1 1 Interactions of RF Antennas with the Edge Plasma

Abstract. Specific phenomena arising in the vicinity of antennas operating in the Ion Cyclotron Range of Frequency (ICRF) or the Lower Hybrid Range of Frequency (LHRF) are identified on the Tore Supra tokamak. The involved mechanisms have to be investigated in order to ensure safe and controlled operation in future fusion devices. These phenomena break the symmetry of the unperturbed scrape-off layer and 2D diagnostics are needed to address this topic. This study is mainly based on measurements provided by the infra-red (IR) imaging diagnostic and the Langmuir probes. The powerful IR diagnostic which monitors the total area of the three ICRF antennas and two LHRF launchers allows a detailed analysis of the heat flux deposition in steady-state condition with a good spatial resolution (∼1cm). 2D mapping of the plasma layer in the vicinity of an ICRF antenna has been performed with a reciprocating probe by scanning the radial position of the probe and the field line tilt for poloidal resolution.. These data are complemented by calorimetric measurements of the energy extracted by the cooling loops on the antennas and their side limiters. A large database of these global measurements allows to estimate the power lost by each specific phenomena and scaling laws are proposed for a LH launcher and an ICRF antenna. This identification of heat flux deposition sources has been integrated in the real-time control system of Tore Supra in order to optimize the RF power output without deleterious effects. In such conditions discharges with 9.5MW fo