An approach to diagnostics along HF high pressure plasma columns by microwave reflectometer

Abstract

Diagnostic results relating to the full length of high frequency discharge plasma columns produced by a VHF surface wave generator (50 W max) are presented and discussed. Such plasmas, highly collisional, are generated in narrow quartz tubes having inner diameters of 2 and 4 mm, in xenon at pressures of 10 and 40 Torr respectively. The radius of the plasma column, the radial profile of the electron density, and the global collision frequency are estimated by measuring the microwave reflection coefficient in the X-band. The experimental results are fitted to the results obtained by a numerical calculation derived from an exact theory of electromagnetic scattering in a rectangular waveguide. Different plasma regimes along the columns may be diagnosed.