The ITER Ion Cyclotron Heating and Current Drive system will deliver 20MW of radio frequency power to the plasma in quasi continuous operation during the different phases of the experimental programme. The system also has to perform conditioning of the tokamak first wall at low power between main plasma discharges. This broad range of reqiurements imposes a high flexibility and a high availabiUty. The paper highlights the physics and design reqiurements on the IC system, the main features of its subsystems, the predicted performance, and the current procurement and installation schedide.

A general variational principle for an ICRF antenna radiating into a slab plasma is presented. The model is three-dimensional and includes the effect of connections to a transmission line. It also assumes an extent of absorption in the plasma that is sufficient to suppress eigenmodes. The variational principle gives the self-consistent currents flowing in the antenna, the fields excited inside the plasma and the antenna impedance at the generator terminals. Numerical computations are made for a TFR and a JET antenna. A study of power coupling shows that the optimum operating frequency lies near the plasma-modified resonance. The fields excited inside the plasma are found to disperse far more in the toroidal than in the poloidal direction. Also, at frequencies far from resonance, the large currents in the connections excite fields of considerably larger spatial extent than at resonance.

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The flexibility provided by a variety of ion cyclotron resonance heating (ICRH) and current drive (CD) scenarios for ITER requires that the antenna should operate at a number of frequencies spread over a wide frequency range (20-85 MHz). A short circuited strip-line antenna in which a long strap is connected in parallel with a very short section is shown to provide the frequency range of operation required for ITER. The short section acts as a matching element located within the antenna and improves the power coupling capability especially at low frequencies where the plasma coupling is generally poor. The short section also supports the feeder-line central conductor. This means there is no longer a need for a ceramic support in the immediate vicinity of the antenna that will be subjected to a harsh neutron environment in a reactor.