Determination of the particles involved in anode initiated vacuum breakdown using a 1-MV, 50-Nanosecond pulse generator

Several experiments have shown that the anode initiates breakdown of vacuum gaps in cases where the anode and cathode field enhancements are approximately equal [1]. The previous understanding was that only explosive emission at the cathode initiates breakdown between metal electrodes in vacuum with nanosecond pulses. Past experiments have shown clear evidence of particles from the anode initiating breakdown when the cathode was not specially roughened or treated to increase field enhancement. However, the type of particles coming from the anode was not known. Now, we have measurements from a specially designed anode-cathode structure that has allowed us to capture these particles. CR-39 film was used as a particle detector. A Thomson parabola and also a Kimfol filter allowed us to determine the particle species.