Patent Number: 047956542
Section: claims

1. A structure for shielding X-ray and gamma radiation, said structure having first and second sides, said X-ray and gamma radiation striking said structure on said first side, said structure comprising three layers of materials different from each other, and wherein each of the first two layers, taken in sequence from said first side toward said second side, comprises an element which converts at least a part of the X-ray or gamma radiation to be shielded or of a secondary radiation emitted by a preceding layer closer to said first side, respectively, into secondary X-ray or gamma radiation, and each of the last two layers comprises an element having a K-edge which is in an energy range between first and second energy levels, said first energy level corresponding to an L.sub.I -edge of an element in an immediately preceding layer closer to said first side, and said second energy level being higher than said first energy level but lower than an energy level of secondary X-ray or gamma radiation emitted by said immediately preceding layer, wherein said layers comprise, in order from said first side: a first layer comprising at least one element selected from the group consisting of uranium, lead, osmium, rhenium, tungsten and tantalum,  a second layer comprising at least one element selected from the group consisting of tin, indium, palladium, rhodium, ruthenium, molybdenum and niobium, and  a third layer comprising at least one element selected from the group consisting of zinc, copper, nickel, cobalt, iron, manganese, chromium, vanadium and titanium. 2. The structure as claimed in claim 1, wherein said layers comprise, in order from said first side, a first layer comprising uranium, a second layer comprising at least one element selected from the group consisting of tin, indium, palladium, rhodium and ruthenium, and a third layer comprising at least one element selected from the group consisting of zinc, copper, nickel, cobalt, iron, manganese, chromium, vanadium and titanium. 3. The structure as claimed in claim 1, wherein said first layer comprises at least one element selected from the group consisting of lead and tungsten, said second layer comprises at least one element selected from the group consisting of tin and molybdenum, and said third layer comprises at least one element selected from the group consisting of zinc, copper, nickel, iron and chromium. 4. The structure as claimed in claim 3, wherein said first one of said layers comprises lead, said second layer comprises tin and said third layer comprises copper. 5. The structure as claimed in claim 1, wherein each of said layers include a plurality of superposed thin layers of identical material and a plurality of thin separating layers disposed between consecutive ones of said superposed thin layers. 6. The structure as claimed in claim 5, wherein said thin separating layers comprise a material selected from the group consisting of aluminum and an oxide of an adjacent one of said superposed thin layers. 7. The structure as claimed in claim 5, wherein the thickness of each of said superposed thin layers is less than 50 .mu.m. 8. The structure as claimed in claim 7, wherein the thickness of each of said superposed thin layers lies in the range between 0.1 and 20 .mu.m. 9. The structure as claimed in claim 5, further comprising a carrier sheet, on said first side of said structure, to which said superposed thin layers and said thin separating layers are applied. 10. The structure as claimed in claim 9, wherein said carrier sheet comprises a material selected from the group consisting of copper and chromium steel. 11. The structure as claimed in claim 9, wherein said superposed thin layers and thin separating layers are applied to said first carrier sheet by vacuum deposition. 12. The structure as claimed in claim 9, further comprising a second carrier sheet on said second side of said structure, wherein said thin layers and said thin separating layers are arranged between said first and second carrier sheets. 13. The structure as claimed in claim 12, wherein said superposed thin layers and said thin separating layers are fastened to each other and to said first and second carrier sheets by gluing or pressing. 14. A structure for shielding X-ray and gamma radiation, said structure having first and second sides, said X-ray and gamma radiation striking said structure on said first side, said structure comprising n layers of materials different from each other, wherein n is an integer greater than or equal to two, and each of the first n-1 layers, taken in sequence from said first side toward said second side, comprises an element which converts at least a part of the X-ray or gamma radiation to be shielded or of a secondary radiation emitted by a preceding layer closer to said first side, respectively, into secondary X-ray or gamma radiation, and each of the last n-1 layers comprises an element having a K-edge which is in an energy range between first and second energy levels, said first energy level corresponding to an L.sub.I -edge of an element in an immediately preceding layer closer to said first side, and said second energy level being higher than said first energy level but lower than an energy level of secondary X-ray or gamma radiation emitter by said immediately preceding layer, wherein each of said layers includes a plurality of superposed thin layers of identical material and a plurality of thin separating layers disposed between consecutive ones of said superposed thin layers.