A water-cooled X-ray monochromator for using off-axis undulator beam

Undulator beamlines at third-generation synchrotron X-ray sources are designed to use the high-brilliance radiation that is contained in the central cone of the generated X-ray beams. The rest of the X-ray beam is often unused. Moreover, in some cases, such as in the zone-plate-based microfocusing beamlines, only a small part of the central radiation cone around the optical axis is used. In this paper, a side-station branch line at the Advanced Photon Source that takes advantage of some of the unused off-axis photons in a microfocusing X-ray beamline is described. Detailed information on the design and analysis of a high-heat-load water-cooled monochromator developed for this beamline is provided.