200 kW pulsed and CW gyrotrons at 28 GHz

Pulsed and CW gyrotron oscillators have been designed and constructed for use in electron cyclotron resonance heating in plasma fusion experiments. The tubes are designed for 200 kW output at 28 GHz with beam input of 80 kV and 8 A. The pulsed design has been operated at duty factors of 5% and pulse lengths up to 40 msec. The CW design has produced output of 200 kW CW with an efficiency of 50%. It also operated with 52% efficiency at an output level of 170 kW CW. The tubes are designed for power output in the TE02circular electric mode in oversize (2.5 inch diameter) circular waveguide. Some investigations of mode purity of the output will be described. The design and operation of waveguide components such as bends and mode filters for use with the gyrotrons will be discussed.