Coherent and Incoherent Radiation from Free Electron Lasers with an Axial Guide Field

摘要

The spontaneous and induced emission from a free electron laser is treated for the case in which an axial magnetic field is imposed in addition to the helical, axially periodic wiggler magnetic field. The classes of possible single-particle trajectories in this configuration are discussed, and the results are applied to a calculation of the incoherent radiation from a beam of relativistic electrons in the system. The coherent radiation is treated by solving the Vlasov-Maxwell equations for the linear gain in the tenuous beam limit, where the beam plasma freuqency is much less than the radiation frequency and self-field effects can be ignored. (Author)