Report on work with the X-ray displacement interferometer. Pt. 3

In the output signal of the X-ray displacement interferometer, the X-ray wave diffracted by the moving crystal, which varies in phase periodically as a function of the spacing of the lattice planes moving post the illuminated crystal section, is made to interfere with a suitable control wave. This way, the radiation flux in the outlet channel, which fluctuates in the same period, yields information on the number of lattice planes in the displacement length measured by light-optical methods. The interplanar spacing can thus be determined independent of the radiation wavelength. Using model examples, it is shown how disturbances in the atomic lattice structure of the moving crystal may affect the output signal and thus cause errors of measurement. (orig./HP)