Comprehensive analysis of beam-driven ion cyclotron range instabilities in mixed species DIII-D plasmas

ORAL

Abstract

Dedicated DIII-D experiments were performed to investigate beam-driven instabilities in the ion cyclotron range of frequencies. Ion cyclotron emission (ICE) occurs at integer harmonics of fci, while global Alfvén eigenmodes (GAEs) occur at substantial fractions of fci. In fusion plasmas, these instabilities may provide valuable diagnostic information about fast ion confinement, once the physics basis is validated. Similar instabilities occur in space plasmas, where controlled parameter scans cannot be performed. In DIII-D, the fast ion distribution was varied by injecting beams with different energy, injection geometry, and species (D and H), while the thermal ion species mix was varied between D, H, and 3He. The instabilities are measured with magnetic loops with 100 MHz bandwidth, covering several fci harmonics. A comprehensive database is analyzed to understand the mode stability and time evolution [1]. Mode excitation is sensitive to the combination of beam and thermal ion species, in reasonable agreement with linear theory. A rich variety of time-dependent behavior is observed, including predator-prey cycles, response to sawtooth crashes, and nonlinear harmonic coupling. The observation of GAEs excited between fcD < f < fcH provides a novel stress test for linear theory, with mixed results.

*Work supported by US DOE under DE-SC0020337, DE-SC0018270, DE-SC0021201, DE-FC02-04ER54698, DE-SC0019352, and DE-SC0011810.

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Publication: [1] W.W. Heidbrink, et al. Three manuscripts submitted to Nuclear Fusion.

Presenters

  • Jeff B Lestz

    • General Atomics

Authors

  • Jeff B Lestz

    • General Atomics

  • William Walter Heidbrink

    • University of California, Irvine

  • Neal A Crocker

    • University of California, Los Angeles

  • Genevieve H DeGrandchamp

    • Lawrence Livermore National Laboratory

  • Kathreen E Thome

    • General Atomics

  • Shelley Tong

    • University of California, Irvine

  • Stephen T Vincena

    • University of California, Los Angeles

  • Kshitish Barada

    • University of California, Los Angeles

  • Xiaodi Du

    • General Atomics

  • William A Peebles

    • University of California, Los Angeles

  • Robert I Pinsker

    • General Atomics

  • Terry L Rhodes

    • University of California, Los Angeles

  • Gregory Allen Riggs

    • West Virginia University

  • Shawn X Tang

    • General Atomics

  • Michael A Van Zeeland

    • General Atomics

  • Lei Zeng

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