Studies of an X-band three-cavity gyroklystron with penultimate cavity tuning

The authors present experimental results of a 10 GHz TE/sub 01/ mode three-cavity gyroklystron. The beam is produced by a pulse line modulator and magnetron injection gun, which can operate to 433 kV and 225 A with 1 mu s flat-top and at a repetition rate of 3 Hz. Microwave power was measured by a mode-selective directional coupler and a flowing methanol calorimeter. Mode purity was determined by a large anechoic chamber. Initial testing of the first three-cavity circuit has produced a peak power of 23 MW with an efficiency of 27% and pulse energy of 36 J. A maximum gain of 39 dB at a peak power of 21 MW was obtained. >