Thermal mechanical analyses of the mm-wave miter bend for the ITER electron cyclotron upper launcher first confinement system

Each of the 4 ITER Electron Cyclotron Heating Upper Launcher (ECHUL) features 8 transmission lines used to inject microwave power of up to 1.31 MW (at the source) per line, into the plasma at 170 GHz. The microwaves are guided from the gyrotrons via (empty set 50 mm) waveguide transmission lines, into the plasma via the First Confinement System (FCS), consisting of a 'Z'-shaped set of straight corrugated aluminum waveguides, totaling similar to 13 m per line, connected by miter bends (MB). The orientation of the transmission line is achieved by reflecting the microwaves with mirrors. The MBs perform these reflections at angles of similar to 90 degrees; they also form part of the primary vacuum boundary and serve as a Tritium barrier, for which SIC-1 safety classification requirements apply.