Intensity corrections for INEL PSD instrument

ianm@au.csiro.dmp
Wed, 10 Aug 94 14:09:29 PDT

We have recently installed a diffraction instrument based on the INEL CPS120 Position Sensitive Detector and intend to perform
Rietveld analysis on the data we collect from both capillary and flat plate geometries. The use of a flat plate sample on the INEL
requires that additional corrections be applied to allow for the fact that the incident and diffracted beams do not make the same
angle to the sample surface. Omitting these corrections produces negative thermal parameters (implying that the low angle intensities
are observed smaller than expected).

To date we have coded corrections for :-
(i) The effect of the different absorption of the incident and diffracted beams
(ii) The fact that different volumes of sample will be contributing to the diffraction process as 2theta varies.

These corrections have markedly improved the situation if the sample makes a small angle (say 2deg) with the incident beam (the
thermal parameters are now only slightly negative). However, as the angle of incidence is increased (to maybe 6deg), the thermal
parameters become more negative once again.

My question is:- Is there another correction which must be applied to the intensity data?

I would be most interested in communicating with anyone who is using INEL data for Rietveld refinement work.

Cheers

Ian C.Madsen
CSIRO Division of Mineral Products
PO Box 124, Port Melbourne,
Victoria 3207
AUSTRALIA
Phone +61 3 647 0366
FAX +61 3 646 3223
Email ianm@dmp.csiro.au