Robustness of RWM Feedback Performance in AT Plasmas

ORAL

Abstract

High-speed actuators with frequency response of dc-40~kHz have been installed to upgrade the resistive wall mode (RWM) feedback capability in \hbox{DIII-D}. These actuators are configured to drive the \hbox{DIII-D} internal coil set (I-coils). The experimental observations qualitatively support that the voltage-controlled feedback does assist achieving long duration high beta plasmas. However, non-reproducibility of the RWM onset makes it harder to provide a quantitative measure of direct feedback and to separate the effects rotational stabilization. Possible causes of non-reproducibility are: (1)~coupling to ELMs, (2)~residual error field persisting even after the dynamic error field correction, (3)~possible coupling of RWM, ELMs and residual error field. The experimental observations will be discussed in light of these possibilities along with MARS-F analysis.

*Work supported by the US DOE under DE-AC02-76CH03073, DE-FC02-89ER53297, and DE-FG03-00ER82791

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Authors

  • M. Okabayashi

  • R. Hatcher

  • H. Takahashi

    • Princeton Plasma Physics Laboratory

  • M.S. Chu

  • G.L. Jackson

    • General Atomics

  • R.J. La Haye

    • General Atomics

  • J.T. Scoville

  • E.J. Strait

    • General Atomics

  • A.M. Garofalo

    • Columbia University

  • G.A. Navratil

  • H. Reimerdes

    • Columbia~U.
    • Columbia University
    • Columbia U.

  • Y. In

    • FARTECH, Inc.