Charged particle distributions and heat transfer in a discharge between geometrically dissimilar electrodes: From breakdown to steady state

The low-current electric discharge from a fine wire anode to a planar catho de in atmospheric pressure air is numerically simulated from high-voltage p rebreakdown through electron temperature growth, then ionization and conseq uent current growth to steady state, limited by a ballast resistor in the e xternal circuit. Conservation of number (mass) for ions and electrons, Gaus s' law for the self-consistent electric field, and energy conservation for electrons have been solved from breakdown to steady state in a body fitted coordinate system generated specifically for these two geometrically dissim ilar electrodes. To facilitate the discussion of the results, the discharge has been categorized under (a) electron acceleration period, (b) charged p article generation period, (c) current increase and voltage drop period, an d (d) current and voltage stabilization period. Results are given for trans ient electron, ion, and temperature distributions in the gap as well as cur rent growth and voltage drop across the gap. Heat flux from the discharge t o the wire is calculated. The numerical simulations were compared with expe riments performed under the same conditions on a wire bonding machine with very close correspondence. (C) 2000 American Institute of Physics. [S1070-6 64X(00)00902-2].