Three-Wave Interactions between Fast-Ion Modes in the National Spherical Torus Experiment

N. A. Crocker, W. A. Peebles, S. Kubota, E. D. Fredrickson, S. M. Kaye, B. P. LeBlanc, and J. E. Menard

Phys. Rev. Lett. 97, 045002 – Published 24 July 2006

Abstract

Simultaneous bursts of energetic particle mode (EPM) and toroidicity-induced Alfvén eigenmode (TAE) activity that correlate with significant fast-ion loss are observed in beam heated plasmas. Three-wave interactions between these modes are conclusively identified, indicating fixed phase relationships. This nonlinear coupling concentrates the energy of the TAEs into a toroidally localized perturbation frozen in the frame of a rigid, toroidally rotating structure formed by the EPMs. This redistribution of energy is significant because it will modify the effect of the TAEs on fast-ion loss.