EFDA-JET-PR(03)48

Alfvén Mode Stability and Wave-Particle Interaction in the JET Tokamak: Prospects for Scenario Development and Control Schemes in Burning Plasma Experiment

We have investigated the effect of different Ion Cyclotron Resonance Frequency (ICRF) heating schemes, of error field modes, of the plasma shape and edge magnetic shear, and of the ion ∇B-drift direction on the stability of Alfvén Eigenmodes (AEs). The use of multi-frequency or 2nd harmonic minority ICRF heating at high plasma density gives rise to a lower fast ion pressure gradient in the plasma core and to a reduced mode activity in the Alfvén frequency range. Externally excited low-amplitude error fields lead to a much larger AE instability threshold, which we attribute to a moderate radial redistribution of the fast ions. The edge plasma shape has a clear stabilising effect on high-n, radially localised AEs. The damping rate of n=1 Toroidal AEs is a factor three higher when the ion B-drift is directed towards the divertor. These results represent a useful step towards the extrapolation of current scenarios to the inclusion of fusion-born alpha particles in ITER, with possible application for feedback control schemes for the various ITER operating regimes.
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EFDP03048 3.10 Mb