X-ray illumination system with multiple target microstructures
An x-ray illumination beam system includes an electron emitter and a target having one or more target microstructures. The one or more microstructures may be the same or different material, and may be embedded or placed atop a substrate formed of a heat-conducting material. The x-ray source may emit x-rays towards an optic system, which can include one or more optics that are matched to one or more target microstructures. The matching can be achieved by selecting optics with the geometric shape, size, and surface coating that collects as many x-rays as possible from the source and at an angle that satisfies the critical reflection angle of the x-ray energies of interest from the target. The x-ray illumination beam system allows for an x-ray source that generates x-rays having different spectra and can be used in a variety of applications.
1. An x-ray illumination beam system comprising:
a vacuum chamber including an electron emitter;
a window transparent to x-rays and attached to a wall of the vacuum chamber;
an electron optical system that focusses an electron beam from the electron emitter;
a target comprising a plurality of microstructures coupled to a substrate, wherein each microstructure includes a material configured to generate x-rays in response to bombardment by the electron beam, and in which a lateral dimension of said material is less than 250 microns;
a support configured to position the target relative to the electron beam; and
a plurality of total external reflection mirror optics, wherein each optic of the plurality of optics is matched to x-ray spectra produced by at least one microstructure of the plurality of microstructures and positioned to collect x-rays generated by the at least one microstructure of the plurality of microstructures when bombarded by the electron beam.
2. The x-ray illumination beam system of claim 1 , wherein one or more optics of the plurality of total external reflection mirror optics have an interior reflecting surface that has a quadric profile and is axially symmetric.
3. The x-ray illumination beam system of claim 2 , wherein a focus of the quadric profile is coincident with an x-ray source spot.
4. The x-ray illumination beam system of claim 1 , wherein each optic of the plurality of total external reflection mirror optics is matched to a characteristic x-ray energy of the material.
5. The x-ray illumination beam system of claim 4 , wherein a reflecting surface of the optic is shaped such that x-rays with the characteristic x-ray energy incident upon a portion of the reflecting surface have incidence angles that are between 30% and 100% of the critical angle of the portion of the reflecting surface.
6. The x-ray illumination beam system of claim 4 , wherein the characteristic x-ray energy is a K-line of the material.
7. The x-ray illumination beam system of claim 1 , wherein the plurality of total external reflection mirror optics are parfocal.
8. The x-ray illumination beam system of claim 1 , wherein a spot size of the electron beam on the target has a length and a width, the ratio of the width to the length being between 2 and 20.
9. The x-ray illumination beam system of claim 1 , wherein the electron beam has a width that corresponds to a width of a microstructure bombarded by the electron beam.
10. The x-ray illumination beam system of claim 1 , wherein a distance from an end of at least one optic of the plurality of optics to an optic focal spot is between 5 millimeters to 50 millimeters.
11. The x-ray illumination beam system of claim 1 , wherein a distance between a source spot of the x-rays and an optic focal spot is between 30 millimeters and 1 meter.
12. The x-ray illumination beam system of claim 1 , wherein the plurality of optics includes two quadric surface profiles.
13. The x-ray illumination beam system of claim 1 , wherein an emitted x-ray beam has a take-off angle of less than 6 degrees with respect to a target surface tangent.
14. The x-ray illumination beam system of claim 1 , wherein one or more of the optics includes a surface coating on an inner surface of the optic.
15. The x-ray illumination beam system of claim 14 , in which the surface coating is a multilayer coating.
16. The x-ray illumination beam system of claim 1 , wherein the target is moveable to allow each microstructure of the plurality of microstructures to be bombarded by the electron beam.
17. The x-ray illumination beam system of claim 1 , wherein the electron beam is movable to allow each microstructure of the plurality of microstructures to be bombarded by the electron beam.
18. The x-ray illumination beam system of claim 1 , wherein at least two microstructures of the plurality of microstructures generate different x-ray spectra when bombarded by the electron beam.
19. The x-ray illumination beam system of claim 1 , wherein the electron beam is rastered over one or more of the microstructures.
20. The x-ray illumination beam system of claim 1 , wherein the microstructures are embedded within the substrate.