The effects of two electron beams on a free-electron laser oscillator

We have analyzed the characteristics of a free-electron laser (FEL) oscillator by using two electron beams of different energies. The evolution of the harmonic output intensity of the two-beam oscillator, the harmonic radiation field intensity relative to the beam’s current ratio, the harmonic field obtained by using both the lower and the higher electron energy beams, and the harmonic field for the higher energy electron beam alone were studied by using an extended 2D simulation code that described the effects of two electron beams with different energies. The 2D effects of the energy spread, higher-order modes, and the transverse mode construction of the optical field were also studied in the two electron beam oscillator model for the low-energy region.