Surface-wave-sustained argon plasma kinetics from intermediate to atmospheric pressure

Abstract

Surface-wave-sustained discharges (SWDs) can operate across a wide range of discharge conditions. From low to atmospheric pressure, plasma sustained by travelling electromagnetic wave is strongly non-equilibrium: the electron energy distribution function (EEDF) is non-Maxwellian; the gas temperature Tg (the translational temperature of the heavy particles) is much lower than the electron temperature Te, i.e. . In this paper, kinetic models of surface-wave-sustained argon plasma based on the Boltzmann equation and its momenta are presented for various discharge conditions (intermediate and high gas pressure and various discharge tube radii). The difference between the models is in the energy level diagrams and the elementary processes taken into account for the various conditions. The models give the EEDF, transport and rate coefficients, mean electron energy, electron–neutral collision frequency for momentum transfer, mean power required to sustain an electron–ion pair in the discharge, and densities of considered atomic and molecular species as a function of the electron density ne. Since the surface-wave plasma is spatially inhomogeneous, all these plasma characteristics change along the plasma column in the axial direction as the wave power absorbed by the electrons and electron density change. The goal is to compare the results obtained from the models with the experimental data and to determine their applicability depending on the SWD conditions.