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.