Hannover 2010 – scientific programme

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P: Fachverband Plasmaphysik

P 18: Poster: Diagnostics

P 18.5: Poster

Thursday, March 11, 2010, 16:00–18:00, Lichthof

Characterisation of the effluent of a He/O₂ atmospheric pressure microplasma jet by molecular beam mass spectrometry — •Dirk Ellerweg¹, Nikolas Knake², Volker Schulz-von der Gathen², Jan Benedikt¹, and Achim von Keudell¹ — ¹AG Reaktive Plasmen, Ruhr-Universität Bochum — ²Anwendungsorientierte Plasmaphysik, Ruhr-Universität Bochum

The experimental characterisation of the plasma chemistry of atmospheric pressure microplasmas is a difficult task due to the high pressure and the small dimensions. A powerful diagnostic suited for this problem is a mass spectrometer (MS) because it can measure directly the densities of almost all species. Thereby one must consider that the MS requires a low pressure whereas the microplasma needs to be operated at atmospheric pressure in an undisturbed manner. Thus a differential pumping system consisting of several pumping stages must be used. Here, a novel gas sampling design is presented that achieves a beam-to-background ratio up to 14 and a sensitivity down to 0.5 ppm. With the help of this gas sampling system the effluent of a He/O₂ microscale atmospheric pressure plasma jet placed in a helium atmosphere has been analysed. The atomic oxygen density and the ozone density was determined as function of the O₂ admixture, the applied electrode voltage and the distance. The obtained atomic oxygen trends are verified by two-photon absorption laser-induced fluorescence spectroscopy measurements. The results are in very good agreement with each other. Additionally, the microplasma jet was placed in ambient air to determine the influence of admixing air.