Quasi-coherent radiation from a train of electron bunches inside a waveguide partially filled with dielectric

Abstract We investigate the quasi-coherent radiation from a train of electron bunches moving along the axis of a cylindrical waveguide, assuming that a part of the waveguide is filled with a dielectric medium. For the permittivity of the latter, the general case of dispersion is considered. It is shown that under certain conditions on the permittivity of the medium and on the values of the problem parameters, the waveguide modes become equidistant. As a consequence, quasi-coherent Cherenkov radiation from the train of bunches may be generated on the first several waveguide modes simultaneously. An example of dispersion law is provided for which the corresponding Cherenkov radiation is suppressed.