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Verfasser Titel Jahr
zeige Details Smither, Robert K.., Fernandez, Patricia B.. Variable-metric diffraction crystals for x-ray optics (abstract)a)
In: Review of Scientific Instruments. - [S.l.] : American Institute of Physics, ISSN 1089-7623, Vol. 63, No. 1 (1992), p. 941-941
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1992
A variable-metric (V-M) crystal is one in which the spacing between the crystalline planes changes with position in the crystal. This variation can be either parallel to the crystalline planes or perpendicular to the crystalline planes of interest and can be produced by either introducing a thermal gradient in the crystal or by growing a crystal made of two or more elements and changing the relative percentages of the two elements as the crystal is grown. A series of experiments was performed in the laboratory to demonstrate the principle of the variable-metric crystal and its potential use in synchrotron beam lines. One of the most useful applications of the V-M crystal is to increase the number of photons per unit bandwidth in a diffracted beam without losing any of the overall intensity. In a normal synchrotron beam line that uses a two-crystal monochromator, the band width of the diffracted photon beam is determined by the vertical opening angle of the beam which is typically 0.10–0.30 mrad or 20–60 arcsec. When the V-M crystal approach is applied, the band width of the beam can be made as narrow as the rocking curve of the diffracting crystal which is typically 0.005–0.050 mrad or 1–10 arcsec. Thus a very large increase of photons per unit bandwidth (or per unit energy) can be achieved through the use of V-M crystals. When the V-M principle is used with bent crystals, new kinds of x-ray optical elements can be generated that can focus and defocus x-ray beams much like simple lenses where the focal length of the lens can be changed to match its application. Thus both large magnifications and large demagnifications can be achieved as well as parallel beams with narrow bandwidths.
beteiligte Personen: Smither, Robert K.. , Fernandez, Patricia B..
Format: Elektronisch
Sprache: English
Erschienen: 1992.
Serie: AIP Digital Archive [Dig. Serial]
Schlagwörter:
URL: http://dx.doi.org/10.1063/1.1143814

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Zurück zur geteilten Ansicht
Verfasser Titel Jahr
zeige Details Smither, Robert K.., Fernandez, Patricia B.. Variable-metric diffraction crystals for x-ray opticsa)
In: Review of Scientific Instruments. - [S.l.] : American Institute of Physics, ISSN 1089-7623, Vol. 63, No. 2 (1992), p. 1755-1762
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1992
zeige Details Shanno, D. F. An example of numerical nonconvergence of a variable-metric method
in: Journal of optimization theory and applications , ISSN 1573-2878, Vol. 46 (1. 1985), p. 87-94
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1985
zeige Details Brownrigg, R. D. A parallel variable-metric dynamic programming algorithm
in: Journal of optimization theory and applications , ISSN 1573-2878, Vol. 28 (2. 1979), p. 163-184
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1979
zeige Details Spedicato, E. A variable-metric method for function minimization derived from invariancy to nonlinear scaling
in: Journal of optimization theory and applications , ISSN 1573-2878, Vol. 20 (3. 1976), p. 315-329
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1976
zeige Details McDowell, D. G. Conditions for variable-metric algorithms to be conjugate-gradient algorithms
in: Journal of optimization theory and applications , ISSN 1573-2878, Vol. 41 (3. 1983), p. 439-450
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1983