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(THP2/19) Drift-Kinetic Alfvén Modes in High Performance Tokamaks

A. Jaun¹⁾, A. F. Fasoli²⁾, D. Testa²⁾, J. Vaclavik³⁾, L. Villard^3)
 
1) Alfven Laboratory, Euratom-NFR Association, KTH, 100 44 Stockholm, Sweden
²⁾ Plasma Science Fusion Centre, MIT, Cambridge MA 02139, USA
³⁾ CRPP-EPFL, 1015 Lausanne, Switzerland

Abstract.  The stability of fast-particle driven Alfvén eigenmodes is modeled in high performance tokamaks, successively with a conventional shear, an optimized shear and a tight aspect ratio plasma. A large bulk pressure yields global kinetic Alfvén eigenmodes that are stabilized by mode conversion in the presence of a divertor. This suggests how conventional reactor scenarii could withstand significant pressure gradients from the fusion products. A large safety factor in the core q₀ > 2.5 in deeply shear reversed configurations and a relatively large bulk ion Larmor radius in a low magnetic field can trigger global drift-kinetic Alfvén eigenmodes that are unstable in high performance JET, NSTX and ITER plasmas.

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