Global Alfven eigenmode stability in thermonuclear tokamak plasmas

Relying on the good agreement observed between the gyrokinetic PENN model a nd the low toroidal mode number n damping measurements from JET, the stabil ity of Alfven eigenmodes (AEs) is predicted for reactor relevant conditions . Full non-local wave-particle power transfers are computed between global wavefields and alpha particles in an ITER reference equilibrium, showing th at low-n eigenmodes (n similar or equal to 2) are strongly damped and inter mediate-n eigenmodes (n similar or equal to 12) with a global radial extens ion are stable with a damping rate gamma/omega similar or equal to 0.02. Ev en though an excitation of alpha particle driven instabilities remains in p rinciple possible in reactors, this study suggests that realistic operation scenarios exist where all the AEs of global character are stable.