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
> anyone done a single crystal rocking curve in an attempt to see these
> tails? I have just done one to characterize the emission spectrum (as
> transmitted through a graphite post monochromator). I observed no "tube
> tails". However, I wasn't looking for them; the crystal was ~27mm in size
> and scan range for the Si 400 line was 68-70.5 two-theta and the instrument
> (a D5000) was set up with the smallest divergence and receiving slits and
> both Soller collimators. These parameters may not be suitable for
> observance of any (and all) spurious x-rays from the anode. Some geometric
> exercises may be needed to design an experiment such that any radiation
> originating from the anode would be diffracted by the single crystal into
> an anxious detector. The "Kalpha3" is apparent in this scan and its
> incorporation into the emission spectrum used for an FPA will address the
> low angle "oddities" shown in the profile of LaB6 (figure a) of the web
> site. However; the high angle debris remains a problem.
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.
J"org Bergmann
[EMAIL PROTECTED]
