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Kratky Camera: Small-Angle X-Ray Scattering

The compact Kratky camera produces a slit-collimated beam by use of the Kratky U-block design. Designed by Otto Kratky of the University of Graz in the 1950s (and redesigned into the compact form in the 1970s), our Kratky camera (made by Anton-Paar, Graz, Austria) can acquire SAXS data down to very low scattering angles (Bragg spacings greater than 100 nm), but the data must be numerically desmeared to yield the true scattering pattern. Our Kratky camera is connected to a one-dimensional position-sensitive detector (Braun OED-50M), which is in turn connected to a PC multichannel analyzer (Tennelec Nucleus PCA-II). Monochromatization is achieved by pulse-height analysis and the detector and by nickel foil filtering upstream of the Kratky U-block. Count rates up to 104 per second can be easily achieved with typical generator settings and strongly-scattering samples, permitting time-resolved measurements with time slices as short as five minutes. We have designed a hot stage which can maintain temperature uniformity within 1°C over the length of the illuminated sample volume; this hot stage is microprocessor-controlled (Fuji PYZ), and by programming the MCA, time- and temperature-sequence data may be acquired automatically. An example is shown below.

Desmeared SAXS data acquired on the Kratky camera, used for the order-disorder transition (ODT) determination for a sphere-forming styrene-isoprene diblock copolymer. Vertical intensity axis is linear; sample temperatures are indicated on curves. ODT temperature is 111±1°C, as indicated by the sudden loss of higher-order peaks, reduction in primary peak intensity, and increase in primary peak width.