Analysis of ionization non-equilibrium in the near-cathode region of atmospheric-pressure arcs

Deviations from ionization equilibrium in the near-cathode region of a high-pressure high-current arc are analysed. Estimates and numerical calculations are given for an atmospheric-pressure argon arc. It is found that the deviations extend over the distance of about 100 μm from the cathode surface and are caused by ambipolar diffusion; convective transport of the charged particles, barodiffusion, thermal diffusion, diffusion caused by thermal non-equilibrium between electrons and heavy particles, and transport due to the presence of the electric current are minor effects.