Three-dimensional codes for simulating electron beam transport and free-electron laser operation including space-charge effects

Three-dimensional models which describe the electron beam transport and electromagnetic (EM) interaction in a Free-electron laser (FEL) are presented. The models are based on single particle force equations, and take into account emittance and space-charge effects in the e-beam, and transverse spatial variation in the radiation field. In the e-beam transport problem, a cylindrically symmetrical transverse density distribution is assumed, having an arbitrary az-imuthal and radial angular spread. The particle trajectories are obtained by solving numerically the equation of motion for a general electric and magnetic field in the presence of space-charge forces. The parameters of the particles in the beam are then displayed in real space and phase space. In the FEL model, the total electromagnetic field (including the RF space-charge field) is expanded in terms of normal modes of the waveguide (including the cut-off modes). The field interaction with the e-beam is described by the force equation for electrons and a set of EM excitation equations for the waveguide modes. The model takes into account 3-D effects of the radiation and space-charge fields, and thus provides a complete description of the FEL interaction for any kind of symmetry of the e-beam and of the waveguide cross-section. The equations are solved numerically to simulate FEL operation in the nonlinear Compton or Raman regimes.