Beam-splitting mirrors for an APS beamline

We describe a set of two cooled mirrors used in tandem on a high-heat-load undulator beamline at the Advanced Photon Source (APS) to spatially split an incoming X-ray beam into two parts, allowing simultaneous operation on two beamlines. Such arrangements have the potential to increase beamline throughput by as much as a factor of two at a modest cost. Conceptual design, engineering analyses, and fabrication steps are outlined.