Channeling of the energy and momentum during energetic-ion-driven instabilities in fusion plasmas.

New features of instabilities driven by energetic ions are revealed. It is found that these instabilities can affect plasma heating and rotation by channeling the energy and momentum of the energetic ions to the region where the destabilized waves are damped. Because of the energy channeling, the plasma core may not be heated by the energetic ions even when these ions have a very peaked radial distribution.

Novel mechanism of anomalous electron heat conductivity and thermal crashes during Alfvénic activity in the Wendelstein 7-AS stellarator.

Enhanced plasma heat conductivity in the presence of kinetic Alfvén waves (KAW) is predicted theoretically. The enhancement is shown to be strongest when the electron collision frequency exceeds the particle transit frequency in the wave field. Alfvén waves (both KAW and ideal MHD Alfvén eigenmodes generating the KAW) are studied in a shot of the Wendelstein 7-AS stellarator.

Small-action particles in a tokamak in the presence of an n = 1 mode.

It is found that an m = n = 1 mode with amplitude exceeding a certain threshold can lead to stochastic motion of energetic ions in tokamaks, the large orbit width particles (potatoes) being most easily affected. An n = 1 mode can redistribute particles also in the absence of stochasticity but only when the perturbation is quickly switched on/off, e.g.