Cerenkov radiation from a relativistic electron beam propagating through a circular waveguide

Abstract

AbstractThe problem of Cerenkov instability by the relativistic electron beam propagating along a constant static magnetic field applied in the axial direction of the slow‐wave structure with a circular cross section is analyzed based on the relativistic equation of motion for cold electrons and Maxwell's equations. As practical slow‐wave structures, a circular corrugated waveguide, a coaxial corrugated waveguide, and a dielectric loaded waveguide have been assumed. The maximum growth rates of the space charge and cyclotron Cerenkov instabilities are calculated numerically for each structure. It is found that for both instabilities, the growth rate is the maximum in the case of a corrugated coaxial waveguide in which the electron beam is propagating near the waveguide wall. In all three slow‐wave structures, the growth rate of the cyclotron Cerenkov instability can be made substantially smaller than that of the space‐charge Cerenkov instability.