Theory of Two-Beam X-Ray Diffractometry Method Using Synchrotron Radiation

An accurate theory of the new method of two-beam X-ray diffractometry using synchrotron radiation has been developed. In this method, a beam from the source is reflected from two monochromator crystals without changing direction and then is collimated by a slit with a relatively small size. A diffraction reflection curve (DRC) is obtained by recording the integrated intensity during crystal sample rotation near the Bragg angle for a certain energy, specified by the monochromator. The theory accurately takes into account the influence of the source sizes, the distances, and the slit size on the formation of experimental DRC. It is shown that a practically intrinsic DRC of crystal sample can be obtained even for symmetric reflections from the monochromator crystals and crystal sample if the Bragg angle in the monochromator crystals exceeds the Bragg angle in the crystal sample by a factor of 2 or more. The slit size should to be optimized to exclude its influence on the DRC.