Author: Freund, W.
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TUP058 First Characterization of the Photon Beam at the European XFEL in July, 2017 180
  • V. Balandin, B. Beutner, F. Brinker, W. Decking, M. Dohlus, L. Fröhlich, U. Jastrow, R. Kammering, T. Limberg, D. Nölle, M. Scholz, A.A. Sorokin, K.I. Tiedtke, M.V. Yurkov, I. Zagorodnov
    DESY, Hamburg, Germany
  • U. Boesenberg, W. Freund, J. Grünert, A. Koch, N.G. Kujala, J. Liu, Th. Maltezopoulos, M. Messerschmidt, I. Petrov, L. Samoylova, H. Sinn
    EuXFEL, Schenefeld, Germany
  North branch of the European XFEL, SASE1, produced first light on May 3rd, 2017, and XFEL operation has been gradually improved then. First characterization of the photon beam has been performed in July / August 2017, just before an official starting date of user experiments (September 1st, 2017). Energy of the electron beam was 14 GeV, bunch charge was 500 pC, photon energy was 9.3 keV. With photon diagnostics available at that time (X-ray gas monitor (XGM) and FEL imager) we measured the gain curve and traced evolution of the FEL radiation mode along the undulator. An important conclusion is that experimental results demonstrate reasonable agreement with baseline parameters. Developed techniques of the photon beam characterization also provided solid base for identification of the problems and means for improving SASE FEL tuning and operation.  
DOI • reference for this paper ※  
About • paper received ※ 20 August 2019       paper accepted ※ 27 August 2019       issue date ※ 05 November 2019  
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Pulse Resolved Photon Diagnostics at MHz Repetition Rates  
  • J. Grünert, F. Dietrich, W. Freund, A. Koch, N.G. Kujala, J. Laksman, J. Liu, Th. Maltezopoulos, M.P. Planas
    EuXFEL, Schenefeld, Germany
  The European X-ray Free Electron Laser (EuXFEL) enables a new era in the research of ultrafast dynamics of microscopic structures with atomic resolution. First light was demonstrated in May 2017 and operation started with three undulator beamlines and six experimental endstations with a commissioning phase from 2017 till early 2019 [1]. The world-wide unique feature of this machine is the combination of immensely brilliant and ultrashort X-ray pulses with a repetition rate in the MHz range. However, this also requires novel photon diagnostics [2] to cope with these extreme conditions, to enable stable machine operation and to deliver beam diagnostic data to the users. In this contribution, we describe the results obtained in the commissioning and operation of the facility diagnostics capable of surviving exposure to multi-bunch operation and resolving the characteristics of individual pulses at MHz rates. In particular we employ for this task gas-ionization monitors, photoelectron spectroscopy of ionized noble gases, gated scintillator imaging, crystal spectrometers and arrival time monitors with fast line detectors, diamond detectors, and multi-channel plate based intensity monitors.
[1] T. Tschentscher et al., Appl. Sci. 7, 592 (2017).
[2] J. Gruenert et al., accepted for publication in J. Synchrotron Rad. (2019).
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Undulator Adjustment with the K-Monochromator System at the European XFEL  
  • W. Freund, J. Grünert, S. Karabekyan, A. Koch, J. Liu
    EuXFEL, Hamburg, Germany
  • L. Fröhlich, D. Nölle, J. Wilgen
    DESY, Hamburg, Germany
  The SASE1 and SASE2 undulator systems of the European XFEL consist of 35 segments with variable-gap planar undulators which are initially tuned to precise on-axis magnetic field strengths in a magnetic measurement lab. After tunnel installation only photon based methods can determine the K-values of undulator segments with a similar accuracy. The spontaneous radiation of single or few undulator cells is spectrally filtered with the K-monochromator (K-mono) and recorded with a sensitive spontaneous radiation imager (SR-imager). By processing the images from the SR-imager and geometrical fitting of the spatial distribution of the spontaneous radiation we obtain very fast the K-parameter and the beam pointing of single segments. This information is used for adjustments of the gap settings and vertical offset positions of the single undulator segments. In this presentation we describe the K-mono system at the European XFEL, the measurement principle, and the measurements that were performed [1].
[1] "First measurements with the K-Monochromator at European XFEL", proceedings of PhotonDiag 2018, JSR (in publication)
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