SAXS Optics

Optics - Hard branch

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Lay-out of the hard-line optics

Schematics of the hard-edge branch

The two techniques on the hard-edge branch (SAXS/WAXS and ID) use focused, monochromatic radiation with a moderate energy resolution.
The first optical element is a double-crystal monochromator with sagittal focusing on the second crystal it is followed by a meridionally focusing mirror with an angle of incidence of 2.8 mrad. Both focusing units are adjustable, so that the X-ray beam can be focused from the SAXS/WAXS sample position (48.6 m from the source) to the center of the ID diffractometer (57.6 m from the source). The minimum spot size at focusing position is 300 x 300 µm.

Two different mirror coatings are used to provide the discrimination against higher harmonics without changing the mirror angles. Using the Pt mirror coating, the beamline operates from 12-30 keV, while with the Si coating the operational energy is 5-12 keV. Together with the possibility of detuning the monochromator, this should yield a harmonic content of less than 10 ^-4 using Si(111) or Si(311), except for very low energies. The appropriate mirror coating is positioned in the beam by a sideways translation.

The characteristics of the optics of the H station are summarized bellow.