A Penning-assisted subkilovolt coaxial plasma source

Abstract

A Penning-assisted 20MW coaxial plasma source (plasma gun), which can achieve breakdown at sub-kV voltages, is described. The minimum breakdown voltage is about 400V, significantly lower than previously reported values of 1–5kV. The Penning region for electrons is created using a permanent magnet assembly, which is mounted to the inside of the cathode of the coaxial plasma source. A theoretical model for the breakdown is given. A 900V 0.5F capacitor bank supplies energy for gas breakdown and plasma sustainment from 4to6ms duration. Typical peak gun current is about 100kA and gun voltage between anode and cathode after breakdown is about 200V. A circuit model is used to understand the current-voltage characteristics of the coaxial gun plasma. Energy deposited into the plasma accounts for about 60% of the total capacitor bank energy. This plasma source is uniquely suitable for studying multi-MW multi-ms plasmas with sub-MJ capacitor bank energy.