ISSN:
1089-7674
Source:
AIP Digital Archive
Topics:
Physics
Notes:
Spectroscopic emission measurements have been made in a microwave plasma and have been compared with results from a collisional-radiative model—one that accounts for a non-Maxwellian electron energy distribution function (EEDF)—to assess the effects of nonequilibrium. Typical operating conditions are 40 Torr pressure, 300 sccm hydrogen, and 3 sccm methane flow rates, and 1.6 kW deposited power. Optical emission measurements of atomic hydrogen's excited state number densities indicate values that are inconsistent, by orders of magnitude, with those predicted by an atomic hydrogen collisional-radiative model if numerically estimated EEDFs (average energy near 2.5 eV) taken from the published literature are used as input. Satisfactory agreement between the experimental and numerical results, however, is obtained if two-step ionization is accounted for in a self-consistent coupled numerical solution for the free and bound–excited electron densities, the electric field, and the EEDF. Two-step ionization is the dominant electron production mechanism and thereby greatly impacts numerical predictions of the electric field, the electron average energy, and thus the EEDF. Self-consistently accounting for two-step ionization reduces the predicted sustaining electric field by 55% and thereby results in a predicted EEDF with an average energy near 1.1 eV. © 1996 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.871867
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