title: Operation of higher harmonic oscillations in free-electron lasers.
abstract: We report for the first time the experimental achievement of a seventh-harmonic free-electron laser (FEL) oscillation. The measured FEL gains and average FEL powers for higher harmonics were identical to those calculated by a one-dimensional FEL theory. The measured linewidths of the higher-harmonic FELs were narrower than that of the fundamental FEL owing to the narrower spectral widths of the spontaneous emissions. By applying the higher-harmonic FEL oscillation to a resonator-type FEL with an advanced accelerator, an x-ray FEL oscillator can be realized at lower electron-beam energy.
authors.affiliation: Research Institute of Instrumentation Frontier, National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan. sei.n@aist.go.jp
authors.forename: N
authors.initials: N
authors.lastname: Sei
authors.forename: H
authors.initials: H
authors.lastname: Ogawa
authors.forename: K
authors.initials: K
authors.lastname: Yamada
mesh_terms: D004583:Electrons; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007834:Lasers; D009991:Oscillometry / Q000295:instrumentation*