We consider the impact of transition particles on the Alfvén waves and electrostatic trapped ion modes in a stellarator with closed contours of the second adiabatic invariant, which do not perfectly coincide with magnetic surfaces (a so-called quasi-isodynamic (QI) stellarator). Due to orbit transitions, the damping rate of Alfvén eigenmodes on localized electrons becomes independent of the collision frequency in the broad range of low-collision rates. Dissipative trapped ion modes (Kadomtsev–Pogutse (KP) modes) induced by the ion temperature gradient (ITG) are strongly stabilized by collisionless orbit transitions.
Alfvén mode stability and wave–particle interaction in the JET tokamak: prospects for scenario development and control schemes in burning plasma experiments