APPLICATION OF POLYCAPILLARY OPTICS FOR PARALLEL BEAM POWDER DIFFRACTION

The use of polycapillary optics for powder diffraction has been evaluated based on intensity, profile shape, and accuracy of lattice parameters for materials with a wide range of absorption coefficients. Measurements of powder samples were made using Bragg-Brentano, traditional parallel beam, and polycapillary/parallel beam instrument configurations. In the case of the polycapillary optic, several configurations of the receiving side optics were tested. The results demonstrate that the intensities obtained using the polycapillary optic range from 0.4 to -7 times that obtained in Bragg-Brentano geometry. In addition, the polycapillary optic provides profile shapes that are essentially gaussian and the small divergence of the beam allows accurate measurements of lattice parameters without calibrating the diffraction peak locations.