High precision grids for neutron, hard X-ray, and gamma-ray imaging systems
AssigneeThe United States of America as represented by the Administrator of the National Aeronautics and Space Administration
InventorJonathan W. Campbell
Life of this patent
Estimating the term…
Abstract
Fourier telescopes permit observations over a very broad band of energy. They generally include synthetic spatial filtering structures, known as multilayer grids or grid pairs consisting of alternate layers of absorbing and transparent materials depending on whether neutrons or photons are being imaged. For hard x-rays and gamma rays, high (absorbing) and low (transparent) atomic number elements, termed high-Z and low-Z materials may be used. Fabrication of these multilayer grid structures is not without its difficulties. Herein the alternate layers of the high-Z material and the low-Z material are inserted in a polyhedron, transparent to photons of interest, through an open face of the polyhedron. The inserted layers are then uniformly compressed to form a multilayer grid.
Claims12
A multilayer grid containing alternate layers of an opaque or absorptive material and a transparent material for a neutron, hard X-ray, gamma-ray, imaging instrument containing a grid tray having openings to receive multilayer grids, the multilayer grid being a regular polyhedron having faces transparent to photons of interest, the polyhedron having two larger faces in the form of congruent polygons forming front and back surfaces of the polyhedron, remaining faces being smaller polygons separating the front and back surfaces a predetermined distance equal to the width of the two materials contained therein, the larger faces being shaped to form a multilayer grid fitting slidably within the grid opening in the grid tray, and the polyhedron containing a piston formed of a material transparent to photons of interest, which, through a drive shaft, compresses and retains the multilayers in place within the polyhedron, and which is allowed to remain in the polyhedron when, as a grid, the polyhedron is placed in the grid tray.
A method for improving a telescope used for neutron, hard X-ray and gamma-ray imaging, the telescope being one containing a grid tray having openings to receive multilayer grids, the improvement including assembling a regular polyhedron utilizing faces transparent to photons of interest, with two larger faces in the form of congruent polygons which form front and back surfaces of the polyhedron, and with smaller polygonal faces separating the front and back surfaces, the two larger faces being shaped to fit slidably within the grid opening in the grid tray, sizing a plurality of strips of absorptive and transparent materials so that their widths are equal to the width of the faces of the smaller polygons, inserting in the polyhedron, through an open face, alternate strips of the sized materials to form a multilayer, and compressing the multilayer to form a multilayer grid for insertion in the telescope grid tray.
Dependencies are inferred from the claim text.