Neutron holography using Fresnel zone plate encoding

Abstract

Zone plate shadow casting is a complementary technique to the Leith–Upatnieks modification of Gabor's interferometric method for producing holograms^1,2. Suggested originally by Mertz³ in 1961 for use in X-ray astronomy, the technique has received considerable attention in nuclear medicine⁴ for imaging radioactive organs via emitted X-rays and γ-rays and, more recently, for examining in a tomographic sense the microscopic spatial source distributions of X rays and charged particles in laser-produced plasmas⁵. A series of simple experiments are described here which demonstrate that zone plate encoded neutron holography can be used to image objects. An object placed in a cold neutron beam from a research reactor scatters neutrons through a Fresnel zone plate, with alternate zones of gadolinium and aluminium, which produces a hologram of the object on an X-ray film. The image is constructed by placing the hologram, linearly reduced in size, in a converging laser beam which produces a real image of the original object. Results are presented for two objects, a pair of 0.01 m diameter rubber spheres and a 0.04 m square Maltese cross made from poly-tetrafluoroethylene (PTFE).