Summary:
This thesis studies the modes, which can develop in coaxial waveguides with
surface corrugations filled with lossy material in the presence of electron
beam. Such waveguides are used in various microwave devices, i.e., traveling
wave tubes (TWT), backward wave oscillators (BWO), gyrotron beam-tunnels. The
interactions between the electron beam and the electromagnetic waves, which may
develop in the beam tunnel, reduce the quality of the beam and the efficiency
of the device, whereas in some cases destroy the beam tunnel. The formulation
of the problem is based on a full wave method for the electromagnetic problem
in combination with the linearized Vlasov kinetic equation for the beam-wave
interaction. Based on this analysis, a numerical code has been developed and
several simplified coaxial gyrotron beam-tunnel geometries have been
considered, whereas the dependence of the interactions on the characteristics
of the structure has been investigated.
Keywords:
Beam tunnels, beam–wave interaction, gyrotrons, parasitic oscillations, slow-wave structures
