Resolution of small-angle neutron scattering with a reflective focusing optic

A small-angle neutron scattering instrument that uses a reflective focusing optic can achieve smaller values of the scattering vector, and with higher resolution, than the usual pinhole collimation. When the focusing mirror images the source onto the detector, the analytic expression for the resolution is independent of the sample area and is principally determined by the beam divergence incident on the sample, modified by the distance between the optic and the sample. The results are applied to a focusing SANS instrument with axisymmetric mirrors.