Measurements of CAE mode structure in DIII-D and identification of intermediate frequency AEs

POSTER

Abstract

New measurements are reported of fast-ion driven compressional Alfvén eigenmodes (CAE, ω ≲ ωci­) and intermediate frequency AEs (vA/R ≪ ω ≪ ωci­). These modes are of interest because they potentially can cause electron energy transport; additionally, these measurements advance the development of AE spectroscopy as a tool for non-invasive diagnosis of fast-ions in DIII-D and burning plasmas. Measurements of ñ mode structure for the CAEs are obtained with an array of eight fixed-frequency reflectometers (55–75 GHz) offering full coverage of the plasma minor radius under the experimental conditions (BT=1.3 T, neL=2.8 x 1019 m-3). Preliminary analysis of some CAEs (with f≈5.5 MHz=0.55 fci­) shows them to be core localized. Intermediate frequency modes were observed in beam-heated ELMing H-mode plasmas (BT=2.1 T, neL=5 x 1019 m-3) with f∼1–2 MHz∼2–5 vA/2πR (where vA/R∼0.03 ωci­). The mode frequencies sweep downward as plasma density rises during the inter-ELM period by an amount Δf/f ∼ −ΔneL/2neL, consistent with their identification as AEs. However, the frequencies are too low for CAEs and too high for toroidicity-induced or reverse shear AEs. Two-point toroidal mode number measurements yield |n|=3–6.

Presenters

  • N A Crocker

    UCLA, Univ of California - Los Angeles, University of California, Los Angeles, University of California Los Angeles, University of California Los Angeles

Authors

  • N A Crocker

    UCLA, Univ of California - Los Angeles, University of California, Los Angeles, University of California Los Angeles, University of California Los Angeles

  • Kshitish Kumar Barada

    Univ of California - Los Angeles, University of California Los Angeles, University of California, Los Angeles

  • Shawn X Tang

    Univ of California - Los Angeles, University of California, Los Angeles

  • K.E. Thome

    GA, General Atomics

  • David Carl Pace

    General Atomics - San Diego, General Atomics

  • Robert I Pinsker

    General Atomics - San Diego, GA, General Atomics, CA, USA, General Atomics

  • William Walter Heidbrink

    Univ of California - Irvine, University of California, Irvine

  • Terry L Rhodes

    Univ of California - Los Angeles, University of California, Los Angeles, UCLA, University of California Los Angeles

  • Robert John La Haye

    General Atomics, General Atomics - San Diego

  • the DIII-D Team

    General Atomics, P.O. Box 85608, San Diego, California 92186-9784