A nonlinear theory is developed for a detailed investigation of the dynamics of relativistic electrons in nonadiabatic undulators with a guide magnetic field. The nonlinear resonance curves differ qualitatively from those obtained for adiabatic undulators. In the region of resonant magnetic fields, which are of the greatest interest, there are no stationary electron trajectories in both cases. The distinctive features of the electron dynamics are examined for active and passive systems. It is shown that the application of nonadiabatic undulators provides a much stronger twist of the beam as compared to adiabatic undulators and looks promising for microwave devices with transverse interaction, particularly for those using resonance scattering.
Department of Physical Electronics, Faculty of Physics, Moscow State University, Leninskie Gory, Moscow, 119992, Russia