ITER ECRH-ECCD system capabilities for extended physics applications

The ability of ITER electron cyclotron (EC) wave launchers to drive localized current at various plasma locations is analyzed by means of beam-tracing codes, looking at extended physics application of EC current drive in ITER and at possible synergy between the two launchers. Calculations for an improved design of the upper launcher, based on four upper ports and front steering mirrors allowing both optimum focusing of the beams and an extended plasma deposition region, show that narrow, high peak current density profiles may be maintained over the radial range 0.4 <= rho(p) <= 0.9. Calculations for the equatorial launcher, where the control of the deposition location is achieved by varying the toroidal injection angle beta, point out that because of poor localization and incomplete power absorption at large toroidal angles (beta > 40 deg), the power deposition and current drive location by this launcher is limited to rho(p) <= 0.55. Moreover, it is shown that performance close to the center can be improved with a poloidal tilt of the low and top front mirrors. The main aim of this study is to provide guidance to the design of both launchers in order to optimize their performance, depending on the physics application.