Transverse effects in a free-electron laser oscillator with two electron beams

We have analyzed the transverse effects in a free-electron laser (FEL) oscillator using two electron beams of different energies referring to a proposed FEL facility operated in the far-infrared and infrared regions. The transverse effects in a free-electron laser oscillator were studied taking into account the electron beam's emittance, offset misalignment errors, energy spreads, and higher-order modes using an extended two-dimensional (2D) FEL code with two electron beams that we developed. The variation in the radiation amplitude depending on the electron beam emittance, offset misalignment errors, and energy spreads was also calculated in the case of betatron oscillations for multiparticles and multipass numbers using a new 2D code. The mode construction was studied for higher-order modes of the wiggler with and without offset misalignment errors for FEL operation with a high-quality electron beam. (C) 2015 The Japan Society of Applied Physics