RE-commissioning of the far-infrared free electron laser for stable and high power operation after the renewal of the L-band linac at Isir, Osaka University

The far-infrared FEL at the Institute of Scientific and Industrial Research (ISIR), Osaka University, which was operated in the wavelength region from 32 to 150 μm and was suspended since 1998, is being commissioned for stable and high power operation. The FEL is based on the L-band electron linac constructed in 1978, but it was largely remodelled for higher stability and reproducibility of operation as well as for long pulse operation for FEL. The long pulse mode has been successfully commissioned using a feed forward control system, which can stabilize the amplitude and the phase of the 1.3 GHz RF power in the macropulse within 0.5 % in amplitude and 0.3° in phase. The FEL system is the same as before except for the strong focusing wiggler based on the edge-focussing scheme, which was recently introduced. The FEL experiment is all set up and we are waiting for the next machine time and lasing.