A 20 MW/5GHz Lower Hybrid Current Drive (LHCD) system was initially due to be commissioned and used for the second mission of ITER, i.e. the Q=5 steady state target. Though not part of currently planned procurement phase, it is now under consideration for an earlier delivery. In this paper, both physics and technology conceptual designs are reviewed.

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.

Long pulse operation on the Tore Supra tokamak has entered a new phase, characterized by the use of heating power level in excess of 10 MW, during pulses lasting several tens of resistive times. This has been made possible by the use of ion cyclotron range of frequency (ICRF) heating (9 MW coupled to the plasma at 57 MHz), combined with lower hybrid current drive (LHCD: 3 MW at 3.7 GHz) and efficient fuelling techniques (supersonic gas injection, pellets). This paper addresses key technological, operational and physics issues related to the long pulse operation of the Tore Supra ICRF system and required for a reactor: R&D on the ICRF plant, real-time control and safety procedures, integration with other tokamak subsystems, experimental investigation and theoretical modelling of the edge ICRF physics (wave coupling, heat loads on antenna front faces). As far as possible lessons are drawn from the experience gained on Tore Supra for the design and operation of a next-step device.

n the framework of the ion cyclotron resonance frequency (ICRF) heating development at CEA Cadarache, a prototype antenna based on the load-resilient electrical layout foreseen for ITER has been built. This prototype was recently tested in Tore Supra. The ITER-like electrical scheme has been validated during fast perturbations at the edge plasma. Clear load resilience properties are reported. Main conclusions and consequences to be learned for the development of ITER antenna are discussed.

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A systematic study of the thermal behaviour of ion cyclotron range of frequencies (ICRF) antenna front faces was undertaken on the Tore Supra tokamak over two years of plasma operation, by means of infrared (IR) and visible light cameras. Among the variety of edge-antenna interaction phenomena observed experimentally, the present paper focuses on the most deleterious effect for ICRH operation, a non-resonant radio-frequency (RF) process causing hot spots on the Faraday screen and bursts of metallic impurities. The hot spots phenomenology (time history, location) is presented. Their magnitude is characterized by semi-quantitative indicators, defined from the IR and visible light films. This makes possible a parametric study of the antenna–plasma interaction, over a wide range of experimental configurations. The roles of the local RF electric field and of the edge density regimes in the spurious process are outlined. The observed hot spot behaviour is compatible with the build-up of RF sheaths. Some ways of reducing the problems are suggested.

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