Influence of the normal Doppler effect on the Cherenkov beam instability in an electrodynamic system of finite length

The possibility is studied of attenuating the feedback wave in electron-beam-based Cherenkov microwave oscillators at the expense of its resonant interaction with the beam cyclotron wave under normal Doppler effect conditions. Oscillators operating in the regimes of the collective and single-particle stimulated Cherenkov effects are considered. Stability conditions for a system with a beam that is subject to the Cherenkov and cyclotron resonances at the emission frequency are found. Applications to particular problems in plasma microwave electronics are discussed