Lachlan:
>Is there GEM related information on available software (or portability
>tools) that are being developed in parallel with the hardware so that GEM
>can produce "usable" and "analyzable" data?
Yes, we have a major software effort to handle these data and reduce them
down to manageable sizes. Files will still be quite a lot bigger than CW
files, because we have the wavelength and angle information which come out
separately, but I am aiming at something like 500Kbites uncompressed (7
patternsx3000 time channelsx 32 bytes of data/errors). The problem is that
the reduction algorithms are not set in stone. The user must be able to
interact with the software and select the optimal way to combine detectors
into groups. Our answer to this challenge, for the moment, is and IDL based
platform called ARIEL, which also has some fortran bits for added speed. It
was designed to be instrument-independent, so it can handle all the ISIS
diffractometers, and, hopefully, other institutions as well. We have
acquired the right to distribute IDL executables free of charge even for the
users who don't have IDL.
Still, this means serious multi-histogram Rietveld (7 patterns or sometimes
more). To make things simpler for the users, I will try to produce data
normalised on an absolute cross-section scale, so that the histogram scales
can be all set to the same value. I'm sure this is possible, because it's
done routinely for liquid-amorphous scattering. Also, I would aim at having
all the patterns on the same Q scale, so that the instrument parameters do
not need to be refined. ARIEL is designed to do all these things, but we
are not quite there yet.
The fast data output poses even more challenges. Ultimately, Rietveld code
will need to be updated to cope with all this.
Paolo
