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Volume 4, Issue 4 (Suppl) J Laser Opt Photonics, an open access journal
ISSN: 2469-410X Optics 2017
November 15-17, 2017
November 15-17, 2017 | Las Vegas, USA
8th International Conference and Exhibition on
Lasers, Optics & Photonics
Wavefront propagation simulations for a hard x-ray split-and-delay unit at the European XFEL
Victor Kärcher
University of Münster, Germany
For the High Energy Density Instrument (HED) at the European XFEL a hard x-ray split-and-delay unit (SDU) is built covering
photon energies in the range between 5 keV and 24 keV. This SDU enables time-resolved x-ray pump / x-ray probe experiments as
well as sequential diffractive imaging on a femtosecond to picosecond time scale. The set-up is based on wavefront splitting that has
successfully been implemented at an autocorrelator at FLASH. The x-ray FEL pulses will be split by a sharp edge of a silicon mirror
coated with Mo/B4C and W/B4C multilayers. Both partial beams then pass variable delay lines. For different wavelengths the angle
of incidence onto the multilayer mirrors is adjusted in order to match the Bragg condition. Hence, maximum delays between +/- 1 ps
at 24 keV and up to +/- 23 ps at 5 keV will be possible. In order to evaluate the influence of the device on experiments with focused
hard x-ray pulses, time-dependent wave-optics simulations have been performed by means of Synchrotron Radiation Workshop
(SRW) software for SASE pulses at hv = 5 keV. This software tool has recently been applied to assess the capability of the SDU to
measure the temporal coherence properties of hard xray FEL-pulses. For this earlier study, diffraction at the beam splitter and a one-
dimensional cut through the surface profile was taken into account. At the HED instrument, the XFEL radiation will be focused by
means of compound refractive lenses (CRL) in order to perform experiments with intense, focused hard x-ray pulses. The results of
these experiments severely depend on the fluence and the spatial shape of the beam that is obtained in the focal area. Therefore, in this
paper the impact of wave-front distortions on the spatial intensity profile in the focus is analyzed. For this purpose, the entire optical
layout of the SDU, including diffraction on the beam splitter edge and the two-dimensional surface profiles of all eight mirrors are
taken into account. The XFEL radiation is simulated using the output of the time-dependent SASE code FAST. For the simulations
diffraction on the beam splitter edge as well as height and slope errors of all eight mirror surfaces are taken into account. The impact
of these effects on the ability to focus the beam by means of compound refractive lenses (CRL) are analyzed.
Biography
Victor Kärcher has completed his Bachelor’s in Physics from the University of Münster, Germany. He works on the simulation of x-ray optics in the Group of Helmut Zach-
arias at the University of Münster.
Victor Kärcher, J Laser Opt Photonics 2017, 4:4 (Suppl)
DOI: 10.4172/2469-410X-C1-017