High-performance asymmetric-cut curved crystal monochromator side-branch X-ray beamlines

Two high-performance asymmetric-cut curved crystal monochromator (ACCM) side-branch x-ray beamlines have been designed to fully utilize the sideway output of a superconducting multipole wiggler (SMPW) source for protein crystallography research. Each of the two ACCM beamlines collects 1 mrad of radiation in the horizontal direction. One of them is located at 4 mrad and the other at 3 mrad away from the centerline of the radiation fan of the wiggler output. These two beamlines will deliver photon flux, through a 100 pm pinhole, of greater than 1 x 10(11) photons/sec with energies from 12 keV to 14 keV and resolution (DeltaE/E) of 1.5 x 10(-3) for standard monochromatic crystallography experiments. A Rh-coated, water-cooled vertical focusing mirror is placed upstream of the ACCM to simplify the energy tuning mechanism and to reduce the heat load of the crystal by cutting off the photon beams at energies above 15 keV. Considering that existing ACCM designs with bender either have insufficient cooling efficiency or are difficult to manufacture, we designed a special cost-effective ACCM that comprises a crystal plate affixed to a water-cooled, bendable Cu substrate, where heat conducts through a paste-like alloy. With this design, the monochromator will provide high photon flux and resolution while maintaining excellent stability.