Internal Alfvén eigenmode observations on DIII-D

Journal Article · Sun Oct 01 00:00:00 EDT 2006 · Nuclear Fusion

DOI:https://doi.org/10.1088/0029-5515/46/10/S03· OSTI ID:1170887

Van Zeeland, M. A. ^[1]; Austin, M. E. ^[2]; Carlstrom, T. N.; Deterly, T. ^[3]; Finkenthal, D. K. ^[3]; Holcomb, C. T. ^[4]; Jayakumar, R. J. ^[4]; Kramer, G. J. ^[5]; Makowski, M. A. ^[4]; McKee, G. R. ^[6]; Nazikian, R. ^[5]; Peebles, W. A. ^[7]; Rhodes, T. L. ^[7]; Solomon, W. M. ^[5]; Strait, E. J.

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1. Oak Ridge Inst. for Science and Education (ORISE), Oak Ridge, TN (United States)
2. Univ. of Texas, Austin, TX (United States)
3. Palomar College, San Marcus, CA (United States)
4. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
5. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
6. Univ. of Wisconsin, Madison, WI (United States)
7. Univ. of California, Los Angeles, CA (United States)

Recent upgrades to many of the diagnostic systems on DIII-D (Luxon J.L. 2002 Nucl. Fusion 42 614), such as the CO₂ interferometer, far-infrared scattering, beam-emission spectroscopy (BES), and quadrature reflectometer, have significantly extended their capabilities and made possible the experimental study of Alfvén eigenmodes (AEs) through observation of the AE induced density perturbation. Measurements have shown the presence of several different classes of AEs in DIII-D discharges, including the toroidal Alfvén eigenmode (TAE), reverse shear AE (RSAE or Alfvén cascade), and ellipticity induced Alfvén eigenmode. Based on a simple model for the RSAE frequency, a sensitive diagnostic for the evolution of the minimum magnetic safety factor (q_min) is presented. Results are compared with motional Stark effect (MSE) measurements. Strong localization of high toroidal mode number RSAEs to regions near the minimum of the magnetic safety factor is exhibited on the CO₂ interferometer and BES measurements. Based on this observation, a method for providing constraints on the radial location of q_min is demonstrated and a favourable comparison to MSE measurements is made. Detailed measurements of TAEs using a new all-digital large bandwidth two-colour CO₂ interferometer system reveal a strong asymmetry between vertical and radial viewing interferometer chords, confirming previously reported results. Additionally, effects related to line-integrated observations are clearly illustrated by comparison to local BES measurements. Potential issues related to this are discussed.

• Research Organization: Oak Ridge Inst. for Science and Education (ORISE), Oak Ridge, TN (United States); Univ. of Texas, Austin, TX (United States); Palomar College, San Marcus, CA (United States); Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Univ. of Wisconsin, Madison, WI (United States); Univ. of California, Los Angeles, CA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: DE-AC05-76OR00033; DE-FC02-04ER54698; DEFG03- 97ER54415; DE-AC02-76CH03073; W-7405-ENG- 48; DE-FG03-96ER54373; DE-FG03-01ER54615
• OSTI ID: 1170887
• Journal Information: Nuclear Fusion, Vol. 46, Issue 10; ISSN 0029-5515
• Publisher: IOP Science
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
Instrumentation and Measurement
Plasma Physics