title: Wavefront analysis of nonlinear self-amplified spontaneous-emission free-electron laser harmonics in the single-shot regime.
abstract: The single-shot spatial characteristics of the vacuum ultraviolet self-amplified spontaneous emission of a free electron laser (FEL) is measured at different stages of amplification up to saturation with a Hartmann wavefront sensor. We show that the fundamental radiation at 61.5 nm tends towards a single-mode behavior as getting closer to saturation. The measurements are found in good agreement with simulations and theory. A near diffraction limited wavefront was measured. The analysis of Fresnel diffraction through the Hartmann wavefront sensor hole array also provides some further insight for the evaluation of the FEL transverse coherence, of high importance for various applications.
authors.affiliation: Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, Gif-sur-Yvette, France.
authors.forename: R
authors.initials: R
authors.lastname: Bachelard
authors.forename: P
authors.initials: P
authors.lastname: Mercère
authors.forename: M
authors.initials: M
authors.lastname: Idir
authors.forename: M-E
authors.initials: ME
authors.lastname: Couprie
authors.forename: M
authors.initials: M
authors.lastname: Labat
authors.forename: O
authors.initials: O
authors.lastname: Chubar
authors.forename: G
authors.initials: G
authors.lastname: Lambert
authors.forename: Ph
authors.initials: P
authors.lastname: Zeitoun
authors.forename: H
authors.initials: H
authors.lastname: Kimura
authors.forename: H
authors.initials: H
authors.lastname: Ohashi
authors.forename: A
authors.initials: A
authors.lastname: Higashiya
authors.forename: M
authors.initials: M
authors.lastname: Yabashi
authors.forename: M
authors.initials: M
authors.lastname: Nagasono
authors.forename: T
authors.initials: T
authors.lastname: Hara
authors.forename: T
authors.initials: T
authors.lastname: Ishikawa