EFFECT OF THE ZERO SPATIAL HARMONIC IN A SLOW ELECTROMAGNETIC-WAVE ONOPERATION OF RELATIVISTIC BACKWARD-WAVE OSCILLATORS

A linear theory of resonant backward-wave oscillators (BWOs) that take s into account the zero spatial harmonic is developed. It is shown tha t, depending on the phase shift, this harmonic can either increase or decrease the starting current of the device. The nonlinear theory show s the some effect of the phase shift on the maximum efficiency of the BWO. The numerical analysis of nonstationary processes has also demons trated the effect of the phase shift on the range of beam current valu es in which the BWO operates in a steady-state single-frequency regime . The effect of boundary conditions at the cathode end of the slow-wav e structure on the phase shift between harmonics is also analyzed. (C) 1997 American Institute of Physics.