Optimization of a spectro-microscopy beamline at BESSY II

For the high brilliance synchrotron radiation source BESSY II a couple of systems performing microscopy and spectromicroscopy at both high spatial and high energy resolution are planned or already under construction. The desired spatial resolution is in the nm-range, and thus monochromators are required which conserve the brilliance of the source throughout the beamline onto the analysed area. To serve the ultrahigh-resolution spectromicroscope SMART, a Petersen monochromator will be installed at an insertion device of 49 mm period length. When operated in highest spatial resolution mode, the field of view of the microscope is about 5 mu m in diameter. To optimize the photon flux density in the microscopes field of view, we studied the performance of the Petersen monochromator for various horizontal demagnification factors. The resulting optical layout produces a monochromatic image of the undulator source on the sample surface, which has a horizontal size of about 9 mu m full width at half maimum. The vertical size of 5 mu m is determined by the exit slit width.