Resonance properties of low-energy electron beams radiation in a two-layer waveguide

We obtain an approximating formula for the low-energy impedance of a two-layer cylindrical waveguide, which allows constructing explicit expressions for the space-time functions that characterize the radiation of a charged particle in a waveguide. The general laws of the evolution of impedance and wake potentials with increasing particle energy and with the change of geometric and electrodynamical parameters of the waveguide are obtained. The settings of waveguides convenient for experimental research and having resonance properties at energies of about 20 MeV are revealed.