The basic optical design for the beamline includes a silicon 111 horizontally deflecting double crystal monochromator (hDCM) followed by two pairs of mechanically bendable flat mirrors in Kirkpatrick-Baez (KB) configuration (see figure above: Vertical mirrors: VFM1,2; horizontal mirrors: HFM1,2). Independent focalisation in both directions is possible at a position from the sample to the full path of the SAXS camera length. Micro beam sizes (~10 μm) are available in the total energy range of the instrument. A three-slit collimation system (S1-S3 in the figure above) is placed between the last mirror and the sample minimising the parasitic contribution. The SAXS detector is a vacuum compatible area system housed in an 18 m long vacuum tube. A two dimensional WAXS detector will also be included in the set-up for simultaneous SAXS/WAXS experiments.
Specifications for CoSAXS optics
| X-ray source (IVU) | In-vacuum undulator (IVU), 2 m magnetic length, 19.3 mm period, 101 periods, 4.2 mm minimal magnetic gap. |
| Energy (wavelength) range | 4 - 20 keV (0.6 – 3.1 Å) using 1st - 11th harmonics of the IVU |
| Monochromator (hDCM) | At ~25 m, Si (111), double crystal monochromator, horizontally deflecting, LN2 side-cooling. |
| Energy bandwidth (ΔE/E) | ~2 x 10-4 |
| Focusing optics | Dual Kirkpatrick-Baez (KB) mirror pair (VFM1,2 and HFM1,2) in four bounce geometry. |
| Vertical mirrors pair (VFMs) | At ~27 m, parabolic shape, 350-400 mm length, 3.5 mrad grazing incidence angle, 0.1 μrad RMS slope error, 1 Å rms roughness. Both are bendable flat mirrors. VFMs can be retracted from the beam. |
| Horizontal mirrors pair (HFMs) | At ~29 m, parabolic shape, 350-400 mm length, 3.5 mrad grazing incidence angle, 0.1 μrad RMS slope error, 1 Å rms roughness. Both are bendable flat mirrors. |
| Harmonic rejection | HFMs and VFMs with Si and Rh stripes. |
| q-range | 6 x 10-4 - 6 Å-1 (with simultaneous SAXS/WAXS) |
| Flux | 1012 - 1013 ph/s |
| Coherent Flux | 1.5 x 1012 ph/s using horizontal adjustable aperture |