Off-specular diffraction on periodic gratings studied by neutron reflectometry

We present results of neutron diffraction on periodic gratings. The periodicities of the gratings range from 2 to 10 mu m. These experiments have been performed on the time-of-flight spectrometer EROS at the Laboratoire Leon Brillouin. We show that dynamical calculations (based on a matrix formalism) can quantitatively account for the results. Experiments have been performed on several systems (with various periodicities, materials and structures) to study the diffraction efficiency effects. We show that optimised gratings can exhibit diffraction efficiencies as high as 30% over a scattering wave-vector range 0 < q(z) < 0.2 nm(-1). We suggest that such gratings could be used as a neutron energy analyser especially well suited for time-of-flight spectrometers. (C) 2000 Elsevier Science B.V. All rights reserved.