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A focusing monochromator for small‐angle diffraction studies with synchrotron radiation
Author(s) -
Webb N. G.,
Samson S.,
Stroud R. M.,
Gamble R. C.,
Baldeschwieler J. D.
Publication year - 1977
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889877012990
Subject(s) - monochromator , synchrotron radiation , optics , diffraction , radiation , materials science , physics , wavelength
An X‐ray focusing monochromator for small‐angle diffraction studies was designed for use with the synchrotron radiation from the storage ring, SPEAR, at the Stanford Linear Accelerator Center. It incorporates a 7 cm long silicon crystal, cut at 8°30′ to the (111) planes and bent to a logarithmic spiral curvature for horizontal focusing and monochromatization. A 120 cm long elliptically curved float‐glass mirror is used for vertical focusing, and provides means of eliminating higher‐order harmonics of smaller wavelength. With SPEAR operating at 3.7 GeV, 20 mA, the two elements produce a 0.5 × 0.5 mm focused beam with an intensity of 6 × 10 8 photons s −1 . The diffraction pattern of frog sciatic nerve myelin obtained with this system was compared with that obtained with a 300 W conventional microfocus X‐ray source and a toroidal camera. The new system shows a 190‐fold gain in the integrated intensity on photographic film. Synchrotron radiation provides a broad X‐ray spectrum. The monochromator is tunable to any wavelength between 0.5 and 3 Å, with a total wavelength spread in the focused beam of about 0.01 at 1.74 Å. The broad spectrum allows wavelength selection for anomalous‐scattering experiments.