We discuss a method, based on the neutron spin echo technique, which can be used to enhance a variety of neutron scattering experiments. In the method, precession of the neutron's spin in a magnetic field is used to code a particular component of the neutron's incident or scattered wavevector. The method allows good resolution to be obtained along any chosen direction in wavevector-and-energy-transfer (Q,E) space and is independent of other resolution elements such as collimators or monochromators. Such components can thus be chosen to maximize signal intensity. The equipment we describe uses thin, magnetic films deposited on silicon substrates to manipulate neutron spins in the manner required to implement the spin echo method. These films and their mounts are inexpensive, easy to build and adjust, and can be added as a "bolt-on" option to any constant-wavelength neutron spectrometer that already provides polarized neutrons. Resolutions comparable with the best achievable with tight collimation or monochromatization should be easily attainable. The gains in intensity achievable for reflectometry and SANS are discussed.
We describe a method that makes use of a magnetized substrate and polarized neutrons to determine a unique density profile from neutron reflectometry measurements. Numerical simulations indicate that the method is capable of detecting subtle features such as slowly varying density profiles.
Patterns of diffuse neutron scattering from thin films are calculated from a perturbation expansion based on the distorted-wave Born approximation. Diffuse fringes can be categorized into three main types: those that occur at constant values of the incident or scattered neutron wavevectors, and those for which the neutron wavevector transfer perpendicular to the film is constant. The variation of intensity along these fringes can be used to deduce the spectrum of surface roughness for the film and the degree of correlation between the film's rough surfaces.