A diode design study of the virtual cathode oscillator with ring-type reflector

A numerical simulation study of the high power microwave generation from the virtual cathode oscillator (vircator) is carried out for various diode configurations by a 3 dimensional particle-in-cell (PIC) code called MAGIC. The coaxial vircator has a cylindrical cathode, cylindrical anode-mesh, and reflector, in order to enlarge the active interaction region in the virtual cathode space. The simulation results show that the output microwave frequency has a narrow bandwidth and its output microwave power depends sensitively on the position and width of ring-type reflector. The maximum microwave output power will be obtained by adopting a ring-type reflector 10 mm in width and 40 mm in downstream of cathode for intense relativistic electron beam. The output microwave mode without the ring-type reflector is mixture of TM and TE mode, however, it has been found to be dominantly to be TM/sub 01/ mode and its resonance frequency was 2.2 GHz under the ring-type reflector.