Anomalous Doppler effect and stimulated Cherenkov effect in a plasma waveguide with a thin-walled annular electron beam

A dispersion relation for the complex frequencies of the E modes excited by a thin-walled annular low-density beam in a cylindrical plasma waveguide is derived using the methods of perturbation theory. The cases of an annular and a uniform plasma filling are considered, and the corresponding wave growth rates are determined. A condition is obtained under which the primary mechanism for the excitation of the waveguide is the anomalous Doppler effect. The possibility is discussed of suppressing Cherenkov generation in a plasma resonator at the expense of the normal Doppler effect.