Scaling: Summary of Kabsch Paper 1988
Evaluation of Single-Crystal X-ray Diffraction Data from a Position-Sensitive Detector
- Program to reduce single crystal diffraction data from a sequence of adjacent rotation pictures recorded at a fixed X-ray wavelength.
- First 5 degrees of crystal rotation pictures used to locate strong diffraction spots and estimate the background.
- Orientation of crystal derived automatically from list of observed spots and all parameters describing the diffraction pattern are refined.
- User input: Space group, Cell dimensions, Detector settings.
- After initialisation the program goes back to the first picture and evaluates all data frames in the order they arrive from the meaurement.
- Each pixel is labelled by the indices of the nearest reflection.
- Pixel close to nearest reflection - counts contribute to the 3-D profile, otherwise they update the background.
- Each profile is represented as if the reflection had followed the shortest path through the Ewald sphere.
- Reflections close to the Ewald sphere are kept in a hash table to allow rapid access for updating the profiles.
- Reflections which have passed completely through the Ewald sphere are removed from table and saved for further processing.
- Intensities are estimated by fitting their profiles to an average shape learned from strong neighboring reflections.