On the confinement of passing alpha particles in a tokamak-reactor with resonant magnetic field perturbations shielded by plasma currents

Alpha-particle losses due to the resonant magnetic field perturbations (RMPs) created by the coil system for edge-localized mode mitigation in ITER are studied numerically. If shielding of RMPs by the plasma is not taken into account, passing α-particles are the main loss channel which, together with the trapped particle contribution leads to a loss of more than 5% of fusion alpha particle power. Shielding of RMPs practically eliminates this channel so that the overall losses are reduced to about 1%. (paper)