Erlangen 2018 – scientific programme
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P: Fachverband Plasmaphysik
P 2: Low Pressure Plasmas I
P 2.7: Talk
Monday, March 5, 2018, 12:15–12:30, KI 1.174
In-situ measurement of optical properties of metallic surfaces using the Doppler-shifted emission of fast neutral atoms in a low density plasma — •Sven Dickheuer1, Oleksandr Marchuk1, Christian Brandt2, Andrei Goriaev1, Mykola Ialovega1, and PSI-2 Team1 — 1Forschungszentrum Jülich GmbH - Institut für Energie- und Klimaforschung - Plasmaphysik, Partner of the Trilateral Euregio Cluster (TEC), 52425 Jülich, Germany — 2Max-Planck-Institut für Plasmaphysik, 17491 Greifswald, Germany
The knowledge about the optical properties of metallic surfaces during plasma exposition is crucial for many plasma diagnostics. In fusion plasmas, for instance, reflection properties of the plasma facing mirror and plasma wall components have a strong impact on the signal in the visible range. Until now no technique exists, which is able to monitor the modification of the optical properties without any additional calibration sources. We present an in-situ technique to measure the reflectance, its dynamic evolution and the polarization of different metallic surfaces (e.g. C, Al, Ti, Fe, Mo, Rh, Pd, Ag, Sn and W) in a H/Ar mixed plasma. The measurements are performed in the linear plasma device PSI-2, operating in the electron density range of 1011 − 1012 cm−3 and electron temperature range of 4−10 eV. The optical properties are measured by analyzing the Doppler-shifted emission of fast hydrogen atoms, backscattered from the metallic surface, at different lines-of-sight at 656.279 nm (Balmer-α line). The comparison between measured reflectance and theoretical data shows a very good agreement (within 10 %).