Alfvén Laboratory, Teknikringen 31, KTH, SE-100 44 Stockholm, Sweden
+) PSFC-MIT, Cambridge MA 02139, USA and
JET, Abingdon, Oxfordshire OX14 3EA, United Kingdom
*) CRPP, EPFL, CH-1015 Lausanne, Switzerland
Alfvén eigenmodes (AEs) with intermediate toroidal mode numbers are modeled using the global gyrokinetic PENN code to determine the stability of high performance tokamak discharges in the presence of energetic particles. A large plasma pressure and a weak magnetic shear in the core give rise to radially extended kinetic AEs, which are stabilized by the high shear at the edge of a divertor (X-point) configuration. Large values for the safety factor and the ion Larmor radius in reversed shear operation may however trigger drift-kinetic Alfvén eigenmodes (DKAE) instabilities that could affect the alpha-particle confinement in a reactor.
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