Diagnostik und Modellierung eines Mikrowellen-Plasmabrenners bei Atmosphärendruck

Atmosphericmicrowaveplasmasofferalargevarietyofapplications.Theseincludeplasma spraying for the deposition of layers, the treatment of surfaces for activation or cleaning purposes, as well as the abatement of waste gases. To develop and optimize the plasma sources used for these processes, experimental as well as theoretical investigations are necessary. Therefore, the main focus of this work lies, in addition to empirical studies, on a stepwise numerical description and simulation of the physical processes taking place in a microwave plasma torch at atmospheric pressure. Individual models help to optimize it andcanlaterbecoupledsuccessivelytogetaself-consistentmodeloftheplasmasource. To perform the simulations the software Comsol MultiphysicsR is used. Moreover, the simulation results are compared with experimental data. A first objective of the present work is to calculate the resonance properties of the plasma torch’s resonators, as well as the occurring electric field distribution. An additional modelthendescribesthecoldgasflow.Later,aheatsourceisincludedinordertoinvestigate the influence of the hot plasma. The optimization of the gas management aims at the envelopment of the plasma to prevent it from touching and damaging the confining quartz tube. Using a Drude theory approach, the plasma can be modelled through its permittivity and electrical conductivity. A further enhanced model considers fluid equations and a set of elementary chemical reactions for an argon plasma. The simulations are verified by experimental results. To this end the spatial position of the plasma is observed qualitatively with a camera. Furthermore there are optical emission spectroscopy measurements [1] available