Physics analysis of the ITER ECW system for an optimized performance

A predictive analysis of the capabilities of the ITER Electron Cyclotron Wave system is presented in this work. Modifications of both the Upper Launcher and the Equatorial Launcher aimed at increasing the potentialities of the system are identified and discussed. A modification of the Upper Launcher has been already incorporated in the updated front steering design called Extended Physics Launcher. By adopting different deposition ranges for the upper and lower steering mirrors, this design offers the flexibility to drive current from the radial region required for the stabilization of neoclassical tearing modes up to that required for sawtooth control, allowing a synergy with the Equatorial Launcher. Here a comparison of the performances of the new design of the Upper Launcher with those of a Dropped Upper Launcher is performed, showing that better performances for both NTM stabilization and sawtooth control may be obtained by lowering the upper port location. An analysis of the EC current driven by the Equatorial Launcher is also presented, showing that adding to the present design the possibility to drive counter-current in addition to the existing co-current capability would significantly increase the flexibility of the system. The behaviour of all launchers at reduced magnetic fields is also discussed. PACS numbers: 52.35.Hr, 52.50.Sw, 52.55.Fa