Feedback-Controlled X-Ray Diffraction Topography

A feedback-controlled scanning X-ray diffraction topography system is described. The system is based on automated Bragg angle control (ABAC). ABAC maintains the operation of the topographic system at all times at the maximum X-ray intensity for exposing the photographic plate. The automatic control is accomplished by a continuous measurement. of the angular derivative of the X-ray rocking curve. The measurement signal is applied to m automatic control system which orients the crystal for operation at the peak of the rocking curve at all times while scanning. A significant reduction in exposure time and background scattering is thus obtained. Picture sharpness is improved and the recording of entire topographs of warped crystal wafers is accomplished.