PPPL-4015 is available in pdf format (3.0 MB).

Observation of Energetic Particle Driven Modes Relevant to Advanced Tokamak Regimes

Authors: R. Nazikian, B. Alper, H.L. Berk, D. Borba, C. Boswell, R.V. Budny, K.H. Burrell, C.Z. Cheng, E.J. Doyle, E. Edlund, R.J. Fonck, A. Fukuyama, N.N. Gorelenkov, C.M. Greenfield, D.J. Gupta, M. Ishikawa, R.J. Jayakumar, G.J. Kramer, Y. Kusama, R.J. La Haye, G.R. McKee, W.A. Peebles, S.D. Pinches, M. Porkolab, J. Rapp, T.L. Rhodes, S.E. Sharapov, K. Shinohara, J.A. Snipes, W.M. Solomon, E.J. Strait, M. Takechi, M.A. Van Zeeland, W.P. West, K.L. Wong, S. Wukitch, and L. Zeng

Date of PPPL Report: October 2004

Presented at: the 20th IAEA Fusion Energy Conference, 1-6 November 2004, Vilamoura, Portugal. The papers will be published by the IAEA as unedited proceedings in electronic format on CD-ROM and on the IAEA Physics Section web site as soon as possible after the conference.

Measurements of high-frequency oscillations in JET [Joint European Torus], JT-60U, Alcator C-Mod, DIII-D, and TFTR [Tokamak Fusion Test Reactor] plasmas are contributing to a new understanding of fast ion-driven instabilities relevant to Advanced Tokamak (AT) regimes. A model based on the transition from a cylindrical-like frequency-chirping mode to the Toroidal Alfvén Eigenmode (TAE) has successfully encompassed many of the characteristics seen in experiments. In a surprising development, the use of internal density fluctuation diagnostics has revealed many more modes than has been detected on edge magnetic probes. A corollary discovery is the observation of modes excited by fast particles traveling well below the Alfvén velocity. These observations open up new opportunities for investigating a "sea of Alfvén Eigenmodes" in present-scale experiments, and highlight the need for core fluctuation and fast ion measurements in a future burning-plasma experiment.