Beamlines

As an X-ray free-electron laser, the European XFEL generates X-ray laser light from accelerated electrons. It does so using undulators: long sections of alternating magnetic fields.

Segments of one of the European XFEL undulators. The large vertical metal girders hold the permanent magnets in place above and below the electron beamline, providing the alternating magnetic field needed for X-ray laser generation. (Photo: Heiner Müller-Elsner / European XFEL)

Undulators are arrays of permanent magnets that are placed in an alternating pattern. When accelerated electrons enter an undulator, they begin to move in a zig-zag "slalom" course. With every turn, the electrons emit X-ray light. Because of the behaviour of the X-rays in relation to the light, and because of the pattern of the magnets in the undulator, the light that emerges is laserlike, with all of its waves in phase with each other.

The European XFEL comprises three different undulators—different light sources providing X-ray flashes with different properties—that generate light for the instruments in the facility's experiment hall.

The undulators comprise 5 m long segments aligned one behind the other with a distance of 1.1 m between them. These gaps between the segments contain devices used for electron beam diagnostics and control.

The strength of the magnetic fields in the undulators can be varied—a higher magnetic field resulting in a wider slalom course and thus in X-ray radiation with a longer wavelength.

Undulators of the European XFEL
  SASE1, SASE2
SASE3
Wavelengths
0.4 nm to below 0.05 nm
4.7 nm to 0.4 nm
Photon energy
3 keV to over 25 keV
0.26 keV to 3 keV
Instruments
SPB/SFX, FXE (SASE 1)
MID, HED (SASE 2)
SQS, SCS
Magnetic length
175 m
105 m