MICROWAVE GENERATION FROM AN AXIALLY EXTRACTED VIRTUAL CATHODE OSCILLATOR WITH A GUIDE MAGNETIC-FIELD

The operation of a virtual cathode oscillator (vircator) with strong a xial magnetic field has been experimentally studied. Depending on the cathode-anode pp and cathode diameter, the operating voltage varies fr om 200 kV up to 480 kV with 2-7 kA diode current. Microwave emission i s produced by the oscillating virtual cathode. The central microwave f requency follows the beam plasma frequency. It varies by 11.5 GHz up t o 22 GHz, depending on the current density. The oscillation frequency does not depend on the guide magnetic field magnitude. A maximal outpu t power of 15 +/- 5 MW in asymmetric transverse magnetic (TM) modes is achieved by the axially extracted vircator. Variation of the magnetic field intensity in a range of 0-40 kG has an insignificant effect upo n the emitted microwave power. An electron beam power to microwave pow er conversion efficiency of approximately 1% is obtained.