Design concept and thermal-structural analysis of a high power reflective mm-wave optical mirror (M2) for the ITER ECH-UL

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 per line (at the FCS diamond window), into the plasma at a frequency of 170 GHz. The millimetre waves are guided through a quasi-optical section consisting of three fixed mirror sets (M1, M2 and M3) and the front steering mirror set (M4).