Internal Kink Mode Dynamics in High-β NSTX Plasmas
Authors: J.E. Menard, R.E. Bell, E.D. Fredrickson, D.A. Gates, S.M. Kaye, B.P. LeBlanc, S.S. Medley, W. Park, S.A. Sabbagh, A. Sontag, D. Stutman, K. Tritz, W. Zhu, and the NSTX Research Team.
Date of PPPL Report: December 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.
Saturated internal kink modes have been observed in many of the highest toroidal beta discharges of the National Spherical Torus Experiment (NSTX). These modes often cause rotation flattening in the plasma core, can degrade energy confinement, and in some cases contribute to the complete loss of plasma angular momentum and stored energy. Characteristics of the modes are measured using soft X-ray, kinetic profile, and magnetic diagnostics. Toroidal flows approaching Alfvénic speeds, island pressure peaking, and enhanced viscous and diamagnetic effects associated with high-beta may contribute to mode nonlinear stabilization. These saturation mechanisms are investigated for NSTX parameters and compared to experimental data.