FEL Applications
Paper Title Page
Preparation for the Two-Color FEL Experiment at SXFEL  
  • W.Y. Zhang, C. Feng, B. Liu, Z. Qi
    SINAP, Shanghai, People's Republic of China
  Generation of double ultra-short radiation pulses with different carrier wavelengths in the x-ray regime is of remarkable interest in the FEL user community. Applications exist over a broad range of wavelengths involving pump-probe experiments. This paper presents the design studies for the two-color FEL experiment at the Shanghai soft x-ray FEL test facility. An optical system has been built to produce the double pulse two-color seed laser. We show the design and measurement results of this seed laser system.  
TUP069 Simulating Beam Dynamics in Coherent Electron-Cooling Accelerator with WARP 1
  • K. Shih
    SBU, Stony Brook, New York, USA
  • Y.C. Jing, V. Litvinenko, I. Pinayev, G. Wang
    BNL, Upton, Long Island, New York, USA
  • K. Mihara
    Stony Brook University, Stony Brook, USA
  • I. Petrushina
    SUNY SB, Stony Brook, New York, USA
  Funding: DoE NP office, grant DE-FOA-0000632, NSF grant PHY-1415252.
Coherent Electron Cooling (CeC) is a novel cooling technique based on amplification of interaction between hadrons and electron by an FEL. If proven, this CeC could bring a revolution in hadron and electron-hadron colliders. A dedicated CeC proof-of-principle experiment is under way at RHIC collider (BNL) using a sophisticated SRF accelerator for generating and accelerating electron beam. This paper is dedicated to studies of beam dynamics in the CeC accelerator and specifically to emittance preservation in its ballistic compressions section. Two 500-MHz RF cavities are used for generating the necessary energy chirp leading in 1.56-MeV, 0.5-nsec-long electron bunched to compress them to 25-psec duration downstream. During the commissioning of the CeC accelerator we noticed that beam emittance can be strongly degraded when electron beam passes these 500 MHz RF cavities off-axis. We used a full 3D PIC code Wrap to simulate effect of the off-axis beam propagation through these
TUP070 Development of Mid-Infrared Photoacoustic Spectroscopy System for Solid Samples at Kyoto University Free Electron Laser Facility 1
  • J. Okumura, T. Kii, H. Ohgaki, H. Zen
    Kyoto University, Kyoto, Japan
  Photoacoustic Spectroscopy (PAS) enables IR absorption spectrum measurements of solid samples without preprocessing of samples. Its sensitivity and resolution depend on the intensity and spectral width of the infrared light, respectively. Mid-infrared free electron laser (MIR-FEL) is an intense, quasi-monochromatic and tunable laser in MIR region, so the method of PAS with FEL (FEL-PAS) was proposed.*,** However, the resolution was not so good since they used the direct FEL beam which has the spectral width of 1%. We considered that the resolution can be significantly increased by inserting a high-resolution grating monochromator before the PAS cell. Based on this consideration, a PAS system using an MIR-FEL with the monochromator is under development. We have already conducted preliminary experiments using a PAS cell which has been used in previous studies and successfully measured quite high PAS signals with this setup.*,** A demonstration of experiments to check the spectral resolution will be conducted soon. In this presentation, the progress of the development including the result of demonstration experiments will be reported.
* M. Yasumoto et al., Proceedings of the 2004 FEL Conference, 703-705 (2004).
** M. Yasumoto et al., Eur. Phys. J. Special Topics, 153, 37-40 (2008).
TUP071 Study on Second Harmonic Generation in SiC Using Infrared FEL 1
  • S. Tagiri
    Kyoto Univeristy, Kyoto, Japan
  • T. Kii, H. Ohgaki, H. Zen
    Kyoto University, Kyoto, Japan
  Mode-selective phonon excitation (MSPE) is an attractive method for studying the lattice dynamics (e.g. electron-phonon interaction and phonon-phonon interaction). In addition, MSPE can control electronic, magnetic, and structural phases of materials. In 2013, we have directly demonstrated MSPE of a bulk material (6H-SiC) with MIR-FEL (KU-FEL) by anti-Stokes (AS) Raman-scattering spectroscopy. Recently, we have certified that the Sum Frequency Generation (SFG) also occurs with AS Raman scattering. For distinguishing between the AS Raman scattering and SFG, we need to know the nonlinear susceptibility and transmittance. The coefficients can be measured by the Second Harmonic Generation (SHG) spectroscopy. In this paper, the outline of the measurement system and the preliminary results with a 6H-SiC sample are reported.  
Observations of Fast Structural Changes with an X-ray FEL: Dynamics Studies on Photoactivated Proteins at SACLA  
  • K. Tono
    JASRI/SPring-8, Hyogo, Japan
  X-ray FELs (XFELs) paved the way for exploring ultrafast structural dynamics in a biological macromolecule. Time-resolved protein crystallography with an XFEL now can reach a resolution of the order of femtosecond. One of the most promising techniques for time-resolved measurement is serial femtosecond crystallography (SFX). We have developed an experimental system for time-resolved SFX at SACLA*. This system has been applied for visualizing structural changes in a photoactivated macromolecule such as bacteriorhodopsin (bR)** or photosystem II (PSII)***. In the application to bR, diffraction measurements cover a wide range of timescales from nanoseconds to milliseconds to fully access the structural transitions in the photocycle. The structural data at more than ten time points provided a cascade of structural changes after photoactivation of the retinal chromophore. This 'movie' clearly shows how bR transports protons through a cell membrane against a chemical-potential gradient. This paper gives an overview of the experimental instruments and techniques for studying ultrafast protein dynamics with XFEL, and recent applications at SACLA.
* K. Tono et al., J. Synchrotron Rad. 22, 532 (2015).
** E. Nango et al., Science 354, 1552 (2016).
*** M. Suga et al., Nature 543, 131 (2017).
Four-Wave Mixing Using Extreme Ultraviolet Transient Gratings at FERMI FEL  
  • F. Bencivenga, F. Capotondi, R. Cucini, L. Foglia, C. Masciovecchio, R. Mincigrucci, E. Pedersoli, E. Principi, A. Simoncig
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  Four-wave mixing (FWM) processes are exploited in the optical domain in a large array of scientific and technological applications. The extension of this approach to the XUV and X-ray range was theoretically conceived,* but not experimentally pursued because of the lack of photon sources with enough brightness and coherence. This situation has changed with the advent of FELs, in particular those stabilized by seeding processes. In this context, the XUV pulses delivered by FERMI have been used to experimentally demonstrate the FWM response stimulated by XUV transient gratings.** More recently the 'twin-seed' double-colour FEL mode of FERMI has been employed in a two-colour XUV FWM experiment.*** These results provide grounds to build up the sophisticated experiments envisioned by theoreticians,* which could provide access to high energy/high-wavevector excitations, with elemental selectivity and nano to atomic spatial resolution. Capabilities that can be exploited in different fields, ranging from thermal transport dynamics in nanoelectronic devices to charge transfer processes in molecules.
* S. Tanaka and S. Mukamel, Phys. Rev. Lett., 2002, 89, 043001
** F. Bencivenga et al., Nature, 2015, 520, 205
*** F. Bencivenga et al., Faraday Discuss., 2014, 171, 487
Two-Temperature Equilibration in Warm Dense Hydrogen Measured With X-Ray Scattering from the Linac Coherent Light Source  
  • L.B. Fletcher
    SLAC, Menlo Park, California, USA
  Funding: This work was supported by the DOE/SC/FES under contract No. SF00515 and supported under FWP 100182 and DOE/SC/BES, Materials Sciences and Engineering Division, contract DE-AC02-76SF00515.
Understanding the properties of warm dense hydrogen plasmas is critical for modeling stellar and planetary interiors, as well as for inertial confinement fusion (ICF) experiments. Knowledge of thermodynamic properties of hydrogen in a fusion environment furthers our ability to accurately model complex systems essential to ICF. Of central importance are the electron-ion collision and equilibration times that determine the microscopic properties in a high energy-density state. Spectrally and angularly resolved X-ray scattering measurements from fs-laser heated hydrogen have resolved the picosecond evolution and energy relaxation from a two-temperature plasma towards thermodynamic equilibrium in the warm dense matter regime. The interaction of rapidly heated cryogenic hydrogen irradiated by a 400-nm, 5x1017-W/cm2, 70-fs laser is visualized with ultra-bright 5.5-keV x-ray pulses from the Linac Coherent Light Source (LCLS) in a 1-Hz repetition-rate pump probe setting. We demonstrate that the energy relaxation is faster than many classical binary collision theories that use ad hoc cutoff parameters used in the Landau-Spitzer determination of the Coulomb logarithm.