Göttingen 2025 – wissenschaftliches Programm
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P: Fachverband Plasmaphysik
P 17: Poster Session II
P 17.45: Poster
Mittwoch, 2. April 2025, 16:15–18:15, ZHG Foyer 1. OG
Feedback Controlled Phase Contrast Imaging at Wendelstein 7-X — •Max Zimmermann1, Adrian von Stechow1, Jan-Peter Bähner2, Søren Kjer Hansen2, Sean Ballinger2, Olaf Grulke1,3, Eric Edlund4, Miklos Porkolab2, and The W7-X Team1 — 1Max Planck Institute for Plasma Physics, 17491 Greifswald, Germany — 2MIT Plasma Science and Fusion Center, Cambridge, MA 02139, USA — 3Technical University of Denmark, 2800 Kongens Lyngby, Denmark — 4SUNY Cortland, Cortland, NY 13045, USA
The phase contrast imaging (PCI) diagnostic at Wendelstein 7-X (W7-X) is used for detection of core turbulence density fluctuations [E.M. Edlund et al. 2018 Rev. Sci. Instrum. 89 10E105]. This is done by imaging electron density fluctuations using a CO2 laser. The laser is aligned using several mirrors, some of which are attached to the outer vessel of W7-X and are therefore subject to vibrations from auxiliary systems (e.g. vacuum pumps). These vibrations lead to movements of the image plane and are visible in the PCI signal as low frequency components up to 250 Hz. A reduction of these vibrations leads to increased beam position stability and a higher signal saturation limit for PCI signals. A digital RST feedback controller is designed and implemented, which together with a piezo-based fast steering mirror and a four quadrant detector forms an active vibration compensation system. The controller design is validated by frequency response measurements and its impact on plasma fluctuation signals is evaluated.
Keywords: phase contrast imaging; feedback control; active vibration compensation