Modulation of relativistic electron beam in a diaphragmed waveguide

Theoretical investigations of the initial stage of automodulation of heavy-current relativistic electron flux by a decelerating structure field are carried out. Expressions for the modulation depth of an electron beam with energy from 50 to 400 keV and current from 30 to 300 A, moving at the velocity different from the phase velocity of an electromagnetic wave of a hollow diaphragmed waveguide, are obtained in hydrodynamic approximation taking account of Coulomb interaction. A dispersion equation, describing beam interaction with the decelerating structure field is obtained and studied. It is shown that the interaction of natural beam charge oscillations with the electromagnetic field, excited by the beam in the diaphragmed waveguide, results in a considerable reconstruction of the electron flux. This effect manifests itself as deep beam density modulation under the resonance conditions. That is why the use of this phenomenon for the increase of efficiency of electron beam particle kinetic energy transformation into the energy of electromagnetic oscillations appear to be perspective enough