Recent progress on ELM suppression in hydrogen and helium at DIII-D and ASDEX Upgrade

ORAL

Abstract

ITER pre-fusion power operation (PFPO) phase operating with hydrogen (H) and helium (He) will be the first opportunity to study suppression of edge-localized modes (ELMs) by magnetic perturbations (MP). ELM suppression has been demonstrated on many tokamaks, however, only in deuterium (D). Recently, ELM suppression has been investigated in H at DIII-D and ASDEX Upgrade.

We find that on DIII-D in H plasmas a weak MP field causes a H-L transition. Diluting the H plasma moderately with He prevents the backtransition and the MP field leads to a weak density pump-out. As such, the density cannot be reduced significantly below the critical density for ELM suppression and, therefore no ELM suppression has been observed in H or H+He plasmas in DIII-D or ASDEX Upgrade.

Progress has been made extending the work reported in [1], which showed ELM suppression at a high density in a low power He plasma. Key signatures characteristic of ELM suppression in D are discovered in He such as an increase of the plasma response to the MP field, a narrowing of the pedestal and increased density fluctuations.

[1] T. Evans et al, Nucl. Fusion 57 (2017) 086016

*Work supported by US DOE under DE-FC02-04ER54698, DE-SC0020298, DE-SC0021968, DE-SC0020284, DE-AC02-09CH11466, DE-AC52-07NA27344, DE-SC0020287.

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Presenters

  • Nils Leuthold

    • Oak Ridge Associated Universities, Oak Ridge, TN 37831, USA

Authors

  • Nils Leuthold

    • Oak Ridge Associated Universities, Oak Ridge, TN 37831, USA

  • Carlos Paz-Soldan

    • Columbia University, New York City
    • Columbia University
    • Columbia

  • Wolfgang Suttrop

    • Max-Planck-Institut für Plasmaphysik, 85748 Garching, Germany
    • Max Planck Institute for Plasma Physics

  • Colin Chrystal

    • General Atomics - San Diego
    • General Atomics

  • Todd E Evans

    • General Atomics - San Diego

  • Edward T Hinson

    • University of Wisconsin - Madison

  • Matthias Knolker

    • General Atomics

  • Florian M. Laggner

    • Princeton Plasma Physics Laboratory

  • Nikolas C Logan

    • Lawrence Livermore Natl Lab
    • Lawrence Livermore National Laboratory
    • LLNL

  • Tom H Osborne

    • General Atomics
    • General Atomics - San Diego

  • Lothar W Schmitz

    • University of California, Los Angeles