Charge-exchange neutral-atom filling of ion diodes: Its effect on diode performance and <i>A</i>-<i>K</i> shorting

Abstract

We present a model, supported by experimental evidence, showing how high-density charge-exchange neutral atoms (&amp;lt;10 keV) are created in a partially ionized anode plasma and flow into an ion-diode, anode-cathode (A-K) gap. The buildup of the neutral atoms in the A-K gap and their ionization can cause early A-K shorting which limits high-power and/or long-pulse, ion-diode operation. Ways to avoid the charge-exchange phenomena are mentioned. The ability to produce large-pulsed fluxes of energetic neutrals may have unique applications of its own. For example, high rep-rate spark gaps could benefit from the reduced gas load of an injected short pulse of high-density neutral atoms. Also discussed is the possibility of using an ion-diode geometry to fill a spark-gap cavity with neutrals and then initiate total volume breakdown by ion-impact ionization, thereby avoiding inductive electron filaments.