title: Analysis of the halo background in femtosecond slicing experiments.
abstract: The slicing facility FemtoSpeX at BESSY II offers unique opportunities to study photo-induced dynamics on femtosecond time scales by means of X-ray magnetic circular dichroism, resonant and non-resonant X-ray diffraction, and X-ray absorption spectroscopy experiments in the soft X-ray regime. Besides femtosecond X-ray pulses, slicing sources inherently also produce a so-called `halo' background with a different time structure, polarization and pointing. Here a detailed experimental characterization of the halo radiation is presented, and a method is demonstrated for its correct and unambiguous removal from femtosecond time-resolved data using a special laser triggering scheme as well as analytical models. Examples are given for time-resolved measurements with corresponding halo correction, and errors of the relevant physical quantities caused by either neglecting or by applying a simplified model to describe this background are estimated.
authors.affiliation: Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Strasse 15, 12489 Berlin, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Schick
authors.affiliation: Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Strasse 15, 12489 Berlin, Germany.
authors.forename: Loïc
authors.initials: L
authors.lastname: Le Guyader
authors.affiliation: Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Strasse 15, 12489 Berlin, Germany.
authors.forename: Niko
authors.initials: N
authors.lastname: Pontius
authors.affiliation: Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Strasse 15, 12489 Berlin, Germany.
authors.forename: Ilie
authors.initials: I
authors.lastname: Radu
authors.affiliation: Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Strasse 15, 12489 Berlin, Germany.
authors.forename: Torsten
authors.initials: T
authors.lastname: Kachel
authors.affiliation: Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Strasse 15, 12489 Berlin, Germany.
authors.forename: Rolf
authors.initials: R
authors.lastname: Mitzner
authors.affiliation: Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Strasse 15, 12489 Berlin, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Zeschke
authors.affiliation: Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Strasse 15, 12489 Berlin, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Schüßler-Langeheine
authors.affiliation: Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Strasse 15, 12489 Berlin, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Föhlisch
authors.affiliation: Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Strasse 15, 12489 Berlin, Germany.
authors.forename: Karsten
authors.initials: K
authors.lastname: Holldack
keywords: X-ray scattering; XMCD; femtosecond slicing; halo; pump–probe