MAD10
NWSGC beamline

Station Description

North West Structural Genomics Centre's Beamline, MAD 10, at the SRS receives the central part of the radiation fan (0.5 mrad vertically, 4 mrad horizontally) produced by a new 2.46 Tesla 10 pole wiggler (MPW10). The optical arrangement of the beamline consists of a Rh coated collimating Si mirror, a double crystal monochromator with saggittal bending for horizontal focussing and a second Rh coated Si mirror for vertical focussing. The double crystal Si (111) monochromator allows data collection in the 5 to 13.5 keV photon energy range with rapid tunability and high energy resolution. The monochromatic beam is optimized through a 200 micron collimator. The end station, being the only experimental station on the beamline allows full access around the sample from both sides even in the "straight-through" position. The beamline end station has been designed around a MAR desktop beamline with high throughput CryoSampleChanger, MAR225 CCD detector, liquid N2 autofill system and an ORTEC C-TRAIN-04 energy resolving high count rate X-ray fluorescence detector. The instrument is optimised for MAD/SAD applications in protein crystallography with additional mode of operation of on line single crystal EXAFS studies on the same crystals. Thus, screening of metals/Se in the crystal can be performed quickly prior to MAD/SAD data collection by exciting the crystal with X-rays of appropriate energy and recording an energy dispersive fluorescence spectrum. In addition, this setting allows for parallel XAFS measurements on the same crystal to monitor ‘radiation-induced’ changes, if any, in e.g. the redox state of metal centres to be detected for a ‘metallic’ functional group during crystallographic data collection. Moreover careful minimisation of the thickness of the Be window maximises the intensity performance for the 2-2.5 Å (softer) wavelength range; an energy range which is finding greater appeal for the use of softer elements for X-ray phasing (Sulfur, Iodine or Xe L edges). This range is also important for a number of important 3d transition metals.The Softer wavelengths also have application to the harnessing of enhanced sulfur f " in protein crystallography. The beamline design principles, based on beamline optical ray tracing, full description and early results are presented in this paper.

Currently, MAD 10 is undergoing commissioning with several important milestones being passed. The latest of which was the successful measurement of monochromatic beam in the experimental hutch. This represents a significant step towards the provision of a fully operational station.

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