Computation of FEL processes

The Free-Electron Laser process is the interaction between an electron beam and a co-propagating radiation field, resulting in a collective instability with an exponential growth of the radiation field and the current modulation in the electron bunch. Although analytical models can describe the fundamental FEL amplification, the complexity of the FEL process with a multi-particle system and the evolution of a radiation field demands numerical calculation. To achieve optimum performance the numerical solvers for FEL codes are highly specialized, using alternative methods than standard PIC codes. This presentation describes the basic algorithm for FEL simulations and addresses in particular the problems and limitations of simulating the FEL process.