A new type of non-thermal atmospheric pressure plasma source based on a waveguide bridge

Abstract

A new type of microwave source of non-thermal atmospheric pressure plasmas, presented earlier by the authors, has both the characteristics of a dielectric barrier discharge (in terms of the configuration and low gas temperature) and an ability to form a “clean” plasma jet like a classical microwave plasma torch. However, the need to use a circulator leads to a significant increase in complexity, cost and weight of the installation as a whole. The basis of the presented plasma source is a three-decibel waveguide bridge with connection through a narrow wall. Both output arms of the bridge are loaded on identical short-circuited segments of waveguides. The discharge tube passes across the waveguides at a distance of a quarter of the wavelength from the short circuit. Since the output arms of the bridge are always loaded symmetrically, the generator’s power which is reflected from the short circuits or not be absorbed in the microwave discharge, enters the decoupled arm of the bridge that is connected to the matched load. Thus, the magnetron is protected from the reflected wave without the need for an expensive circulator, in any case.