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EP-4735873-A1 - METHOD OF OPERATING A SPECTROMETER

EP4735873A1EP 4735873 A1EP4735873 A1EP 4735873A1EP-4735873-A1

Abstract

A method of operating a spectrometer includes positioning a crystal analyzer such that a first reciprocal lattice vector corresponding to a first crystal plane of the crystal analyzer is coplanar with a source axis and a detector axis, and performing a first scan by varying a first angle between the source axis and the first crystal plane and varying a second angle between the detector axis and the first crystal plane such that the first angle is substantially equal to the second angle, rotating the crystal analyzer such that a second reciprocal lattice vector corresponding to a second crystal plane of the crystal analyzer is coplanar with the source axis and the detector axis, and performing a second scan by varying the first angle and varying the second angle such that the first angle is substantially equal to the second angle.

Inventors

  • SEIDLER, Gerald, Todd
  • GIRONDA, Anthony

Assignees

  • University of Washington

Dates

Publication Date
20260506
Application Date
20240627

Claims (20)

  1. 1. A method of operating a spectrometer comprising a crystal analyzer that defines a Rowland circle, a source configured to emit x-rays along a source axis, and a detector configured to detect x-rays travelling along a detector axis, the method comprising: positioning the crystal analyzer such that a first reciprocal lattice vector corresponding to a first crystal plane of the crystal analyzer is coplanar with the source axis and the detector axis; performing, while the first reciprocal lattice vector is coplanar with the source axis and the detector axis, a first scan by varying a first angle between the source axis and the first crystal plane and varying a second angle between the detector axis and the first crystal plane such that the first angle is substantially equal to the second angle; rotating the crystal analyzer such that a second reciprocal lattice vector corresponding to a second crystal plane of the crystal analyzer is coplanar with the source axis and the detector axis; and performing, while the second reciprocal lattice vector is coplanar with the source axis and the detector axis, a second scan by varying the first angle and varying the second angle such that the first angle is substantially equal to the second angle.
  2. 2. The method of claim 1, wherein the crystal analyzer is a spherically bent crystal analyzer.
  3. 3. The method of any one of claims 1-2, wherein a diameter of the Rowland circle is equal to a radius of curvature of the crystal analyzer.
  4. 4. The method of any one of claims 1-3, wherein the source comprises an x-ray tube or a synchrotron.
  5. 5. The method of any one of claims 1-4, wherein performing the first scan further comprises: illuminating a sample with first x-rays using the source such that second x-rays are emitted by the sample and incident on the crystal analyzer; and detecting, using the detector, third x-rays that are reflected from the crystal analyzer via Bragg reflection of the second x-rays.
  6. 6. The method of claim 5, wherein performing the first scan and performing the second scan each comprises performing x-ray emission spectroscopy (XES).
  7. 7. The method of claim 5, wherein performing the first scan and performing the second scan each comprises performing wavelength-dispersive x-ray fluorescence spectroscopy (WD-XRF).
  8. 8. The method of any one of claims 1-4, wherein performing the first scan further comprises: illuminating the crystal analyzer with first x-rays using the source such that second x- rays are emitted from the crystal analyzer via Bragg reflection and incident on a sample; and detecting, using the detector, the second x-rays that transmit through the sample.
  9. 9. The method of claim 8, wherein performing the first scan and performing the second scan each comprises performing x-ray absorption fine structure (XAFS) analysis.
  10. 10. The method of any one of claims 1-9, wherein the source comprises an entrance slit on the Rowland circle.
  11. 11. The method of any one of claims 1-10, wherein the detector comprises an entrance slit on the Rowland circle.
  12. 12. The method of any one of claims 1-11, wherein performing the first scan comprises translating the source and/or the crystal analyzer such that (i) the source axis is coplanar with the detector axis and the first reciprocal lattice vector and (ii) a source distance between the source and the crystal analyzer along the source axis is substantially equal to a diameter of the Rowland circle multiplied by a sine of a sum of (a) the first angle and (b) a third angle formed by the first crystal plane and a third crystal plane that is nominally parallel to a curved surface of the crystal analyzer.
  13. 13. The method of claim 12, wherein performing the second scan comprises translating the source and/or the crystal analyzer such that (i) the source axis is coplanar with the detector axis and the second reciprocal lattice vector and (ii) the source distance is substantially equal to the diameter of the Rowland circle multiplied by a sine of a second sum of (a) the first angle and (b) a fourth angle formed by the second crystal plane and the third crystal plane.
  14. 14. The method of any one of claims 1-13, wherein performing the first scan comprises translating the detector and/or the crystal analyzer such that (i) the detector axis is coplanar with the source axis and the first reciprocal lattice vector and (ii) a detector distance between the detector and the crystal analyzer along the detector axis is substantially equal to a diameter of the Rowland circle multiplied by a sine of a difference of (a) the first angle minus (b) a third angle formed by the first crystal plane and a third crystal plane that is nominally parallel to a curved surface of the crystal analyzer.
  15. 15. The method of claim 14, wherein performing the second scan comprises translating the detector and/or the crystal analyzer such that (i) the detector axis is coplanar with the source axis and the second reciprocal lattice vector and (ii) the detector distance is substantially equal to the diameter of the Rowland circle multiplied by a sine of a second difference of (a) the first angle minus (b) a fourth angle formed by the second crystal plane and the third crystal plane.
  16. 16. The method of any one of claims 1-15, wherein performing the first scan comprises detecting monochromatic x-rays from the crystal analyzer while varying the first angle and the second angle.
  17. 17. The method of any one of claims 1-16, wherein performing the second scan comprises detecting monochromatic x-rays from the crystal analyzer while varying the first angle and the second angle.
  18. 18. The method of any one of claims 1-17, wherein positioning the crystal analyzer such that the first reciprocal lattice vector is coplanar with the source axis and the detector axis comprises rotating the crystal analyzer about a rotation axis that is coplanar with the source axis and the detector axis.
  19. 19. The method of any one of claims 1-18, wherein performing the first scan comprises detecting x-rays within a first energy range, and performing the second scan comprises detecting x-rays within a second energy range that does not overlap with the first energy range.
  20. 20. The method of claim 1, wherein performing the first scan comprises operating the spectrometer in an emission mode, an absorption mode, a transmission mode, or a florescence mode.

Description

Method of Operating a Spectrometer CROSS-REFERENCE TO RELATED APPLICATION [001] This application claims priority to U.S. Provisional Patent Application No. 63/510,518, filed on June 27, 2023, the entire contents of which are incorporated by reference herein. STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT [002] This invention was made with government support under Grant No. DE- NE0009158, awarded by the U.S. Department of Energy. The government has certain rights in the invention. BACKGROUND [003] Many x-ray spectrometers use a curved crystal analyzer (CCA) as a type of monochromator to selectively scatter x-rays that are emitted from, or transmitted through, a material sample under test. A CCA is typically fabricated by gluing or bonding a silicon or germanium wafer to a concave glass lens or other concave form. The crystallographic orientation of the wafer surface is chosen so that the lattice spacing of crystal planes nominally parallel to the surface is appropriate, via Bragg’s law, to generate constructive interference of x-rays within the energy or wavelength range of interest. However, using the same spectrometer to investigate a sample’s response within a different energy or wavelength range generally requires using a second CCA. The second CCA is selected such that the crystal planes nominally parallel to the surface of the second CCA have a lattice spacing that is different from the lattice spacing of the original CCA. Swapping CCAs out of a spectrometer to investigate different wavelength or energy ranges can be tedious and timeconsuming. SUMMARY [004] A first example is a method of operating a spectrometer comprising a crystal analyzer that defines a Rowland circle, a source configured to emit x-rays along a source axis, and a detector configured to detect x-rays travelling along a detector axis, the method comprising: positioning the crystal analyzer such that a first reciprocal lattice vector corresponding to a first crystal plane of the crystal analyzer is coplanar with the source axis and the detector axis; performing, while the first reciprocal lattice vector is coplanar with the source axis and the detector axis, a first scan by varying a first angle between the source axis and the first crystal plane and varying a second angle between the detector axis and the first crystal plane such that the first angle is substantially equal to the second angle; rotating the crystal analyzer such that a second reciprocal lattice vector corresponding to a second crystal plane of the crystal analyzer is coplanar with the source axis and the detector axis; and performing, while the second reciprocal lattice vector is coplanar with the source axis and the detector axis, a second scan by varying the first angle and varying the second angle such that the first angle is substantially equal to the second angle. [005] A second example is a non-transitory computer readable medium storing instructions that, when executed by one or more processors of a spectrometer, cause the spectrometer to perform the method of the first example. [006] A third example is a spectrometer comprising: a source configured to emit x-rays along a source axis; a detector configured to detect x-rays travelling along a detector axis; an analyzer stage configured to hold a crystal analyzer that defines a Rowland circle, wherein the analyzer stage is configured to rotate the crystal analyzer about an analyzer axis that is coplanar with the source axis and the detector axis; and an alignment apparatus comprising: a source stage that is configured to hold the source; a detector stage that is configured to hold the detector; and a goniometer configured to (i) adjust a fifth angle between the analyzer stage and the detector axis and (ii) adjust a sixth angle between the analyzer stage and the source axis, wherein the alignment apparatus is configured to move the source stage, the detector stage, and/or the analyzer stage to adjust a first distance between the source and the analyzer stage along the source axis and adjust a second distance between the detector and the analyzer stage along the detector axis. [007] The contents of the following documents are incorporated by reference herein: Anthony J. Gironda et al., “Asymmetric Rowland circle geometries for spherically bent crystal analyzers in laboratory and synchrotron applications.” J. Anal. At. Spectrom., 2024, 39, 1375. https://pubs.rsc.org/en/content/articlelanding/2024/ja/d3ja00437f. [008] When the term “substantially” or “about” is used herein, it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including, for example, tolerances, measurement error, measurement accuracy limitations, and other factors known to those of skill in the art may occur in amounts that do not preclude the effect the characteristic was intended to provide. In some examples disclosed herein, “substantially” or “about” me