Patent Number: 
Section: claims

1. A lightweight collimator, having at least a top and a bottom and incorporating shielding about a cylindrical detector having at least a top and a bottom, said detector affixed near said top of said collimator for collecting collimated radiation through said bottom of said collimator, at least said shielding shaped externally according to the quartic relationship:      L    0    2    =            y      2        +          [                                    y            2                    ⁢                      z            2                                                (                          y              +              D                        )                    2                    ]      where y is the minimum thickness of encased shielding needed to shield said collimator from un-collimated radiation entering said collimator at a distance, z, along said longitudinal axis of said collimator, z measured from the bottom of said detector, and D is the inner diameter of said collimator as established by the outer diameter of said detector,wherein at least said shielding incorporated in said collimator has a variable wall thickness that decreases gradually from a thickness L0 at the end of said collimator containing said detector to a thickness, y, measured at a distance, z, away from the bottom of said detector. 2. The collimator of claim 1 made by machining solid shielding material. 3. The collimator of claim 1 made by pouring molten shielding material into forms shaped in accordance with said quartic relationship. 4. The collimator of claim 1 in which said radiation comprises at least gamma rays and said detector is at least a gamma ray detector. 5. The collimator of claim 4 in which said shielding material comprises at least in part lead. 6. A method for making a lightweight collimator for collecting radiation, said collimator having at least a top and a bottom, said collimator for collecting collimated radiation through said bottom of said collimator, comprising:providing a cylindrical detector, said detector having at least a top and a bottom, wherein said detector is affixed near said top of said collimator;providing a cylindrical tube having an inside diameter of at least the outside diameter of said detector, said tube for collecting said radiation;connecting said cylindrical tube to said detector so as to be in operable communication with said bottom of said detector;providing shielding to be incorporated within said collimator and about said detector and said cylindrical tube, at least said shielding to be shaped in accordance with the quartic relationship:      L    0    2    =            y      2        +          [                                    y            2                    ⁢                      z            2                                                (                          y              +              D                        )                    2                    ]      where y is the minimum thickness of encased shielding needed to shield said collimator from un-collimated radiation entering said collimator at a distance, z, along said longitudinal axis of said collimator, z measured from the bottom of said detector, and D is the inner diameter of said collimator as established by the outer diameter of said detector;fabricating a configuration to enclose said detector, said shielding, and said tube; andenclosing said detector, said shielding and said tube in said configuration, wherein said collimator is shaped externally according to said quartic relationship, and wherein at least said shielding material has a variable wall thickness that decreases gradually from a thickness L0 at said top of said collimator to a thickness, y, measured at a distance, z, away from said bottom of said detector. 7. The method of claim 6 said shielding made by machining solid shielding material. 8. The method of claim 6 said shielding made by pouring molten shielding material into forms shaped in accordance with said quartic relationship. 9. The method of claim 6 said radiation comprising at least gamma rays and said detector comprising at least a gamma ray detector. 10. The method of claim 9 said shielding material comprising at least in part lead.