A TM01-mode axial vircator

Summary form only given. The generation of pulsed high-power microwaves from an axial vircator has been investigated experimentally at diode voltages of 200-300 kV and beam currents of 5-8 kA. The major feature of this vircator is that a pseudomicrowave cavity which consists mainly of a stepped electron-drift tube with two different radii of 3.9 cm and 4.9 cm has been introduced. For a proper cathode-anode gap matched to the diode voltage and beam current, very pure and narrowband TM₀₁-mode microwaves have been generated with a pulse duration of ≲10 ns in the dispersed microwave spectrum of a 145.6-m waveguide delay line. The short duration of the microwave pulse indicates that its frequency spread is ≲0.06 GHz with a center frequency at 8.2 GHz, which corresponds to a bandwidth of ~0.7%. At this condition, a microwave peak power of 30 MW has been reached and the electron-beam-to-microwave-power conversion efficiency is 2%