Design of thick apertures for high-resolution neutron penumbral imaging

A general technique is presented for designing the thick apertures required to image penetrating radiation with high resolution. The new apertures are tapered in such a way that the radius of curvature varies inversely with distance from the source plane. The technique is used to design a high-resolution neutron penumbral-aperture microscope planned for the Nova laser. The design provides a resolution (determined by the sharpness of the aperture point-spread function) of ⩽10 μm over a field of view of 150 μm. The point-spread function of these apertures is sufficiently isoplanatic and distortion-free to allow linear reconstruction of complex source imaging techniques, such as high-resolution neutron or gamma-ray pinhole imaging