The diffusion processes and the role of demixing in arcs with copper electrodes

The role of transport processes in forming the self-organized structure of electric arc plasmas between evaporating electrodes is discussed. The diffusion of vapour derived from copper electrodes in air is investigated, using the approximation of a binary mixture. In the case of low temperatures, the problem is studied analytically for free-burning and wall-stabilized electric arcs; the influence of thermal diffusion is also examined. For a wider temperature range, the problem is solved numerically. The `catastrophic´ increase in copper vapour concentration seen in spectroscopic measurements is shown to be due an artefact resulting from the effects of radiative transfer. Further ways of investigating electric arc properties are discussed from the viewpoint of methods of self-organization.