Additional Heating Experiments on JET with Ion-Cyclotron Waves

The physics aspects of tokamak plasma heating with ion-cyclotron waves are reviewed in the light of initial experiments in JET. The power coupled to the plasma has reached 5.5 MW. Central temperatures of both the ions and electrons have more than doubled. Peak values reached 5 keV. The data are well represented by a law (Δ T_e0 + Δ T_i0) = aP_RF/< n_e> with a = (1.5-2) × 10¹³ keV W^-1 m^-3. The power deposition appears highly localized in the vicinity of the cyclotron resonance and preliminary experiments on the effect of local deposition on confinement have been performed. The best heating conditions are obtained with central power deposition or with a slightly outboard shift for best ion heating. These optimum conditions also correspond to large sawtooth relaxation of the temperature of the plasma core.