Design considerations for future DEMO gyrotrons : a review on related gyrotron activities within EUROfusion
J. Jelonnek, G. Aiello, S. Alberti, K. Avramidis, F. Braunmueller, A. Bruschi, J. Chelis, J. Franck, T. Franke, G. Gantenbein, S. Garavaglia, G. Granucci, G. Grossetti, S. Illy, Z. Ioannidis, J. Jin, P. Kalaria, G. Latsas, I. Pagonakis, T. Rzesnicki, S. Ruess, T. Scherer, M. Schmid, D. Strauss, C. Wu, I. Tigelis, M. Thumm, M. Tran
Fusion engineering and design, 2017, Sep, 123, pp. 241–246
Abstract
Long-term options for a steady-state DEMOnstration power plant may require the availability of gyrotrons with an operating frequency significantly above 200 GHz together with an RF output power of more than 1 MW and a total gyrotron efficiency of better than 60%. Frequency tuning in steps of around 2–3 GHz might be needed for control of plasma stability. Multi-purpose operation at frequencies with leaps of about 30 GHz might be considered for plasma start-up, heating and current drive at different operation scenarios. The combination of those requirements clearly challenges present-day technological limits. The R&D work within the EUROfusion WP HCD EC Gyrotron R&D and Advanced Developments is focusing on named targets. In particular, a centre frequency of around 240 GHz is under investigation. The coaxial-cavity gyrotron technology, and, as a possible fallback solution, the conventional hollow-cavity are under investigation. Both options are studied with regards to maximum achievable output power versus efficiency, operation stability and tolerances. Concerning the coaxial-cavity technology, an additional experimental investigation shall verify the predicted operation capabilities. Various promising concepts for multi-stage depressed collectors (MSDC) are under investigation. The research and development are completed by advancing the simulation and test tools capabilities significantly.