Influence of inner conductor on operation band selection in relativistic backward wave oscillator

A compact gigawatt relativistic backward wave oscillator with coaxial extractor is investigated using the KARAT 2-5 D particle simulation code. Detailed physical interaction pictures of beam and wave in the oscillator are presented. Simulation results show that under the same parameters (electron beam of 700 keV energy and 11.5 kA current, guiding magnatic field of 10 T), an Lband microwave with an average output power of 2.66 GW can be obtained using an inner conductor, and an S-band microwave with an average output power of 2.0 GW for no inner conductor condition. The average power efficienices are about 34% and 24%, respectively．