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P: Fachverband Plasmaphysik

P 5: Poster Session - Low Temperature Plasmas

P 5.3: Poster

Montag, 2. März 2015, 16:30–18:30, Foyer Audimax

Studies on plasma-microwave interaction in space and time: experiment and modelling — •Margarita Baeva, Mathias Andrasch, Jörg Ehlbeck, Detlef Loffhagen, and Klaus-Dieter Weltmann — INP Greifswald, Felix-Hausdorff-Str. 2, 17489 Greifswald, Germany

The temporal and spatial evolution of a microwave induced plasma at a field frequency of 2.45 GHz in argon is studied at pressures of 20 and 40 millibars, flow rates between 200 and 500 sccm, and incident powers of up to 300 W. Experiments based on heterodyne reflectometry and microwave interferometry at 45.75 GHz provided the temporal behaviour of the complex reflection coefficient, the microwave power in the plasma, and the electron density in the afterglow zone. A self-consistent time-dependent, spatially two-dimensional model complements the analysis of the plasma-microwave interaction delivering the plasma and electromagnetic field parameters. The discharge is initiated by means of background electrons and ions at the pulse beginning. Modelling results and measured data show that the electron density, the volume occupied by the plasma, and the absorbed power increase with increasing power. Within 12 µs, the front edge approaches the source wall. The high electric field region is pushed in the same direction. A plasma core with an electron density of about 1×10²⁰ m⁻³ is observed. It moves towards the microwave when increasing the power level. The plasma expands in the downstream, being heated up to about 1400 K mainly due to elastic collisions between heavy particles and electrons and up to 30% due to convection.