Cerenkov radiation excited by a thin annular relativistic electron beam in a slow-wave structure consisting of an annular-plasma-filled cylindrical waveguide with a dielectric lining

By using a self-consistent and relativistic field theory, Cerenkov radiation for a configuration in which a thin annular relativistic electron beam (TAREB) propagates through an annular-plasma-filled dielectric lining enclosed within a perfect conducting wall is studied in the absence of a longitudinal guided magnetic field. Determinant dispersion equations of the beam–wave interactions for (a) the TAREB inside the annular plasma; (b) the TAREB penetrating through the annular plasma; and (c) the TAREB outside the annular plasma and the simultaneous condition producing the Cerenkov radiation are derived. These dispersion equations show that the beam–wave interaction results from the coupling of the TM mode in the annular-plasma-filled dielectric lined slow-wave waveguide to the beam mode via the electron beam. Finally, the dispersion equations are directly solved numerically, and the operation frequency and the growth rate of the system are obtained.