SOFTWARE FOR HIGH PRESSURE CRYSTALLOGRAPHY USING AREA DETECTORS. A P Hammersley, D Hausermann, M Kunz, and C Reul Wassilew, Synchrotron Radiation Facility, BP 220, 38043 Grenoble Cedex, France

Accurate processing of area detector data is of fundamental importance in High Pressure crystallography. The quality of structural information depends heavily on image processing for distortion and geometrical corrections, and for integration. Detector evaluation, experiment calibration, and scientific data analysis, all share common needs and benefit from versatile software.

Area detector evaluation has emphasized the importance of calibration and correction even for systems with very little distortion. The ultimate test of detectors is the quality of scientific results which they produce, but since this a "convolution" of a large number of factors, many external to the detectors, simple characterisation techniques are of value. To assist in efficient exploitation of experimental facilities automated calibration of beam centre, detector non-orthogonality, sample to detector distance, and wavelength using calibrants is highly desirable.

The integration of 2-D data to 1-D "2-theta scans" is well understood, but the realities of experiments and samples means that flexibility and user interaction are of much value in extracting structural information from the data. Non-ideal powders, with texture, or maybe deviatoric stress make interpretation more complicated and demand new techniques allowing arbitrary selection and integration of different azimuthal regions.

As well as providing sophisticated functionality, software ideally needs to be easy to understand and operate, and provide a large amount of feed-back

to the user.