State of the theory of cathode spot phenomena in vacuum arcs

The most important near cathode phenomena and processes in the plasma expansion region is discussed. The experimental results with different spot types are summarized. The theoretical models and existing equation systems are discussed. The results of influence of the cathode material, geometry and its surface state, peculiarity of nonfree near cathode plasma flow and plasma acceleration mechanisms in vacuum arc jet are considered. The spot motion and the temporal dynamics of different cathode spot types and conditions of its appearance are presented.