Output Characteristics of the Axially Extracted Virtual Cathode Oscillator With a Cathode-Wing

Having the merits of conceptual simplicity, high-output-power capacity, and wide tuning characteristics, the vircator (virtual cathode oscillator) has been investigated as a high-power microwave (HPM) generator. In axial vircator, the power, frequency, and pulsewidth are all sensitive to the cathode shape, and the frequency depends strongly on the anode-cathode gap distance. The efficiency of the vircator is reported to only a few percent. Therefore, we devised the new type cathode to enhance the output power. The new type cathode is adding the ring to the cathode with velvet, so-called cathode-wing. The electron beam is only emitted from cathode with velvet, while a cathode-wing forms the electric fields to prevent the backstream electrons due to virtual cathode from leaking to the diode chamber wall. We investigated the axial vircator with the cathode-wing by the HPM generator ldquoChundoongrdquo (max 600 kV, 88 kA, 60 ns). It is found that the cathode-wing contributes to enhancement of the output microwave power efficiency to 7% in comparison with 3% for a conventional axial vircator without cathode-wing.