EXAFS spectrometer
AssigneeNorthwestern University
InventorPanayotis Georgopoulos
Life of this patent
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Abstract
An apparatus for performing extend X-ray absorption fine structure (EXAFS) measurements on materials. The EXAFS apparatus is constructed using a conventional X-ray powder diffractometer assembly with a rotating anode X-ray source affixed to the diffractometer assembly, a monochromator crystal rotatably positioned at the center of the assembly and a specimen stage and detectors slidingly mounted on a receiving track of the assembly. The monochromator crystal is automatically and elastically distorted to provide a monochromatic X-ray beam flux from the crystal. The angle of incidence of the source X-ray beam with the crystal surface is changed to provide a different monochromatic X-ray wavelength with changing energy, which enables measurement of the desired EXAFS spectra for the material.
Claims40
An apparatus for performing X-ray absorption fine structure measurements on a specimen by using a source X-ray beam and an assembly adapted to carry out a set of predetermined operating conditions, comprising:
- a monochromator crystal means rotatably positioned at the center of said assembly for diffracting said source X-ray beam to provide a monochromatic X-ray beam for selected angles of incidence of said source X-ray beam with respect to said crystal means, and in accordance with said predetermined operating conditions said crystal means providing said monochromatic X-ray beam having a different wavelength upon changing to a different respective associated one of said angles of incidence;
- deforming means for automatically distorting said monochromator crystal means at said angles of incidence to provide said monochromatic X-ray beam having said different wavelength at said respective associated angles of incidence;
- detector means for measuring the intensity of said monochromatic X-ray beam before and after passing through said specimen;
- and
- stage means for supporting said specimen and said detector means, said stage means being slidingly engaged with a receiving track of said assembly to enable movement on said track to an angular position twice that of said respective associated angle of incidence of said X-ray beam with said crystal means.
An apparatus for performing X-ray absorption fine structure measurements on a specimen by adapting an X-ray powder diffractometer assembly to carry out a set of predetermined operating conditions, comprising:
- a rotating anode X-ray beam source affixed to said diffractometer assembly;
- a diamond shaped single crystal means rotatably positioned at the center of said diffractometer assembly for diffracting said source X-ray beam to provide a monochromatic X-ray beam for selected angles of incidence of said source X-ray beam with respect to said crystal means, and in accordance with said predetermined operating conditions, said crystal means providing said monochromatic X-ray beam having a different wavelength upon changing to a different respective associated one of said angles of incidence;
- deforming means for automatically and elastically distorting said monochromator crystal means at each of said angles of incidence to provide said monochromatic X-ray beam having said different wavelength at each of said respective associated angles of incidence;
- a first and second proportional counter positioned to detect said monochromatic X-ray beam, before and after, respectively, passing through said specimen;
- and
- stage means for supporting said specimen and said proportional counters, said stage means slidingly engaged with a receiving track of said diffractometer assembly to enable movement on said track to an angular position twice that of said respective associated angle of incidence of said X-ray beam with said crystal means.
A method of performing EXAFS measurements on a specimen by adapting an X-ray powder diffractometer assembly to carry out a set of predetermined operating conditions, comprising:
- providing a source X-ray beam by operating an X-ray source;
- positioning a monochromator crystal on a rotatable crystal holder disposed at the center of said diffractometer assembly;
- diffracting said source X-ray beam from said monochromator crystal to provide a monochromatic X-ray beam for selected angles of incidence of said source X-ray beam with respect to said crystal, and in accordance with said predetermined operating conditions said crystal providing said monochromatic X-ray beam having a different wavelength upon changing to a different respective associated one of said selected angles of incidence of said source X-ray beam with respect to said crystal;
- distorting automatically and elastically said monochromator crystal at each of said angles of incidence to provide said monochromatic X-ray beam having said different wavelength at each of said respective associated angles of incidence;
- detecting with X-ray detectors said monochromatic X-ray beam before and after passing through said specimen;
- rotating said monochromator crystal to a next one of said angles of incidence to provide said different wavelength;
- and
- moving said specimen and said X-ray detector along a receiving track of said diffractometer assembly to an angular position twice that of said next one of said angles of incidence of said X-ray beam with said crystal.
An apparatus adapted for use for EXAFS measurements, said apparatus adapted from an X-ray powder diffractometer assembly and providing a monochromatic X-ray beam having an adjustable wavelength, comprising:
- X-ray means for providing a source X-ray beam wherein said X-ray means is fixed with respect to said diffractometer assembly;
- a monochromator crystal means rotatably positioned at the center of said X-ray diffractometer assembly to diffract said source X-ray beam to provide a monochromatic X-ray beam associated with selected angles of incidence of said source X-ray beam with respect to said crystal means, said crystal means producing a different wavelength upon changing to a different respective associated one of said angles of incidence;
- deforming means for automatically and elastically distorting said monochromator crystal means at each of said angles of incidence to provide said monochromatic X-ray beam having said different wavelength at each of said respective associated angles;
- and
- stage means for holding a specimen for irradiation by said monochromatic X-ray beam.
Dependencies are inferred from the claim text.