This was a precision, computer-controlled, Michelson-type interferometer used to measure the important physics parameter, the fine structure constant. The device could make diffraction angle measurements within an accuracy of +/- 0.005”. To maintain the physical dimensions accurately all critical parts of the apparatus, which measures ~60 cm in width, were machined out of Invar, which has an almost zero expansion coefficient over a wide temperature range. The apparatus was designed and assembled at CRNL by H. Bird as a PhD thesis project and was used for a number of years for measuring X and gamma ray scattering precisely by J. W. Knowles and his experimental group.
Overall computer control was achieved with a PDP-8 computer. During measurements there were a number of delicate and complex optical lenses and mirrors used. Unfortunately most of these were badly damaged over the years of storage.
