title: Hartmann wavefront sensors and their application at FLASH.
abstract: Different types of Hartmann wavefront sensors are presented which are usable for a variety of applications in the soft X-ray spectral region at FLASH, the free-electron laser (FEL) in Hamburg. As a typical application, online measurements of photon beam parameters during mirror alignment are reported on. A compact Hartmann sensor, operating in the wavelength range from 4 to 38 nm, was used to determine the wavefront quality as well as aberrations of individual FEL pulses during the alignment procedure. Beam characterization and alignment of the focusing optics of the FLASH beamline BL3 were performed with λ(13.5 nm)/116 accuracy for wavefront r.m.s. (w(rms)) repeatability, resulting in a reduction of w(rms) by 33% during alignment.
authors.affiliation: Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22607 Hamburg, Germany.
authors.forename: Barbara
authors.initials: B
authors.lastname: Keitel
authors.affiliation: Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22607 Hamburg, Germany.
authors.forename: Elke
authors.initials: E
authors.lastname: Plönjes
authors.affiliation: Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22607 Hamburg, Germany.
authors.forename: Svea
authors.initials: S
authors.lastname: Kreis
authors.affiliation: Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22607 Hamburg, Germany.
authors.forename: Marion
authors.initials: M
authors.lastname: Kuhlmann
authors.affiliation: Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22607 Hamburg, Germany.
authors.forename: Kai
authors.initials: K
authors.lastname: Tiedtke
authors.affiliation: Laser-Laboratorium Göttingen e.V., Hans-Adolf-Krebs-Weg 1, 37077 Göttingen, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Mey
authors.affiliation: Laser-Laboratorium Göttingen e.V., Hans-Adolf-Krebs-Weg 1, 37077 Göttingen, Germany.
authors.forename: Bernd
authors.initials: B
authors.lastname: Schäfer
authors.affiliation: Laser-Laboratorium Göttingen e.V., Hans-Adolf-Krebs-Weg 1, 37077 Göttingen, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Mann
keywords: Hartmann sensor; free-electron laser; soft X-rays; wavefront