Key results of long pulse ICRH operation in Tore Supra

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.