Magnets for 150 GHz gyrotrons

The development of three magnet sets for a 150-GHz gyrotron is described. This development has the ultimate goal of producing a 150-GHz gyrotron unit with 1-MW power in steady-state operation for plasma heating. The design criteria and the problems and difficulties during development phase are discussed. The first set, consisting of normal-conducting and superconducting solenoids and normal-conducting steering coils, showed problems during operation. The second magnet set, with only two normal-conducting magnets in the emitter zone, is working without any problems. The third set, (in the construction phase), is all superconducting. Using the second set an output RF power of 200 kW was achieved for a few milliseconds