Neutron imaging with multi-wafer monochromators

. Multi-wafer monochromators for neutron scattering have been developed at MURR. Units made from commercial thin silicon [100] wafers and from non-standard [511] and [110] wafers were fabricated for stress-mapping machines at MURR, NIST and ORNL. The phase-space optics of multi-wafer assemblies was worked out. This revealed that, with thick packets of wafers, neutron imaging can be done at the spatial resolution of a single thin wafer. The imaging may be dispersive (as with prisms), with respect to the neutron wavelength, direction, or a combination of these, but it may also be non-dispersive (as with mirrors). Experiments have confirmed these conclusions. Dispersive and non-dispersive images were obtained with multi-wafer units at spatial resolutions comparable to those of single wafers. For non-dispersive imaging the acceptance window indeed did not depend on the neutron wavelength.