Generation of single-frequency coherent transition radiation by a prebunched electron beam traversing a vacuum beam tunnel in a periodic medium

A classical Maxwell equation longitudinal boundary value problem analysis of a prebunched ac electron beam traversing a vacuum tunnel in a periodic layered dielectric medium is used to calculate the single-frequency coherent transition radiation power generated per unit length. For low voltage electron beams in the kilovolt range, only transition radiation is produced, the Cerenkov effect being below threshold. A numerical example indicates that power levels of the order of milliwatts per centimeter can be produced in the 35 GHz range with 3-10 keV beams. An interesting aspect of transition versus Cerenkov radiation is that the transition "cone" of radiation is in the backward direction of the charge beam.