First lasings at IR and FIR range using the FELI FEL facility 4

First lasing at 18 μm was achieved by using a 2.7 m long hybrid-type undulator (undulator 4) for far-infrared FELs and a 6.72 m long optical cavity installed at the 33 MeV beam line of the downstream of the FEL facility 1 (FEL-1). We are challenged at two-color FEL oscillation in mid-infrared range using the undulator 1 (λu=3.4 cm) and in far-infrared range using the undulator 4 (λu=9 cm). At first, a 30 MeV, 40 A beam passed through the undulator 1 without lasing is transported using a QFQDBQFQDBQFQDQF system and was used for lasing at the undulator 4. r, six pairs of steering coils had to be attached on the beam duct to reduce the deviation of the electron beam trajectory due to the vertical field distribution induced by the built-in electromagnets and the steering coils attached on the beam duct increased the gap up to 52 mm. Therefore, the hybrid-type undulator was replaced by a new Halbach-type one (λu=8 cm, N=30) after the first lasing at 18 μm on 24 October 1996. w FEL facility 4 was installed in the middle of December and first lasing at 18.6 μm was achieved on December 26 using 33 MeV, 40 A beam passed through the undulator 1 without lasing. This paper describes first lasings at IR and FIR range using a Halbach-type undulator (undulator 4) and 33 MeV, 40 A beam passed through the undulator 1 without lasing and a challenge at two-color FEL oscillation using the FEL facilities 1 and 4.