New line plasma source excited by 2.45 GHz microwave at atmospheric pressure

A new device for the production of atmospheric-pressure microwave line plasma is proposed. By using a loop-structure waveguide and a circulator, only traveling waves transmitted in the waveguide are superimposed in phase with each other by impedance matching of an EH tuner. The spatiotemporal behavior of the plasma and the spatial distribution of the emission intensity were investigated using a high-speed camera and a digital still camera. A stable discharge is sustained inside a slot of 60 cm length and 0.1 mm width in pure helium gas at a microwave power of 1.0 kW in the cw mode.