Microwave N2-Ar plasma torch. II. Experiment and comparison with theory

Spatially resolved emission spectroscopy techniques have been used to determine the gas temperature, the electron, and N-2(+) ion densities and the relative emission intensities of radiative species in a microwave (2.45 GHz) plasma torch driven by a surface wave. The experimental results have been analyzed in terms of a two-dimensional theoretical model based on a self-consistent treatment of particles kinetics, gas dynamics, and wave electrodynamics. The measured spatial variations in the various quantities agree well with the model predictions. The radially averaged gas temperature is around 3000 K and varies only slowly along the discharge zone of the source but it drops sharply down to about 400 K in the postdischarge. The experimental wave dispersion characteristics nearly follow the theoretical ones, thus confirming that this plasma source is driven by a surface wave. (C) 2011 American Institute of Physics. [doi:10.1063/1.3532056]