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 at Austin
    • University of Texas Austin

  • Neal A Crocker

    • University of California, Los Angeles

  • William A Peebles

    • University of California, Los Angeles