THEORETICAL-MODELS OF THE CATHODE SPOT IN ARC DISCHARGES .1. FUNDAMENTALS

Presuppositions, theoretical basis, results and general experiences of numerical model calculations of quasi-stationary cathodic spots in (vacuum) arcs are summarized. The results (mainly related to copper cathodes) comprise the essential physical quantities of the cathode spot surface and (partially) of the cathode spot plasma, i.e. possible states of existence within the space of parameters. Especially, the dependence of these results on changes of the parameters and equations is investigated. Several examples are presented and interpreted. In any case, the surface roughness of the cathode is taken into account. Finally, the limitations of the model are discussed, and the great importance of non-stationary (e.g. explosive) processes within the arc spot is emphasized, though such processes are beyond the scope of this model. The paper is published in two parts. This first part comprises an introduction to several aspects of arc spot modeling, the discussion of the physical processes in cathode arc spots and the development of relevant equations to be used in the model.