ULTRAWIDE-BANDWIDTH GAIN IN A COAXIAL DIELECTRIC CHERENKOV MASER

A coaxial waveguide partially filled with a dielectric as the slow-wav e structure of a dielectric Cherenkov maser is investigated. The dispe rsion of the fundamental made of this waveguide is very weak at phase velocities close to the velocity of light, and for this reason a very wide gain bandwidth is possible under conditions of an interaction wit h a relativistic electron beam. The dispersion equation for an infinit ely thin tubular beam in a coaxial waveguide with a dielectric liner a djoining either the outer or inner conducting surface is derived. The gain bandwidth as a function of the parameters of the electron beam an d the slow-wave system are investigated on the basis of numerical solu tion of the dispersion equation, and a comparison with similar depende nces for the conventional configuration of a dielectric Cherenkov mase r is made. The structural features of the coaxial configuration which enable novel approaches to the problems of matching the microwave sign al at the entrance and exit of the system are discussed. (C) 1997 Amer ican Institute of Physics. [S1063-7842(97)01504-3].