Stimulated undulator radiation from relativistic electrons and the physical processes in an "electron laser"

A theoretical study is made of the amplification and generation of coherent radiation in the optical range based on the undulator mechanism of stimulated magnetic bremsstrahlung from relativistic electrons. Expressions are obtained for the gain and the efficiency. It is shown that the reaction of the radiation plays an important part in the nonlinear saturation regime and in the mode of operation in which the beam is used repeatedly. Physically possible versions of the parameters of an electron laser are given for different spectral regions.