Thermal analyses of the mm-waveguide cooling concepts for the ITER electron cyclotron upper launcher first confinement system

The ITER Electron Cyclotron Heating Upper Launcher (ECHUL) will be used to drive current locally inside magnetic islands located at the q = 2 (or smaller) rational surfaces in order to stabilize neoclassical tearing modes (NTMs). Each antenna consists of eight beam lines that are designed for the transmission of up to 1.5 MW of mm- wave power at 170 GHz, with at least 90% of the power in the main HE11 mode. Mm-wave power is assumed to be converted into heat by ohmic dissipation in the waveguide, with intensity peaks reaching up to 9000 W/m(2), consequently to enable continuous working operation at nominal transmitted power, temperature control of the waveguide is required via an active cooling system. Available commercial solutions for the cooled waveguide are incompatible with the FCS, which will be subject to higher heat fluxes and shall comply with ITER SIC-1 requirements. Therefore a dedicated cooling system must be designed. This study presents the results of the thermal mechanical analyses of two different cooling concepts, and concludes the most suitable concept for the final Upper Launcher FCS system design. (C) 2017 Elsevier B.V. All rights reserved.