Performance simulation of infrared free electron laser at the Pohang Light Source test linac

Numerical simulation studies are performed for the proposed infrared self-amplified spontaneous-emission free-electron laser (SASE-FEL) at the existing PLS test linac. It is shown that a high-gain SASE-FEL with a 1.5 μm radiation wavelength could be driven by a 61-MeV electron beam from the S-band rf linac and a 5-m long undulator. Third-harmonic generation to 0.5 μm radiation wavelength was also investigated to enhance the usefulness of the infrared SASE-FEL facility. Bunching fractions of the nonlinear third harmonic to the fundamental mode in the designed SASE-FEL is estimated and showed that the third-harmonic emission resulted in the same trend as the fundamental. This paper attempts to investigate the effect of the beam parameters such as the emittance, the energy spread, the beam energy, and the peak beam current to the designed infrared SASE-FEL. The wake effects due to the surface roughness of beam chamber in the undulator are also estimated.