LH-induced SOL density profile asymmetries on Alcator C-Mod

ORAL

Abstract

On Alcator C-Mod, the LHCD has a density limit where the current drive efficiency drops abruptly significantly below the classical density limit. One possible explanation is LH wave absorption in SOL. A suite of SOL diagnostics have been used to diagnose the LH-SOL interaction: a X-mode reflectometer installed at three poloidal locations adjacent to the LH launcher is used to measure the density profile, a visible video camera that images the LH launcher measures the emissivity, and gas puff imaging diagnostic magnetically connected to the LH launcher measures the poloidal velocity. These measurements have confirmed that the LH absorption in SOL drives ExB drifts that are consistent with a density vortex. The poloidal density profile asymmetries scale with LH power, launched spectrum and are correlated with the video camera emissivity measurements. Using a diffusive-convective transnport model, these density profiles modifications are shown to be consistent with the measured plasma flows. The impact of these poloidal density profile asymmetries on LH coupling and SOL absorption models will be discussed.

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Authors

  • Cornwall Lau

    MIT Plasma Science and Fusion Center

  • G.R. Hanson

    ORNL, ORNL/UT-Battelle, Oak Ridge National Laboratory

  • B. LaBombard

    MIT PSFC, MIT-PSFC, PSFC-MIT, MIT Plasma Science and Fusion Center, PSFC, MIT, PSFC MIT

  • Yijun Lin

    PSFC-MIT, Plasma Science and Fusion Center, Massachusetts Institute of Technology, MIT Plasma Science and Fusion Center

  • Roman Ochoukov

    MIT, MIT Plasma Science and Fusion Center, PSFC MIT

  • Ron Parker

    PSFC-MIT, MIT PSFC, MIT-PSFC, MIT Plasma Science and Fusion Center, PSFC, MIT

  • Syun'ichi Shiraiwa

    MIT - PSFC, PSFC, MIT PSFC, MIT Plasma Science and Fusion Center, PSFC, MIT

  • James Terry

    Massachusetts Institute of Technology, MIT PSFC, MIT, MIT-PSFC, MIT Plasma Science and Fusion Center, PSFC, MIT, PSFC MIT

  • Greg Wallace

    MIT Plasma Science and Fusion Center

  • John Wilgen

    ORNL, Oak Ridge National Laboratory

  • S. Wukitch

    MIT PSFC, PSFC-MIT, MIT Plasma Science and Fusion Center, PSFC MIT, MIT-PSFC