Surface Flute Wave Excitation by Annular Electron Beam for Microwave Generation

The interaction of annular relativistic electron beams rotating in an axial magnetic field along large Larmor orbits in cylindrical metal waveguides partially filled with plasma with electromagnetic surface waves of extraordinary (X) polarization with zero axial wavenumber is studied theoretically for RF generation. The linear theory of beam excitation of these surface flute waves (SFWs) is developed with taking into account numerous features inherent in real devices: the difference between the shape of the cross-section of the plasma column and the circle, dissipations, and the presence of an internal metal conductor in coaxial waveguides. The fundamentals of nonlinear theory of SFW excitation by annular electron beams are presented.