Asymptotic modelling of a narrow gap, high pressure glow discharge

Summary form only given. Atmospheric pressure non-thermal plasmas are now being used for various applications such as pollution control, light sources, medical and waste. Here a self-consistent continuum model is presented for a narrow gap plane-parallel DC glow discharge. The set of governing equations consisting of continuity and momentum equations for positive ions, fast (emitted by the cathode) and slow electrons (generated by fast electron impact ionization) coupled with Poisson´s equation is treated by the technique of matched asymptotic expansions (Nayfeh, 1973). This analytic procedure reduces the unnecessary computational effort associated with Monte-Carlo approach with acceptable accuracy. In addition it is more physically transparent. Explicit results are obtained in the asymptotic limit: pL/spl Gt/1, (/spl chi//spl delta/)/spl Lt/1, where p is the gas pressure, L is the gaplength, /spl chi/ is the normalised applied voltage, and /spl delta/=(r/sub D//L)/sup 2/ where r/sub D/ is the Debye radius. In the limit of large pL the electron energy relaxation length is much smaller than gap length and local field approximation is valid. The discharge space divides naturally into a cathode fall sheath, a quasineutral plasma region and an anode fall sheath. The length of each region is derived. The electric field and charge density distribution obtained for each region (in a (semi)-analytical form) is asymptotically matched to the adjoining one in the region of overlap. The effects of the gas pressure, gap length and applied voltage on the discharge properties are investigated. The cathode fall parameters predicted by the asymptotic model are in reasonable agreement with available experimental data (Novak et al., 1987). Work is underway to apply this method for the calculation of dielectric barrier discharge characteristics.