title: Evidence for microbunching "sidebands" in a saturated free-electron laser using coherent optical transition radiation.
abstract: We report the first measurements of z-dependent coherent optical transition radiation (COTR) due to electron-beam microbunching at high gains ( >10(4)) including saturation of a self-amplified spontaneous emission free-electron laser (FEL). In these experiments the fundamental wavelength was near 530 nm, and the COTR spectra exhibit the transition from simple spectra to complex spectra ( 5% spectral width) after saturation. The COTR intensity growth and angular distribution data are reported as well as the evidence for transverse spectral dependencies and an "effective" core of the beam being involved in microbunching.
authors.affiliation: Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: A H
authors.initials: AH
authors.lastname: Lumpkin
authors.forename: R
authors.initials: R
authors.lastname: Dejus
authors.forename: J W
authors.initials: JW
authors.lastname: Lewellen
authors.forename: W
authors.initials: W
authors.lastname: Berg
authors.forename: S
authors.initials: S
authors.lastname: Biedron
authors.forename: M
authors.initials: M
authors.lastname: Borland
authors.forename: Y C
authors.initials: YC
authors.lastname: Chae
authors.forename: M
authors.initials: M
authors.lastname: Erdmann
authors.forename: Z
authors.initials: Z
authors.lastname: Huang
authors.forename: K-J
authors.initials: KJ
authors.lastname: Kim
authors.forename: Y
authors.initials: Y
authors.lastname: Li
authors.forename: S V
authors.initials: SV
authors.lastname: Milton
authors.forename: E
authors.initials: E
authors.lastname: Moog
authors.forename: D W
authors.initials: DW
authors.lastname: Rule
authors.forename: V
authors.initials: V
authors.lastname: Sajaev
authors.forename: B X
authors.initials: BX
authors.lastname: Yang