Time resolved measurements of light produced by onset of plasma formation on electrodes of fast pulsed high voltage diodes

Abstract

Despite years of research on electrical breakdown of fast pulsed high vacuum diodes, the mechanisms of the process are far from being fully discovered. It is well known that electrical breakdown with plasma formation on the electrode surfaces, but there is disagreement on how this occurs. The most widely accepted model, the Explosive Electron Emission model predicts plasma formation on the cathode by means of ohmic heating caused by a field emitted current. Anode plasma formation under this model is explained as due to energy deposition by fast electrons. A new model proposes that adsorbed neutral molecules on the electrode surfaces play a key role in developing the conditions where unipolar arcs cause plasma formation on both electrodes. In this work, simultaneous measurements of the light produced at the electrodes shows that plasma is produced on the anode in less than 2 nanoseconds after it is produced at the cathode. These findings support the new model.