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Point-Focusing Small-Angle X-Ray Scattering System (Molecular Metrology)


The Molecular Metrology point-focusing small-angle x-ray scattering (SAXS) system is capable of making measurements on oriented or unoriented materials at scattering angles which cover the range of Bragg spacings from 0.7 to 100 nm. This high-resolution system is particularly well-suited to the characterization of materials created through guided self-assembly. The instrument employs Cu Kα radiation from a sealed-tube generator (PANalytical PW3830), focused in the vertical and horizontal directions by separate, bent Si (111) crystals. The two-dimensional multiwire Xe-filled detector is of the Gabriel design, with a maximum count rate of 105/sec. SAXS patterns can also be acquired on Kodak image plates. The entire beampath is evacuated, including the large sample chambers, which have feedthroughs to control a variety of sample environments. Sample heating to 300°C and cooling to -10°C, as well as temperature scanning with a Linkam DSC600 hot stage, are presently possible.

Representative 2D small-angle x-ray scattering pattern: DuPont-blown film of a  semicrystalline polymer (polyethylene), 2 mils thick. Left: 2D SAXS pattern (peak at q = 0.32 nm-1). Right: same pattern transformed to row-column format for quantitative analysis.  Insight into the structure-property relationships of such materials will enable the design of higher-performance, lower-weight packaging materials.