Scientific Instrument FXE

7th Call for User Proposals Open! 

Capabilities of FXE offered for Users in this call

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.

Instrument specifications

for past User Experiments


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
50 fs FWHM
Beam size
8–200 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 (200 µJ) 800 nm (50 fs, 15fs possible), harmonics, TOPAS adjustable UV-vis-NIR 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)
Jungfrau (2D, 1024 x 1024 px, 75 x 75 µm pixel size, 10Hz)
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 1x104 per pixel)