Method of analysing a sample of material by diffractometry and associated diffractometer

Patent metadata

Field	Value
Publication number	US-9285329-B2
Application number	US-201214368748-A
Country	US
Kind code	B2
Filing date	Dec 26, 2012
Priority date	Dec 28, 2011
Publication date	Mar 15, 2016
Grant date	Mar 15, 2016

Abstract

A method for analyzing a sample by diffractometry and a diffractometer, where the diffractometer includes a collimated source, a detection collimator, and a spectrometric detector, the detection axis of the detector and the collimator form a diffraction angle with the central axis of an incident beam and an energy spectrum is established for each pixel of the detector. The measured spectra are readjusted by a change in variable that takes into account the energy of the scattered radiation and the angle of observation. The measured are combined and a check is made on the implementation of at least one multi-material criterion representative of the presence of a plurality of layers of materials and groups of pixels are formed according to the results of this check, where each group corresponds to a single layer of material and the measured spectra obtained for the pixels of the group are combined.

First claim

The invention claimed is:

1. A method of analyzing a sample of material by diffractometry, the method comprising:
providing a diffractometer that comprises:
a source adapted to emit an incident beam with a central axis,
a detector that includes

a detector material having a detection plane a proximate to the sample of material,
spectrometry measurement means, adapted to measure an energy released by each photon interaction with the detector material and to establish at least one energy spectrum S(E); and
a detection collimator associated with the detector, the detector and the detection collimator arranged so as to have a detection axis D forming a diffraction angle θ with the central axis X of the incident beam; and

irradiating the sample with the incident beam;
establishing a plurality of energy spectra; and
combining the energy spectra,
wherein the detector comprises a pixelated detector including means for locating an interaction of a photon with the detector material, and
the method further comprises:
defining a partition of the detector in virtual pixels, and associating one of the virtual pixels with each photon interaction;
establishing a measured energy spectrum Si(E) for each virtual pixel (Pi) of the detector; and
combining energy spectra measured for different virtual pixels (Pi) of the detector.

2. A method according to claim 1 , wherein the detector comprises a detector having a pixelated detection plane.

3. A method according to claim 1 , wherein a pitch between two adjacent pixels in a transverse direction orthogonal to the detection axis D and contained in a diffraction plane (X, D), is less than or equal to 0.5 mm.

4. A method according to claim 1 further comprising, prior to combining the energy spectra, adjusting the measured energy spectra, where each measured energy spectrum Si(E) is expressed according to a new variable (x) which takes into account an energy of scattered radiation and an angle of observation θ i of the corresponding pixel, and obtaining an adjusted spectrum Si(x) for each pixel (Pi) of the detector.

5. A method according to claim 4 , wherein,
in adjusting the measured energy spectra, for each pixel (Pi), a spectrum Si(x) is established which is adjusted according to momentum transfer based on the energy spectrum measured for the pixel, by performing a change in variable according to the formula:

x
=

sin
⁡

(

θ
i

/
2

)

λ

=

E
⁢

⁢

sin
⁡

(

θ
i

/
2

)

hc

where θ i is the observation angle corresponding to the pixel Pi and λ is the wavelength corresponding to the energy E, and
in combining the energy spectra, a sum is calculated of at least some of the momentum transfer of the spectrum Si(x).

6. A method according to claim 4 , wherein before combining the energy spectra and after adjusting the measured energy spectra, verifying at least one multimaterial criterion representing the presence of several layers of material, the method further comprising
forming groups of pixels using results of the verifying step, each group corresponding to a layer of material, where different groups correspond to different layers of material, and
wherein combining the energy spectra is carried out by group, such that the adjusted energy spectra obtained for the pixels (Pi) of the same group are combined.

7. A method according to claim 4 , wherein
in adjusting the measured spectra, the adjusted spectra comprise momentum transfer spectra Si(x), the change in variable is carried out using the formula:

x
=

sin
⁡

(

θ
i

/
2

)

λ

=

E
⁢

⁢

sin
⁡

(

θ
i

/
2

)

hc

,

where θ i designates the diffraction angle corresponding to the pixel Pi such that the angle between the axis X of the incident beam and the axis Di passing by the center of the pixel Pi and the center of the detection collimator, and λ is the wavelength corresponding to the energy E; and
in combining the energy spectra, for each group, the adjusted spectra Si(x) of the pixels of the group are summed.

8. A method according to one of claim 6 , wherein the multimaterial criterion comprises one of:
a variation greater than 10% of the position in the adjusted spectra of a first local maximum, between two adjacent pixels in a transverse direction (T), orthogonal to the detection direction (D), or
a variation greater than 10% of the position in the adjusted spectra of a second local maximum, between two adjacent pixels in the transverse direction, or
a variation greater than 10% of the sum of the channels of the adjusted spectrum of each pixel, between two adjacent pixels in the transverse direction.

9. A method according to claim 8 further comprising constructing a curve, wherein the y-axis represents the position in the spectrum of the first or second local maximum and wherein the x-axis represents the lateral position (Yi) of the pixel (Pi) or its angle of observation (θi).

10. A method according to claim 6 , wherein the detection collimator comprises an open collimator having a slot with a height greater than 1 mm.

11. A diffractometer comprising:
a source adapted to emit

Assignees

• Commissariat Energie Atomique

Inventors

• Ghammraoui Bahaa
• Tabary Joachim
• Paulus Caroline

Classifications

• G01N2223/501

  array · CPC title

• G21K1/02

  using diaphragms, collimators · CPC title

• G01N23/20091

  Measuring the energy-dispersion spectrum [EDS] of diffracted radiation · CPC title

• G01N23/2076 Primary

  for spectrometry, i.e. using an analysing crystal, e.g. for measuring X-ray fluorescence spectrum of a sample with wavelength-dispersion, i.e. WDXFS · CPC title

• G01T1/366

  with semi-conductor detectors · CPC title