Simultaneous two-color lasing in the mid-IR and far-IR region with two undulators and one RF linac at the FELI

Abstract Simultaneous two-color FEL lasing on the same electron macropulse has been demonstrated at 4.65 and 19.4 μ m using a 33 MeV electron beam and two FEL facilities (FEL-1 and FEL-4) of the FELI. The average powers are 11 mW at 4.65 μ m and 2 mW at 19.4 μ m. Their spectral widths (FWHM) are 0.85% and 1.06%. They are delivered to users through two evacuated optical pipes. FEL-1 achieved lasing in the mid-infrared region with the undulator-1 (UND-1; λ u =34 mm , K =0.5–1.5, N u =34) in 1994 and FEL-4 achieved lasing at far-infrared region with the undulator-4 (UND-4; λ u =80 mm , K =1.26–3.37, N u =30) in 1996. UND-4 is installed at the downstream of the UND-1 and an electron beam is transported through an S-type electron beam transport line including two 45° bending magnets.