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(TH/4-4) Collective Effects and Self-Consistent Energetic Particle Dynamics in Advanced Tokamaks

F. Zonca¹⁾, S. Briguglio¹⁾, L. Chen²⁾, G. Fogaccia¹⁾, G. Vlad^1)
 
1) Associazone EURATOM-ENEA sulla Fusione, Frascati, Rome, Italy.
²⁾ Department of Physics and Astronomy, University of California, Irvine, CA, USA

Abstract.  In the present paper, we address the issue of fast ion and fusion product transport in conditions that are typically relevant for burning plasmas operating in so called ``Advanced Tokamak'' regimes. Our results have direct implications, e.g., on the choice of current profiles for ITER steady state operations. We demonstrate that in a Tokamak equilibrium with hollow-q profile, in general, two types of EPM (Energetic Particle Modes) gap modes may exist near the minimum-q surface and that EPM gap modes are described by the same dispersion relation of the usual resonant EPMs with, however, different dominant damping mechanisms. This work also presents a discussion of EPM stability and mode structures in connection with energetic ion transport. Numerical simulations using a Hybrid MHD-Gyrokinetic Code (HMGC), demonstrate that very fast radial redistributions of energetic ions take place above the EPM excitation threshold. These results are interpreted within the framework of non-linear phase space ``hole'' dynamics. It is found that a ``sensitive'' parameter for tokamak equilibria with hollow-q profiles is q at the minimum-q surface, higher q corresponding to larger particle transport.

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