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

TL;DR

This paper develops a coupled electromagnetic and chemical model for a miniature microwave nitrogen plasma jet, validating it against experimental data and analyzing the discharge regime at high power levels.

Contribution

It introduces a comprehensive model combining electromagnetic fields and nitrogen chemistry tailored to the MMWICP device, providing detailed plasma behavior predictions.

Findings

Good agreement with experimental plasma parameters at high power

Spatial distribution of the discharge matches measurements

Discharge operates in an E/H-hybrid mode at high electron density

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.