Predictive nonlinear studies of TAE-induced alpha-particle transport in the Q=10 ITER baseline scenario

We use the HAGIS code to compute the nonlinear stability of the Q = 10 ITER baseline scenario to toroidal Alfven eigenmodes (TAE) and the subsequent effects of these modes on fusion alpha-particle redistribution. Our calculations build upon an earlier linear stability survey (Rodrigues et al 2015 Nucl. Fusion 55 083003) which provides accurate values of bulk ion, impurity ion and electron thermal Landau damping for our HAGIS calculations. Nonlinear calculations of up to 129 coupled TAEs with toroidal mode numbers in the range n = 1-35 have been performed. The effects of frequency sweeping were also included to examine possible phase space hole and clump convective transport. We find that even parity core localised modes are dominant (expected from linear theory), and that linearly stable global modes are destabilised nonlinearly. Landau damping is found to be important in reducing saturation amplitudes of coupled modes to below delta B-r/B-0 similar to 3 x 10(-4). For these amplitudes, stochastic transport of alpha-particles occurs in a narrow region where predominantly core localised modes are found, implying the formation of a transport barrier at r/a approximate to 0.5, beyond which, the weakly driven global modes are found. We find that for flat q profiles in this baseline scenario, alpha particle transport losses and redistribution by TAEs is minimal.