The "Bio-imaging and diffraction beamline P11" at PETRA III is dedicated to imaging and diffraction experiments of biological samples. The beamline provides two different endstations: A crystallography experiment operating between 5.5 keV and 30 keV and an X-ray microscope which is currently under construction and will utilize tender X-rays between 2.4 and 10 keV.
The main basis of idea for the beamline design is to provide an extremely stable and flexible setup ideally suited for micro- and nano-beam applications. For the design of the beamline optics special care was taken to preserve the coherence properties of the beam and to deliver most of the photons from the source into a very small focal spot at the sample position.
The P11 X-ray optics consist of a LN2 cooled double crystal monochromator and two horizontal deflecting and one vertical deflecting X-ray mirrors. All three mirrors are dynamically bendable and are used to generate an intermediate focus at 65 m from the source with a size of 16 x 96 µm rms (v x h) and a divergence of 8 x 15 μrad rms (v x h). A second refocusing KB system which is installed in the P11 experimental hutch is used for refocusing the X-ray beam with full flux from the source (2 × 1013 ph/s at 12 keV). With this, beam sizes between 4 × 9 μm2 (2nd KB system fully bent) and 300 × 300 μm2 (2nd KB system flat, FWHM, v × h) can be generated at the sample position. Smaller beam sizes down to 1 × 1 µm2 with more than 2 × 1011 ph/s in the focus can be obtained by slitting down the secondary source at the cost of flux.
The flexible X-ray optics allow to tailor the beam properties to the needs of the experiment: A large parallel beam is available for investigations of large unit cell systems, such as large molecular complexes and virus crystals. For structure determinations from microcrystals a highly intense microbeam can be generated which allows serial crystallography experiments using e.g. liquid delivery systems or silicon microchips.
The P11 crystallography endstation is equipped with a high precision single axis goniostat. A Pilatus 6M-F detector allows for fast data collection with frame rates of up to 25 Hz. Crystals can be mounted in less than 10 s using an automatic sample changer. The robot (uni-puck format) is combined with a large storage Dewar which provides space for 368 samples. This makes P11 ideally suited for high-throughput crystallography and fast crystal screening.