Wave-beam interaction in coaxial relativistic backward wave oscillator

The physical model is established according to the characteristics of coaxial relativistic backward wave oscillator(CRBWO) to study the wave-beam interaction in CRBWO employing the finite-difference time-domain method. The research indicates that the output efficiency of the wave-beam interaction in CRBWO is sensitively dependent on the reflections on both ends of the wave-beam interaction region. And the distribution of the field in CRBWO is beneficial for the promotion of the output efficiency. In the case of electron beam of 500 keV and 4.0 kA, the calculated output efficiency more than 38% through optimizing and the starting time 7 ns agree with those obtained from previous numerical simulation and experiment results very well. The space charge effect can be considered as a small influence on the wave-beam interaction in CRBWO compared with that in hollow relativistic backward wave oscillator.