FEL Applications
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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
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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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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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THP041 Interaction of Powerful Electro-Magnetic Fields With Bragg Reflectors 673
  • I. Bahns, W. Hillert, P. Rauer, J. Roßbach
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  • H. Sinn
    EuXFEL, Schenefeld, Germany
  Funding: supported by BMBF FKZ 05K16GU4
The interaction of an X-ray free electron laser (XFEL) with a Bragg Reflector can cause a change of the lattice constant, which has a direct influence on the stability of the reflection conditions [1] and can also excite modes of vibration [2]. The dynamical thermoelastic effects of the photon-matter-interaction are simulated with a finite-element-method (FEM) using the assumptions of continuums mechanics. To compare the simulation results with measured signals, a Michelson interferometer with ultrafast photodiodes (risetime <175ps, bandwith >2GHz) has been built up. To test the experimental setup in an in-house environment a pulsed UV laser is used to introduce a temporal displacement field in a silicon crystal created by about 0.26µJ of absorbed energy. The measured signal is in agreement with the FEM simulation and has shown that if averaging over thousands of pulses is applied a resolution <0.5pm is feasible. This makes this experimental setup useful to investigate the X-ray-matter-interaction of Bragg reflectors at modern X-ray facilities.
[1] S. Stoupin et al., Physical Review B 86.5 (2012): 054301.
[2] B. Yang, S. Wang and J. Wu, J. Synchrotron Rad. (2018) 25, 166-176.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP041  
About • paper received ※ 23 August 2019       paper accepted ※ 31 October 2019       issue date ※ 05 November 2019  
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THP044 The Simulation Study for Single and Multi Turn ERL Based EUV FEL 677
  • K.M. Nam, G.S. Yun
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  • Y.W. Parc
    PAL, Pohang, Kyungbuk, Republic of Korea
  Photolithography technology is the core part of the semiconductor manufacturing process. It has required light having stronger power for higher throughput. ERL based EUV FEL is emerging as a next generation EUV source which can produce the light over 10 kW. In this study, first, EUV-FEL design, which is based on single turn, is represented. It accelerates 40 pC electron beam to 600 MeV and produces EUV, whose wavelength and power are 13.5 nm and 37 kW. Second, multiturn based design is represented. It improved compactness to make it more suitable for industrial use. As a result, the electron beam was able to obtain the kinetic energy and circulate, and the size was reduced to about half without reducing the power greatly. This study is expected to increase the practical industrialization potential of ERL-based photolithography.  
poster icon Poster THP044 [0.584 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP044  
About • paper received ※ 20 August 2019       paper accepted ※ 28 August 2019       issue date ※ 05 November 2019  
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