23 GHz ferroelectric electron gun based gyrotron

Ferroelectric cathodes have been explored as an alternative electron source for microwave tubes. Past experiments have demonstrated operation at frequencies of 2-10 GHz. Since the ferroelectric cathode is based on surface plasma, the relatively high energy spread limits the tube operation frequency. Hence, the possibility to obtain higher frequencies remained questionable. In this experimental work a gyrotron oscillator was designed with the operation frequency increased toward that of millimeter waves. A cylindrical tube with a cutoff frequency of ∼22 GHz was integrated to a ferroelectric electron gun. Pulses of ∼0.5 μs duration with a frequency of 23 GHz were obtained.