Impact of Direct Current Conditioning on Cathode Dark Current in High Vacuum

In an unloaded high voltage vacuum system, a stable current is typically observed, which increases with the supply voltage. This current is commonly referred to as “dark current” and it is both a loss mechanism and an initiator of surface flashover, which is one of the most challenging issues in insulator design for vacuum environments. Therefore, suppressing dark currents is critical in preventing the first step of surface flashover - electron emission from triple junction points. The primary objective of this study is to examine the effectiveness of direct current conditioning in reducing dark current levels. To achieve this goal, a standardized test sample was subjected to a gradually increasing DC voltage within a vacuum environment of le-8 Torr. In addition to voltage and cathode current measurements, the changes in pressure and video were monitored and analyzed throughout the experiment. The physical and chemical conditions of the samples were examined before and after the test using laser profilometry, and Auger electron spectroscopy.