title: A novel monochromator for experiments with ultrashort X-ray pulses.
abstract: Aiming at advancing storage-ring-based ultrafast X-ray science, over the past few years many upgrades have been undertaken to continue improving beamline performance and photon flux at the Femtoslicing facility at BESSY II. In this article the particular design upgrade of one of the key optical components, the zone-plate monochromator (ZPM) beamline, is reported. The beamline is devoted to optical pump/soft X-ray probe applications with 100 fs (FWHM) X-ray pulses in the soft X-ray range at variable polarization. A novel approach consisting of an array of nine off-axis reflection zone plates is used for a gapless coverage of the spectral range between 410 and 1333 eV at a designed resolution of E/ΔE = 500 and a pulse elongation of only 30 fs. With the upgrade of the ZPM the following was achieved: a smaller focus, an improved spectral resolution and bandwidth as well as excellent long-term stability. The beamline will enable a new class of ultrafast applications with variable optical excitation wavelength and variable polarization.
authors.affiliation: Institute for Nanometer Optics and Technology, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, Berlin 12489, Germany.
authors.forename: Maria
authors.initials: M
authors.lastname: Brzhezinskaya
authors.forename: Alexander
authors.initials: A
authors.lastname: Firsov
authors.forename: Karsten
authors.initials: K
authors.lastname: Holldack
authors.forename: Torsten
authors.initials: T
authors.lastname: Kachel
authors.forename: Rolf
authors.initials: R
authors.lastname: Mitzner
authors.forename: Niko
authors.initials: N
authors.lastname: Pontius
authors.forename: Jan Simon
authors.initials: JS
authors.lastname: Schmidt
authors.forename: Mike
authors.initials: M
authors.lastname: Sperling
authors.forename: Christian
authors.initials: C
authors.lastname: Stamm
authors.forename: Alexander
authors.initials: A
authors.lastname: Föhlisch
authors.forename: Alexei
authors.initials: A
authors.lastname: Erko
keywords: diffractive optics; elliptical undulators; femtosecond X-ray pulses; reflection zone plates; slicing; storage ring; time-resolved X-ray spectroscopy