THA —  Thursday - Early Morning   (29-Aug-19   09:00—10:45)
Chair: Y.U. Jeong, KAERI, Daejon, Republic of Korea
Paper Title Page
THA01
Serial Femtosecond Crystallography at MHz XFELs  
 
  • M.L. Grünbein
    Max Planck Institute for Medical Research, Heidelberg, Germany
 
  The new megahertz (MHz) X-ray free-electron lasers (XFEL) promise data collection in an extremely rapid and sample-efficient manner. However, this can only hold true under the condition that pristine sample is provided at a rate commensurate to the XFEL pulse rate, imposing severe constraints on sample delivery. Liquid jet injection is ideally suited for this task and the method of choice for biological samples. However, the high intensity of the XFEL pulse not only allows to capture diffraction data from tiny samples, but it subsequently also destroys the exposed sample in the jet. The energy deposited by the XFEL beam results in an explosion, generating a gap in the liquid jet transporting the sample [1]. Moreover, a shock wave is launched, propagating along the jet and producing ns-long pressure jumps on the order of 0.1-1 GPa, possibly affecting the sample [1]. We will discuss recent experiments performed at European XFEL, demonstrating that meaningful data collection of unaffected sample is possible at 1 MHz repetition rate [2,3] as well as findings and implications from serial femtosecond crystallography experiments performed at the LCLS using much higher X-ray repetition rate.
[1] C. A. Stan et al., (2016). Nat Phys 12(10): 966-971
[2] M. L. Grünbein et al., (2018). Nat Commun 9: 3487
[3] M. O. Wiedorn et al., (2018). Nat Commun 9: 4025
 
slides icon Slides THA01 [0.051 MB]  
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THA02
Searching for the Hypothesized Liquid-Liquid Critical Point in Supercooled Water with X-Ray Free Electron Laser  
 
  • K.H. Kim
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  • K. Amann-Winkel
    FYSIKUM, AlbaNova, Stockholm University, Stockholm, Sweden
  • A. Nilsson
    Stockholm University, Stockholm, Sweden
 
  Funding: This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT)(No. 2019R1C1C1006643).
Water is the most important liquid for our existence on Earth and plays an essential role in physics, chemistry, biology, and geoscience. In the liquid form, water has numerous anomalous properties as compared to other liquids such as density maximum at 4-degree C. As an explanation for these anomalous experimental observations, a hypothetical liquid-liquid transition (LLT) and a liquid-liquid critical point (LLCP) has been proposed deep in the supercooled regime. Recently a new method of rapid cooling and ultrafast probing with wide-angle X-ray scattering (WAXS) using FELs (LCLS, SACLA, and PAL-XFEL) has allowed the venture into no man’s land and we found the first experimental evidence of the existence of the Widom line which is supposed to emanate from the LLCP [1]. By introducing optical pulse to the setup, pump-probe type measurements are also possible to study the liquid-liquid transition.
[1] K. H. Kim et al., "Maxima in the Thermodynamic Response and Correlation Functions of Deeply Supercooled Water", Science, 358, 1589-1593 (2017)
 
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THA03
IR-FEL Project at the cERL and Future EUV-FEL Lithography  
 
  • R. Kato, Y. Honda, H. Kawata, T. Miyajima, N. Nakamura, H. Sakai, M. Shimada, Y. Tanimoto, K. Tsuchiya
    KEK, Ibaraki, Japan
 
  Recently KEK has launched an infrared FEL project with a competitive funding from NEDO (New Energy and Industrial Technology Development Organization). The purpose of this project is to build a mid-infrared FEL at the compact Energy Recovery Linac (cERL), and to use that FEL as a light source for construction of the processing database required for industrial lasers. The FEL system is composed of two 3 m undulators and a matching section between them, and generates light with a maximum pulse energy of 1 µJ at the wavelength of 20 µm with an 81.25 MHz repetition rate. The FEL is also expected to become a proof-of-concept machine for ERL base FELs for future EUV lithography. The detail of the project will be presented, and the relationship of the technical development between the mid-infrared FEL and the future EUV-FEL will be discussed.  
slides icon Slides THA03 [5.424 MB]  
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THA04 Ultrafast Magnetisation Dynamics at the Low-Fluence Limit Supported by External Magnetic Fields 574
 
  • M. Riepp, K. Bagschik, T. Golz, G. Grübel, L. Müller, A. Philippi-Kobs, W.R. Roseker, R. Rysov, N. Stojanovic, M. Walther
    DESY, Hamburg, Germany
  • F. Capotondi, M. Kiskinova, D. Naumenko, E. Pedersoli
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • R. Frömter, H.P. Oepen
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
 
  We report on ultrafast magnetisation dynamics in ferro-magnetic cobalt/platinum multilayers upon pumping by near and mid to far infrared radiation, utilizing sub-100 femtosecond free-electron laser pulses. The evolution of the excited magnetic state is studied on femtosecond timescales with nanometre spatial resolution and element selectivity, employing time-resolved magnetic small-angle X-ray scattering. The obtained results contribute to the ongoing discussion to what extent either coupling of the electromagnetic field or rather quasi-instantaneous heating of the electron-system is the driving force for phenomena like ultrafast demagnetization or all-optical helicity-dependent switching.  
slides icon Slides THA04 [4.980 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THA04  
About • paper received ※ 19 August 2019       paper accepted ※ 19 September 2019       issue date ※ 05 November 2019  
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