An automated drum scanner for rapid collection of X-ray crystallographic data

A drum-scanning microdensitometer has been automated with a minicomputer equipped with a magnetic disk memory. Part of the disk is used for temporary data storage, in a manner allowing rapid retrieval. X-ray diffraction photographs from macromolecular crystals can be measured at rates up to about 25 reflections per second, with the flexibility of an `on-line' system. The method can also be used when the computer is time-shared, but with lowered film-processing rates dependent on the number of `simultaneous' (time-sharing) users.