Imaging of Si-crystal lattice by phase-contrast X-ray microscopy [for Avogadro constant determination]

X-ray Moire topography has been improved by the application of phase modulation, imaging, and computing to provide images of lattice distortion with unprecedented sensitivity inside near-perfect Si monocrystals. The technique here presented is based on differential phase modulation to permit the detection of the spatially varying phase shift at the output of an X-ray interferometer of the triple Laue type by the use of a multi-element detector. Information was obtained about the degree of perfection of the crystals being used in the determination of the Avogadro constant and about the effects of machining and etching on the performances of X-ray interferometers.