Computer-controlled diffractometer

Abstract

A computer-controlled neutron diffractometer is described for the collection of Bragg intensities from a single crystal, the computer is a PDP-8 with a store of 4096 12-bit words, the diffractometer is a "4-circle" instrument with the axes driven by pulsed stepping-motors, while axis movement is checked by light-beam markers. The programs include procedures for centring reflections, rotating about the scattering vector, calculating the setting angles in the "bisecting" and "parallel" positions, scanning over diffraction peaks, measuring backgrounds and generating ranges of Miller indices. Two similar diffractometers may be operated simultaneously.