Design of a high power millimeter wave launcher for EC H&CD system on ITER

Kajiwara, Ken; Takahashi, Koji; Kobayashi, Noriyuki; Kasugai, Atsushi; Sakamoto, Keishi

An optimization procedure of the quasi-optical system for millimeter wave launcher is developed for the ITER electron cyclotron heating and current drive (EC H&CD) launcher. In the launcher, the radiated RF beams from 8 corrugated waveguides are reflected sequentially by two finite-sized mirrors and radiated into a plasma through the small aperture of the blanket shield module on the top of the launcher. Using a steepest decent method, the heat load on the mirrors are successfully reduced to the acceptable level by flattening the RF power profile on the mirrors keeping the spilling out of the RF power minimum from the mirrors. It is found that 20 MW injection will be acceptable even when the resistivity of 2.64 m for the surface of the mirror (Dispersion strengthened copper, 151C assumed) is increased by factor 10 with a contamination.