Stability Properties of Toroidal Alfvén Modes Driven by Fast Particles
Authors: N.N. Gorelenkov, S. Bernabei, C.Z. Cheng, K. Hill, R. Nazikian, S. Kaye, Y. Kusama, G.J. Kramer, K. Shinohara, T. Ozeki, and M.V. Gorelenkova
Date of PPPL Report: November 1999
Published in: Nucl. Fusion 40 (July 2000) 1311-1323.
In this report, the issues of Alfvén mode stability in advanced tokamak regimes are addressed based on recent developments in theory, computational methods, and progress in experiments. The instability of Toroidal Alfvén Eigenmodes (TAE) is analyzed for spherical tokamaks, such as the National Spherical Torus Experiment NSTX at the Princeton Plasma Physics Laboratory using the NOVA-K code. Chirping modes in the Alfvén frequency range observed in JT-60U during the NNBI heating at energies Eb0 = 360keV , and in the Tokamak Fusion Test Reactor (TFTR) at the Princeton Plasma Physics Laboratory during Ion Cyclotron Resonance Heating (ICRH) experiments, are analyzed using the kinetic nonperturbative code HINST, which is able to resolve new resonant branches of the toroidal Alfvén modes called resonant TAE (RTAE). However, the chirping mechanism may be different for different experiments. In TFTR frequency chirping results from the slow variation of the q-profile between sawteeth. In Japan Atomic Energy Research Institute Tokamak (JT-60U) experiments some frequency chirping modes have very short time scale which suggests the cause is due to the change in the fast particle distribution.