Interaction of ICRF power and edge plasma in Tore Supra ergodic divertor configuration

The coupling of ICRF power to plasma is a crucial problem in Tore Supra for high power and long pulse operations and depends greatly on the edge param eters, in particular on the edge density. Conversely, the behaviour of the bulk plasma is related to the edge conditions and the injection of RF power also induces major modifications on the edge plasma. Moreover, the Ergodic Divertor (ED) of Tore Supra imposes a complex configuration at the edge du e to the presence of the magnetic perturbation. Several diagnostics are ava ilable to study the interaction of ICRF power with the edge plasma: Langmui r probes on the ED modules, infra red (IR) cameras, charge exchange neutral analysers. In minority heating scheme, the edge density is very sensitive to any perturbation in the high recycling regime which is always found in t he ED configuration for relevant plasma parameters. Partially detached regi mes, with or without inhomogeneities of density and temperature induced by the flux tubes of the laminar layer, are obtained for high resistance coupl ing values. The coupling is then not very robust and feedback control or an tenna automatic matching techniques are developed. In fast wave electron he ating scheme with ED, various fast wave absorption mechanisms (minority hea ting, Mode Conversion, Alfven resonance) are present at the plasma edge due to the large size of the plasma. The ICRF coupling is difficult due to the low fast wave direct electron damping, even with high hydrogen minority sc heme. An increase of the injected ICRF power could improve this situation. (C) 2000 Elsevier Science B.V. All rights reserved.