On transient radiation of a linear impedance antenna exited by the electron bunch

A linear impedance antenna of transient radiation exited by the electron bunch scattered on its end face is considered. The radiation is analyzed at the stage of a bunch approach to the antenna. The radiation is an induced or diffraction one and has a nature of forced oscillations. The radiation spectrum has an extremum. The dispersion equation of an antenna is derived. The expressions for the components of the discrete spectrum of the current force and the strengths of electric and magnetic fields, radiated by the antenna, are constructed as a series in the antenna eigen functions. It is shown, that the antenna element is radiative if the strengths of extrinsic and intrinsic electric fields are in phase and in antiphase accordingly to the antenna current. In this case the extrinsic electric field strength accelerates the conductivity electrons and the intrinsic electric field strength brakes electrons, producing the radiation of latter ones.