The Combined Effect of EPM and TAE Modes on Energetic Ion Confinement and Sawtooth Stabilization
Authors: S. Bernabei, R. Budny, E.D. Fredrickson, N.N. Gorelenkov, J.C. Hosea, C.K. Phillips, R. White, J.R. Wilson, C.C. Petty, R.I. Pinsker, R.W. Harvey, and P. Smirnov
Date of PPPL Report: November 2000
Date of Revised PPPL Report: May 2001
Presented at: the 18th International Atomic Energy Agency's (IAEA) Fusion Energy Conference 2000 (FEC-2000) held in Sorrento, Italy, October 4-10, 2000. Submitted to the Nuclear Fusion Journal for publication.
It is shown in this paper for the first time, that the chirping Alfvén instabilities observed mostly during ion cyclotron range of frequency (ICRF) heating have been positively identified as Energetic Particle Modes (EPM). This has been possible because of the detailed measurement of the q-profile with the MSE (motional Stark effect) diagnostic in DIII-D. The EPMs are shown to be the leading cause of the monster sawtooth crash. It is also shown that TAEs are excited either directly or indirectly by the EPMs and they cause fast ion losses. A scenario for the stabilization and the crash of the monster sawtooth and for the degradation of the ICRF heating efficiency at high power is presented.