Bochum 2015 – wissenschaftliches Programm
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P: Fachverband Plasmaphysik
P 15: Poster Session - Magnetic Confinement
P 15.8: Poster
Dienstag, 3. März 2015, 16:30–18:30, Foyer Audimax
Phase Contrast Imaging diagnostic for Wendelstein 7-X — •Lukas-Georg Böttger1 and Olaf Grulke2 — 1Ernst-Moritz-Arndt-Universität Greifswald — 2Max Planck Institute for Plasma Physics, 17491 Greifswald, Germany
The Phase Contrast Imaging (PCI) diagnostic allows non-invasive measurements of density fluctuations in high temperature plasmas.
The index of refraction in a plasma depends approximately linearly on its density. Therefore an incoming probing laser beam is shifted in phase by the density fluctuations. This phase shift information can be translated into intensity variations by interference after a phase plate.
In general the signal contains only the line-integrated information along the beam path. This limitation can be overcome by the fact that the density fluctuations form filament structures well aligned with the local magnetic field. If the pitch angle of the magnetic field varies significantly along the beam path, optical filtering allows for localization of the density fluctuations. First estimates show that a resolution of about 15 cm in W7-X can be achieved, which will allow for a clear separation of edge and core fluctuations.
The process of integration starts with the development of a virtual diagnostic revealing the specific behaviour of the PCI diagnostic at W7-X for standard operation scenarios. In this contribution first results of these investigations are presented.