Near-infrared Free Electron Laser Experiment with the Storage Ring Niji-iv

FEL experiments in the NIR region were carried out with a compact storage ring NIJI-IV at the National Institute of Advanced Industrial Science and Technology. Spontaneous emission spectra from the optical klystron ETLOK-III were measured at wavelengths around 850 nm. High-reflectance cavity mirrors were set in mirror chambers this August. The cavity loss was measured to be about 0.2%, and the maximum FEL gain was estimated to be about 0.4% at beam current of 5 mA. Experiments of the FEL oscillations in the NIR region will be started next month. INTRODUCTION Studies of free electron lasers have been progressed with a compact storage ring NIJI-IV at the National Institute of Advanced Industrial Science and Technology (AIST). The storage ring NIJI-IV dedicated to FELs was constructed in 1990 [1]. A 6.3 m optical klystron ETLOK-II, which was developed for short-wavelength FEL oscillations, was installed in one of the straight sections of the NIJI-IV in 1992. The first lasing was achieved at wavelengths of 595 and 488 nm this year [2]. The first lasing in the UV region was achieved at a wavelength of 350 nm in 1994 [3]. To increase the FEL gain, several improvements of the NIJI-IV have been performed. The wavelength of the NIJI-IV FEL was down to 212 nm in 1998, and it was the shortest record in the FEL wavelength [4]. In 2003, the FEL oscillation was achieved at a wavelength of 198 nm, the NIJI-IV FEL system became the third device which realized storage ring FELs in the VUV region [5]. Application experiments with using the DUV FELs have been also developed at the AIST. Because work function of transition-metals lays around 5 eV, FELs with the wavelength around 200 nm are suitable as an intense light source to observe chemical reactions on the surface of the transition-metals in combination with the photoelectron emission microscopy (PEEM). We achieved to observed catalytic CO oxidation on Palladium surface with video-rate time resolution [6]. This FELLong-wavelength FEL section (1 10 micron)