches

Summary form only given. An inverse pinch plasma device is being developed for plasma opening switch applications. The physical principles behind its operation are essentially the same as the coaxial plasma gun except the inverse pinch utilizes an axial current sheet that expands and ejects plasma radially. It is therefore ideally suited for placement inside the center conductor of a cylindrically symmetric opening switch and has the potential of filling the switch region uniformly with plasma from a single source. Our source has been designed to operate inside a vacuum where a fast puff valve coupled with an annular nozzle injects a suitable amount of gas between two, concentric, disc shaped electrodes supported by a 1 inch diameter insulating quartz sleeve. Upon application of a high voltage pulse (20 kV), a cylindrical current sheet is formed near the insulator that expands radially due to magnetic pressure creating a snowplow front. Plasma is ejected from the device when the front reaches the end of the disc. This device can produce a range of plasma mass densities that extends over two orders of magnitude. Mass density control is exercised by varying the type of gas and the magnitude of the gas puff. We will present time resolved radial and axial plasma density profiles in a POS gap for H, Ne, and Ar plasmas as well as measurements of the average ionization state in the Ne and Ar plasmas.