Patent Number: 
Section: claims

1. A narrow band x-ray filter comprising:a substrate; anda sheaf of one or more reflection units stacked upon each other on the substrate, each reflection unit includinga first set of at least two discrete spacers on a respective underlying structure,a reflector disposed on the first set of spacers so as to form a void between the respective underlying structure and the reflector, anda first set of at least two discrete shims disposed on the first set of at least two spacers, each shim being at least substantially the same thickness as the reflector. 2. The filter of claim 1, wherein each reflector includes:a base layer; anda stack of one or more mirrors, each mirror includinga heavy Z metal layer, anda layer of carbon on the metal layer. 3. The filter of claim 2, wherein the heavy Z metal includes at least one of gold, platinum and iridium. 4. The filter of claim 3, wherein each stack includes 2-200 mirrors. 5. The filter of claim 1, wherein the filter further includes a top member on the sheaf. 6. The filter of claim 1, wherein the sheaf includes between 2 and 300 reflection units. 7. An apparatus, to produce a substantially narrow band x-ray beam; the apparatus comprising:a source of a first x-ray beam; anda narrow band x-ray filter having a first end, a second end and a focal point located nearer to the first end than to the second end, andthe source being disposed substantially at the focal point such that a substantially narrow band x-ray beam emanates from the second end of the filter; andthe filter being configured and disposed so as to receive at the focal point at least a majority of the cross-section of the first x-ray beam;wherein the filter includes the following,a substrate, anda sheaf of one or more reflection units stacked upon each other on the substrate, each reflection unit including the following,a first set of at least two discrete spacers on a respective underlying structure,a reflector disposed on the first set of spacers so as to form a void between the respective underlying structure and the reflector, anda first set of at least two discrete shims disposed on the first set of at least two spacers, each shim being at least substantially the same thickness as the reflector. 8. The apparatus of claim 7, wherein the filter is configured and disposed so as to receive at the focal point substantially the entire cross-section of the first band x-ray beam. 9. The apparatus of claim 7 wherein the filter is an X-ray telescope such that the narrow band x-ray beam is formed of substantially parallel x-rays. 10. The apparatus of 7, wherein the narrow band x-ray beam is formed of x-ray that diverge from the second end of the filter. 11. The apparatus of 7, wherein each reflector includes:a base layer; anda stack of one or more mirrors, each mirror including the following,a heavy Z metal layer, anda layer of carbon on the metal layer. 12. The apparatus of claim 7, wherein: the filter is movable in at lease one dimension; and the apparatus further comprises an adjustment unit to move the filter in the at least one dimension. 13. The apparatus of claim 7, wherein the first x-ray beam is a broad band x-ray beam. 14. An apparatus to make an x-ray image of a subject, the apparatus comprising:a source of a first x-ray beam; anda narrow band x-ray filter having a first end, a second end and a focal point located nearer to the first end than to the second end,the source being disposed substantially at the focal point such that a substantially narrow band x-ray beam emanates from the second end of the filter, andthe filter being configured and disposed so as to receive at the focal point at least a majority of the cross-section of the first x-ray beam;an x-ray detector arranged to receive the narrow band x-ray beam so that a subject disposed between the second end of the filter and the detector casts an image thereon;wherein the filter includes the following,a substrate, and,a sheaf of one or more reflection units stacked upon each other on the substrate, each reflection unit including the following,a first set of at least two discrete spacers on a respective underlying structure,a reflector disposed on the first set of spacers so as to form a void between the respective underlying structure and the reflector,a first set of at least two discrete shims disposed on the first set of at least two spacers, each shim being at least substantially the same thickness as the reflector,each reflector including a base layer, anda stack of one or more mirrors, each mirror including the following,a heavy Z metal layer, anda layer of carbon on the metal layer. 15. A method of making a narrow band x-ray filter, the method comprising;providing a substrate; andstacking two or more reflection units in succession upon the substrate such that the two or more reflection units are aligned according to a plurality of radial planes that share a common origin, respectively;wherein the step of stacking, for each reflection unit, the following,disposing a first set of at least two discrete spacers on a respective underlying structure,disposing a reflector on the first set of spacers so as to form a void between the respective underlying structure and the reflector, anddisposing a first set of at least two discrete shims on the first set of at least two spacers, each shim being at least substantially the same thickness as the reflector. 16. The method of claim 15, further comprising:mechanically connecting the two or more successively-stacked units to the substrate so as to form a sheaf of reflection units. 17. The method of claim 15, wherein each reflector includes:a base layer; anda stack of one or more mirrors, each mirror includinga heavy Z metal layer, anda layer of carbon on the metal layer. 18. The method of claim 17, wherein the heavy Z metal includes at least one of gold, platinum and iridium. 19. The method of claim 17, wherein each reflector includes 2-200 mirrors. 20. The method of claim 15, further comprising:disposing a top member on the sheaf. 21. The method of claim 15, wherein the sheaf includes between 2 and 300 reflection units. 22. The method of claim 15, wherein the step of stacking, for each reflection unit, includes:disposing a first set of at least two rails on a respective underlying structure, anddisposing a reflector on the first set of rails so as to form a void between the respective underlying structure and the reflector. 23. The method of claim 22, wherein:the step of stacking further includes the following,configuring each rail to exhibit, in cross section, a shape resembling a staircase including at least first and second steps;a first step portion of the rail, being located relatively upward from the respective underlying structure, corresponds to a first surface upon which the reflector is disposed; anda second step portion of the rail corresponds to a second surface which can support another rail disposable thereon. 24. The method of claim 15, wherein the step of stacking includes orienting each reflection unit such that leading edges of the reflection units are subjected to substantially the same angle of incidence with respect to a source of x-rays located at the common origin.