F. Automation and real-time creep software
The physical machinery and analytical equipment for in-situ deformation
at mantle pressures has developed rapidly under RGC phase I, the
methods of data reduction, especially for the white beam experiments,
have lagged behind. Much larger quantities of diffraction data
must be taken during a dynamic experiment such as creep, and unless
the methods are in place for processing these data as fast as
they are generated, the operator of a creep experiment will be
“flying blind.” Much as not knowing temperature until
after an experiment concludes, the lack of real-time knowledge
of pressure and rheology (i.e., stress and strain rate), hinders
the operator’s ability to control the experiment and understand
current behavior. One piece of valuable knowledge to the operator
is recognizing when steady state is reached; another is knowing
whether mean stress (pressure) is changing or is constant. Only
gross measures of stresses (±several 0.1 GPa) are currently
available real time, far too coarse to monitor behavior at the
requisite10-MPa scale. We must manipulate a data stream from 10
rather than 4 detectors for the white radiation data and handle
the image processing of the monochromatic data from the CCD detector.
We must achieve near real-time conversion of diffraction spectra
to measured stress, in order to operate in the conventional style
of a dynamic experiment, wherein the operator observes variables
(e.g., stress and strain) as a function of time, while monitoring
key environmental conditions, and makes operational decisions
on the basis of how the experiment is proceeding. The entire system—
deformation apparatus, diffraction and imaging detectors, as well
as beam defining optics—should be integrated in operation.
All materials that are in the cell should be known to the data
analysis program with the ability to recognize them in the diffraction
pattern and calculate relative amounts of the different materials
in the scattering volume. Peak fitting should be done with a Rietveld
type philosophy of accounting for every bump that can come from
the materials in question.
