Control of sub-critical microwave filamentary plasma in dense gases

Successful initiation and guiding of microwave plasma filaments with a low-energy pulsed laser is described. A 50 kW, 2.45 GHz microwave power with 1 ms pulse length is directed into a waveguide-based resonant cavity filled with room air. The electric field in the cavity is kept below that needed for self-initiated breakdown. The development of a laboratory-scale supersonic wind tunnel with microwave plasma is also described. A 2D dielectric nozzle is mounted inside the microwave waveguide, so that the flow direction coincides with that of the microwave propagation. Microwave plasmas are generated in the supersonic section, and results are discussed.

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