X-ray fluorescence analyzer, and a method for performing X-ray fluorescence analysis

Patent metadata

Field	Value
Publication number	US-11360036-B2
Application number	US-201817049262-A
Country	US
Kind code	B2
Filing date	Apr 20, 2018
Priority date	Apr 20, 2018
Publication date	Jun 14, 2022
Grant date	Jun 14, 2022

Abstract

An X-ray fluorescence analyzer includes an X-ray tube for emitting incident X-rays in the direction of a first optical axis. A slurry handling unit is configured to maintain a constant distance between a sample of slurry and the X-ray tube. A first crystal diffractor is located in a first direction from the slurry handling unit and configured to separate a predefined first wavelength range from fluorescent X-rays that propagate into the first direction. The first crystal diffractor is configured to direct the fluorescent X-rays in the separated predefined first wavelength range to a first radiation detector. The first crystal diffractor includes a pyrolytic graphite crystal that has a diffractive surface, which is a simply connected surface. The first radiation detector is a solid-state semiconductor detector.

First claim

The invention claimed is:

1. An X-ray fluorescence analyzer, comprising:
an X-ray tube for emitting incident X-rays in the direction of a first optical axis,
a slurry handling unit configured to maintain a constant distance between a sample of slurry and said X-ray tube,
a first crystal diffractor located in a first direction from said slurry handling unit, said first crystal diffractor being configured to separate a predefined first wavelength range from fluorescent X-rays that propagate into said first direction, and configured to direct the fluorescent X-rays in the separated predefined first wavelength range to a first radiation detector, wherein:
the first crystal diffractor comprises a pyrolytic graphite crystal that has a diffractive surface, and
said first radiation detector is a solid-state semiconductor detector;
characterized in that
the diffractive surface of said pyrolytic graphite crystal is a simply connected surface; and
the crystal is the wavelength-dispersive component of the crystal diffractor.

2. The X-ray fluorescence analyzer according to claim 1 , wherein the diffractive surface of said pyrolytic graphite crystal is curved in one direction only.

3. The X-ray fluorescence analyzer according to claim 1 , wherein the first crystal diffractor comprises a substrate to which said pyrolytic graphite crystal is attached, and wherein a three-dimensional geometrical shape of the entity constituted by said pyrolytic graphite crystal and said substrate is that of a prism, one side face of which is cut away by the curved diffractive surface.

4. The X-ray fluorescence analyzer according to claim 1 , wherein said first radiation detector is one of: a PIN di-ode detector, a silicon drift detector, a germanium detector, a germanium drift detector.

5. The X-ray fluorescence analyzer according to claim 1 , wherein the first crystal diffractor comprises:
a first slit on a first optical path between said slurry handling unit and said pyrolytic graphite crystal, and
a second optical path between said pyrolytic graphite crystal and said first radiation detector.

6. The X-ray fluorescence analyzer according to claim 5 , wherein:
the diffractive surface of said pyrolytic graphite crystal is curved in one direction only, with a radius of curvature in a plane defined by said first and second optical paths, and
said first slit is a linear slit oriented perpendicular against said plane.

7. The X-ray fluorescence analyzer according to claim 5 , wherein:
the diffractive surface of said pyrolytic graphite crystal is curved in two directions, forming a part of a toroidal surface, and
said first slit is a curved slit with a first radius of curvature oriented perpendicular against said first optical path.

8. The X-ray fluorescence analyzer according to claim 5 , wherein:
the diffractive surface of said pyrolytic graphite crystal is curved in two directions, forming a part of a rotationally symmetric surface, the rotational axis of which is in the plane defined by said first and second optical paths, and
said first slit is point-like.

9. The X-ray fluorescence analyzer according to claim 6 , wherein:
the first crystal diffractor comprises a second slit on said second optical path between said pyrolytic graphite crystal and said first radiation detector,
a center point of said diffractive surface, said first slit, and said second slit are located on a Rowland circle the radius of which is R,
a radius of curvature of said diffractive surface in the plane defined by said first and second optical paths is 2R, and
a radius of curvature of reticular planes in said crystal is 2R; so that the first crystal diffractor has a Johann geometry.

10. The X-ray fluorescence analyzer according to claim 6 , wherein:
the first crystal diffractor comprises a second slit on said second optical path between said pyrolytic graphite crystal and said first radiation detector,
a center point of said diffractive surface, said first slit, and said second slit are located on a Rowland circle the radius of which is R,
a radius of curvature of said diffractive surface in the plane defined by said first and second optical paths is R, and
the radius of curvature of reticular planes in said crystal is 2R; so that the first crystal diffractor has a Johansson geometry.

11. The X-ray fluorescence analyzer according to claim 9 , wherein R is at most 40 centimeters.

12. The X-ray fluorescence analyzer according to claim 6 , wherein:
said first crystal diffractor is enclosed in a casing delimited by a first planar surface and a second planar surface that is parallel to said first planar surface.

13. The X-ray fluorescence analyzer according to claim 6 , comprising a plurality of other crystal diffractors in addition to said first crystal diffractor, each of said first and other crystal diffractors being located at a respective rotation angle around said first optical axis and each of said first and other crystal diffractors being configured to separate a predefined wavelength range from fluorescent X-rays that propagate into the respective direction, and configured to direct the fluorescent X-rays in the respective separated predefined wavelength range to a respective radiation detector.

14. The X-ray fluorescence analyzer according to claim 13 , wherein:
said plurality of other crystal diffractors comprises a second crystal diffractor comprising a second crystal, configured to direct the fluorescent X-rays in the respective separated second predefined wavelength range to a respective second radiation detector,
said second crystal is of a material other than pyrolytic graphite, and
said first and second crystal diffractors are con-figured to direct to their respective radiation detectors characteristic fluorescent radiation of a same element.

15. The X-ray fluorescence analyzer according to claim 14 , wherein said second crystal is one of: a silicon dioxide crystal, a lithium fluoride crystal, an ammonium dihydrogen phosphate crystal, a potassium hydrogen phthalate crystal.

16. The X-ray fluorescence analyzer according to claim 14 , wherein said second radiation detector is a gas-filled proportional counter.

17. The X-ray fluorescence analyzer according to claim 14 , wherein said element is gold.

18. The X-ray fluorescence analyzer according to claim 14 , wherein:
said slurry handling unit is configured to maintain a planar surface of said sample of slurry on a side facing said X-ray tube,
said first optical axis is at an oblique angle against said planar surface,
said first crystal diffractor is located at that rotational angle around said first optical axis at which said planar surface of said sample covers the largest portion of a field of view of the first crystal diffractor, and
said second crystal diffractor is located at another rotational angle around said first optical axis.

19. The X-ray fluorescence analyzer according to claim 6 , wherein an energy resolution of said first radiation detector is better than 300 eV at a reference energy of 5.9 keV.

20. The X-ray fluorescence analyzer according to claim 6 , wherein the in-put power rating of said X-ray tube is at least 400 watts.

21. The X-ray fluorescence analyzer according to claim 20 , wherein the input power rating of said X-ray tube is at least 1 kilowatt, preferably at least 2 kilowatts, and more preferably at least 4 kilowatts.

22. The X-ray fluorescence analyzer according to claim 6 , wherein the optical path betwee

Assignees

• Outotec Finland Oy

Inventors

• Koskinen Tommi
• Pelli Antti
• Sipilä Heikki

Classifications

• G01N23/223 Primary

  by irradiating the sample with X-rays or gamma-rays and by measuring X-ray fluorescence · CPC title

• G01N2223/076

  X-ray fluorescence · CPC title

• G21K1/06

  using diffraction, refraction or reflection, e.g. monochromators (G21K1/10, G21K7/00 take precedence) · CPC title

• G21K2201/064

  having a curved surface · CPC title

• G01N33/24

  Earth materials (G01N33/42 takes precedence) · CPC title