title: Free-electron-laser oscillator with a linear taper.
abstract: We present experiments and simulations showing the behavior of a free-electron laser (FEL) with both positive and negative linear tapers along the wiggler. We show the power desynchronism curve widths, efficiency, exhaust electron energy spread, and wavelength dependence as a function of taper for 3- and 6-microm optical wavelengths and for resonators with 10% and 2% loss/pass. Simulations of the experiments, using a multimode analysis, are seen to be in general agreement with the experimental results, carried out at the IR Demo FEL at Thomas Jefferson National Accelerator Facility. We find that short-pulse effects are more effective than tapers in producing high efficiency with low exhaust energy spread, and the expected performance enhancement of FEL tapering is not achieved.
authors.affiliation: Naval Postgraduate School, Monterey, California 93943, USA.
authors.forename: A
authors.initials: A
authors.lastname: Christodoulou
authors.forename: D
authors.initials: D
authors.lastname: Lampiris
authors.forename: K
authors.initials: K
authors.lastname: Polykandriotis
authors.forename: W B
authors.initials: WB
authors.lastname: Colson
authors.forename: P P
authors.initials: PP
authors.lastname: Crooker
authors.forename: S
authors.initials: S
authors.lastname: Benson
authors.forename: J
authors.initials: J
authors.lastname: Gubeli
authors.forename: G R
authors.initials: GR
authors.lastname: Neil