title: Lasing of middle-infrared free-election lasers using the storage ring NIJI-IV.
abstract: We report for the first time to our knowledge the experimental realization of a storage ring free-electron laser (FEL) in the middle-infrared (MIR) region. A technique to adjust the optical cavity using higher harmonic FELs was developed for a fundamental FEL in the MIR region. The MIR FELs were oscillated in the wavelength region of 2475 to 2673 nm, and the relative linewidth was 5×10⁻⁴. A quasi-monochromatic x-ray beam with an energy of 700 keV was generated using FEL Compton backscattering. We were able to realize a quasi-monochromatic x-ray beam, whose energy is difficult to generate even in advanced synchrotron radiation facilities.
authors.affiliation: Research Institute of Instrumentation Frontier, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan. sei.n@aist.go.jp
authors.forename: Norihiro
authors.initials: N
authors.lastname: Sei
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ogawa
authors.forename: Kawakatsu
authors.initials: K
authors.lastname: Yamada