Dr.Joerg Bergmann wrote:
> Indeed, such simple crystal measuring is unable to detect tube tails.
> Tube tails are out of the Bragg-Brentano focusing conditions. That means
> their diffraction vector is not orthogonal to the specimens surface
> (to the lattice planes of the single crystal). So, single crystals do not
> reflect tube tails.
I have been trying to follow this discussion with little success.
Perhaps I am missing something, but if you can't see these tube tails in
a measurement with a single crystal (where signal to noise is optimal),
why would you see the effect with a powder, which is a collection of
single crystals? What is different about the physics of the powder
experiment that allows this tube tails phenomenon to be observed? The
only difference I see is Bragg-Brentano focusing, which is effectively
disabled by the narrow Darwin width of the single crystal.
Could someone please elaborate?
Thanks,
Brian
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Brian H. Toby, Ph.D. Leader, Crystallography Team
[EMAIL PROTECTED] NIST Center for Neutron Research, Stop 8562
voice: 301-975-4297 National Institute of Standards & Technology
FAX: 301-921-9847 Gaithersburg, MD 20899-8562
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