TUA —  SASE FELs   (22-Aug-17   08:30—10:00)
Chair: Z. Huang, SLAC, Menlo Park, California, USA
Paper Title Page
TUA01 Recent FEL Experiments at FLASH 1
  • S. Schreiber, E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg, Germany
  The FLASH free-electron laser user facility at DESY (Hamburg, Germany) provides high brilliance SASE FEL radiation in the XUV and soft X-ray wavelength range. With the recent installation of a second undulator beamline (FLASH2), variable-gap undulators are now available. They now allow various experiments not possible with the FLASH1 fixed gap undulators. We report on experiments on tapering, harmonic lasing, reverse tapering, frequency doubling at FLASH2 and experiments using double pulses for specific SASE and THz experiments at FLASH1.  
Design and Modelling of the Baseline Layout for the Soft X-Ray Laser (SXL) at MAX IV Laboratory  
  • F. Curbis, S. Werin
    MAX IV Laboratory, Lund University, Lund, Sweden
  The Soft X-ray Laser (SXL) is a project aiming to build a new beamline that will exploit the potential of the MAX IV 3 GeV linac and its Short Pulse Facility (SPF). In fact, this injector, which is routinely used as an electron source for the two rings in the laboratory, is capable of delivering ultra-brilliant electron pulses and possibly driving a Free Electron Laser (FEL). While the necessary technical improvements and features of the linac are described in another contribution, this paper presents the baseline layout of the SXL FEL and point out the features of the photon source that should deliver brilliant pulses between 1 and 5 nm. The baseline design consists of a SASE FEL with variable polarization undulators. However, the plan is to develop a comprehensive system of external sources at various wavelength in order to enable various pump-probe schemes, thereby satisfying the requests of the users community. Moreover the design needs to take into account the possibility of accommodating two-pulse-two-color capability and the production of femtosecond or even attosecond pulses.  
slides icon Slides TUA02 [2.345 MB]  
Generation of High Power, Short X-Ray FEL Pulses  
  • M.W. Guetg, F.-J. Decker, Y. Ding, Z. Huang, A.A. Lutman, T.J. Maxwell
    SLAC, Menlo Park, California, USA
  X-ray Free Electron Lasers combine high pulse power, short pulse length, narrow bandwidth and a high degree of transverse coherence. Increasing the photon pulse power, while shortening the pulse length, is of key importance on the way to single molecule imaging. This letter shows experimental results at the Linac Coherent Light Source improving its power to more than 300 GW, while reducing the photon pulse length to 10fs. This was achieved by removing residual transverse-longitudinal centroid beam offsets and correction of dispersion when operating over 6 kA peak current.  
TUA04 Suppression of the CSR Effects at a Dogleg Beam Transport Using DBA Lattice 1
  • T. Hara, T. Inagaki, C. Kondo, H. Maesaka, Y. Otake, H. Tanaka, K. Togawa
    RIKEN SPring-8 Center, Hyogo, Japan
  • K. Fukami
    JASRI/SPring-8, Hyogo, Japan
  • T. Hasegawa, O. Morimoto, S. Nakazawa, M. Yoshioka
    SES, Hyogo-pref., Japan
  Multi-beamline, multi-user operation is an important issue of linac-based XFELs to improve usability and efficiency of facilities. At SACLA, the multi-beamline operation had been tested since 2015 using two beamlines (BL2 and BL3). But the CSR effects at a 3-degree dogleg beam transport of BL2 caused a projected emittance growth and instability of the beam orbit due to a high peak current of 10 kA and a short bunch duration of SACLA. Consequently, stable lasing was obtained only for elongated electron bunches with low peak currents below 3 kA. To mitigate the CSR effects, the beam optics of the dogleg was rearranged. The new beam optics are based on two DBA (double bend achromatic) structures and the transverse effects of CSR are cancelled between four bending magnets. To avoid the bunch length change, the electron beam passes an off-center orbit at the quadrupole magnets of DBA. Under the new beam optics, stable lasing has been successfully obtained with 10 kA electron bunches, and the parallel operation of the two beamlines will be started in September 2017 for user experiments.  
slides icon Slides TUA04 [7.330 MB]  
Generating Subfemtosecond Hard X-Ray Pulses with Optimized Nonlinear Bunch Compression  
  • S. Huang
    PKU, Beijing, People's Republic of China
  • Y. Ding, Y. Feng, E. Hemsing, Z. Huangpresenter, J. Krzywinski, A.A. Lutman, A. Marinelli, T.J. Maxwell, D. Zhu
    SLAC, Menlo Park, California, USA
  Funding: This work is supported by the U.S. Department of Energy Contract No. DE-AC02-76SF00515 and the National Key Research and Development Program of China (Grant No. 2016YFA0401904).
A simple method for generating single-spike hard x-ray pulses in free-electron lasers (FELs) has been developed at the Linac Coherent Light Source (LCLS). By optimizing the electron bunch compression in experiments, we have obtained half of the hard x-ray FEL shots containing single-spike spectrum. At 5.6-keV photon energy, the single-spike shots have a mean pulse energy of about 10 J with 70% intensity fluctuation and the pulse width (full width at half maximum) is evaluated to be at 200-attosecond level.