Electrical and spatial correlations between direct current pre-breakdown electron emission characteristics and subsequent breakdown events

An experimental study has established that correlations exist between the pre-breakdown electron emission characteristics and the associated breakdown events that occur in a high-voltage vacuum gap formed by OFHC Cu electrodes. A tin-oxide-coated 'transparent anode' imaging technique was employed to display the spatial distribution of pre-breakdown emission sites and the locations of subsequent direct current breakdown events. By using a real-time video recording technique, it has been possible to demonstrate that a correlation exists between the spatial location of a pre-breakdown emission site and a subsequent direct current breakdown event, and to investigate the time evolution of the two processes. The pre-breakdown electrical characteristics of emission sites, namely their switch-on fields and B values, are also correlated with the threshold field for direct current breakdown. A new breakdown-initiating mechanism is considered, and subsequently used to explain the findings that emerged from this study.