Cathode processes in free burning and stabilized by axial magnetic field vacuum arcs

Collective behavior of the cathode spots (CS) has been investigated in free burning and stabilized by axial magnetic field (AMF) vacuum arcs. Experiments carried out proved previously discovered phenomenon of CS group formation to be a general phenomenon for a short high-current vacuum arc. Application of the AMF with low intensity decreases velocity of expansion of the current channel, and provides homogeneous distribution of the CS on the cathode surface. In the short arc application, AMF hinders formation of the spots group and consequently reduces thermal stress applied to the electrodes. Further increase of the AMF leads to decrease of diameter of area occupied by CS. Correlation between arc voltage and CS dynamics is found. A qualitative model of CS dynamics is suggested