EFDA-JET-PR(02)02

Measurement of the Damping Rate of n = 1 Toroidal Alfvén Eigenmodes as a Function of the Neutral Beam Heating Power and plasma β on JET.

The dependence of the measured damping rate upon the Neutral Beam Heating power (PNBI) and plasma β has been experimentally investigated for n = 1 Toroidal Alfvén Eigenmodes (TAEs) in JET limiter plasmas with a monotonic safety factor profile and low edge magnetic shear. The mode frequency is observed to decrease with increasing Beta, as predicted by various theoretical models. For low PNBI<3MW, a single n = 1 TAE splits into two modes closely spaced around the expected TAE frequency, and the mode damping rate decreases with increasing β. On the other hand, at higher PNBI>6MW, no frequency splitting is observed and there are indications that the mode damping rate increases with increasing β.
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EFDP02002 497.20 Kb