The design of a 1 MW, 280 GHz gyrotron suitable for ECR heating is complete and under construction at MIT. A highly overmoded cylindrical cavity with linear tapers at each end will operate in the whispering gallery mode; TE42,7,1. The magnetron injection gun (MIG) was optimized to produce a 90 kV, 50 A annular electron beam with an α = υ/υ|| =1.6 and a perpendicular velocity spread of approximately 5 %. The MIG and a 12 Tesla superconducting magnet with a 5 inch warm bore are presently under construction. Initial operation is planned for early next year.
T. L. Grimm,
"Design of a 1 mw, 280 Ghz gyrotron oscillator", Proc. SPIE 1514, 15th International Conference on Infrared and Millimeter Waves, 15142K (1 December 1990); doi: 10.1117/12.2301502; https://doi.org/10.1117/12.2301502