Laser-monitor-assisted investigation of the regions of closure of current on the electrodes of an atmospheric-pressure low-current carbon arc

The results are given of observations of regions of closure of current on the electrodes of an atmospheric-pressure low-current carbon arc, performed using a laser monitor immediately during the time of burning of the arc. It is found that the time of existence of a cathode crater on a graphite cathode is $0.2$–$0.3$ s. An analysis of images of the region of closure of current on a pyrographite cathode reveals evidence of melting of pyrographite. A comparison of images of the region of closure of current on the electrodes of a carbon arc with the available literature data on the conditions of closure of current on the anode and cathode enables one to establish the origins of the various details of images of the region of closure of current on the cathode and anode of a low-current carbon arc. The results of this comparison further lead one to conclude that a low-current electric arc is an arc with liquid cathode and anode spots, and that the melting process is a stabilizing factor as regards the current density in those spots.