Experimental verification of the European 1 MW, 170 GHz industrial CW prototype gyrotron for ITER

The EU 1 MW, 170 GHz gyrotron with hollow cylindrical cavity have been designed within the European GYrotron Consortium (EGYC) in collaboration with the industrial partner Thales Electron Devices (TED) and under the coordination of Fusion for Energy (F4E). In the frame of the EU program, the short-pulse (SP) version of this tube was designed and manufactured by KIT in collaboration with TED. The experimental verification of the SP gyrotron prototype was successfully completed in 2015. The achieved experimental results show a very stable gyrotron operation with RF output power above 1 MW at good cavity interaction efficiency around 35%. The gyrotron was operated up to 10 ms pulse length; the nominal cavity mode TE32,9 has been excited at the frequency 170.1 GHz in agreement with the corresponding ITER specification. The Gaussian mode content of the output RF beam was about 98% and the total level of internal stray radiation was in the range of 2-3%. The manufacturing of the first industrial continuous-wave (CW) prototype gyrotron, based on the SP gyrotron design, was completed in November 2015 at TED. The tube was delivered to KIT and the experimental verification started in February 2016. Operation of the gyrotron with ms pulse duration resulted in stable excitation of the nominal mode at 170.22 GHz for a wide range of operating parameters and with a level of stray radiation comparable with the SP version. The maximum RF power achieved up to now in short-pulse operation at a level of 1 MW. The measured Gaussian mode content of the RF beam is 97%. Currently, further preparation for the CW operation of the gyrotron is in progress. (C) 2017 Published by Elsevier B.V.