Energy coupling efficiency of a hydrogen microwave plasma reactor

Zero-dimensional and two-dimensional plasma models and optical emission spe ctroscopy are used in tandem to investigate the power coupling efficiency f or a pure hydrogen microwave plasma. The zero-dimensional model accounts fo r the vibrational kinetics of H-2, the chemistry of H-2 and H excited state s, and the kinetics of ground-state species. The set of species conservatio n equations are then coupled to the electron Boltzmann equation (to account for the non-Maxwellian electron energy distribution function) and the tota l energy equation for solution. The two-dimensional model makes use of a si mpler thermochemical description of the plasma. The chemistry is described with nine species and thirty chemical reactions. Three energy modes are con sidered to describe the plasma's thermal nonequilibrium, and Maxwellian dis tribution functions for kinetic and vibrational modes are assumed. The non- Maxwellian nature of the electron energy distribution function is separatel y accounted for. Experimentally, the absolute line emission intensity is ut ilized to obtain number densities of up to five hydrogen excited states usi ng the following transitions: H alpha (6563 Angstrom), H beta (4861 Angstro m), H gamma (4340 Angstrom), H delta (4102 Angstrom), and H epsilon (3970 A ngstrom). The first three transitions were used for a 38 Torr, 1000 W hydro gen discharge, and all five transitions were used for a 121 Torr, 4000 W hy drogen discharge. The absolute continuum emission from the plasma was compa red to numerical predictions. The comparison of the numerical and experimen tal data indicates that 90%-100% of the input power is deposited in the pla sma and that both the line and continuum emission match within a factor of 3, with the exception of the high energy excited states for the 4000 W plas ma. A control volume heat transfer analysis validates the energy coupling. (C) 2001 American Institute of Physics.