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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 Keudell11AG 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.

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