Development of high power window prototypes for ECH&CD launchers

Torus window prototypes for electron cyclotron (EC) heating and current drive (H&CD) systems are developed for different launcher concepts in accordance with the specific transmission requirements. For ITER, single-disk windows are designed for 2 MW power transmission at fixed frequency (170 GHz) in two variants. For the RS launcher, the remote steering unit is placed close to the torus window in the launcher back-end which calls for a large window aperture (95 mm) to avoid beam vignetting at the extreme steering angles of ±12°. For the FS launcher with the steering mechanism placed in the front shield of the launcher, the aperture and the disk thickness are reduced as the torus window is integrated into a cylindrical waveguide configuration with an inner diameter of 63.5 mm. The reduced absorbed power and cooling paths allow to consider indirect cooling as an alternative to edge cooling which eliminates the risk of tritium contact to the cooling water in case of crack formation in the diamond disk. For the multifrequency torus window at ASDEX Upgrade (aperture: 80 mm), a double-disk configuration is realised with the disk separation of 5 mm, fine tuneable over ±1 mm. Prototypes of the high power windows were manufactured. First results of the current thermo-hydraulic and of the mm-wave performance tests support the feasibility of the concepts. For the ITER torus windows, the tool development is described which provides on-site replacement by automated cutting and welding tools.