Localized Phase Contrast Imaging of Turbulence and Magnetohydrodynamic Modes at the Wendelstein 7-X Stellarator

ORAL

Abstract

Phase contrast imaging (PCI) measures line-integrated electron density fluctuations along the line-of-sight (LoS) of a laser beam. At the Wendelstein 7-X stellarator, the PCI system has been used to investigate turbulence [1] and magnetohydrodynamic (MHD) modes individually [2], as well as the interplay between plasma turbulence and MHD modes [3]. In the above studies, PCI was limited by the lack of localization of the signal along the LoS. While the location of the main turbulence features could be inferred through modeling and synthetic PCI techniques [1,4], no localization of the MHD modes could be obtained from PCI alone. In the recently completed W7-X experimental campaign, masks allowing localization by blocking the signal from part of the LoS [5] were used to confirm the inferred location of the dominant turbulent fluctuations and to locate other features observed by PCI, including MHD modes. Specifically, these investigations showed that localized measurements of short-wavelength MHD modes on the outboard side of W7-X are possible, while the ability to locate long-wavelength modes is limited, which is supported by synthetic PCI results [4].

[1] J.-P. Bähner et al., J. Plasma Phys. 87, 905870314 (2021)

[2] C. Slaby et al., Nucl. Fusion 60, 112004 (2020)

[3] S. Vaz Mendes et al., submitted to: Plasma Phys. Controlled Fusion (2023)

[4] S. K. Hansen et al., Plasma Phys. Controlled Fusion 64, 095011 (2022)

[5] J. R. Dorris, J. C. Rost, and M. Porkolab, Rev. Sci. Instrum. 80, 023503 (2009)

*Support for the MIT and SUNY-Cortland participation was provided by the US Department of Energy, Grant DE-SC0014229.

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Publication: Journal paper inferring the location of the main turbulence features at Wendelstein 7-X through modeling and synthetic diagnostic techniques:
J.-P. Bähner, J. A. Alcusón, S. K. Hansen, A. von Stechow, O. Grulke, T. Windisch, H.M. Smith, Z. Huang, E.M. Edlund, M. Porkolab, M. N. A. Beurskens, S. A. Bozhenkov, O. P. Ford, L. Vanó, A. Langenberg, N. Pablant, G. G. Plunk, A. Bañón Navarro, F. Jenko and The W7-X Team, Journal of Plasma Physics Vol. 87, 905870314 (2021)

Journal paper about synthetic phase contrast imaging at the Wendelstein 7-X stellarator confirming the localization results:
S. K. Hansen, M. Porkolab, J.-P. Bähner, Z. Huang, A. von Stechow, O. Grulke, E. M. Edlund, F. Wilms, A. Bañón Navarro, F. Jenko, and E. Sánchez, Plasma Physics and Controlled Fuison Vol. 64, 095011 (2022)

Poster about the localization mask design utilized at Wendelstein 7-X:
S. K. Hansen, M. Porkolab, J.-P. Bähner, E. M. Edlund, A. von Stechow, O. Grulke, and the Wendelstein 7-X Team, "Localization Masks for Phase Contrast Imaging at Wendelstein 7-X", 64th Annual Meeting of the APS Division of Plasma Physics (Spokane, WA, October 17-22, 2022); URL: https://meetings.aps.org/Meeting/DPP22/Session/NP11.46

Poster and conference paper about the theoretical limitations of the localization achievable by phase contrast imaging localization masks:
S. K. Hansen, M. Porkolab, J.-P. Bähner, A. von Stechow, O. Grulke, E. M. Edlund, and the Wendelstein 7-X Team, "Localized Phase Contrast Imaging Measurements at Wendelstein 7-X", 49th EPS Conference on Plasma Physics (Bordeaux, France, July 3-7, 2023)

Journal paper on the mask design, theory, and results from Wendelstein 7-X in preparation:
S. K. Hansen, M. Porkolab, J.-P. Bähner, A. von Stechow, O. Grulke, E. M. Edlund, and the Wendelstein 7-X Team, "Localized phase contrast imaging at the Wendelstein 7-X stellarator"

Presenters

  • Søren Kjer Hansen

    • MIT Plasma Science and Fusion Center

Authors

  • Søren Kjer Hansen

    • MIT Plasma Science and Fusion Center

  • Miklos Porkolab

    • Massachusetts Institute of Technology (MIT)

  • Jan-Peter Bähner

    • MIT Plasma Science and Fusion Center

  • Adrian von Stechow

    • Max Planck Institute for Plasma Physics
    • Max Planck Institute for Plasma Physics, Greifswald, Germany

  • Olaf Grulke

    • Max Planck Institute for Plasma Physics

  • Eric Edlund

    • SUNY Cortland