Cathode spots dynamics on pure metals and composite materials in high-current vacuum arcs

An investigation has been carried out of cathode spot dynamics in a triggered vacuum arc. A rectangular pulse, amplitude (1-5) kA, and duration of up to 5 ms has been used. Sufficient statistics were collected. The expansion of a cathode spot ring on a clean pure metal surface was corroborated to be a retrograde movement in the self magnetic field which obeys the same law as the movement of a single cathode spot in an external transversal magnetic field. The influence of a contact gap (0.5-8) mm and current on the dynamics of cathode spots was investigated. The distinctions between cathode processes on pure metals and composite materials were studied. A phenomenon was discovered, where a group of cathode spots form in the short arcs on the CuCr cathodes. The follow-up investigation revealed that an interrelation exists between cathode and anode processes in short arcs. The qualitative explanation of the phenomena observed is presented