Abstract

Efficiency enhancement in Backward Wave Oscillator (BWO) device at low magnetic field is a matter of concern. With decrease in guiding magnetic field, the quality of beam gets reduced along with increase in transverse motion of electrons. The transverse motion of electrons extracts energy from the RF field and undergo multipacting with the Slow Wave Structure (SWS) surface under influence of periodic accelerating electric field of microwaves. Hence, electron beam to microwave conversion efficiency gets reduced. Lowering magnetic field can also lead to two types of cyclotron absorptions i) Forward cyclotron absorption & ii) Backward cyclotron absorption. The simulation results of High-Power Microwave (HPM) generation from a non-uniform X-band BWO device having circular profiled SWS have been presented in this paper. Output power of 810 MW has been observed at 9.8 GHz with 27% efficiency, guided by 0.6T magnetic field. Also, overbunching & backstreaming of electron beam was observed in PIC simulation using CST studio. These phenomena restrict the device efficiency.