Research

Serial Femtosecond Crystallography (SFX) has become increasingly important during the last years, following the opening of the first X-ray Free Electron Laser LCLS in 2009. The ultrashort pulses allow conventional damage limits of (bio)macromolecular crystallography to be overcome and the high brilliance, many orders of magnitude higher than at synchrotron sources, allows for x-ray crystallography of tiny, nanometer-sized crystals from biological macromolecular samples which were not accessible to x-ray crystallography before. Therefore, serial femtosecond crystallography will be very important for structure determination of biologically relevant macromolecules such as, e.g., membrane proteins. The SFX user consortium will build an experimental instrument explicitly dedicated to serial femtosecond crystallography at the European XFEL.





 

Schematic layout of the SFX instrument at the SPB instrument of the European XFEL

The SFX instrument will be installed downstream of the SPB sample chamber and detector. After the direct XFEL beam will have passed the AGIPD-1M detector, it will be refocussed by a system of Beryllium Compound Refractive Lenses (CRL) to a 2nd focal plane. This allows to run experiments parallel to SPB experiments in a “parasitic” operation mode. Beside the CRL lens system, the SFX setup will consist of an injector system for fast sample replenishment, inherent to serial femtosecond crystallography experiments at XFELs, and a 4 Mpixel detector (AGIPD-4M) for fast data acquisition to high resolution at low noise and high dynamic range.




Sample injection system

Sample-injection system, based on the gas-dynamic virtual nozzle. Fully-hydrated protein nanocrystals are injected into the sample chamber by means of a micrometer-sized liquid jet of flowing protein solution (a). Photograph (b) of the sample-injection system with multiple nozzles for quick sample exchange inside the vacuum chamber. This allows for reliable operation and experiments at high-throughput conditions. The technical concept, design, and fabrication was done within our group, i.e., the Coherent Imaging Division at CFEL. The system was tested and operated succesfully at various beamtimes at LCLS.





 

Photon detector

European XFEL timing scheme

Pulses at European XFEL will be provided in pulse trains of 2,700 pulses/train. The repetition rate of the pulse trains is 10 Hz, while the intra-pulse repetition rate is 4.5 MHz, thereby posing challenging requirements to the detector and data acquisition systems.

 



Adaptive Gain Integrating Pixel Detector (AGIPD)

AGIPD-1M system with 4 movable quadrants for adjustable size of the central hole at the SPB detector. For the SFX AGIPD-4M system, the final technical design is still under consideration.

 
Schematic view of a veto system

Schematic view of a veto system to only keep useful diffraction data (e.g., the “hits”)








 

Rapid Dataset Acquisition

Data acquisition and sample consumption for SFX experiments at the European XFEL is much improved. For a single structure, we should need about 10,000 oriented patterns. This could be achievable with ≤ 100,000 shots (with 1010 crystals/ml) with the continuous flowing jet consuming about 10 μl/min.