The onset of breakdown in a fast pulsed vacuum diode

Abstract

The mechanism by which plasma forms in a fast pulsed vacuum diode is not yet well understood. The most popular model of the phenomenon is the explosive emission model. Current densities required by the explosive emission model are much larger than can be provided by space charge limited currents. This study presents experimental results to support a new model which takes into account the ion current density resulting from ionization processes in front of the cathode surface. It is shown that ion heating of the surface is several orders of magnitude more efficient than Joule heating in exploding a whisker. The treatment of the model for an ideal diode predicts the voltage at which plasma formation begins. It also predicts the time delay between the voltage onset and the onset of plasma formation. The voltage at which the onset of plasma formation occurs and the time delay between the voltage onset and the plasma onset have been experimentally determined in this work. The experimental results compare favorably to the new model. (Author)