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  • 1
    Electronic Resource
    Electronic Resource
    Sagittal focusing of high-energy synchrotron X-rays with asymmetric Laue crystals. II. Experimental studies (2001)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 34 (2001), S. 646-653 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The use of bent asymmetric Laue crystals to focus synchrotron X-rays sagittally from 15 to 50 keV is described. A four-bar bender, bending a rectangular planar crystal, produced the necessary sagittal and meridional bending for this unique application. Adjustments of the tilt angle and height of the bent crystal resulted in first- and second-order corrections, respectively, to the dependence of the angle of diffraction on the horizontal position on the crystal. After these corrections, the remaining variation of the diffraction angle was of the order of 10 µrad. The theoretical sagittal focal length was verified. A prototype of a double-crystal sagittally focusing monochromator was constructed and tested, using two identical Laue crystals. A horizontal divergence of 3 mrad was focused to a horizontal dimension of about 0.4 mm. The X-ray flux density at the focus was a few hundred times larger than that of unfocused X-rays.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889801010627
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  • 2
    Electronic Resource
    Electronic Resource
    A graphite double-crystal monochromator for X-ray synchrotron radiation (1988)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 21 (1988), S. 911-915 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: An X-ray monochromator using two consecutive reflections by mosaic crystals is shown to be an effective source of well collimated broadband radiation. The use of mosaic crystals in this arrangement is well suited to the study of diffuse scattering phenomena or to the simultaneous recording of several Bragg reflections of crystals with large unit cells and/or very small size. The monochromator can also be used downstream of a focusing mirror. In the present study a monochromator based on pyrolytic graphite gave an intensity gain of 72 in comparison with silicon (111) crystals in the same geometry but with a bandwidth of 3.3%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889888007484
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  • 3
    Electronic Resource
    Electronic Resource
    Small-angle X-ray scattering at high energies (1990)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 23 (1990), S. 401-405 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Initial tests are described of a high-resolution small-angle X-ray scattering apparatus adapted for operation at high photon energies. The energy chosen was 50 keV, and was limited by the available source. All orders of scattering out to the seventh were observed from a sample of 0.9 μm diameter latex spheres in a 4 h experiment. Phase separation in a binary Al–Li alloy was studied by the observation of spherical Al3Li precipitates. This demonstrates that the use of perfect-crystal collimators and analyzers yields a resolution function which does not depend on photon energy. New sources of high-energy photons will make such an apparatus invaluable for the study of highly absorbing samples, or samples in difficult environments such as ovens or high-pressure cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889890005787
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  • 4
    Electronic Resource
    Electronic Resource
    Sagittal focusing of high-energy synchrotron X-rays with asymmetric Laue crystals. I. Theoretical considerations (2001)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 34 (2001), S. 504-509 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The ability of asymmetric Laue crystals to focus X-rays sagittally is demonstrated. The extent of such focusing is similar to that of sagittal focusing by a Bragg crystal, except for a factor related to the asymmetry angle. The anticlastic bending facilitates the use of inverse-Cauchois geometry in the meridional plane to provide better energy resolution and to increase the photon flux by an order of magnitude compared with traditional sagittal focusing with Bragg crystals. Furthermore, for sagittal focusing at X-ray energies above 30 keV, a Laue crystal is preferred to a Bragg crystal because the length of the beam's footprint on a Laue crystal, unlike on a Bragg crystal, is small and insensitive to energy. The conditions imposed on the asymmetry angle of the Laue crystal to achieve simultaneous sagittal focusing and inverse-Cauchois geometry in the meridional plane are derived for both single-crystal and double-crystal fixed-exit sagittally focusing monochromators.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889801006409
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  • 5
    Electronic Resource
    Electronic Resource
    Facilities for solution scattering and fibre diffraction at the Daresbury SRS (1985)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 18 (1985), S. 396-403 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The small-angle scattering facility at Daresbury has been constructed for diffraction studies of a wide range of naturally occurring and synthetic materials. The high brightness of the SRS is combined with focusing optics, resulting in exposure times that can be two or three orders of magnitude less than those required on a conventional source. Spacings of 2000 Å in the vertical direction and 300 Å in the horizontal direction can be observed, while the resolution between diffraction orders is 5000 and 600 Å. In addition, preliminary results have been obtained on a double-crystal diffractometer that has a resolution, in one dimension, of better than 26 000 Å. For high-angle fibre diffraction studies, a camera with pinhole collimation has been constructed. Examples from solution scattering and fibre diffraction are used to illustrate the performance of these facilities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889885010615
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  • 6
    Electronic Resource
    Electronic Resource
    X-ray focusing using an inclined Bragg-reflection lens (1999)
    Chester : International Union of Crystallography (IUCr)
    Journal of synchrotron radiation 6 (1999), S. 973-978 
    Details
    ISSN: 1600-5775
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: An experimental demonstration showing that a one-dimensional focus can be produced by using the principle of inclined diffraction from a perfect crystal is presented. By machining a groove with a controlled cross-sectional profile it is shown that it is possible to vary the out-of-plane deviations in a controlled manner and hence generate a focus. Also demonstrated is the use of four reflections in (−,+,+,−) dispersive geometry resulting in the cancellation of all beam-spreading in the orthogonal direction. The experiment used an energy of 15 keV with a source-to-crystal distance of 13.5 m and crystal-to-focus distance of 4.5 m. A focus of width 0.29 mm was produced from an incident beam of width 2.7 mm. It is clear from the measurements that a better surface finish would result in a smaller focal spot.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0909049599005385
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  • 7
    Electronic Resource
    Electronic Resource
    Transmission-type X-ray linear polarizer with perfect crystals (1998)
    Chester : International Union of Crystallography (IUCr)
    Journal of synchrotron radiation 5 (1998), S. 738-740 
    Details
    ISSN: 1600-5775
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Even though conventional X-ray polarizers with multiple-reflection channel-cut structures perform well, they suffer from the disadvantage that the polarized beam is non-stationary as the energy is scanned. In this paper the possibility of using a thin Bragg reflector as a polarizing filter is investigated, so that the transmitted beam (rather than the Bragg-reflected beam) is used. Consequently, the position and direction of the transmitted beam are unchanged as the energy is changed, or even when the polarization direction to be filtered out is changed. Theoretical considerations as well as experimental results on the performance characteristics of the proposed transmission-type X-ray linear polarizer are presented. A polarization ratio, defined as IH/IV, higher than 105 was obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0909049597019560
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  • 8
    Electronic Resource
    Electronic Resource
    Applications of high-order Laue-case rocking curves (1983)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 39 (1983), S. 199-202 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Spherical-wave Pendellösung fringes have been used for many years to make absolute measurements of X-ray coherent scattering amplitudes. Bonse & Teworte [J. Appl. Cryst. (1980), 13, 410-416] have suggested that the corresponding fringes seen in Laue-case rocking curves between two crystals with almost equal thicknesses might have important applications and they showed that agreement to within ½% could be achieved in structure factor measurements on silicon. Two further applications are demonstrated in this paper. By a simple construction the range of double-crystal topography, using only a Lang camera, has been extended to the region δd/d 〈 10-9. In another experiment it is found that the Pendellösung method can be extended to very high orders (the 10,10,0 reflection in silicon for example) so that attention can be focused, for the first time with high precision, on the coherent Bragg scattering at very high sin θ/λ.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767383000458
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  • 9
    Electronic Resource
    Electronic Resource
    Direct measurements of the complex X-ray atomic scattering factors for elements by X-ray interferometry at the Daresbury Synchrotron Radiation Source (1986)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 42 (1986), S. 456-464 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: A scanning X-ray interferometer system [Hart & Siddons (1981). Proc. R. Soc. London Ser. A, 376, 465-482] has been rebuilt for operation at the SERC Daresbury Synchrotron Radiation Source (SRS). The SRS permits an increase in energy resolution by one decade and simultaneously an intensity gain of one thousand times, though in practice the solid-state detector employed limited the peak intensity utilized so that experiments which hitherto demanded one month of counting time are now performed at higher spectral resolution in 2-4 h. Absolute measurements are reported of f' and f” for the K edges of most elements between 34Se and 26Fe and for L edges of 79Au and 74W over energy ranges of about ± 2 keV near absorption edges and scans with better than 1 eV energy resolution of X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectra near the edges. Over wide energy ranges the results are compared with the most recent calculations of Cromer & Liberman [Acta Cryst. (1981), A37, 267-268], which are now easily available to workers in the field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767386098884
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  • 10
    Electronic Resource
    Electronic Resource
    X-ray topography of a lysozyme crystal (1996)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 52 (1996), S. 498-499 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: X-ray topography methods were employed to identify defects in lysozyme crystals. White-beam and monochromatic topographs of lysozyme crystals obtained at the National Synchrotron Light Source are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767395014553
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