Plasma heating of a Tokamak plasma by wave coupling in the ion cyclotron range of frequency has been investigated during the last decade along several schemes: in a two-ion plasma containing comparable amounts of the ion components, wave conversion heating is expected to couple the main part of the power to the electrons. For a small fraction of one of the two components, the power will be coupled by minority heating to the low density ion species. Heating of a single ion plasma requires power coupling at the second harmonic frequency. The theoretical basis for those three mechanisms will be qualitatively reviewed.Wave conversion heating has been particularly investigated in the TFR Tokamak. The experimental results will be reviewed underlining the important role played by metallic impurities on the evolution of ion and electron temperatures and the severe limitation on electron temperature observed in all conditions.The principal results on minority heating have been obtained on PLT and JET Tokamaks where up to 5 M W of radio frequency power have been coupled to the plasma. In both cases. evolution of the electron temperature is limited by the occurence of large amplitude sawtooth oscillations. While the ion temperature reaches much larger values than the electron temperature in PLT, this is not the case in JET where the sawteeth determine also the evolution of the ion temperature. 'This can be explained by the large difference in the central power density in the two machines.Decay of the energy containment time is observed in all ion cyclotron heating experiments. This is particularly evidenced by the very small heating efficiency in JET outside the q = 1 surface.The experimental data obtained until now on second harmonic heating will be briefly summarized.

The power deposition profile in the ion cyclotron range of frequencies (ICRF) has been investigated experimentally in JET by means of a square wave modulated RF perturbation. The study has been conducted in D(H) and D(3He) plasmas for two heating scenarios. In D(3He) plasmas and for central heating in a scenario where mode conversion to Bernstein waves is accessible, the direct power deposition profile on electrons has been derived. It accounts for 15% of the total coupled power and extends over 25% of the minor radius. Outside the RF power deposition zone, the electron thermal diffusivity χe inside the inversion radius surface (ri) can be estimated through observation of the diffusive electronic transport. In discharges without monster sawteeth and for a low central temperature gradient (∇Te(r ≤ ri) ≤ ∇Te(r ≥ ri) ≈ 5 keV·m−1) the value obtained is small (≈ 0.24 ± 0.05 m2·s−1), typically ten times ower than χe values deduced from heat pulse propagation in similar discharges at radii larger than the inversion radius. For the D(H) minority heating scheme, a large fraction of the ICRF modulated power is absorbed by minority ions, and the minority tail is modulated with a characteristic ion-electron (i–e) slowing-down time. In this scheme, electron heating occurs only through collisions with the minority ion tail and no modulation of the electron temperature is observed in sawtoothing discharges. This is interpreted as a consequence of the long i–e equipartition time, acting as an integrator for the modulated ICRF signal. Finally, a correlation between the time of the sawtooth crash and the periodic turn-off of the ICRF power is found and its consequence for modulation experiments is reviewed.

The interaction of ultraintense laser beams with underdense plasma slabs has been investigated with two-dimensional particle-in-cell numerical simulations, showing a strong absorption and a correlatively low transmission. Energetic electrons in the multi-MeV range are produced. At very high intensities the plasma transparency is recovered. These results are interpreted in terms of the development of electron parametric instabilities in the self-consistently heated plasma.