Theoretical and experimental investigations of the cyclotron interaction effect on relativistic backward wave oscillator operation

Abstract

Microwave sources based on backward-wave oscillators (BWOs) driven by relativistic electron beams are capable of producing high power coherent radiation in the cm and mm wavelength region. When the axial magnetic field is used in these devices to confine the electron beam satisfies the condition of cyclotron resonance there is a significant modification in the behavior of BWO due to beam coupling to cyclotron modes. A time-dependent, self-consistent theory of BWOs is developed taking into account a possible cyclotron interaction. The analysis of the system near the cyclotron resonance yields a number of physical effects including the power drop due to the cyclotron absorption observed in many BWO experiments. A series of experiments has been conducted to compare the measured BWO characteristics with the theoretically predicted ones.