Development of advanced gyrotrons

Beyond ITER, a future nuclear fusion demonstration power plant (DEMO) demands gyrotron frequencies above 200 GHz and gyrotron efficiencies of higher than 60 %. The unit power must well exceed 1 MW. Fast frequency tunability in steps of 2-3 GHz (in a few seconds) using broadband or tunable CVD-diamond windows is required. Beside these fundamental requirements, slow frequency tunability (in a few minutes) in leaps of 30-40 GHz, related to the transmission maxima of plane CVD-diamond windows is considered to be advantageous for a possible multi-purpose use of these future gyrotrons. Initial feasibility studies have been performed already. Physical design studies, including the cavity, magnetron injection gun (MIG), quasi-optical output coupler and collector, have been started. This presentation will provide a comprehensive overview of the feasibility, constraints, basic design ideas and current status in the development.