Scaling of Kinetic Instability Induced Fast Ion Losses in NSTX
Authors: E.D. Fredrickson, D. Darrow, S. Medley, J. Menard, H. Park, L. Roquemore, D. Stutman, K. Tritz, S. Kubota, and K.C. Lee
Date of PPPL Report: June 2005
To be presented at: the Thirty-Second EPS Conference on Plasma Physics (EPS 2005), 27 June - 1 July 2005, Tarragona, Spain.
During neutral beam injection (NBI) in the National Spherical Torus Experiment (NSTX), a wide variety of fast ion driven instabilities is excited by the large ratio of fast ion velocity to Alfvén velocity, together with the relatively high fast ion beta, βf. The fast ion instabilities have frequencies ranging from a few kilohertz to the ion cyclotron frequency. The modes can be divided roughly into three categories, starting with Energetic Particle Modes (EPM) in the lowest frequency range (0 to 120 kHz), the Toroidal Alfvén Eigenmodes (TAE) in the intermediate frequency range (50 to 200 kHz) and the Compressional and Global Alfvén Eigenmodes (CAE and GAE, respectively) from approximately equal to 300 kHz up to the ion cyclotron frequency. Each of these categories of modes exhibits a wide range of behavior, including quasi-continuous oscillation, bursting, chirping and, except for the lower frequency range, turbulence.