Development in Russia of Megawatt Power Gyrotrons for Fusion

Full text: During last years several new gyrotrons were designed and tested at IAP/GYCOM. Main development efforts were spent for development 170 GHz/1 MW/50%/CW gyrotron for ITER and multi-frequency gyrotrons. The applied test facility at Kurchatov Institute was upgraded to extend its testing capabilities and to approach them to the ITER specifications. The use of evacuated waveguide assumed for ITER will thoroughly solve a problem of RF arcing. The industrial production prototype of the ITER gyrotron was tested at power 1.02 MW in 200 second pulses, 0.65 MW in 800 second pulses. For 1 MW power regime the gyrotron efficiency is 52%. The pulse energies were limited by overheating of the collector insulator. For the new gyrotron version the modifications have been made in the collector insulator cooling system and they will allow the gyrotron to run at ITER nominal parameters. The last gyrotron version operates in LHe-free magnet. In 2008/2009 an advanced short-pulse (100 mcs) gyrotron model operating with TE28.12 mode was tested at IAP. The model showed a very robust operation (microwave power up 2 MW with electronic efficiency of 34%) at relatively high electron energies necessary to achieve the high goal power. A gyrotron capable to operate at several frequencies is very attractive for plasma experiments. Now the main problem in development of multi-frequency gyrotron is a construction of reliable or tuneable window. Now three diamond window concepts are under consideration: Brewster-angle window, window with matched surfaces and double-disc resonant window. (author)