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New insights into ELM-free Enhanced D<sub>α</sub> H-mode with near zero NBI torque and stationary operation in the DIII-D tokamak

ORAL

Abstract

Enhanced Dα (EDA) H-mode, an ELM-free H-mode, has been observed in DIII-D with good energy confinement (H98y2~1), βN~2, high density, at low NBI power with near zero torque. EDA H-mode operation has also been extended to stationary regime (~24 energy confinement times). Fluctuation diagnostics have revealed that the associated quasi-coherent mode (QCM) exists in a wide range of kθρs~0.1–1.2 with multiple harmonics in the edge (0.88<ρ<1.02) and propagates with a small phase velocity in the plasma frame (ρ is the normalized toroidal flux coordinate, kθ the binormal wavenumber, and ρs the ion sound radius). Linear gyrokinetic CGYRO simulations of the EDA H-mode discharge indicate that the trapped electron mode (TEM) and electron temperature gradient mode are the dominant instabilities where the QCM is observed. Several properties of TEM, such as the wavenumber range, real frequency close to zero, substantial particle transport, comparable electron and ion heat flux, and a non-negligible electromagnetic flux at low wavenumbers, are consistent with the characteristics of the QCM.



Supported by US DOE under DE-SC0022563, DE-SC0019352, DE-FC02-04ER54698, DE-AC02-09CH11466, DE-FG02-08ER54999, DE-AC52-07NA27344 and DE-FG02-97ER54415.

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Publication: Macwan et al, Phys. Plasmas 31, 122503 (2024); doi: 10.1063/5.0216865

Presenters

  • Tanmay Macwan

    Lawrence Livermore National Laboratory

Authors

  • Tanmay Macwan

    Lawrence Livermore National Laboratory

  • Kshitish Barada

    University of California, Los Angeles

  • Jason F Parisi

    Princeton Plasma Physics Laboratory, Princeton University

  • Richard Joseph Groebner

    General Atomics

  • Terry L Rhodes

    University of California, Los Angeles

  • Santanu Banerjee

    Princeton Plasma Physics Laboratory (PPPL)

  • Colin Chrystal

    General Atomics

  • Quinn T Pratt

    Princeton Plasma Physics Laboratory, Princeton Plasma Physics Laboratory (PPPL)

  • Zheng Yan

    University of Wisconsin Madison, University of Wisconsin - Madison

  • Huiqian Wang

    General Atomics

  • Lei Zeng

    University of California Los Angeles, University of California, Los Angeles

  • Max E Austin

    University of Texas Austin, University of Texas at Austin

  • Neal A Crocker

    University of California, Los Angeles

  • William A Peebles

    University of California, Los Angeles