Instability and chopping phenomena of a low-current vacuum arc

In order to elucidate instability and chopping phenomena at low current in a vacuum, we observed the phenomena while varying such parameters as the arcing time, the breaking current, the gap distance, and the parallel circuit parameters. We measured the instability initiation current, chopping current, arc voltage, arc voltage oscillation peak, and transient recovery voltage values using copper, copper chromium, and silver tungsten carbide electrodes. It was found that the instability initiation current and the chopping current increased with increasing arcing time and decreased with increasing breaking current amplitude and gap size. In addition, the chopping current, the arc voltage oscillation peak, and the transient recovery voltage were dependent on the parallel circuit parameters, but the instability initiation current and the arc voltage were not dependent on them. We also found that the instability phenomena depended primarily on the cathode material. (C) 2003 Wiley Periodicals, Inc.