On the mechanism of a retrograde cathode spot motion

Nonlocal effects in electron kinetics have been shown to play a substantial role in plasma phenomena near a cathode spot. A simplified physical model of a cathode spot motion has been developed. The electron subsystem near the cathode is assumed to consist of two components: (1) a flux of fast electrons accelerated by a cathode potential drop (their role in electric current transfer is of basic importance); and (2) low energy electrons formed at inelastic collisions of fast electrons and trapped by a potential well. Within the model suggested the experimental results of examining of the retrograde cathode spot motion in a magnetic field find their explanation. It is shown that the seeming retrograde motion of the cathode spot is none other than a movement of the ionization boundary in the direction opposite to Ampere force action