X-ray interferometric imaging system
An x-ray interferometric imaging system includes an x-ray source with a target having a plurality of discrete structures arranged in a periodic pattern. The system further includes a beam-splitting x-ray grating, a stage configured to hold an object to be imaged, and an x-ray detector having a two-dimensional array of x-ray detecting elements. The object is positioned between the beam-splitting x-ray grating and the x-ray detector, the x-ray detector is positioned to detect the x-rays diffracted by the beam-splitting x-ray grating and perturbed by the object to be imaged.
1. An x-ray interferometric imaging system comprising:
a source of x-rays comprising:
a vacuum chamber;
an electron beam emitter; and
a target comprising:
a substrate comprising a first material; and
a plurality of discrete structures embedded in the substrate, the plurality of discrete structures comprising a second material that generates x-rays in response to electron irradiation, said plurality of discrete structures arranged in a periodic pattern to produce a periodic pattern of sub-sources of x-rays when irradiated by electrons from the electron beam emitter;
a beam-splitting x-ray grating comprising periodic structures that introduce a phase shift for a predetermined x-ray wavelength, the periodic structures comprising two-dimensional structures arranged in a checkerboard pattern, said beam-splitting x-ray grating positioned to diffract x-rays generated by the periodic pattern of sub-sources of x-rays;
a stage configured to hold an object to be imaged; and
an x-ray detector comprising a two-dimensional array of x-ray detecting elements, said object positioned between the beam-splitting x-ray grating and the x-ray detector, said x-ray detector positioned to detect the x-rays diffracted by the beam-splitting x-ray grating and perturbed by the object to be imaged.
2. The x-ray interferometric imaging system of claim 1 , in which a ratio (Z 2 ρ 2 )/(Z 1 ρ 1 ) for the second material and the first material is greater than 12, where Z 1 and ρ 1 are the atomic number and the mass density, respectively, of the first material and Z 2 and ρ 2 are the atomic number and the mass density, respectively of the second material.
3. The x-ray interferometric imaging system of claim 1 , in which the first material is selected from the group consisting of: beryllium, diamond, graphite, silicon, boron nitride, silicon carbide, sapphire and diamond-like carbon.
4. The x-ray interferometric imaging system of claim 1 , in which the plurality of discrete structures have similar shapes.
5. The x-ray interferometric imaging system of claim 1 , in which the periodic pattern of the plurality of discrete structures is a regular grid and a width in at least one dimension of one or more discrete structures of the plurality of discrete structures is less than 10 microns.
6. The x-ray interferometric imaging system of claim 1 , in which the periodic pattern of the plurality of discrete structures is a set of parallel lines and a width in one dimension of one or more discrete structures of the plurality of discrete structures is less than 10 microns, and a length in a perpendicular dimension is greater than 20 microns.
7. The x-ray interferometric imaging system of claim 1 , in which the phase shift of the beam-splitting x-ray grating is approximately π radians for the predetermined x-ray wavelength.
8. The x-ray interferometric imaging system of claim 1 , in which the phase shift of the beam-splitting x-ray grating is approximately π/2 radians for the predetermined x-ray wavelength.
9. The x-ray interferometer imaging system of claim 1 , in which the x-ray detector is positioned at a distance from the beam-splitting x-ray grating that corresponds to an odd multiple of 1/16 th of a Talbot Distance for the beam-splitting x-ray grating when used with spherical wave x-rays of a predetermined wavelength spectrum and spatial coherence, the x-ray detector having a spatial resolution at least three times a Talbot fringe period for a Talbot interference pattern at said odd multiple of 1/16 th of the Talbot Distance for the beam-splitting x-ray grating when used with x-rays of said predetermined wavelength spectrum and spatial coherence.
10. The x-ray interferometric imaging system of claim 1 , in which an orientation of at least two discrete structures of the plurality of discrete structures of the target are such that, when simultaneously bombarded by electrons from the electron beam emitter, the x-rays generated by a first discrete structure of the at least two discrete structures overlap in part the x-rays generated by a second discrete structure of the at least two discrete structures, and the overlapping x-rays propagate together towards the beam-splitting x-ray grating.
11. The x-ray interferometric imaging system of claim 1 , wherein the stage is configured to adjust a position of the object relative to the beam-splitting x-ray grating.
12. The x-ray interferometric imaging system of claim 11 , wherein the stage is configured to move the object along each of three orthogonal axes and to rotate the object along each of three orthogonal axes.
13. The x-ray interferometric imaging system of claim 1 , additionally comprising: an analyzer grating placed in close proximity to a surface of the x-ray detector.
14. The x-ray interferometric imaging system of claim 13 , in which the analyzer grating comprises periodic structures that form an x-ray absorption grating, in which the periodic structures of the analyzer grating have a period p 2 given approximately by:
p
2
=
p
0
D
L
where p 0 is the period of the periodic pattern of sub-sources of x-rays, D is the distance between the beam-splitting x-ray grating and the analyzer grating, and L is the distance between the target and the beam-splitting x-ray grating.
15. The x-ray interferometric imaging system of claim 13 , wherein the stage is configured to adjust a position of the object relative to the analyzer grating.
16. The x-ray interferometric imaging system of claim 1 , additionally comprising:
a cooling system comprising:
a reservoir for storing a cooling fluid;
a channel within the substrate for conducting the cooling fluid;
an additional channel to conduct the cooling fluid from the reservoir to the channel within the substrate;
an additional channel to conduct the cooling fluid from the channel within the substrate to the reservoir; and
a pumping mechanism to pump the cooling fluid through the cooling system.
17. An x-ray tomography system comprising:
an x-ray source comprising:
a vacuum chamber;
an electron beam emitter; and
a target comprising:
a substrate comprising a first material; and
a plurality of discrete structures embedded in the substrate, the plurality of discrete structures comprising a second material that generates x-rays in response to electron irradiation, said plurality of discrete structures arranged in a periodic pattern to produce a periodic pattern of sub-sources of x-rays when irradiated by electrons from the electron beam emitter;
a beam-splitting x-ray grating comprising periodic structures that introduce a phase shift for a predetermined x-ray wavelength, the periodic structures comprising two-dimensional structures arranged in a checkerboard pattern, said beam-splitting x-ray grating positioned to diffract x-rays generated by the periodic pattern of sub-sources of x-rays;
a stage configured to hold an object for tomographic data collection; and
an x-ray detector comprising a two-dimensional array of x-ray detecting elements, said object positioned between the beam-splitting x-ray grating and the x-ray detector, said x-ray detector positioned to detect the x-rays diffracted by the beam-splitting x-ray grating and perturbed by the object to be imaged.
18. The x-ray tomography system of claim 17 , wherein the stage is configured to controllably change a position and an orientation of the object relative to the x-ray source.
19. The x-ray tomography system of claim 18 , in which the stage is configured to controllably change an angle of incidence of the x-rays on the object.
20. The x-ray tomography system of claim 19 , in which the stage and the x-ray detector are configured to make a plurality of images of the object in which each of the plurality of, images is collected using a different setting for the angle of incidence of the x-rays on the object.
21. An x-ray interferometric imaging system comprising:
a source of x-rays comprising:
a vacuum chamber;
an electron beam emitter; and
a target comprising:
a substrate comprising a first material; and
a plurality of discrete structures embedded in the substrate, the plurality of discrete structures comprising a second material that generates x-rays in response to electron irradiation, said plurality of discrete structures arranged in a periodic pattern to produce a periodic pattern of sub-sources of x-rays when irradiated by electrons from the electron beam emitter;
a beam-splitting x-ray grating comprising periodic structures that introduce a phase shift for a predetermined x-ray wavelength, said beam-splitting x-ray grating positioned to diffract x-rays generated by the periodic pattern of sub-sources of x-rays;
a stage configured to hold an object to be imaged; and
an x-ray detector comprising a two-dimensional array of x-ray detecting elements, said object positioned between the beam-splitting x-ray grating and the x-ray detector, said x-ray detector configured to detect the x-rays diffracted by the beam-splitting x-ray grating and perturbed by the object to be imaged, the x-ray detector positioned at a distance from the beam-splitting x-ray grating that corresponds to an odd multiple of 1/16 th of a Talbot Distance for the beam-splitting x-ray grating when used with spherical wave x-rays of a predetermined wavelength spectrum and spatial coherence, the x-ray detector having a spatial resolution at least three times a Talbot fringe period for a Talbot interference pattern at said odd multiple of 1/16 th of the Talbot Distance for the beam-splitting x-ray grating when used with x-rays of said predetermined wavelength spectrum and spatial coherence.
22. An x-ray interferometric imaging system comprising:
a source of x-rays comprising:
a vacuum chamber;
an electron beam emitter; and
a target comprising:
a substrate comprising a first material; and
a plurality of discrete structures embedded in the substrate, the plurality of discrete structures comprising a second material that generates x-rays in response to electron irradiation, said plurality of discrete structures arranged in a periodic pattern to produce a periodic pattern of sub-sources of x-rays when irradiated by electrons from the electron beam emitter;
a beam-splitting x-ray grating comprising periodic structures that introduce a phase shift for a predetermined x-ray wavelength, said beam-splitting x-ray grating positioned to diffract x-rays generated by the periodic pattern of sub-sources of x-rays;
a stage configured to hold an object to be imaged, the stage configured to adjust a position of the object relative to the beam-splitting x-ray grating by translating the object along each of three orthogonal axes and rotating the object along each of three orthogonal axes; and
an x-ray detector comprising a two-dimensional array of x-ray detecting elements, said object positioned between the beam-splitting x-ray grating and the x-ray detector, said x-ray detector positioned to detect the x-rays diffracted by the beam-splitting x-ray grating and perturbed by the object to be imaged.