Gyrotron: Basics and Trends

Europe develops and manufactures megawatt-class gyrotrons for electron cyclotron heating and current drive of nuclear fusion experiments. For the gyrotron R&D at Europe, two important fusion experiments are the stellarator Wendelstein W7-X at Greifswald, Germany and the tokamak ITER at Cadarache, France. Considering the 10 MW ECRH system of W7-X, 140 GHz, 1 MW CW (1800 s) gyrotrons were built by European industrial partner THALES, Vélizy-Villacoublay, France (Thales TH1507). The gyrotrons performed reliably during the first experimental campaign of W7-X. Based on that success, an ongoing development targets for a W7-X 140 GHz, 1.5 MW gyrotron upgrade (THALES TH1507U). Already operating is another variant of the W7-X TH1507 gyrotron, it is the dual-frequency 126 GHz / 84 GHz, 1 MW (2 s) gyrotron for the TCV tokamak at SPC, EPFL, Switzerland (THALES TH1510). Considering ITER, the European GYrotron Consortium (EGYC) completed the main development of the European 170 GHz, 1 MW CW gyrotron (THALES TH1509). In parallel, long-term options for a European DEMOnstration power plant are under consideration. It requires the development of gyrotrons with an operating frequency starting from 136 GHz up to, possibly, 240 GHz. ... mehrAn RF output power of 2 MW is considered. Frequency tuning in steps of around 2–3 GHz is considered for plasma control. Multi-purpose operation at frequencies with leaps of about 34 GHz is considered for plasma start-up, heating and current drive at different operating scenarios. To achieve efficiencies significantly above 50 %, a concept for a multi-stage depressed collectors (MDC) is under investigation. Considering advanced gyrotron operation, technologies for electronic stability control, second harmonic operation and frequency-/phase-locking are under consideration. Finally, to be properly equipped for testing of future DEMO gyrotrons, KIT built its new gyrotron test facility named FULGOR. This presentation introduces into gyrotron basics in combination with providing a view over ongoing activities and trends at Europe.