Resonant interaction of energetic ions with bulk-ion plasma micro-turbulence

Abstract

A significant fast ion-induced stabilization is observed in linear and nonlinear GENE gyrokinetic simulations, which can be attributed to a resonant interaction between energetic particles and the main-ion-temperature gradient driven plasma turbulence. Elaborating on the findings in Di Siena et al. [Nucl. Fusion 58, 054002 (2018)], a detailed study of this mechanism is conducted for realistic JET-like parameters. In view of further exploitation of the beneficial role of energetic ions and corresponding confinement optimization, linear scans over the main fast ion parameters and magnetic plasma geometry are performed. All these results can be reproduced with a reduced Vlasov-Poisson theoretical model and be explained in terms of modifications on the fast ion energy production/dissipation in the energy balance equation. Finally, despite the essentially linear nature of the resonant interaction, a corresponding nonlinear analysis is also performed and its main dependences are captured with a quasi-linear model.