Fast Ion Loss in a "Sea-of-TAE"
Authors: E.D. Fredrickson, N.N. Gorelenkov, R.E. Bell, J.E. Menard, A.L. Roquemore, S. Kubota, N.A. Crocker, and W. Peebles
Date of PPPL Report: July 2006
Published in: Nuclear Fusion 46:10 (2006) S926-S932
Super-thermal fast ions provide a source of free energy to excite instabilities, which in turn can enhance the loss of fast ions. It has been proposed that when multiple modes with resonances closely spaced in phase space reach sufficient amplitude that the fast ion trajectories overlap, very rapid nonlinear growth can occur. The modification of the fast ion distribution by this loss may in turn excite additional, otherwise stable, modes, leading to an "avalanche" effect greatly enhancing the transport of fast ions [Nucl. Fusion 35 (1995) 1661]. It has been proposed that in ITER [Nucl. Fusion 39 (1999) 2137], the transport of fast ions will be through a similar interaction of many modes. In NSTX [Nucl. Fusion 40 (2000) 557] bursts of multiple TAE-like instabilities are correlated with fast-ion losses in a manner which qualitatively resembles avalanche behavior.