Modelling of a miniature microwave driven nitrogen plasma jet and comparison to measurements

Abstract

The MMWICP (Miniature MicroWave ICP) is a new plasma source using the induction principle. Recently Klute et al. presented a mathematical model for the electromagnetic fields and power balance of the new device. In this work the electromagnetic model is coupled with a global chemistry model for nitrogen, based on the chemical reaction set of Thorsteinsson and Gudmundsson and customized for the geometry of the MMWICP. The combined model delivers a quantitative description for a non-thermal plasma at a pressure of $p=1000\,\mathrm{Pa}$ and a gas temperature of $T_\mathrm{g}=650\mbox{-}1600\,\mathrm{K}$. Comparison with published experimental data shows a good agreement for the volume averaged plasma parameters at high power, for the spatial distribution of the discharge and for the microwave measurements. Furthermore, the balance of capacitive and inductive \linebreak coupling in the absorbed power is analyzed. This leads to the interpretation of the discharge regime at a electron density of $n_\mathrm{e} \approx 6.4 \!\times\!10^{18} \, \mathrm{m}^{-3}$ as $E/H$-hybridmode with an capacitive and inductive component.