Photo: Daniel Michon, ARTECHNIQUE
BM26B is dedicated to SAXS/WAXS measurements. The small-angle and wide-angle patterns can be acquired simultaneously. Two Pilatus photon counting area detectors are used to collect the data.
SAXS images are collected using a Pilatus 1M detector (169mm x 179mm active area). The minimum q-value attainable with our maximum 7m sample-to-detector distance and a photon wavelength of 1.54 Å is about 0.0175 nm-1 (equivalent to a real-space d = 500 nm) .
WAXS patterns are collected using a 300K linear Pilatus detector ( 254mm x 33.5mm active area). The maximum diffraction angle is about 2Ɵ = 40 °.
If required, a SAXS/WAXS setup without gap between the two measured patterns is available.
The beam size can be tuned from few millimeters down to about 300 x 300 micrometers in standard configurations. Post-focusing systems are available in order to achieve a smaller beam size. The experimental hutch contains the SAXS camera with a maximal and minimal camera length of 7 and 1.3 m, respectively. This allows simultaneous SAXS/WAXS measurements with a time resolution down to a few msec/frame.
A heavy-duty '2+3' type diffractometer (combined '2+2' and 'z-axis') allowing horizontal and vertical sample orientation for interface and surface diffraction experiments is mounted in the same hutch.
The low angle resolution of the SAXS station is dependent on the X-ray wavelength and the sample-to-detector distance.
Data are normalised for the incident beam intensity using an in-air ionization chamber and the sample transmission is measured using a pin-diode integrated in the lead beamstop. These values are usually stored in the header of the edf or hdf5/nexus data files provided to the users.
Links and Documentation
For a presentation of the SAXS basic theory, techniques and applications, you can download the book Small Angle X-ray Scattering (O. Glatter and O. Kratky Eds., Academic Press, 1982) from http://physchem.kfunigraz.ac.at/sm/ (Scattering Methods at the Chemistry Department, University of Graz).
For a more biologically oriented introduction one can download Structure Analysis by Small-Angle X-Ray and Neutron Scattering (L. A. Feigin and D. I. Svergun, Plenum Press / Springer, 1987) from http://www.embl-hamburg.de/biosaxs/publications.html
From a practical point of view, you might want to take a look at the Beamline Manuals page. We have posted a short Users' survival manual, the full manual for the data acquisition and reduction software for collecting and pre-processing SAXS and/or WAXS data for both static and time-resolved measurements on beamline BM26B, as well as a list of basic Unix commands.
Last but not least, the Data Reduction and Analysis page provides the response of the detector in use, together with links to data reduction and analysis software.
To estimate your sample absorption click here.