Scientific Instrument SPB/SFX

The Single Particles, Clusters, and Biomolecules & Serial Femtosecond Crystallography (SPB/SFX) instrument of the European XFEL is primarily concerned with three-dimensional diffractive imaging, and three-dimensional structure determination, of micrometre-scale and smaller objects, at atomic or near-atomic resolution.

A particular emphasis is placed on biological objects—including crystals of macromolecules and macromolecular complexes as well as viruses, organelles, and cells—though the instrument will also be capable of investigating non-biological samples using similar techniques. Furthermore, the SPB/SFX instrument aims to study structural dynamics in these biological systems on the millisecond to femtosecond timescale.

The SPB/SFX instrument consists of two experiment endstations (upstream and downstream), based on the combined contributions of European XFEL and the Serial Femtosecond Crystallography (SFX) user consortium.

Published description of the SPB/SFX instrument is online

The SPB/SFX instrument at the European XFEL is an important new tool in studying the structure of biomolecules, atomic and molecular clusters, and novel materials using a variety of X-ray scattering techniques. While this webpage describes the instrument in general terms, a publication in the Journal of Synchrotron Radiation provides a peer-reviewed description of the technical background and science case.

The article describes the various scientific components of the instrument. This includes the rationale for their use and how they enable various types of experiments, including single-particle imaging, serial femtosecond crystallography, and a variety of time-resolved experiments. The development of the instrument is also described, along with a detailed list of current (as of April 2019) instrument properties.

From vacuum systems to optics to sample environment and to the very fast X-ray detector AGIPD, the article details the instrument design. These unique features allow the instrument to use high-intensity X-ray laser pulses at femtosecond time scales to investigate the structure and function of molecular samples. Also discussed is the downstream region of the instrument, where the unused beam from the first sample chamber will be refocused for a second experiment. Additionally, the paper references detailed descriptions of other important systems, including optical lasers and data acquisition and storage.

The article is open access and can be read in its entirety here.

Key (expected) features
Electron bunch charge
50–1000 pC
Photon energy range
3–16 keV (upstream), 6–16 keV (downstream), up to 25 keV (3rd harmonic)
Bandwidth
0.1% (SASE bandwidth, no monochromator installed)
Pulse energy
Up to 4 mJ (depending on photon energy)
Pulse duration
5–300 fs (depending on photon energy and bunch charge
Polarization
linear (horizontal)
Focus size
~1 µm or ~0.1 µm upstream, 1 µm downstream
X-ray optics
upstream interaction region: micro-focus KB mirror system, nano-focus KB mirror system (photon energy range: 3–16 keV, best 5–16 keV)

downstream interaction region: compound refractive lenses (photon energy range: 6–16 keV, best 8–16 keV)
Sample delivery
fixed-target stage system, liquid/aerosol/gas injection systems
Detectors
AGIPD 1 Mpx (upstream), AGIPD 4 Mpx (downstream)
Lasers
fundamental wavelenghts 800nm (15 fs pulse duration and 1030 nm (500 ps, after compression 850 fs) available, conversion to visible and UV via OPA/SHG/THG/FHG possible, pulse energy µJ–mJ (depending on repetition rate)