Optimization of millimeter wave system in ITER Equatorial EC H&CD Launcher

• We improved the millimeter wave design of the ITER Equatorial EC H&CD Launcher.
• The transmission efficiency inside the launcher is increased to 99.1% while maintaining the narrow opening and beam concentration at plasma.
• An effect of the high order mode inside the launcher is estimated by using the high power beam pattern.
• The 1–2% additional loss inside the launcher is appeared, which is the first quantitative analysis of the high order mode effect in the launcher.

A high power (20 MW) and CW millimeter wave (mm-wave) injection is planned for Electron Cyclotron Heating and Current Drive (EC H&CD) in ITER. An optimization of the mm-wave system for the ITER EC H&CD Equatorial Launcher (EL) is performed. The optimization of the system is aimed to obtain the maximum transmission efficiency on the condition that 1.8 MW injection per waveguide, ∼20 cm in beam radius at the resonance layer and narrow opening of the Blanket Shielding Module (BSM). The transmission efficiency of 99.1% from the end of the waveguide inside the launcher to the output of the BSM is achieved.The mm-wave propagation with high order modes is also calculated by using an experimentally obtained high power mm-wave beam pattern that includes 95%HE11, 0.6%LP11, 0.2%LP02 and 4.2% other higher order modes. The analysis predicts the 1–2% additional loss will be induced by the high order modes.