Beamline design for a bionanoprobe: stability and coherence

For scanning x-ray microprobes, the angle of the incident beam is required to be stable to better than one microradian during the course of an experiment. This is a very stringent requirement, even more so for micro-XAS measurements when the monochromator energy has to be scanned over hundreds of eV. At the same time, the horizontal emittance of the electron source at most synchrotron facilities is much too large to provide coherent illumination of the microfocusing optics. A beamline design is proposed here that makes use of the large horizontal emittance to provide a very stable beam for the operation of a BioNanoprobe, while also increases the coherence to ensure diffraction-limited resolution in the horizontal direction.