S-band vircator with E-beam premodulation based on compact HV pulser with inductive energy store

An S-band vircator with electron beam premodulation, without external magnetic field, based on a compact HV pulse generator with inductive energy store, was realized in experiment. The primary capacitor of the HV pulser was switched by means of a five-channel multigap discharger onto serially connected inductance and wire fuse. The short-circuit current of the generator was 65 kA with quarter-period of oscillation 6.6 mcs. The arising voltage made a peaking discharger operate thereby connecting the storing inductance with the electron vacuum diode of the vircator. The pulse width at the cathode could be varied within 50 - 150 ns using a slicer. The microwave power of the vircator was measured using calibrated dipole antennas by integrating over the radiation pattern, and a 60-dB directed coupler built in the single-mode output waveguide of the vircator. The vircator operated at the mode TE10. The output microwave power was 300 MW with 5% efficiency and 50 ns pulse width. The generation frequency was 2.65 GHz, stable during the pulse despite the fact that the decrease in the vacuum diode impedance during the pulse was a factor of three. The generation frequency was tunable within 15% at half power level. The maximum microwave output corresponded to 20 - 30% excess of electron beam current above the critical one.