Abstract
It is known that the hold-off voltages of vacuum gaps can be improved by the spark conditioning with repetitive electrical breakdowns. At the early stage of spark conditioning process, small pulse currents (not breakdowns) were observed, and in turn hold-off voltages were improved. To investigate the characteristics of the pulse current occurrences and the reason of the improvement in hold-off voltages, experiments on pulse current observations for a vacuum gap were carried out, and chemical compositions on the electrode surfaces were analyzed before and after the experiments by an X-ray photoelectron spectroscopy (XPS). Pulse current observations confirmed that the currernt peak value decreases with repetitive voltage applications and then the phenomena occurring during the conditioning process change over from pulse current event to breakdowns. The XPS analysis revealed that the electrode surface was cleaned by repetitive pulse current occurrences. This result suggests that cleaning the electrode surface by repetitive pulse current occurrences would be one of causes of the improvement in hold-off voltages of a vacuum gap at the early stage of conditioning process.
