Characterization and explorative application of a novel miniature micorwave ICP

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High-frequency or microwave-powered plasma jets represent an attractive alternative to conventional plasma chambers and enable many innovative plasma technology applications. The inherent advantages of plasma jets are low cost and small spatial dimensions. However, their efficiency is currently unsatisfactory: The usual capacitive coupling of the electromagnetic energy leads to sheath voltages and thus to high electrical losses. As part of an earlier project, it was possible for the first time to transfer the principle of inductive coupling to a miniaturized microwave plasma jet. Very high electron densities (3.5 x10^19) were achieved, while the discharge was still far from thermal equilibrium. The core of the concept is a compact, microwave-operated resonator, which can be seen as a parallel connection of a plate capacitor with two cylindrical coils with a turn number of one. A strong azimuthal vortex field is induced in these coils, which can maintain a plasma with a low surface layer tension in the ceramic tubes through which gas flows. The focus of the project is the further investigation of basic, plasma-physical questions and technical aspects of the operation, as well as a first exploration of the application potential of the new source. A coordinated approach based on experimental and theoretical methods is planned. Experimentally spatially resolved emission and absorption spectroscopy as well as time resolved electrical measurements of the complex S11 parameters are planned. Of particular interest are the characterization of the source with various gases, the characterization of the mode transitions and the plasma chemistry of the radical species. The time-dependent electrical measurements allow insights into the dynamics of the source, during the ignition and the mode transitions. At a theoretical level, it is initially planned to describe the more complex plasma chemistry of the new operating gases in a global model. Furthermore, an adequate electromagnetic simulation of the resonator structure is planned based on a commercial simulation software. With the addition of an existing plasma tool, this is to be expanded and combined into a hybrid model. From a technical point of view, the exploration of the parameter range with regard to pressure, power, gas composition is important in order to be able to assess the suitability of the source for the diverse potential applications. The operation of a double ICP with two different operating gases is also planned. Of particular interest will be the possibility of interconnecting several sources to form a linear source. As a first step in this direction, the interconnection of two double ICPs is planned.