Theoretical explanation and experimental observation of effective cyclotron coupling of traveling and near-cutoff modes on a phase-synchronized electron beam

For a Cyclotron Resonance Maser (CRM) with a helical axis-encircling electron beam, the possibility of a strong interaction between cutoff (gyrotron) and traveling Doppler-up-shifted Cyclotron Autoresonance Maser (CARM) modes, which are in resonance with the electrons at the same frequency, is demonstrated. This effect can be used in a CRM-oscillator of a new type, where the feedback and the mode selectivity for the operating traveling mode are provided due to the excitation of the cutoff mode. According to both the theory and experiment, such a scheme can provide an effective excitation of the traveling mode with negligibly low losses associated with the cutoff mode.