One-dimensional numerical simulation of ac discharges in a high-pressure mixture of Ne+0.1% Ar confined to a narrow gap between insulated metal electrodes

Abstract

The present work is concerned with a one-dimensional dynamic simulation, incorporting a self-consistent treatment of space-charge effects, of the buildup and decay of ac discharges in a high- (≳100 Torr) pressure mixture of Ne+0.1% Ar confined to a narrow gap (∼10-2 cm) between insulator (MgO) covered metal electrodes. Numerical modeling has been done of the dynamics of successive avalanches triggered by the electric-field-dependent secondary emission of electrons at the cathode due to ionic species, metastables, and photons. The basic continuity equations of the problem deal with the following collisional phenomena in the gas volume: (i) electron impact excitation and ionization of neon atoms, (ii) collisional ionization involving excited neon states, (iii) two-body and three-body collisional processes involving energy transfer, and (iv) absorption and reemission of imprisoned resonant radiation. The computed results show a satisfactory agreement with measured parameters on a single cell of a specially constructed "one-dimensional" ac plasma panel whose electrode linewidths were made an order of magnitude larger than the gas gap. Neon ions were found to play a dominant role in the secondary electron emission from the MgO surfaces, while photoemission was negligible. The theoretical and experimental results were fitted to yield a value of 0.45 for the intrinsic secondary-emission coefficient of MgO surfaces caused by the arrival of neon ions under vacuum conditions. Finally, sample results are presented for the spatial and temporal profiles of the electric field, charged particle concentrations, and the volume density of various excited species of the host gas.