München 2019 – wissenschaftliches Programm

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P: Fachverband Plasmaphysik

P 18: Postersitzung

P 18.38: Poster

Donnerstag, 21. März 2019, 16:30–18:30, Foyer Audimax

Phase-resolved study of plasma filaments occurring in an RF plasma jet — •Florian Sigeneger, Jan Schäfer, Rüdiger Foest, and Detelf Loffhagen — Leibniz Institute for Plasma Science and Technology, Felix-Hausdorff-Straße 2, 17489 Greifswald

The filamentary plasma generated in a plasma jet is investigated by means of a spatially two-dimensional fluid model. The coaxial jet is driven by an RF voltage at a frequency of 27.12 MHz supplied to the upper of both ring-shaped electrodes attached to the capillary. The lower electrode is grounded. The combination of a phase-resolved description of the RF plasma with a hydrodynamic model of gas flow and gas heating allows to study the influence of the gas flow on the plasma generation. A curved trajectory representing the filament is obtained which guides the current between the powered and grounded electrode. Along this path, the electron density reaches values of about 10²⁰ m⁻³. The gas flow causes density profiles of all species which are shifted in downstream direction. The asymmetry also concerns the generation of striations which arise predominantly from the upstream side. These striations are induced by the nonlinear dependence of the ionization rate on the electron density as well as by the dominant volume recombination in the wings of the filament and in the minima of the spatial structures. Despite the pronounced alterations of the electric field in the striations, only weak modulations of the mean electron density are found there compared to the remarkable amplitudes of the mean energy in the sheath regions in front of the electrodes.