Fokussierung des Röntgen-Freie-Elektronen-Lasers für die Abbildung und Erzeugung von Materie unter Extrembedingungen

• Antragsteller: Professor Dr. Christian Schroer
• Fachliche Zuordnung: Experimentelle Physik der kondensierten Materie
• Förderung: Förderung von 2012 bis 2016
• Projektkennung: Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 225455836

• Erstellungsjahr: 2016

Zusammenfassung der Projektergebnisse

The project to implement nanofocusing capabilities at the Linac Coherent Light Source (LCLS) turned out to be very successful and received a strong interest in x-ray imaging and high-energydensity science. First nano-beams were created during the first experimental campaign at LCLS in May 2012. Beam characterization is important for a quantitative data analysis, and it could be demonstrated in various experiments at LCLS that scanning coherent x-ray microscopy (ptychography) provides the full information on the nanofocused XFEL beam. However, since beamtime at XFEL sources is precious, the time required for beam characterization had to be reduced as much as possible and can now be done almost in real time. This was achieved by using a fast CSPAD detector to measure the diffraction patterns at a repetition rate of 120 Hz and was complemented by ptychographic reconstruction software developed for graphic cards (GPU). In this way, both data acquisition and phase retrieval can be carried out within minutes. Data processing between these two steps is still the most time consuming step and we are currently working on improving this. The evolution of shock waves could be monitored with high spatial resolution using phasecontrast imaging (PCI). The method provides detailed information on the compression of the material and the shock velocity. In the first measurement campaign in May 2012 this experiment was carried out on different materials using a short picosecond optical drive laser pulse. Although a second beamtime was not granted we could complement these measurements in different succeeding experiments, mainly during commissioning of the PCI setup, using the nanosecond drive laser available at MEC. We further combined PCI with powder diffraction by implementing additional detectors positioned at larger scattering angles and close to the sample. In this way structural information of shock-compressed matter could be obtained on the nanometer and atomic scale at the same time. The powder diffraction data gave insight into potential phase changes that materials often undergo at high pressures and temperatures. We aim to further develop imaging on the nanoscale at the LCLS by implementing techniques to characterize a nanofocused beam for each single pulse. However, this step requires additional imaging diagnostics, which are able to measure the intensity distribution close to the optics for every XFEL pulse. Heating of matter with a nanofocused XFEL beams requires an optimum performance of the optics. To improve on the peak fluence in the nanofocus current aberrations in x-ray optics need to be reduced. For this purpose and with the detailed knowledge of the shape of the nanofocused beam measured by ptychography, we developed a phase plate for refractive optics. It corrects residual phase errors, resulting in nearly optimal Gaussian nanofocusing of the XFEL radiation. The interest for this project was broad and led to numerous invitations to distinguished conferences. Main objectives were successfully accomplished and magnified phase-contrast imaging of fast dynamical processes was demonstrated at the example of imaging elastic wave in diamond. The prototype setup was further developed and the new design was implemented and commissioned at the Matter in Extreme Conditions (MEC) instrument in May 2015.

Projektbezogene Publikationen (Auswahl)

• Developing a platform for high-resolution phase contrast imaging of high pressure shock waves in matter. In S. P. Moeller, M. Yabashi, and S. P. Hau-Riege, editors, Proc. of SPIE, volume 8504, page 85040F. SPIE, San Diego (2012)
  A. Schropp, J. Patommel, F. Seiboth, B. Arnold, E. C. Galtier, H. J. Lee, B. Nagler, J. B. Hastings, and C. G. Schroer
  
• Ronchi test for characterization of nanofocusing optics at a hard x-ray free-electron laser. Opt. Lett. 37(24), 5046–5048 (2012)
  D. Nilsson, F. Uhlén, A. Holmberg, H. M. Hertz, A. Schropp, J. Patommel, R. Hoppe, F. Seiboth, V. Meier, C. G. Schroer, E. Galtier, B. Nagler, H. J. Lee, and U. Vogt
  
• Damage investigation on tungsten and diamond diffractive optics at a hard x-ray free-electron laser. Optics Express 21(7), 8051–8061 (2013)
  F. Uhlén, D. Nilsson, A. Holmberg, H. M. Hertz, C. G. Schroer, F. Seiboth, J. Patommel, V. Meier, R. Hoppe, A. Schropp, H. J. Lee, B. Nagler, E. Galtier, J. Krzywinski, H. Sinn, and U. Vogt
  
• Full spatial characterization of a nanofocused x-ray free-electron laser beam by ptychographic imaging. Scientific Reports 3, 1633 (2013)
  A. Schropp, R. Hoppe, V. Meier, J. Patommel, F. Seiboth, H. J. Lee, B. Nagler, E. C. Galtier, B. Arnold, U. Zastrau, J. B. Hastings, D. Nilsson, F. Uhlén, U. Vogt, H. M. Hertz, and C. G. Schroer
  
• Focusing XFEL SASE pulses by rotationally parabolic refractive x-ray lenses. In Journal of Physics: Conference Series, 499, 012004. IOP Publ. (2014)
  F. Seiboth, A. Schropp, R. Hoppe, V. Meier, J. Patommel, H. J. Lee, B. Nagler, E. C. Galtier, B. Arnold, U. Zastrau, J. B. Hastings, D. Nilsson, F. Uhlén, U. Vogt, H. M. Hertz, and C. G. Schroer
  
• Focus characterization at an X-ray free electron laser by coherent scattering and speckle analysis. Journal of Synchrotron Radiation 22(3), 599–605 (2015)
  M. Sikorski, S. Song, R. Alonso-Mori, M. Chollet, Y. Feng, K. Gaffney, J. Hastings, H. T. Lemke, A. Robert, A. Schropp, F. Seiboth, D. Sokaras, T. Weng, W. Zhang, and D. Zhu
  
• Imaging Shock Waves in Diamond with Both High Temporal and Spatial Resolution at an XFEL. Scientific Reports 5, 11089 (2015)
  A. Schropp, R. Hoppe, V. Meier, J. Patommel, F. Seiboth, Y. Ping, G. W. Collins, J. S. Wark, H. J. Lee, B. Nagler, E. C. Galtier, B. Arnold, U. Zastrau, J. B. Hastings, and C. G. Schroer
  
• The Matter in Extreme Conditions instrument at the Linac Coherent Light Source. Journal of Synchrotron Radiation 22(3), 520–525(2015)
  B. Nagler, B. Arnold, G. Bouchard, R. F. Boyce, R. M. Boyce, A. Callen, M. Campell, R. Curiel, E. Galtier, J. Garofoli, E. Granados, J. Hastings, G. Hays, P. Heimann, R. W. Lee, D. Milathianaki, L. Plummer, A. Schropp, A. Wallace, M. Welch, W. White, Z. Xing, J. Yin, J. Young, U. Zastrau, and H. J. Lee