Metal microarrays for collimating neutrons and x rays

We describe the theory, fabrication and experimental results of novel, compact optical elements for collimating and/or focusing beams of x-rays or thermal neutrons. These optical elements are solid composites consisting of regular stacks of alternating micro-foils, analogous in action to Soller slits. They are made out of pairs of metals with suitable refractive indices for reflection and/or absorption of the radiation. The performance of these proof-in-principle collimating elements is limited only by the choice of micro-foil materials and the uniformity of their interfaces.