Computer Simulation of the Dynamics of Plasma-Surface Interactions in Vacuum Arc Cathode Spots

Abstract

After an introductory definition of the vacuum arc cathode spot, its main theoretical aspects are highlighted. Most of the review is being devoted to the E-diagram method as well as to advanced nonstationary cathode spot models. A survey of the aim of the present computer simulation and its development following the author's very first concept of "dynamic field emission" is also given. The cathode spot model subjected to the computer simulation is described in detail, considering the laws of conservation of charge, mass, and energy in the complete cathode spot system. A short survey of the computational procedure is also given here. The main computational results may be summarized as follows: Within the actual model assumptions, a steady-state self-sustaining cathode spot does not exist. On the one hand, plasma-wall interactions with steady-state thermal equilibrium exist below the balance conditions of mass and energy, while on the other hand, real cathode spots that meet the requirements of both mass and energy balance never show thermal equilibrium but are characterized by thermal runaway. Therefore, instability is an inherent feature of cathode spots. Finally, a comparison between computational values and representative experimental results of cathode spot characteristics shows a rather good agreement, further supporting the principal validity of a model devoted particularly to a theoretical specification of the vacuum arc cathode spot.