Beam instabilities in the collective Cherenkov effect and anomalous Doppler effect in a spatially bounded system near the nontransparency band

Beam instabilities of the type of the collective induced Cherenkov effect and the anomalous Doppler effect, which develop in a longitudinally bounded electrodynamic system near its nontransparency band (i.e., when the electromagnetic wave excited by the beam has zero group velocity), are considered. The dispersion equation is derived, which defines the instability increments taking into account the emission of radiation from the electrodynamic system. The solutions to the dispersion equation are analyzed for various parameters of the electron beam and of the electrodynamic system.