.

Global Alfvén Eigenmodes Stability in
Thermonuclear Tokamak Plasmas

A.JAUN¹, A.FASOLI^2,3, J.VACLAVIK⁴, L.VILLARD<sup>4

1</sup> Alfvén Laboratory, EURATOM-NFR Association, KTH, 100 44 Stockholm, Sweden

² Plasma Science and Fusion Center, MIT, Cambridge MA 02139, USA

³ JET Joint Undertaking, Abingdon, Oxfordshire OX14 3EA, United Kingdom

⁴ CRPP, Association EURATOM-Confédération Suisse, EPFL, 1015 Lausanne, Switzerland

Relying on the good agreement observed between the gyrokinetic PENN model and the low toroidal mode number n damping measurements from JET, the stability of Alfvén 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 that low $n\simeq 2$ eigenmodes are strongly damped and intermediate $n\simeq 12$ eigenmodes with a global radial extension are stable with a damping rate $\gamma/\omega\simeq 0.02$. Even though an excitation of $\alpha -$particle driven instabilities remains in principle possible in reactors, this study suggests that realistic operation scenarii exist where all the AEs of global character are stable.

Subject classification code: D0Tt