Version 1
R. Ghosh, June 1995
At a preliminary stage of the experiment, and throughout, the resolution ellipsoid of the instrument in the four dimensional Qx, Qy, Qz and Energy transfer space is paramount to a successful measurement. The standard program RESCAL, to which many members of the Three-axis group have contributed over the years, fulfils this fundamental requirement.
FILING
It is sometimes useful to combine similar, or compatible measurements and treat the groups as a whole. This program allows standard raw data files to be merged and rescaled, and can be used also to subtract background effects.
PKFIT
This fitting program is the workhorse of the Three-axis group, with variants working on Unix, Macintosh and OpenVMS. It allows a number of simple models to be fitted to data, including some effects of finite resolution, and absorption, to yield peak intensities and positions. Many authors have contributed to it. Present developments are being continued by A. Filhol and A. Bouvet.
More sophisticated programs include effects of intensity variation as a function of dispersion, which lead to a displacement of the true peak centre. This must be taken into account in studies of effects at high resolution. It is then necessary to have good models of the presumed scattering surface, and these programs are hence dependent on the crystals being studied.