THE HIGH-ENERGY MONOCHROMATOR FOR THE ALOISA BEAMLINE AT ELETTRA

At the ALOISA beamline the photon energy range 0.25 to 8 keV will be provided by switching between a plane mirror/grating monochromator and a crystal monochromator sharing the same beamline mirror optics. All dispersing elements are used in a collimated beam, which is focused downstream by means of vertically mounted mirrors. It is shown that the variations in the geometry of the light spot at the sample remain within acceptable limits over the requested energy range even if a simple nonfixed-exit ''channel-cut'' crystal is used. The crystal will have an inclined cut which allows to spread the power load delivered by the wiggler source sufficiently over the first reflecting crystal surface to allow for simple back-side cooling. In addition a new type of power filter has been designed based on a rotating, water-cooled Be disk. This design reduces the effective absorbed power density in the filter by two orders of magnitude with respect to commonly used static multifoil solutions, resulting in a cool, clean, UHV-compatible device. © 1995 American Institute of Physics.