A frictionless steering mechanism for the Front Steering ECCD ITER Upper Port Launcher

A FS launcher is being designed for the ITER upper port, which offers enhanced physics performance over the RS launcher. A two mirror system is used to decouple the focusing and steering aspects of the launcher and provide a relatively small beam waist (<20 mm) projected far into the plasma (>1.6 m from the steering mirror). The resulting NTM stabilization efficiency (maximum CD density divided by the local bootstrap current >1.6) is above marginal for the q=2 and 3/2 rational flux surfaces of the relevant ITER equilibria (scenarios 2, 3a and 5) and a factor of ~3 relative to an equivalent RS launcher. The performance of the FS launcher strongly depends on the reliability of the steering mechanism, which is used to rotate the plasma facing steering mirror. CRPP has designed a frictionless steering mechanism assembled in a compact cartridge capable of up to plusmn7deg rotation (corresponding to a poloidal steering range of up to plusmn14deg for the microwave beam around a fixed axis of rotation) that offers a high operation reliability despite the close proximity to the thermal and neutron flux coming from the ITER plasma