Scientific Instrument FXE

The FXE instrument enables ultrafast pump–probe experiments on ultrafast timescales—below 100 femtoseconds—for a broad scientific user community.

The instrument comprises two independent secondary X-ray emission spectrometers next to a 1-Mpx detector for scattering studies. Its main research is devoted to dynamic studies of chemical and biochemical reactions in liquids next to different solid-state applications. With a powerful laser as pump source, it permits studies with femtosecond time resolution exploiting different observables via a suite of hard X-ray tools (which may be further expanded over time):

  • X-ray diffraction (XRD)
  • X-ray diffuse scattering (XDS), or wide-angle X-ray scattering (WAXS)
  • X-ray emission spectroscopies (XES): non-resonant, or resonant inelastic X-ray scattering (RIXS)
  • X-ray absorption spectroscopies: X-ray absorption near-edge structure (XANES), or extended X-ray absorption fine structure (EXAFS)

The FXE scientific instrument serves a broad scientific community and embraces several fields of ultrafast X-ray science and their applications. State-of-the-art femtosecond instrumentation and techniques, both for X-rays and optical lasers, delivers new information about geometric and electronic structures serving applications in many fields, and particular in the areas of

  • Chemical dynamics
  • Photovoltaic applications
  • Photosynthesis
  • Catalytic processes
  • Material physics

Operation of the FXE instrument started in September 2017. A more detailed description of the science case of FXE can be found in the FXE TDR and CDR.

The main specifications and beam parameters of FXE are summarized in table 1 below. Further technical details about the available equipment at FXE is available here and in the TDR and CDR or by contacting the FXE group.

Full instrument specifications

  • for the 2nd run of Early User Experiments, 3rd, 4th run

  • for the 5th run

Bandwidth ΔE/E
1x10-3 (natural FEL source) , 1x10-4 (standard Si(111) 4-bounce mono)
Photon energy range
5–20 keV
Linear (horizontal), circular (future option)
X-ray pulse duration
1–300 fs FWHM
Beam size
1–300 µm adjustable (via several Be lenses)
Special optics
1 primary 4-bounce Si(111) mono
2 secondary (von Hamos, Johann) spectrometers
Optical laser wavelengths
Pump–probe (0.1–1 mJ) 800 nm (15–100 fs)
Pump–probe (1 µJ) 1030 nm (275 fs) NOPA adjustable UV-vis-NIR (10 fs possible)
Pump–probe (>20 mJ) 1030 nm (850 fs)
Pump–probe (>50 µJ) 1 mm (=0.3 THz) generated via optical rectification
X-ray detectors
APD (0D, full rep. rate with MHz DAQ)
Gotthard (1D, 1280 px, 50 µm pixel pitch, 0.9 MHz)
LPD (2D, 1 Mpx, (500 µm)2 pixel size, 512 frames at 4.5 MHz, 3-fold dynamic gain covering 1 (SP at 12keV) to 1x105 per pixel)