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

Simultaneous two-color FEL lasing on the same electron macropulse has been demonstrated at 4.65 and 19.4 μm 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 μm and 2 mW at 19.4 μm. 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; λu=34 mm, K=0.5–1.5, Nu=34) in 1994 and FEL-4 achieved lasing at far-infrared region with the undulator-4 (UND-4; λu=80 mm, K=1.26–3.37, Nu=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.