High-flux normal incidence monochromator for circularly polarized synchrotron radiation

Abstract
A 6.5‐m normal incidence monochromator installed at the storage ring BESSY, which is optimized for a high throughput of circularly polarized off‐plane radiation at moderate resolution is described. The monochromator employs two exit slits and is specially designed and used for low‐signal experiments such as spin‐ and angle‐resolved photoelectron spectroscopy on solids, adsorbates, free atoms, and molecules. The Monk–Gillieson mounting (plane grating in a convergent light beam) allows for large apertures with relatively little astigmatism. With two gratings, a flux of more than 1011 photons s1 bandwidth1 (0.2–0.5 nm) with a circular polarization of more than 90% in the wavelength range from 35 to 675 nm is achieved.