Patent Number: 
Section: claims

1. An x-ray source comprising:a vacuum chamber;at least one electron beam emitter within the vacuum chamber; andat least one target within the vacuum chamber and having a surface facing the at least one electron beam emitter, the at least one target comprising a substrate comprising a first material and a plurality of discrete structures comprising a second material configured to generate x-rays in response to bombardment by electrons from the at least one electron beam emitter, at least some of the x-rays emitted from the at least one target having propagation paths with path segments through the second material of the discrete structures, the propagation paths parallel to a direction having a take-off angle of less than 6 degrees relative to the surface and each of the propagation paths having a sum of the lengths of the path segments of the propagation path being less than of equal to 4 times a linear attenuation length of the second material at an x-ray energy of x-rays generated from the second material. 2. The x-ray source of claim 1, in which the first material is selected from the group consisting of: beryllium, diamond, polycrystalline diamond, diamond-like carbon, graphite, silicon, boron nitride, silicon carbide and sapphire. 3. The x-ray source of claim 1, in which the at least one target, when bombarded by the electrons, comprises a contiguous x-ray generating volume consisting of:first portions of the plurality of discrete structures, the first portions generating the x-rays; andsecond portions of the substrate between the first portions, wherein the first portions are more than 10% and less than 70% of the x-ray generating volume. 4. The x-ray source of claim 3, in which the first portions are between 30% and 50% of the x-ray generating volume. 5. The x-ray source of claim 3, in which the take-off angle is less than 3 degrees. 6. The x-ray source of claim 1, in which the discrete structures are embedded into the substrate of first material, such that the x-ray generating volume comprises both the first material and the second. 7. The x-ray source of claim 6, in which a length for any one of the discrete structures along the direction is less than or equal to 10 microns. 8. The x-ray source of claim 6, in which the separation distance between any two of the discrete structures is greater than or equal to 0.5 micron and less than or equal to 10 microns. 9. The x-ray source of claim 1, in which the second material is selected from the group consisting of: aluminum, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, gallium, zinc, yttrium, zirconium, molybdenum, niobium, ruthenium, rhodium, palladium, silver, tin, iridium, tantalum, tungsten, indium, cesium, barium, germanium, gold, platinum, lead and combinations and alloys thereof. 10. The x-ray source of claim 1, in which electrons from the at least one electron beam emitter have an energy greater than twice said x-ray energy. 11. The x-ray source of claim 1, in which the plurality of discrete structures are arranged in a linear array. 12. The x-ray source of claim 1, additionally comprising at least one overcoat having a thickness of less than 20 microns covering at least the discrete structures. 13. The x-ray source of claim 12, in which the at least one overcoat comprises a material selected from the group consisting of: beryllium, diamond, polycrystalline diamond, CVD diamond, diamond-like carbon, graphite, silicon, boron nitride, silicon carbide and sapphire. 14. The x-ray source of claim 12, in which the at least one overcoat comprises a material selected from the group consisting of: graphene, silver, copper, gold, tungsten, aluminum, chromium, tin and titanium. 15. The x-ray source of claim 1, additionally comprising: a mechanism to rotate the at least one target while the at least one target is being bombarded with electrons from said at least one electron beam emitter. 16. The x-ray source of claim 15, in which the at least one target is cylindrically symmetric, and the substrate of the at least one target is attached to a supporting core. 17. The x-ray source of claim 16, in which the supporting core comprises copper. 18. The x-ray source of claim 16, in which the substrate has a thickness greater than or equal to 5 micrometers and less than or equal to 2 millimeters. 19. The x-ray source of claim 16, in which a radius of curvature of the substrate is greater than 20 millimeters. 20. The x-ray source of claim 1, wherein at least some of the discrete structures comprise an adhesion layer or an anti-diffusion layer. 21. An x-ray source comprising:a vacuum chamber;at least one electron beam emitter within the vacuum chamber; andat least one target within the vacuum chamber and having a surface facing the at least one electron beam emitter, the at least one target comprising a substrate comprising a first material and a plurality of discrete structures comprising a second material configured to generate x-rays in response to bombardment by electrons from the at least one electron beam emitter, at least some of the x-rays emitted from the at least one target having propagation paths with path segments through the second material of the discrete structures, the propagation paths within an angular range greater than or equal to 2 milliradians and less than or equal to 50 milliradians relative to a direction having a take-off angle of less than 105 milliradians relative to the surface and each of the propagation paths having a sum of the lengths of the path segments of the propagation path being less than or equal to 4 times a linear attenuation length of the second material at an x-ray energy of x-rays generated from the second material. 22. The x-ray source of claim 21, in which the at least one target comprises a contiguous x-ray generating volume consisting of:first portions of the plurality of discrete structures, the first portions generating the x-rays; andsecond portions of the substrate between the first portions, wherein the first portions are more than 10% and less than 70% of the x-ray generating volume. 23. The x-ray source of claim 22, wherein the discrete structures are embedded into the substrate. 24. The x-ray source of claim 23, wherein in which a length for any one of the discrete structures along the direction is less than or equal to 10 microns. 25. The x-ray source of claim 21, in which the first material is selected from the group consisting of: beryllium, diamond, polycrystalline diamond, diamond-like carbon, graphite, silicon, boron nitride, silicon carbide and sapphire. 26. The x-ray source of claim 21, in which the second material is selected from the group consisting of: aluminum, germanium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, gallium, zinc, yttrium, zirconium, molybdenum, niobium, ruthenium, rhodium, palladium, silver, tin, iridium, tantalum, tungsten, indium, cesium, barium, germanium, gold, platinum, lead and combinations and alloys thereof. 27. The x-ray source of claim 21, wherein the sum of the lengths of the path segments of at least some of the propagation paths is greater than or equal to 0.3 times the linear attenuation length and less than or equal to 4 times the linear attenuation length. 28. The x-ray source of claim 21, in which the sum of the lengths of the path segments of the at least some of the propagation paths is greater than or equal to the linear attenuation length and less than or equal to 2 times the linear attenuation length. 29. The x-ray source of claim 21, wherein the plurality of discrete structures are arranged in a linear array.