Spin-Echo Resolved Grazing Incidence Scattering (SERGIS) at Pulsed and CW Neutron Sources

We have used SERGIS to probe the surface structure of a silicon diffraction grating of period 140 nm. Experiments were performed at: the Los Alamos Neutron Science Center (LANSCE) pulsed neutron source and the National Institute of Standards and Technology (NIST) continuous wave (CW) reactor neutron source. Although both sets of data show peaks of the spin echo polarization at integer multiples of the grating period, as expected, the results differ in detail. We have developed a dynamical theory, based on a Bloch wave expansion, to describe neutron diffraction from a grating. The theory explains the differences between the two sets of data without any adjustable parameters.