PROXIMA 2A (PX2-A) is a microfocus beamline dedicated to biological crystallography and innovative micro-beam methodologies. Opened to the scientific community since 2013, the topics treated on the beamline go beyond standard protein crystallography and include drug discovery, membrane proteins crystallography, virus crystallography, small molecule crystallography, powder diffraction and even crystalluria. The beamline is highly automated and designed to help scientists tackle the most challenging structural targets and biological systems.
Its source is an in-vacuum U24 undulator, and the optical layout includes a cryogenically cooled channel-cut Si monochromator, a convex horizontal pre-focussing mirror (HPM) and a pair of focusing bimorph mirrors in Kirkpatrick-Baez (KB) configuration. This innovative optical scheme, harnesses a convex mirror to produce a virtual secondary source, which permits the KB mirrors to refocus the X-rays down to 5 μm from a relatively large horizontal source size. Focussing with the KB mirrors alone delivers a focal spot size of 10 μm × 5 μm (H×V FWHM), but in fully focussed mode, the cross-section of the beam at the sample position will be approximately 5.0 μm × 3.5 μm (H×V FWHM). PX2-A delivers a photon flux of 1×1013 – 4×1011 ph/s over the range of 5 – 15 keV with a desired positional stability better than 0.5 μm rms over several hours. To achieve such stability, the supports for the optical elements are designed to minimise the effects of vibrations transmitted from the surroundings, and accelerometers will be mounted in situ to monitor these effects. For long term drifts, the experimental hutch is temperature controlled to within 0.1°C, and a preparation laboratory acts as a buffer zone. Two types of X-ray Beam Position Monitors (XBPMs), single crystal CVD diamond and thin foil-diode devices, have been developed to improve their robustness and signal-noise ratio. Due to the limitations of space, three compact and modular “slit boxes” have been designed: These vessels house a variety of beam conditioning elements such as slits, XBPMs, attenuators, imagers and a fast shutter. At the end of the station, a micro-diffractometer, a cryostream, an X-ray fluorescence detector and an area detector (ADSC Q315) have been installed. The fine focus of the X-ray beam is readily used to select the best part of the crystal under staudy and the X-ray diffraction data are of excellent quality.
This beamline is not part of CALIPSOplus financing program, but you can ask for iNEXT financing program (http://www.inext-eu.org/)