The cathode spot of a high-current vacuum arc as a multiecton phenomenon

The operation of the cathode spot of a high-current vacuum arc is treated in terms of the ecton model. It has been demonstrated that in this case the cathode spot cells are grouped to adjoin one another. The existence of such a collective spot is due to the cumulative effect of a number of microexplosions, resulting in that the current density in the spot increases by almost an order of magnitude. Moreover, in such a spot, conditions are realized which are energetically profitable for the repetition of ecton processes, namely, an elevated temperature of the surface and an increased density of the near-cathode plasma. The prediction that a cathode spot has a substructure has been confirmed by observations of changes in the intensity of the light emitted by collective cathode spots, by their electron-optical records, and by the erosion traces left by these spots on the cathode surface. The parameters of a collective cathode spot, such as the crater diameter, the current density, and the lifetime, have been related to the arc current. The predicted relationships are in good agreement with experimental results. If the vacuum arc current becomes over some limiting current, a new cathode spot appears and then operates simultaneously with the old one. It has been shown that as the arc current increases, the current density in the cathode spot drops, resulting in division of the spot. An estimate of the limiting arc current per unit spot has been obtained