Resonant-cavity microwave plasma at atmospheric pressure - Preliminary results

In this paper, argon and nitrogen plasmas at atmospheric pressure. generated in one cylindrical and one rectangular resonant cavities. are studied. The electromagnetic field in vaccum is calculated by a finite element method. Ignition of the plasma is discussed. The plasma is characterised by measurements of the absorbed power which is equal to the difference between incident and reflected powers. At low flow rates, the plasma of argon is inhomogeneous and unstable. For flow rates higher than 2 1/mn, the discharge becomes a streamer. The plasma of nitrogen is stable at now rates higher than 1.5 1/mn. Only the first negative system of nitrogen is observed by optical emission spectroscopy of the plasma. Spatially resolved EOS shows the possible presence of a pink afterglow.