Effective coupling of cyclotron autoresonance maser and "gyrotron" modes on a phase-synchronized electron beam

For a cyclotron resonance maser (CRM) with a helical axis-encircling electr on beam, the possibility of a strong interaction between cutoff (gyrotron) and traveling Doppler-up-shifted (cyclotron autoresonance maser) modes, whi ch are in resonance with the electrons at the same frequency, is demonstrat ed. This effect can be used in a CRM oscillator of a new type, where the fe edback and the mode selectivity for the operating traveling mode are provid ed due to the excitation of the cutoff mode. According to both the theory a nd the experiment, such a scheme can provide an effective excitation of the traveling mode with negligibly low losses associated with the cutoff mode.