Hello III
At 07:20 AM 3/29/00 +0200, you wrote:
>On Tue, 28 Mar 2000, Jim Cline wrote:
>
> > Hello II,
> >
> > I went back to the "tube tails" web site mentioned by J"org Bergmann: Has
>---snip---
>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 te lattice planes of the single crystal). So, single crystals do not
>reflect tube tails. We have measured they directly by projecting them
>through a 50um hole in a lead foil (at specimen position) into a fine
>receiving slit (50um). Intensity decrease by this small hole is sufficient
>for direct observing of the primary beam.
Indeed, the origin of the X-rays which give rise to the "tube tails" is not
in the Bragg-Brentano focusing condition. But I'm certain that an
experiment could be designed to detect, and characterize, them via the
single crystal method. Such an experiment may involve mounting the tube
shield on a translation stage with the translation direction being parallel
to the anode surface. This would permit the selection of the position on
the anode from which the diffracted X-rays would originate. I would add
that if this phenomenon is indeed responsible for the problems were having
with the profiles, then the tube manufacturers should challenged to address
the matter. It would appear that a simple shield, with a slot in it,
between the filament and the anode would solve this (most unpleasant)
problem. [Or you can install and incident beam monochromator and be done
with it.]
Regards,
Jim
James P. Cline [EMAIL PROTECTED]
Ceramics Division Voice (301) 975 5793
National Institute of Standards and Technology FAX (301) 975 5334
100 Bureau Dr. stop 8523
Gaithersburg, MD 20899-8523 USA
