Patent Number: 052895106
Section: claims

1. A position sensitive, two dimensional radiation detector comprising nuclear reaction sensing means defined by adjacently disposed first and second planar arrays of elongated optical fibers oriented perpendicular to one another in X and Y directions and with said first and second planar arrays each being provided by a plurality of elongated optical fibers disposed in an abutting side-by-side relationship, a planar layer of nuclear reactive material disposed between the first and second optical fiber arrays in a contacting relationship with surface regions extending over a substantial length of each of the optical fibers in at least one of the first and second optical fiber arrays, said layer of nuclear reactive material being characterized by undergoing a nuclear reaction therein when contacted by a nuclear particle or ray for providing in said layer of nuclear reactive material at least two energetic particles that are virtually simultaneously discharged from said layer with one of said energetic particles being received by one of the optical fibers in the first planar array and another of said energetic particles being received by one of the optical fibers in the second planar array for essentially simultaneously effecting light pulse producing scintillation reactions in both of the optical fibers contacted by the energetic particles for providing said light pulse in the single optical fiber in each optical fiber array, and circuit means including coincidence counting means adapted to receive the light pulses from both of the single optical fibers for providing a signal indicative of the coordinates of said nuclear reaction in said X and Y directions. 2. A position sensitive, two dimensional radiation detector as claimed in claim 1, wherein the optical fibers in the first and second planar arrays are each of a rectangular or cylindrical cross section, and wherein each optical fiber is of a cross-sectional thickness of less than about 1 millimeter for determining the position of the nuclear reaction in an X-Y plane within less than about 1 millimeter in each direction. 3. A position sensitive, two dimensional radiation detector as claimed in claim 2, wherein the cross sectional thickness of each optical fiber is less than about 0.1 millimeter for determining the position of the nuclear reaction in the X-Y plane within less than about 0.1 millimeter in each direction. 4. A position sensitive, two dimensional radiation detector as claimed in claim 1, wherein said circuit means comprises pulse amplifying means coupled to each of said optical fibers in the first and second planar arrays with said pulse amplifying means having means associated therewith adapted to provide a signal from each planar array of optical fibers to said coincidence counting means that is indicative of the X and Y locations of the nuclear reaction. 5. A position sensitive, two dimensional radiation detector as claimed in claim 4, wherein said pulse amplifying means comprises photomultiplier tube means. 6. A position sensitive, two dimensional radiation detector as claimed in claim 1, wherein said nuclear reaction sensing means comprises a plurality of stacked pairs of adjacently disposed first and second planar arrays of elongated scintillation optical fibers oriented in the X and Y directions, wherein a planar layer of said nuclear reactive material is disposed between the first and second planar arrays in each pair of said plurality of stacked pairs of first and second optical fiber arrays, and wherein optical fibers in the same X or Y location in each pair of said plurality of pairs of first and second optical fiber arrays are coupled to a common location on said circuit means for providing a signal indicative of the coordinates of the nuclear reaction in said X and Y directions regardless of in which pair of optical fiber arrays in said plurality of stacked pairs of optical fiber arrays the nuclear reaction occurs. 7. A position sensitive, two dimensional radiation detector as claimed in claim 1, wherein said layer of nuclear reactive material comprises .sup.6 Li, .sup.10 B, .sup.235 U, or .sup.238 U. 8. A position sensitive, two dimensional radiation detector as claimed in claim 7, wherein said layer of nuclear reactive material is of a thickness substantially corresponding to the shortest range of travel of any of said energetic particles. 9. A position sensitive, two dimensional radiation detector as claimed in claim 8, wherein the layer of nuclear reactive material comprises .sup.6 Li, wherein the nuclear particle or ray providing the reaction with the layer of nuclear reactive material is a neutron for producing a .sup.6 Li(n.alpha.)T reaction with the layer of nuclear reactive material, wherein said at least two energetic particles are provided by an .alpha. particle and a triton, and wherein said thickness of said layer of .sup.6 Li is up to a thickness corresponding to the range of the .alpha. particle. 10. A position sensitive, two dimensional radiation detector as claimed in claim 9, wherein the layer of nuclear reactive material consists essentially of .sup.6 LiF, and wherein said thickness of said layer of nuclear reactive material is up to about 10 microns.