Hello everyone,
Here is a general question for anyone that has pertinent
information or just cares to give some input. Basically, here at Oregon
State we have, coexisting in one lab, an INEL PSD detector set up for a
horizontal line focus and a Rigaku rotating anode generator set for a
vertical line focus (for thin films, etc, work). For quite some time I
have been musing on the possibility to hook both up in order to give me a
primary beam with higher intensity in the instrument we use for variable
temperature experiments. Unfortunately, most powders refuse to defy
gravity and stick conveniently to a vertical sample holder (well, one
could stuff it into a capillary, of course) and, thus, what I am
considering doing is using a monochromator at 45 degrees with the
horizontal to give me a horizontal line. This should work fine (in
theory). Preliminary experiments with lots of wire and duct tape and
geiger counters shows things in practice do work out.
My question then is, has anyone here done this (possibly one of
you chaps that get to play at synchrotrons)? If you have, can you share
your experiences (successes, failures, caveat with the design, etc.)? If
you haven't and you think you have some insight please also fell free to
share (as if you weren't going to anyway...).
Some secondary concerns:
On the use of a concentrating crystal monochromator - how
advisable is it to cut the crystal so as to concentrate the diffracted
beam vs. leaving the s.v. perfectly normal to the crystal's face? So you
know, right now we're using Ge 111 crystals cut so 111 is perpendicular to
the surface. Works ok.
Or, how much do you know of the monochromating, etc, properties of
total reflectance or multi-layered mirror systems? Would I be able to get
a parallel and as monochromatic incident beam out of one of these set-ups
as with a monochromator? And, of course, would the one order of magnitude
increase in cost be worth the gains.
Finally, concerning polarization corrections and other such
parameters. In such programs as Fullprof and GSAS, I believe the
assumption is that the primary, monochromated and diffracted beams all lie
on one plane. However, this will no longer be the case and we'll need to
worry with cross polarization terms, etc. Is there any software that will
take goffy geometries into account (or is there a way to do this in the
above mentioned packages?). I could, of course, choose to ignore the
polarization corrections, in which case the displacement parameters will
take care of absorbing the errors. Such a solution would be one of last
resort and would set my fur on edge - not a good solution, of course.
Well, thank you all in advance for all the profound insights I'm,
certain to get in response.
AlexY
P.S.- You'll notice that I refrained from using y'all in that last
sentence there even though that is one of my favourite words I learnt in
Texas.
P.P.S.- If you think I'm kidding about the fur bit, you've evidently never
seen my swimming era unshaved, untapered photographs.
P.P.P.S.- If you think I'm not making much sense, I just came back from
the dentist to have a filling replaced. It's either the chemicals that
still have an effect or the amalgam's mercury finally got to my brain. Or
maybe I'm just naturally crazy, which my wife seems to believe.
Dr. Alexandre F. T. Yokochi
Director, X-ray Crystallographic Facilities
Department of Chemistry
Oregon State University
Corvallis, OR 97331-4003
Ph# (541) 737-6724 Email: [EMAIL PROTECTED]
Fax# (541) 737-2062 Web Page: crystal.chem.orst.edu/~alexy
