Virtual Cathode Oscillator under various cathode radii with intense relativistic electron beam

It has been reported that the virtual cathode is formed when the electron beam current in the drift region exceeds the space charge limiting current. In this study, the axially-extracted virtual cathode oscillator, which is new conceptual device and the ultra-high power microwave generator consists of the “Chundoong” intense relativistic electron beam pulser (Max: 600 kV, 88kA, and 60 ns duration). In this experiments, Maximum power of extracted microwave is about 520 MW and its conversion efficiency about 8.2 % under cathode radius of 2.5 cm and the Anode-Cathode (A-K) gap is 5 mm. It has been also found that the propagating microwave mode is the combination of TM01 and the other higher mode based on the electric field(Ez) profile versus cathode radius. The dominant microwave frequency is shown to be 6.07 GHz from this experiment.