NONLINEAR-ANALYSIS OF THE TOROIDICITY-INDUCED ALFVEN EIGENMODE

A fast and efficient numerical algorithm using energy conservation is developed to study the interaction of high energy particles with a tor oidicity induced Alfven eigenmode (TAE). A Hamiltonian guiding centre code is used to simulate the alpha particle motion and a non-linear de lta f scheme is employed to calculate the wave-particle energy exchang e. For a single TAE mode, the particle radial excursion is much less t han the spacing between the resonances produced by the poloidal harmon ics for International Thermonuclear Experimental Reactor parameters. M odification of the particle distribution leading to mode saturation is observed. A TAE is found in some cases to cause loss through induced ripple trapping.