Electromagnetic stability of high-power ion diodes

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Abstract
The stability of high‐power magnetically insulated ion diodes is investigated. Interactions between the fields, the electron flow, and the ion beam in the diode gap lead to instabilities. These instabilities are (i) low‐frequency (below electron plasma frequency) instabilities that include a two‐stream type instability at ω≊0 and ion transit time instabilities at finite frequency, and (ii) high‐frequency instabilities (also called ‘‘magnetron instabilities’’) at a frequency above the electron plasma frequency. Under certain experimental conditions, one of the ion transit time instabilities is found to be broadbanded and may become absolutely unstable. Analysis based on realistic parameters shows the elimination of this broadband instability at diode operation close to insulation threshold, and implications of this finding are discussed.