WED —  Wednesday - Late Afternoon   (28-Aug-19   16:15—17:45)
Chair: J. Grünert, EuXFEL, Schenefeld, Germany
Paper Title Page
WED01 Experience with Short-Period, Small Gap Undulators at the SwissFEL Aramis Beamline 564
 
  • T. Schmidt, M. Aiba, A.D. Alarcon, C. Arrell, S. Bettoni, M. Calvi, A. Cassar, E. Ferrari, R. Follath, R. Ganter, N. Hiller, P.N. Juranič, C. Kittel, F. Löhl, E. Prat, S. Reiche, T. Schietinger, D. Voulot, U.H. Wagner
    PSI, Villigen PSI, Switzerland
  • N.J. Sammut
    University of Malta, Faculty of Engineering, Msida, Malta
 
  The SwissFEL Aramis beamline provides hard X-ray FEL radiation down to 1 Angström with 5.8 GeV and short period, 15 mm, in-vacuum undulators (U15). To reach the maximum designed K-value of 1.8 the U15s have to be operated with vacuum gaps down to 3.0 mm. The thirteen-undulator modules are 4 m long and each of them is equipped with a pair of permanent magnet quadrupoles at the two ends, aligned magnetically to the undulator axis. Optical systems and dedicated photon diagnostics are used to check the alignment and improve the K-value calibration. In this talk the main steps of the undulator commissioning will be recalled and a systematic comparison between the magnetic results and the electron and photon based measurements will be reported to highlight achievements and open issues.  
slides icon Slides WED01 [13.825 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WED01  
About • paper received ※ 28 August 2019       paper accepted ※ 06 November 2019       issue date ※ 05 November 2019  
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WED02 Absorbed Radiation Doses on the European XFEL Undulator Systems During Early User Experiments 569
 
  • F. Wolff-Fabris, J. Pflüger, H. Sinn
    EuXFEL, Schenefeld, Germany
  • W. Decking, D. Nölle, F. Schmidt-Föhre
    DESY, Hamburg, Germany
  • A. Hedqvist, F. Hellberg
    Stockholm University, Stockholm, Sweden
 
  The EuXFEL is a FEL user facility based on a superconducting accelerator with high duty cycle. Three gap movable SASE Undulator Systems using hybrid NdFeB permanent magnet segments are operated. Radiation damage on undulators can impact the quality of the SASE process and ultimately threaten user operation. We observed [1] in the commissioning phase doses up to 4 kGy and 3% demagnetization effect in a diagnostic undulator. Currently all SASE systems are used for user photon delivery and in this work we present characteristics of the absorbed radiation doses on undulators under stable conditions. Doses on the upstream segments are found to be originated in the event of occasional high energy electron losses. In contrast, towards the downstream end of a SASE system, individual segments show persistent absorbed doses which are proportional to the transmitted charge and are dominated by low energy radiation. This energy-dependence depiction shall result in distinct radiation damage thresholds for individual segments. Portable magnetic flux measurement systems allow in-situ tunnel assessment of undulator properties in order to estimate radiation dose limits for future user operation.
[1] F. Wolff-Fabris et al., J. of Phys. - Conf. Series 1067, 032025 (2018)
 
slides icon Slides WED02 [7.344 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WED02  
About • paper received ※ 19 August 2019       paper accepted ※ 27 August 2019       issue date ※ 05 November 2019  
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WED03
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).
 
slides icon Slides WED03 [4.921 MB]  
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WED04
Undulator Adjustment with the K-Monochromator System at the European XFEL  
 
  • W. Freund, J. Grünert, S. Karabekyan, A. Koch, J. Liu
    EuXFEL, Schenefeld, 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)
 
slides icon Slides WED04 [13.278 MB]  
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