Author: Krzywinski, J.
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MOP061 X-ray Regenerative Amplifier Free-Electron Laser Concepts for LCLS-II 192
  • G. Marcus, Y. Ding, J.P. Duris, Y. Feng, Z. Huang, J. Krzywinski, T.J. Maxwell, D.F. Ratner, T.O. Raubenheimer
    SLAC, Menlo Park, California, USA
  • K.-J. Kim, R.R. Lindberg, Yu. Shvyd'ko
    ANL, Argonne, Illinois, USA
  • D.C. Nguyen
    LANL, Los Alamos, New Mexico, USA
  High-brightness electron beams that will drive the next generation of high-repetition rate X-ray FELs allow for the possibility of optical cavity-based feedback. One such cavity-based FEL concept is the Regenerative Amplifier Free-Electron Laser (RAFEL). This paper examines the design and performance of possible RAFEL configurations for LCLS-II. The results are primarily based on high-fidelity numerical particle simulations that show the production of high brightness, high average power, fully coherent, and stable X-ray pulses at LCLS-II using both the fundamental and harmonic FEL interactions.  
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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. Huang, 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.
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Fresh Slice Self-Seeding and Fresh Slice Harmonic Lasing at LCLS  
  • C. Emma, C. Pellegrini
    UCLA, Los Angeles, California, USA
  • J.W. Amann, M.W. Guetg, J. Krzywinski, A.A. Lutman, C. Pellegrini, D.F. Ratner
    SLAC, Menlo Park, California, USA
  • D.C. Nguyen
    LANL, Los Alamos, New Mexico, USA
  We present results from the successful demonstration of fresh slice self-seeding at the Linac Coherent Light Source (LCLS).* The performance is compared with SASE and regular self-seeding at photon energy of 5.5 keV, resulting in a relative average brightness increase of a factor of 12 and a factor of 2 respectively. Following this proof-of-principle we discuss the forthcoming plans to use the same technique** for fresh slice harmonic lasing in an upcoming experiment. The demonstration of fresh slice harmonic lasing provides an attractive solution for future XFELs aiming to achieve high efficiency, high brightness X-ray pulses at high photon energies (>12 keV).***
* C. Emma et al., Applied Physics Letters, 110:154101, 2017.
** A. A. Lutman et al., Nature Photonics, 10(11):745-750, 2016.
*** C. Emma et al., Phys. Rev. Accel. Beams 20:030701, 2017.
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High-Flux, Fully Coherent X-Ray FEL Oscillator  
  • K.-J. Kim, S.P. Kearney, T. Kolodziej, R.R. Lindberg, X. Shi, D. Shu, Yu. Shvyd'ko
    ANL, Argonne, Illinois, USA
  • K.L.F. Bane, Y. Ding, P. Emma, W.M. Fawley, J.B. Hastings, Z. Huang, J. Krzywinski, G. Marcus, T.J. Maxwell
    SLAC, Menlo Park, California, USA
  • V.D. Blank, S. Terentiev
    TISNCM, Troitsk, Russia
  • W.M. Fawley
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • C. Grizolli
    LNLS, Campinas, Brazil
  • W. Qin
    PKU, Beijing, People's Republic of China
  • S. Stoupin
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • J. Zemella
    DESY, Hamburg, Germany
  Funding: The ANL part of this work is supported by the U.S. DOE Office of Science under Contract No. DE-AC02-06CH11357 and the SLAC part under contract No. DE-AC02-76SF00515.
By optimizing the parameters of the accelerator, undulator, and the optical cavity, an XFELO driven by an 8-GeV superconducting linac is predicted to produce 10zEhNZeHn photons per pulse at the important photon energies around 14.4 keV.* This is an order of magnitude larger than that in previous designs.** With a BW of 3 meV (FWHM), rep rate of 1 MHz, and taking into account the full coherence, the spectral brightness is then 2×1026 photons per (mm2mr2 0.1\% BW), which is higher than any other source currently operating or anticipated in the future. Experiments at APS beam lines have shown that a high-quality diamond crystal can survive the power density (~15 kW/mm2) expected at the XFELO intra-cavity crystals preserving the high reflectivity.*** The compound refractive lenses can serve as the focusing element. Adding an XFELO to the suite of other FEL sources will, at a minor incremental cost but with a major scientific payoff, significantly expand the scientific capabilities at superconducting linac-based XFEL facilities, such as the European XFEL, the proposed LCLS-II High Energy upgrade and the XFEL project in Shanghai.
* W. Qin et al., this conference.
** R.R. Lindberg et al., Phys. Rev. ST Accel. Beams, vol 14, 403 (2011).
*** T. Kolodziej et al., this conference.
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WEP048 Coherent Undulator Radiation From a Kicked Electron Beam 515
  • J.P. MacArthur, Z. Huang, J. Krzywinski, A.A. Lutman
    SLAC, Menlo Park, California, USA
  The properties of off-axis radiation from an electron beam that has been kicked off axis are relevant to recent Delta undualtor experiments at LCLS. We calculate the coherent emission from a microbunched beam in the far-field, and compare with simulation. We also present a mechanism for microbunches to tilt toward a new direction of propagation.  
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Fresh-Slice X-Ray Free Electron Laser Schemes for Advanced X-Ray Applications  
  • A.A. Lutman, R.N. Coffee, Y. Ding, J.P. Duris, M.W. Guetg, Z. Huang, J. Krzywinski, J.P. MacArthur, A. Marinelli, T.J. Maxwell, S.P. Moeller, J. Zemella
    SLAC, Menlo Park, California, USA
  • N. Berrah
    University of Connecticut, Storrs, Connecticut, USA
  • C. Emma
    UCLA, Los Angeles, USA
  Funding: This work was supported by Department of Energy contract nos DE-AC02-76SF00515 and DE-SC0012376
The novel fresh-slice XFEL scheme grants control on the temporal slice of the electron bunch lasing in each undulator section. The technique relies on a time-dependent electron bunch trajectory impressed by the transverse wakefield of a corrugated structure and subsequent orbit manipulation in the undulator section. Fully saturated double pulses are produced in two different undulator sections. The wavelength of each pulse is controlled by the undulator magnetic strength and the delay between the pulses can be scanned from a few femtosecond advance of the pulse generated on the bunch head in the second section to a picosecond delay provided by the magnetic chicane. Three-color saturated pulses are demonstrated by using three undulator sections and the polarization of the pulse generated in the last section can be controlled by the variable polarization Delta undulator. In this work we also show the early results for the first multi-stage amplification scheme, producing ultra-short single-pulses with a 100-GW power level in the soft X-rays. The multi-stage amplification is also demonstrated to improve the performance in power and pulse duration control for the two-color FEL scheme.
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