Specifications
The insertion device
The wiggler for the SAXS beamline consists of three 1.5 m long segments, each having 19 poles. The device can work with a minimum gap of 20 mm, which corresponds to K=20 at 2 GeV. The main parameters of the wiggler are:
· Critical Energy 4.1 keV
· Radiation Power 8.6 kW
· Flux 3.5x1014 ph/s/mrad/0.1%BW (at 400 mA)
The wiggler radiation cone has a horizontal width of 9 mrad. From this the SAXS-beamline accepts vertically 0.3 mrad, and horizontally +/-0.5 mrad at a 1.25 mrad off-axis position. The resulting source size for 8 keV photons is 3.9 x 0.26 mm2 (horiz. x vert.).
The beamline optics
The optics common with the diffraction beamline consists of:
· Carbon-Filter to reduce the power load on the first optical elements by a factor of 2
· Beryllium windows to separate the beamline vacuum from the storage ring
· Beam defining slit chamber before the SAXS monochromator
The SAXS beamline optics consists of:
· A double-crystal monochromator
· A baffle chamber after the monochromator is used as an adjustable straylight fenditure
· A segmented toroidal mirror focuses the light in horizontal and vertical direction with a 1/2.5 magnification onto the SAXS-detector
· An aperture slit reduces the straylight after the monochromator and the toroidal mirror
· A guard slit defines the illuminated region on the sample
Scientific applications
Low Contrast Solution Scattering, Grazing Incidence Surface Diffraction, Micro-Spot Scanning, X-ray Fluorescence Analysis, Time-Resolved Studies > 11 µs and Simultaneously Performed Small- and Wide-Angle Measurements (SWAXS) on:
· Gels and colloids
· Liquid Crystals
· (Bio) Polymers
· Amorphous Materials
· Muscles
· Proteins
· Metals, cements, oils
· Quantum dots
· and much more ...
Source characteristics
The photons are provided by a Wiggler (NdFeB Hybrid) with the following specifications:
| Period: | 140 mm |
| Number of full poles: | 57 |
| Gap: | 20 mm |
| Bmax: | 1.607 T |
| Critical Energy Ec: | 4.27 eV (at 2 GeV) |
| Power (9 mrad): | 8.6 kW (at 2 GeV, 400 mA) |
| effective source size FWHM: | 3.9 x 0.26 mm2(HxV) (at 2 GeV, 400 mA) |
Optics
| Double crystal monochromator: | 18.4 m from source, Si (111) asym. cut, water cooled |
| Focussing mirror: | 26.5 m from source, two segments, toroidal, Pt coated |
| Acceptance: | 1 mrad/0.3 mrad (HxV) |
| Energy (3 selectable): | 5.4, 8, 16 keV (0.077, 0.154, 0.23 nm) |
| Energy resolution deltaE/E: | 0.7-2.5 x 10-3 |
| Focal spot size FWHM: | 1.2 x 0.6 mm2 (HxV) |
| Spot at Sample FWHM: |
< 1.4 x 1.8 mm2(HxV) (using slits or pinhole) smallest possible spot: 10 µm |
| Flux at sample: | 1 x 1013 ph s-1 (2 GeV, 400 mA, 8 keV) |
| Flux density at sample: | 1 x 1012 ph s-1 mm-2 (2 GeV, 400 mA, 8 keV) |
Experimental resolution
Small angle:
Real space: 1-140 nm
Wide angle:
0.1- 0.9 nm
Accessible SAXS and WAXS range
Small angle:
Real space: 1-140 nm (8 keV)
1-63 nm (16 keV)
Wide angle:
angular region from 17 - 85o (2Theta)
SWAXS:
Simultaneous SAXS- and WAXS-measurements can be performed using a Pilatus3 1M detector for the SAXS signal, and a Pilatus 100k detector for the WAXS-range.
For transmission experiments, also a specially designed vacuum chamber (SWAXS-nose, see Annual Report of 1996/97, p. 32) can be used which allows to use both scattering areas below (for SAXS) and above (for WAXS) the direct beam, respectively. The overall length of the SWAXS-nose in horizontal direction, measured from the sample position, is 512 mm and the fixed sample to WAXS-detector distance is 324 mm. Therefore, at the shortest SAXS camera-length an overlap in the d-spacings covered by the SAXS- and WAXS-detectors, respectively, is possible: then, the common regime lies around 9 Å (at 8 keV, using for WAXS the 2Theta = 9.4 - 27.6o range).
