Method of performing X-ray spectroscopy and X-ray absorption spectrometer system
A method for performing x-ray absorption spectroscopy and an x-ray absorption spectrometer system to be used with a compact laboratory x-ray source to measure x-ray absorption of the element of interest in an object with both high spatial and high spectral resolution. The spectrometer system comprises a compact high brightness laboratory x-ray source, an optical train to focus the x-rays through an object to be examined, and a spectrometer comprising a single crystal analyzer (and, in some embodiments, also a mosaic crystal) to disperse the transmitted beam onto a spatially resolving x-ray detector. The high brightness/high flux x-ray source may have a take-off angle between 0 and 105 mrad. and be coupled to an optical train that collects and focuses the high flux x-rays to spots less than 500 micrometers, leading to high flux density. The coatings of the optical train may also act as a “low-pass” filter, allowing a predetermined bandwidth of x-rays to be observed at one time while excluding the higher harmonics.
1. A method for performing x-ray absorption spectroscopy, the method comprising:
illuminating an object using an x-ray beam with an energy bandwidth greater than 0.1% and inclusive of the energy corresponding to an absorption edge of an atomic element;
acquiring a first x-ray absorption spectrum from the object at a first energy resolution better than 3 eV, using a single crystal spectrometer, over a first energy bandwidth inclusive of the absorption edge;
acquiring a second x-ray absorption spectrum from the object using a mosaic crystal spectrometer at a second energy resolution coarser than the first energy resolution and over a second energy bandwidth wider than the first energy bandwidth; and
processing the first and second x-ray absorption spectra to produce a third x-ray absorption spectrum in which the second x-ray absorption spectrum within the first energy bandwidth corresponding to the first x-ray absorption spectrum is refined using the first x-ray absorption spectrum.
2. The method of claim 1 , further comprising focusing the x-ray beam on the object using at least one capillary reflective x-ray focusing optic, the energy bandwidth of the x-ray beam inclusive of the absorption edge and having energies greater than 100 eV above the absorption edge.
3. The method of claim 1 , wherein the single crystal spectrometer comprises a single crystal curved at least in the dispersion plane.
4. The method of claim 3 , wherein acquiring the first x-ray absorption spectrum comprises using a spatially resolving detector to detect x-rays dispersed by single crystal while the sample, the single crystal, and the spatially resolving detector are in an off-Rowland circle geometry.
5. The method of claim 1 , wherein the first x-ray absorption spectrum contains at least part of an x-ray absorption near edge structure (XANES) spectrum.
6. The method of claim 1 , wherein the mosaic crystal spectrometer comprises a mosaic crystal curved at least in the sagittal direction of dispersion, and acquiring the second x-ray absorption spectrum comprises using a spatially resolving x-ray detector to detect x-rays dispersed by the mosaic crystal while the mosaic crystal and the spatially resolving detector are in an Von Hamos geometry.
7. A system for performing x-ray absorption spectroscopy, the system comprising:
an x-ray source;
a mount configured to support an object to be examined;
at least one focusing x-ray optic configured to collect x-rays from said x-ray source with an energy bandwidth greater than 0.1% of an x-ray energy corresponding to an absorption edge of an atomic element to be detected in the object, the energy bandwidth inclusive of the x-ray energy corresponding to the absorption edge, the at least one focusing x-ray optic further configured to focus a portion of the collected x-rays onto a focal spot at the object with a focus size less than 500 micrometers;
at least one single crystal spectrometer with an energy resolution better than 3 eV, the at least one single crystal spectrometer comprising:
at least one single crystal analyzer curved at least in the dispersion direction, and
at least one spatially resolving x-ray detector configured to detect x-rays transmitted through the object;
and in which the focal spot, said at least one single crystal analyzer, and said at least one spatially resolving x-ray detector are positioned in an off-Rowland circle geometry.
8. The system of claim 7 , wherein the at least one focusing x-ray optic comprises a capillary x-ray optic having an interior reflecting surface, wherein at least a portion of the interior reflecting surface is a portion of a quadric surface.
9. The system of claim 7 , wherein a reflecting surface of the at least one focusing x-ray optic comprises multilayer coatings.
10. The system of claim 7 , wherein the x-ray source comprises a plurality of x-ray target materials and an electron beam generator configured to generate an electron beam and to bombard a selected x-ray target material of the plurality of x-ray target materials with the electron beam.
11. A system for performing x-ray absorption spectroscopy, the system comprising:
an x-ray source;
a mount configured to support an object to be examined;
at least one focusing x-ray optic configured to collect x-rays from the x-ray source and to focus at least a portion of the collected x-rays onto a focal spot at the object with a focus size less than 500 micrometers;
at least one spatially resolving x-ray detector;
at least one single crystal curved at least in the dispersion direction, the focal spot, the at least one single crystal, and the at least one spatially resolving x-ray detector configured to be in an off-Rowland circle geometry;
at least one mosaic crystal curved at least in the sagittal direction, the focal spot, the at least one mosaic crystal, and the at least one spatially resolving x-ray detector configured to be in a Von Hamos geometry; and
a processing system configured to normalize and align a single-crystal x-ray absorption spectrum obtained with the single crystal and a mosaic-crystal x-ray absorption spectrum obtained with the mosaic crystal to produce a combined x-ray absorption spectrum in which the mosaic-crystal x-ray absorption spectrum within an energy bandwidth corresponding to the single-crystal x-ray absorption spectrum is refined using the single-crystal x-ray absorption spectrum.
12. The system of claim 11 , wherein the single-crystal x-ray absorption spectrum has an energy resolution better than 3 eV over an energy bandwidth of 10 eV to 100 eV.
13. The system of claim 11 , wherein the mosaic-crystal x-ray absorption spectrum has an energy resolution coarser than 3 eV over an energy bandwidth over 100 eV.
14. The system of claim 11 , wherein the said at least one focusing x-ray optic is configured to collect the x-rays from the x-ray source with an energy bandwidth greater than 0.1% of an absorption edge of a predetermined atomic element and inclusive of the absorption edge of the predetermined atomic element.
15. The system of claim 14 , wherein the at least one focusing x-ray optic comprises a capillary x-ray optic having an interior reflecting surface, wherein at least a portion of the interior reflecting surface is a portion of a quadric surface.
16. The system of claim 15 , wherein the portion of the interior reflecting surface is coated with a material with atomic number greater than 26 and is axially symmetric.
17. The system of claim 14 , furthermore comprising an aperture configured to selectively pass x-rays transmitted through the object while not passing fluorescence x-rays from the object.
18. The system of claim 11 , wherein the x-ray source comprises a plurality of x-ray target materials and an electron beam generator configured to generate an electron beam and to bombard a selected x-ray target material of the plurality of x-ray target materials with the electron beam.
19. The system of claim 11 , wherein the focal spot, the single crystal, and the at least one spatially resolving x-ray detector are configured to change a distance between the focal spot and the single crystal to select the energy bandwidth of the single-crystal x-ray absorption spectrum.
20. The method of claim 5 , wherein the second x-ray absorption spectrum contains at least extended x-ray absorption fine structure (EXAFS) data.