Experimental and simulation studies of new configuration of virtual cathode oscillator

A new configuration of a virtual cathode oscillator (VCO) has been studied for high-power microwave generation. In this VCO configuration, a resonant cavity is used to enhance the beam-field interaction in order to improve the microwave efficiency. Experiments were carried out on a repetitive pulsed power generator "ETIGO-IV" (400 kV, 13 kA, 120 ns, 1 Hz). The output microwaves are diagnosed for peak power and dominant mode by using horn antennas and E-field probes. The microwave frequency is obtained by fast-Fourier transformation of the signal recorded by a high-speed digital oscilloscope. The initial experimental results obtained by E-field probes have indicated a beam-to-microwave conversion efficiency of ∼10%. In addition, three-dimensional particle-in-cell simulations were carried out by using simulation code "MAGIC". Simulation results are compared with experimental results to examine the effect of the cavity and possible ways of further improvement of microwave efficiency.