Generation of coherent radiation by a beam of relativistic electrons in an undulator

The radiation instability of a beam of relativistic electrons in an undulator is investigated in detail. The possibility of producing a strong source of coherent radiation over a wide range of wavelengths is examined. The characteristics of the radiation of such a source are studied. It is shown that the mass of the longitudinal motion can be used to stabilize the mode by introducing a supplementary longitudinal magnetic field into the undulator. A numerical example for a source in the submillimeter region is presented