Conceptual Design of a Modular EC System for EU-DEMO

The DEMO reactor studies within EUROfusion aim to develop a fusion power plant concept. The large tokamak device needs an auxiliary heating power which, at the present stage, is provided by the Electron Cyclotron (EC) Heating system with up to 130 MW foreseen to reach different regions of plasma for heating, suppression of instabilities and possibly supporting ramp-up and ramp-down phases. The present conceptual design of the system is based on 2-MW coaxial-cavity gyrotron sources, a transmission line using both circular corrugated waveguides and a quasi-optical evacuated multi-beam transmission line, and mirror antennas located in the Equatorial port. In order to create a modular system, the sources are grouped in "clusters", whose power is combined in the quasi-optical transmission line, up to the tokamak building, where they are split and routed as single waveguides. In the launcher, they are combined together again on the launching mirrors, to save space for the apertures in the Breeding Blanket. The present EC system has a certain flexibility to adapt to changing design guidelines, as the foreseen transition to a lower DEMO aspect ratio. The system and the development status of each subsystem will be presented.