The effects of self-fields on the electron trajectory in a two-stream free electron laser with a helical wiggler and an axial guiding magnetic field

A theory for the two-stream free-electron laser (TSFEL) with a helical wiggler and an axial guide magnetic field is developed. In the analysis, the effects of self-fields are taken into account. An analysis of the two-stream steady-state electron trajectories is given by solving the equation of motion. Numerical calculations show that there are seven groups of orbits in the presence of self-fields instead of two groups reported in the absence of self-fields. The stability of the trajectories is studied numerically.