IUCr journals news
New apparatus combination creates outstanding performance of Kratky SAXS systems
J. Appl. Cryst. (2000). 33, 869-875 [doi:10.1107/S0021889800000881]
|Conventional block collimation (a) and improved block collimation using the parallel beam from a Göbel mirror (b). f = focus, S = slit, B1 and B2 = blocks, R = registration plane.|
In this context, Bergmann, Orthaber, Scherf & Glatter [J. Appl. Cryst. (2000). 33, 869-875] have recently reported on a significant improvement of long-slit systems by taking advantage of the above-mentioned technical developments (Göbel mirrors) for the Kratky camera. Using a parallel, monochromatic X-ray beam from a Göbel mirror, a slight modification of the Kratky block collimation system leads to an intensity gain of a factor of four without loss of resolution. This is simply due to the fact that in contrast to the classical system the whole focus illuminates the registration plane R and that the parallel beam results in a rectangular instead of a triangular beam profile (see figure). Together with the advanced characteristics of the Göbel mirror (15-20 mrad angular acceptance from the source) and the use of a rotating-anode X-ray generator, a total intensity gain of a factor of about 40 in comparison with a conventional Kratky system was reached by the authors. In terms of primarybeam intensity, this would nearly be comparable with some SAXS instruments on second-generation synchrotron radiation sources (bending magnets). This remarkable gain puts Kratky cameras again on a competitive basis for laboratory SAXS instruments, as long as fully isotropic scattering systems are concerned. As quite a significant number of SAXS applications deal with solution scattering (e.g., particles or polymers in solution), the improved Kratky camera can be expected to cover a wide field of applications with up to now unmatched primary-beam intensity.
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Erich Schmid Inst., Austrian Academy of Sciences, Leoben, Austria