Active Control of Alfve acute accent n Eigenmodes by Externally Applied 3D Magnetic Perturbations

The suppression and excitation of Alfve ' n eigenmodes have been experimentally obtained, for the first time, by means of externally applied 3D perturbative fields with different spatial spectra in a tokamak plasma. The applied perturbation causes an internal fast-ion redistribution that modifies the phase-space gradients responsible for driving the modes, determining, ultimately their existence. Hybrid kinetic-magnetohydrodynamic simulations reveal an edge resonant transport layer activated by the 3D perturbative field as the responsible mechanism for the fast-ion redistribution. The results presented here may help to control fast-ion driven Alfve ' nic instabilities in future burning plasmas with a significant fusion born alpha particle population.