Opticsconcept for apair of undulatorbeamlines for MX

We describe a concept for X-ray optics to feed a pair of macromolecular crystallography (MX) beamlines, which view canted undulator radiation sources in the same storage ring straight section. It can be deployed at NSLS-II and at other low-emittance third-generation synchrotron radiation sources where canted undulators are permitted, and makes the most of these sources and beamline floor space, even when the horizontal angle between the two canted undulator emissions is as little as 1-2 mrad. The concept adopts the beam-separation principles employed at the 23-ID (GM/CA-CAT) beamlines at the Advanced Photon Source (APS), wherein tandem horizontally deflecting mirrors separate one undulator beam from the other, following monochromatization by a double-crystal monochromator. The scheme described here would, in contrast, deliver the two tunable monochromatic undulator beams to separate endstations that address rather different and somewhat complementary purposes, with further beam conditioning imposed as required. A downstream micro-focusing beamline would employ dual-stage focusing for work at the micron scale and, unique to this design, switch to single-stage focusing for larger beams. On the other hand, the upstream, more highly automated beamline would only employ single-stage focusing.