Observation of Plasma Propagation in an Array of Microchannels

Discharge dynamics in an array of microscale channels fabricated in Al/Al$_{2}$O$_{3}$ has been investigated at atmospheric pressure in He and Ar. Microplasmas in channels having a width of 200-300 $\mu $m, a length up to 50 mm, and a volume of 1-15 mm$^{3}$ have been generated on a static or flowing gas basis. Fabricated by micromachining and wet chemical processes, these channels are situated in a dielectric barrier structure fabricated in 125-250 $\mu $m thick Al foil and having a buried electrode geometry. Spatiotemporally-resolved optical emission profiles, recorded with a gated CCD camera and a telescope, reveal a plasma propagation speed (and direction of excited emission along the microchannel) which varies with gas inlet pressure. For 1 atm of Ar, the velocity of the excitation wave is $\sim $15 km/s.