München 2019 – wissenschaftliches Programm

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P: Fachverband Plasmaphysik

P 18: Postersitzung

P 18.10: Poster

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

Measurements with optical tweezers in the sheath of a CCP discharge and the effect of UV irradiation on the charge of SiO2 microparticles. — •Viktor Schneider and Holger Kersten — Institute of Experimental and Applied Physics (IEAP), Kiel University

We use SiO2 microparticles in an optical trap to manipulate them in the environment of a CCP discharge. In contrast to common plasma diagnostic tools, e.g. Langmuir probes, calorimetric probes, mass spectrometers etc., the µPLASMA experiment uses microparticles as noninvasive probes [1]. From the displacement of a single probe particle in the optical trap we measure a force while it is moving relatively to the plasma, either deeper into the sheath or towards the plasma bulk. The benefit of the presented technique is the possibility to retain the particle even after the plasma is turned off. Residual charges on the sphere after switching off the plasma have been measured. Furthermore, charging of the sphere by UV radiation in an external electric field is investigated and discussed. The measurements indicate electron induced secondary electron emission from the particle and an emission yield above unity for energies about 100  eV.
[1] V. Schneider and H. Kersten, "An optical trapping system for particle probes in plasma diagnostics", Rev. Sci. Instrum. 89, (2018)

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