RF heating and current drive for burning plasma experiments

The main world effort on burning plasma experiments is presently focused on ITER. RF heating and current drive techniques include ion cyclotron resonance frequency (ICRF), electron cyclotron resonance frequency (ECRF) and lower hybrid current drive (LHCD) systems. The role of RF is not only for bulk plasma heating, but is now essential to optimize both the reference scenario (MHD stabilization) and the advanced scenarios (current profile control) in ITER. High power RF systems with good reliability are clearly a challenge in a burning plasma environment. Launchers are first wall components facing large thermal and neutron loads and shall also provide for an effective neutron shielding. High efficiency RF sources have to be located at a large distance from the machine and very low losses transmission lines have to be provided. High unit power RF tubes with very long pulses, i.e. in effect steady state, have to be developed, which is more and more difficult when the frequency increases. Actuators using RF systems for real time plasma control have to be inserted in real time control loops for optimization of ITER performances. A brief review of the role, of the technical constraints and of the technical features of the RF systems foreseen for ITER is given indicating the areas where technical progress remains to be made.