A method of obtaining an extremely parallel X-ray beam by successive asymmetric diffractions and its applications

For obtaining X-ray beams of extremely narrow angular spread, a monochromator system consisting of three crystals, prepared from a block of silicon single-crystal, in which asymmetric 422 diffractions of Cu Kα are repeated, is constructed. The narrowest angular width of the beam thus obtained is estimated to be 0.01′′. By utilizing this monochromator system in place of the monochromator crystal in a double-crystal spectrometer of parallel setting, rocking curves are measured for both the Bragg- and Laue-case diffractions. No appreciable broadening of the half-value width is observed for the Bragg-case diffraction, compared with that of the intrinsic curve. The narrowest half-value width observed is 0.16′′. Several subsidiary maxima are observed in the rocking curve of Laue-case diffraction from a thin crystal.