Cathode spot initiation under plasma

Abstract

Abstract. By using the procedure of current detection from individual cathodes 5-7 p m distant from each other and by scanning electron microscopy, the initiation of new vacuum arc cathode spots has been studied. Ion current bursts of duration 10-50 ns with an amplitude of 0.1-1 A, and inceptive craters on the initially virgin cathode, have been detected just before the spot transition from one cathode to another. The current density estimated over inceptive craters is > 10" A m+. The power flux density of the jet from plasma onto the cathode exceeds 10l2

Behaviors of Cathode Spot in Alternative Current Helium TIG Welding of Aluminum

“…The division of the cathode spot is correlated to the initiation of several new spots from the old one. The mechanism of the initiation of the new spot was supposed to be the impact of positive metal ions flux from the old one 22) . The positive metal ions from the cathode spot could include Al + , Al 2+ , Al 3+ 23) .…”

Ecton or electron avalanche from metal

“…This effect was observed in Ref. [48]. Plasma affects the concentration of energy m u c h m o r e if there is a dielectric film or a dielectric e m b e d m e n t at the c a t h o d e [49].…”

“…[4], In Ref. [48] an ecton was observed at the cathode, the surface of which was t h o r o u g h l y purified from oxides and impurities, when the plasma source was placed at a very small distance (5 um) from the cathode. T h e plasma concentration was 1 0 2 0 c m -3 and the density of current to the cathode was 10 7 A c m -2 .…”

Study on Dynamic Characteristic in Force Interrupted DC Vacuum Arc

“…Arc mode under rapidly changed current was analyzed in [4]. In [5], the cathode spot mode was studied. In this paper, a series of arc images is presented to show the dc arc dynamic characteristic under forcing interruption.…”