A two-dimensional modelling study of a coaxial plasma waveguide

We present a two-dimensional (2D) plasma model for a coaxial microwave discharge. The microwave energy at driving frequency of 2.45 GHz is fed into a coaxial configuration in which the plasma acts as an outer conductor in such a way that a spatially extended surface wave is created. This geometry permits large surface treatment, especially if a set of such coaxial lines are used. The 2D model describes the plasma as a two-temperature non-chemical equilibrium fluid sustained by electromagnetic surface waves. We present results for argon as a working gas. The importance of wave-plasma power coupling and electron heat transport is discussed. The radial localization of electron density in the coaxial plasma waveguide is observed and compared with experimental results. Moreover, a parameter study allows one to investigate the dependence of radial contraction of the electron density as a function of pressure in the range 2-8 mbar, and also the dependence of electron density with power input in the range 120-1200W. In order to verify the model, the modelling results are compared with experimental results for the electron density and temperature and good agreement is found.