Patent Number: 
Section: claims

1. A graduated collimating aperture for providing a beam of increasing average energy as a function of distance measured from a central axis, the collimating aperture comprising a plurality of concentric areas, each of the areas defined in a plane substantially perpendicular to the central axis, such that any specified area is characterized by an opacity to the beam exceeding that of any area interior to the specified area. 2. The graduated collimating aperture according to claim 1, wherein at least one of the plurality of concentric areas is the surface of an x-ray attenuating material. 3. The graduated collimating aperture according to claim 1, wherein the plurality of concentric areas includes a central area of substantially no attenuation. 4. The graduated collimating aperture according to claim 1, wherein a subset of the plurality of concentric areas comprise, surfaces of frames of radially increasing opacity. 5. An inspection system for inspecting an object, the system comprising:a. a source for generating a penetrating radiation beam for irradiating the object, the beam having, at each instant of time, an instantaneous power spectrum of intensity as a function of energy;b. a shaper for modulating the generated beam, thereby creating a shaped beam, the shaper comprising at least a first section and a second section, the first section attenuating the intensity of a portion of the generated beam by a first attenuation factor and the second section attenuating the intensity of another portion of the generated beam by a second attenuation factor;c. a scanner for scanning the first and second sections of the penetrating radiation beam with respect to the inspected object andd. at least one detector for detecting the shaped beam after the shaped beam interacts with the objectwherein the shaper spatially separates the shaped beam into a first beam and a second beam, the first beam including the portion of the generated beam attenuated in the first section of the shaper and the second beam including the portion of the generated beam attenuated in the second section of the shaper. 6. The inspection system according to claim 5, wherein the at least one detector detects the first beam after the first beam interacts with the object, further comprising a second detector for detecting the second beam after the second beam interacts with the object. 7. The inspection system according to claim 6, wherein the at least one detector further detects photons of energies in the first beam exceeding a first fiducial energy and wherein the second detector further detects photons of energies in the second beam exceeding a second fiducial energy.