Stanford Synchrotron Radiation Lightsource

Small-angle X-ray scattering (SAXS) is a well-established characterization method for microstructure investigations in various materials. It probes electron density differences to give information about structural inhomogeneities from the near atomic scale (1 nm) to the micron scale (1 000 nm). The method involves measuring the scattered X-ray intensity as a function of (typically small) scattering angles and is generally performed in transmission. SAXS is used to characterize the size scale of inhomogeneities (e.g. pores, inclusions, second phase regions) in polymer blends, micro-emulsions, geological materials, bones, cements and ceramics.

Instrumentation

SAXS measurements is performed at Beamline 1-4. Available sample environments include an oven, multi-sample capillary holder and tensile tester for transmission SAXS and a goniometer for grazing incidence measurements (GISAXS).

Additionally, if you have your own sample environment you wish to bring to the beamline, a multi-purpose X-Y positioner exists to be adapted to hold and position most sample environments brought by the experimenter (e.g. electrochemical cell; humidity chamber; multi-sample oven, etc). Contact staff to arrange to integrate it optimally on the beamline.

Data Handling

• Data Acquisition: Uses SPEC running on a RedHat Linux OS control computer, which controls the shutter, all sample motors, a temperature controller and also the detector via an additional Linux-based PC over a local-area network. Data is stored on the file server: specfs.slac.stanford.edu and be accessed remotely using secure ftp.
• Data Reduction: Uses in-house macros to collapse 2d X-ray images to 1d profiles either radially, I(q) vs q, or azimuthally, I(Φ) vs Φ),  or collapse GISAXS images rectangularly in both I(q_xy) vs q_xy and I(q_z) vs q_z. For general operation of the beamline, see the BL1-4 cheat sheet.
• Data Analysis: In general SAXS analysis is model dependent, and will, in general, depend on the material under investigation (e.g., degree of order, nature of the inhomogeneities, concentration of the inhomogeneities). We have developed a novel method of analyzing SAXS data from random or suitably disordered two-phase materials [Hedstrom]. A data analysis station runs the small angle scattering analysis tool Irena.

For more information, contact John Pople or Mike Toney. See deadlines to submit proposals and beam time requests.