An electromagnetic approach to a small-scale microwave ICP-plasmajet

Microwave-driven plasmas-jets offer attractive properties for various technical applications. They are usually operated in a capacitive mode, known as E-Mode. Experimental experience however show a number of disadvantages for capacitive coupling such as high boundary sheath voltage and thus high electrical losses. Therefore in large scale plasmas inductive coupling, known as H-mode, is attractive. Recently \textit{Porteanu et al.}[1] proposed a small scale plasma-jet operated as an inductive discharge. The key characteristic of the proposed plasma-jet is the implementation of an LC-resonance-circuit into a cavity resonator. In this work the proposed plasma-jet is examined theoretically. A global model for the electromagnetic fields and energy balance is presented. Consequent mathematical analysis of the electromagnetic fields leads to a description based on a sum of different modes. It is found that the modes of zero and first order can be identified with inductive and capacitive coupling. In a second step the matching network and its frequency depended characteristic are taken into account. Finally an investigation of stable working points and possible hysteresis effects is done. \newline [1]H. E. Porteanu et al. \textit{Plasma Sources Sci.Technol.}\textbf{22}, 035016(2013)