Design of the remote-steering ITER ECRH upper-port launcher

In order to exploit the capability of electron cyclotron waves (ECW) for localized heating and current drive over a large range of plasma radii in ITER, the electron cyclotron heating (ECH) and current drive (CD) upper port launcher needs a beam steering capability. In this paper the remote steering (RS) option is described as it is being studied by a number of European institutes. For the remote-steering approach a number of critical design issues were identified by the EFDA and ITER-IT teams. All technical design issues could be solved but the performance of the system, as far as stabilization of neoclasical tearing modes (NTMs) is concerned was not sufficient for all the required ITER plasma scenarios. In order to overcome this, new design efforts are ongoing in order to improve the performance of the RS setup at the relevant NTM positions. An increase of the square wave-guide length to around 9 m is foreseen to enhance the current-drive capability to the minimum levels that are needed to stabilize the 3/2 and 2/1 NTM modes in nearly all ITER scenarios.