This listing does not cover Bruker area detectors ! But rather some of the
statement made by Stan.
> This may not be exactly on-topic but a year ago we collected some powder
> data with Hi-Star at ESRF Grenoble and had a hard time gluing pieces of
> the pattern together. No matter how hard we tried the mismatch of the peak
> positions between adjacent pieces of the pattern always remained. Only
> intensities were really reproducible. However we did not use software from
> Bruker but the general-purpose "fit2d". The integrating software from
> Bruker might be better, but we hardly had a chance to try it on the spot
> - our beam time was too short.
In our hands, FIT2D is versatile and powerful tool. We have yet to come
across data that could not be successfully reduced. The successfull
treatment of synchrotron data depends on a good calibration of the
instruments, e.g. sample to detector distance, detector center,
wavelength...
> Another point is that the parallel beam optics and area detectors don't
> make a good match. For Hi-Star I would rather use a pinhole collimator.
> However, I know little about D8 design and may be wrong here.
The match of parallel beam optics and area detectors is good for
powder data at the ESRF, where intensity is abundant !
> The resolution may be a problem. The detector I used to work with had 60
> micron pixel size which gives 0.017 deg angular resolution with 200 mm
> radius of the diffractometer. Not really impresive. Another point is
> diffraction geometry - beam size, focusing conditions etc may add to the
> peak broadening.
Concerning the resolution you mention, you should be aware that adjusting
the wavelength (which may be rather difficult) and the sample to
detector distance (which often is trivial) allow you to vary the effective
resolution. If really high resolution is required, BM16 and BM1 (the
Swiss-Norvegian-Beamline) offers access to extremely high resolution
(inherent peak widths < 0.008 degrees). These set-ups are evidently not
using area detectors. The price for the speed of area detectors is
currently a loss in resolution.
Henrik Birkedal & Marc Hostettler
Institute of Crystallography
University of Lausanne
Switzerland
