Anode modes in vacuum arcs

This paper reviews the five different anode discharge modes which can occur in a vacuum arc. These modes are diffuse arc (low current, with or without anode sputtering), footpoint (intermediate current), and anode spot or intense arc (high current). Descriptions of the various modes are presented, based primarily on experimental results. The hot anode vacuum arc mode, which occurs only with thermally isolated anodes, is also described. The effects of external magnetic fields on anode modes are briefly stated. Cathode modes and arc column modes are also discussed, primarily as they correspond to anode modes.