MULTIPLE MICRODISCHARGE DYNAMICS IN DIELECTRIC BARRIER DISCHARGES

Dielectric barrier discharges (DBDs) are pulsed atmospheric pressure d evices in which the plasma forms as an array of microdischarges having diameters expanding from 10 to 100's mu m and area densities of 10 to 100's cm(-2). The microdischarges are <10's ns in duration and are te rminated by charging of the dielectric barrier which removes voltage f rom the gap. If microdischarges are spaced sufficiently close together they may interact during their expansion. In this article, we discuss results from a two-dimensional plasma hydrodynamics model for microdi scharge development in DBDs with the goal of investigating the interac tion between closely spaced microdischarges. We find that the efficien cy of ionization is only moderately affected by microdischarges which expand into physical contact. The residual charge left on the dielectr ic following a current pulse can, however, significantly impact the sp atial extent of the subsequent microdischarges. During expansion the u nderlying dielectric charges to progressively larger radii as the micr odischarge expands. This leads to voltage collapse in the center of th e microdischarge prior to the outer radius. In attaching gas mixtures larger rates of attachment relative to ionization at the lower values of the electric field/number density produce cores which are highly el ectronegative, surrounded by shells of higher electron density. (C) 19 98 American Institute of Physics. [S0021-8979(98)07620-8].