TITLE

A ‘beam cleaner’ for harmonic selection/rejection

AUTHOR(S)
Karanfil, C.; Chapman, L. D.; Bunker, G. B.; Segre, C. U.; Leyarovska, N. E.
PUB. DATE
June 2000
SOURCE
AIP Conference Proceedings;2000, Vol. 521 Issue 1, p276
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
A ‘beam cleaner’ for selection of a harmonic from the beamline monochromator and rejection of other harmonics has been developed using a bent Laue crystal post-monochromator. This is a set of cylindrically bent Si (111) crystals that are aligned to diffract the 2nd harmonic (3× fundamental) from the beamline Si (111) monochromator. This device will reject the fundamental and other harmonics up to the Si (999) reflection from the monochromator. It has particular advantages over a flat crystal device since the reflectivity width is approximately 0.2 milliradian. This makes it insensitive to vibration and alignment errors. Over a narrow energy range it does not require adjustment. The diffraction efficiency of each crystal at 25 keV is ∼80% with an overall efficiency of the crystal pair ∼60%. The device is intended to be used for EXAFS at higher x-ray energies using the beamline monochromator harmonic. An additional benefit is that the crystal set can be passively adjusted to nearly eliminate (to the micron level) the vertical beam motion of a channel-cut mode beamline monochromator. Measurements and plans are presented. © 2000 American Institute of Physics.
ACCESSION #
6029367

 

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