A spectroscopic method is used to study atomic and ionic emission from the anode surface in an intermediate-current, multi-cathode-spot vacuum arc. Vacuum arcs with approximately 20 different anode-cathode material combinations, including surface-coated anodes of molybdenum, copper, aluminum and zinc, were studied. It was found that the spectral line intensity of anodic atoms or ions is attenuated during a series of arcs, if melting of the anode surface has not occurred. Line intensity of anodic atoms or ions decreases strongly with the axial distance from the anode, even when melting of anode surface has occurred. Peak intensity for anodic ion lines occurs before that of the anodic atom. It is shown that layers of cathodic material deposited on the anode surface become significant sources of anodic emitter material. The line intensity of both anodic atoms and ions depends also on arc current waveform and amplitude. At sufficient large peak currents, anode surface melting is obtained, followed by an order of magnitude increase in line intensity.
|Number of pages||4|
|State||Published - 1984|