THP2WD —  WG-D   (08-Mar-18   16:00—18:00)
Chair: J. Pflueger, DESY, Hamburg, Germany
Paper Title Page
THP2WD01 Construction and Optimization of Cryogenic Undulators at SOLEIL 193
 
  • M. Valléau, P. Berteaud, F. Briquez, P. Brunelle, N. Béchu, M.-E. Couprie, J. Da Silva Castro, J.M. Dubuisson, A. Ghaith, C. Herbeaux, J. Idam, C.A. Kitegi, F. Lepage, A. Lestrade, M. Louvet, O. Marcouillé, F. Marteau, A. Mary, A. Nadji, L.S. Nadolski, P. Rommeluère, M. Sebdaoui, A. Somogyi, K.T. Tavakoli, M. Tilmont, T. Weitkamp
    SOLEIL, Gif-sur-Yvette, France
 
  Funding: Synchrotron SOLEIL, L'Orme des Merisiers, 91 192 BP 34 Gif-sur-Yvette, France,
With permanent magnets undulator operation at cryogenic temperature, the magnetic field and the coercivity can be enhanced, enabling shorter periods with high magnetic fields. The first full scale (2 m long, 18 mm period) hybrid cryogenic undulator [1] using PrFeB [2] magnets operating at 77 K was installed at SOLEIL in 2011. Photon spectra measurements, in good agreement with the ex-pectations from magnetic measurements, were used for precise alignment and taper optimization. The second and third 18 mm PrFeB cryogenic undulators, modified to a half-pole/magnet/half-pole structure, were optimized without any magnet or pole shimming after assembly but mechanical sortings and some geometrical corrections had been done before assembly. A systematic error on individual magnets on the third U18 was also compensated. In-situ measurement benches, including a Hall probe and a stretched wire to optimize the undulator field at room and cryogenic temperature are presented. An upgrade of these in-situ benches will be detailed with the fabrication of a 15 mm 3 m long PrFeB cryogenic undulator at SOLEIL.
[1] C. Benabderrahmane, M. Valléau, M. E. Couprie, Phys. Rev. Accel. Beams 20, 033201(2017)
[2] C. Benabderrahmane, M. Valléau, M. E. Couprie, NIMA 669, 1-6, (2012)
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FLS2018-THP2WD01  
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THP2WD02
Optimisation of Superconducting Undulators for X-ray FELs  
 
  • J.A. Clarke
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
 
  When superconducting undulators (SCUs) are optimised specifically for Free Electron Lasers (FELs) rather than storage rings a number of interesting implications emerge. In particular these relate to the vacuum requirement, the heat deposition within the SCU due to wakefield effects, and the undulator geometry itself. The impact of these considerations is that the peak field level achievable in an SCU specifically optimised for an FEL is significantly enhanced. For example, a planar SCU, utilising NbTi, with a 15mm period and 5mm aperture optimised for an FEL instead of a storage ring will generate a peak field of 2.1T compared to 1.4T. This radical increase in undulator performance will have a major impact on the optimisation of future X-ray FELs. This paper describes how an SCU for an X-ray FEL will be able to generate magnetic field levels far beyond those currently foreseen by any other magnet technology. It will also describe the prototype SCU being assembled now in the UK and the planned demonstration with beam on the CLARA test accelerator in early 2018.  
slides icon Slides THP2WD02 [9.412 MB]  
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THP2WD03
Partial Coherence in Undulator Beamlines at Ultra-low Emittance Storage Rings  
 
  • M. Sanchez del Rio
    ESRF, Grenoble, France
 
  The modelling of the radiation through the beamline is essential when dealing with synchrotron beamlines. Incoherent radiation from synchrotron can be analyzed using methods such as Monte Carlo ray tracing. Coherent radiation is analyzed by physical optics. None of these methodologies can be directly applied to partial coherence without some approximations. We introduced a new exact numerical method based on its decomposition in coherent modes for fully calculating the cross spectral density of the synchrotron radiation*. All parameters of the beam can be calculated from the numeric decomposition using COMSYL**. Moreover, the spectrum of the modes along the beamline gives additional precious information, as it is a direct measure of how much coherence has the beam. Coherent fraction becomes a natural measure of the amount of coherence in the beam. Some examples of simulations for the EBS (Extreme Brilliant Source) under construction at ESRF are shown.
* Glass, M. & Sanchez del Rio, M (2017) EPL 119 34004
** github.com/mark-glass/comsyl
 
slides icon Slides THP2WD03 [5.732 MB]  
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