CN113218974A - X-ray absorption spectrum measuring system - Google Patents
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- 238000004998 X ray absorption near edge structure spectroscopy Methods 0.000 claims abstract description 25
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Abstract
The invention relates to an X-ray absorption spectrum measuring system, comprising: an X-ray source configured to generate X-rays by bombarding a target with an electron beam; an X-ray crystal group including at least two X-ray crystals of different types and switchable use, the two X-ray crystals being perpendicular to an X-ray diffraction direction and configured to perform XANES spectral measurement or EXAFS spectral measurement; the detector array comprises a first X-ray area array detector and a second X-ray area array detector and is configured to realize X-ray detection of XANES spectral measurement and EXAFS spectral measurement, wherein detection surfaces of the first X-ray area array detector and the second X-ray area array detector are arranged orthogonally; a signal receiver configured to process the received detection signal to obtain an X-ray absorption spectrum measurement. The invention can ensure that the obtained X-ray absorption spectrum has higher energy resolution, the near-edge absorption spectrum and the far-edge absorption spectrum are optimized and measured in a segmented manner, and the measurement efficiency is improved.
Description
Technical Field
The invention belongs to the technical field of chemical characterization of environmental samples in laboratories and factories, and particularly relates to an X-ray absorption spectrum measurement system for multifunctional and efficient characterization of an atomic chemical valence state and an atomic coordination environment.
Background
X-ray absorption spectroscopy (XAS-X-ray absorption spectroscopy) is a widely used chemical characterization technique that can be used to characterize the electronic structure of atoms, the type, number and distance of adjacent atoms. The basic principle of XAS is that an atom core layer electron is transited to an unoccupied state in energy levels under the excitation action of an X ray with specific energy, and the size of the energy level of the unoccupied state is closely related to the electronic configuration of the atom. When the energy of incident X-rays interacting with an atom is scanned near the characteristic absorption edge of the atom, there is a significant change in the absorption rate of the atom to the X-rays. The X-ray energy and edge spectral characteristics corresponding to the absorption edge of the element reflect the electronic configuration information. In addition, the absorption coefficient of the atoms to the X-ray is modulated by surrounding atoms, so that the X-ray absorption spectrum presents a periodic oscillation characteristic in a wider energy range, and the characteristic is related to the type, the number and the distance of the surrounding atoms. XAS is therefore an effective method to characterize the local chemical environment of a material on an atomic scale.
There are generally three existing XAS measurement modalities: (1) a transmission type measurement method (transmission XAS), namely directly inverting the absorption coefficient of X-rays by comparing the intensity change of the X-rays before and after passing through a sample, wherein the method is suitable for the condition that the content of atoms to be measured in the sample is large (> 1%); (2) fluorescence yield measurement (fluorescence XAS), i.e. inversion of the absorption coefficient by comparing the X-ray fluorescence intensity with the incident X-ray intensity, is generally applicable in cases where the content of the atoms to be measured in the sample is low (< 1%); (3) the electron yield measuring method is to obtain X-ray absorption spectrum by measuring the electron yield of surface escaping under the excitation of X-ray, and the detection mode can detect the chemical information of the surface layer of the sample with the detection depth of several nanometers. Measurements of XAS are typically performed in large synchrotron radiation devices. The large-scale synchrotron radiation X-ray light source has the advantages of high flux, good directivity, wide energy range and the like. Measurements of XAS can also be performed in the laboratory using X-ray light tubes as the light source. Compared with synchrotron radiation light sources, the brightness of the X-ray light tube is several orders of magnitude lower, so that the X-ray absorption spectrum with the same quality is obtained, and the laboratory light source needs quite long spectrum acquisition time.
In a laboratory X-ray absorption spectrum measuring device, a crystal dispersion element is generally adopted to realize the measurement of an X-ray spectrum, and the measurement mode comprises (1) an X-ray energy scanning mode; (2) a dispersive mode. The X-ray energy scanning mode is a point-to-point scanning mode in which the X-ray source, the focused single crystal and the sample slit are all placed on a rowland circle. The dispersion mode adopts a von Hamos structure, in the mode, an X-ray crystal is a cylindrical crystal, an X-ray source is positioned at the central axis of the cylindrical surface and is incident to the surface of the crystal at a certain angle, and a detector is a linear array or an area array detector, so that the analysis of the X-ray in a wide energy range is realized.
In the above two ways, the energy resolution of the measured X-ray absorption spectrum has a direct relationship with the size of the X-ray source. The larger the X-ray source spot, the poorer the resolution. Therefore, the current laboratory X-ray absorption spectroscopy systems all use a microfocus X-ray source. For a micro-focus X-ray source, the power of the micro-focus X-ray source is generally low due to the limitation of the thermal conductivity of a target material, so that the measurement efficiency of an X-ray absorption spectrum system adopting the micro-focus X-ray source as the X-ray source is low.
Disclosure of Invention
In view of the above problems, an object of the present invention is to provide an X-ray absorption spectrum measurement system including an X-ray source, an X-ray crystal group, a first X-ray area array detector, a second X-ray area array detector, and a signal receiver, which can effectively improve the measurement efficiency of the X-ray absorption spectrum.
In order to achieve the purpose, the invention adopts the following technical scheme: an X-ray absorption spectroscopy measurement system, the system comprising:
an X-ray source configured to generate X-rays by bombarding a target with an electron beam;
an X-ray crystal set comprising at least two X-ray crystals of different types and switchable use, the two X-ray crystals being perpendicular to an X-ray diffraction direction and configured to perform XANES spectral measurement or EXAFS spectral measurement;
the detector array comprises a first X-ray area array detector and a second X-ray area array detector and is configured to realize X-ray detection of XANES spectral measurement and EXAFS spectral measurement, wherein detection areas of the first X-ray area array detector and the second X-ray area array detector are arranged orthogonally;
a signal receiver configured to process the received detection signal to obtain an X-ray absorption spectrum measurement.
In the above X-ray absorption spectrum measurement system, preferably, a sample to be measured is disposed near an exit aperture of the X-ray source, the X-ray penetrates through the sample to be measured and then enters the X-ray crystal group, and the X-ray beam effectively collected is characterized by a "linear light source", that is, the minimum cross section of the X-ray beam has a limited size in at least one dimension direction, and the size in the other dimension orthogonal to the minimum cross section of the X-ray beam reaches a millimeter level.
In the above X-ray absorption spectrum measuring system, preferably, the X-ray beam is generated in a manner of controlling the angle between the target surface and the X-ray collecting direction or in a manner of linear electron beam spot in a "linear light source" characteristic.
The above-mentioned X-ray absorption spectrum measurement system preferably further includes an X-ray focusing mirror, which is disposed at the light-emitting position of the X-ray source, and configured to collect X-rays radiated by the X-ray source and focus the X-rays on the surface of the sample to be measured.
In the above X-ray absorption spectrum measurement system, preferably, the X-ray focusing mirror is a surface reflection type X-ray focusing device, and has an axisymmetric characteristic, the focal point and the X-ray source are in an object-image relationship, and the X-ray focusing mirror includes two types of X-ray optical devices: (1) an X-ray reflecting surface with a paraboloid or I-shaped Wolter profile; the X-ray is changed into parallel light after passing through the first reflecting surface, and the parallel light enters the second reflecting surface and is focused; (2) the surface is an X-ray reflecting surface of an ellipsoid, and X-rays are directly focused on the surface of a sample to be measured after being reflected by the ellipsoid.
The above X-ray absorption spectrum measurement system, preferably, the system further comprises a fluorescent XAS detection system, the fluorescent XAS detection system comprising an X-ray collimator, an X-ray monochromatic optical train, an X-ray scattering film, a detector and an X-ray detector;
the X-ray source radiates X-rays and becomes parallel light after passing through the X-ray collimator, and the parallel light becomes monochromatic light after passing through the X-ray monochromatic optical system; the X-ray scattering film is arranged on the X-ray scattering film, the detector is close to the X-ray scattering film, a small part of monochromatic light is scattered by the X-ray scattering film and detected by the detector, signals received by the detector serve as reference intensity of X-rays, most of the monochromatic light penetrates through the X-ray scattering film and then acts on a sample to be detected, under the excitation action of the X-rays, the sample to be detected emits X-ray fluorescence, the intensity of the X-ray fluorescence is detected by an X-ray detector with energy resolution, and in the XAS spectrum measuring process, the angle of an X-ray incident angle is changed by rotating an X-ray monochromatic optical system, so that the XAS spectrum is measured in an energy scanning mode.
The above-mentioned X-ray absorption spectrum measuring system preferably further comprises one or more slits disposed in front of the X-ray beam spot and the detector for limiting the size of the X-ray beam and removing scattered X-rays, so as to improve the signal-to-noise ratio of the detection signal.
In the above X-ray absorption spectrum measurement system, preferably, the X-ray source is provided with two X-ray light-emitting holes, and a certain angle is formed between the light-emitting holes, one of the X-ray light-emitting holes is used for perspective XAS measurement, and the other one of the X-ray light-emitting holes is used for fluorescence yield XAS measurement.
In the above X-ray absorption spectrum measurement system, preferably, the system further includes one or more movable platforms, and the switching of different crystals in the X-ray crystal group and the position adjustment of each X-ray component are realized in a translational or rotational manner.
In the above X-ray absorption spectrum measurement system, preferably, the X-ray dispersive crystal is a von Hamos type crystal or a planar crystal in the EXAFS measurement; the X-ray dispersive crystal used for XANES spectral measurement is a Johannson crystal with a cylindrical structure.
Due to the adoption of the technical scheme, the invention has the following advantages:
1. the X-ray absorption spectrum measuring system can adopt a large-area high-power X-ray light tube as an X-ray source, can ensure that the obtained X-ray absorption spectrum has higher energy resolution, and can effectively improve the measuring efficiency by optimizing and measuring the near-edge absorption spectrum (XANES) and the far-edge absorption spectrum (EXAFS) in a segmentation way, and the measuring efficiency is one order of magnitude higher than that of the existing system;
2. the X-ray tube can adopt a large-area electron beam focusing X-ray source, and compared with a micro-focus light source, the power of the X-ray source which can be used for a high-resolution X-ray absorption spectrum device is improved by orders of magnitude;
3. the EXAFS detection X-ray light path plane and the XANES detection X-ray light path plane are designed orthogonally, and the two-area array detector is used for respectively carrying out optimized detection on EXAFS signals and XANES signals, so that the detection efficiency is obviously improved;
4. the invention can be provided with an X-ray focusing device to realize a micro-focus linear light source and can realize the measurement of the micro-area X-ray absorption spectrum;
5. the invention also adds a bicrystal monochromator to realize the function of measuring the X-ray absorption spectrum of the fluorescence yield, so that the device can be used for measuring the X-ray absorption spectrum of the low-concentration element, and the system can integrate two X-ray absorption spectrum measuring modes of transmission and fluorescence;
in summary, the present invention can be used for static as well as in situ characterization of samples in a laboratory environment.
Drawings
Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Like reference numerals refer to like parts throughout the drawings. In the drawings:
FIG. 1 is a schematic diagram of the structural principle of an X-ray absorption spectroscopy system according to an embodiment of the present invention;
FIG. 2 is a schematic illustration of a small angle collection to produce a "linear light source" in accordance with an embodiment of the present invention;
FIG. 3 is a schematic illustration of an embodiment of the present invention for generating a "linear light source" by electron beam scanning or linear electron beam targeting;
FIG. 4 is a schematic diagram showing the measurement of an EXAFS spectrum using a von Hamos structure in accordance with an embodiment of the present invention;
FIG. 5 is a schematic diagram showing the measurement of an EXAFS spectrum using a planar crystal according to an embodiment of the present invention;
FIGS. 6(A) - (C) are schematic diagrams of XANES spectra measured using Johannson crystals according to embodiments of the present invention;
FIG. 7 is a schematic diagram of the structural principle of an X-ray absorption spectrum system with a focusing device optimized according to an embodiment of the present invention;
FIG. 8 is a schematic representation of a fluorescent XAS measurement apparatus configuration according to an embodiment of the present invention;
FIG. 9 is a schematic diagram of a system configuration that illustrates an integrated transmission XAS and fluorescence XAS measurement mode, according to an embodiment of the present invention;
FIG. 10 is a schematic diagram of a dual-aperture X-ray source and a dual-mode X-ray absorption spectrum measurement method according to an embodiment of the present invention.
Detailed Description
Exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the invention are shown in the drawings, it should be understood that the invention can be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
It is to be understood that the terminology used herein is for the purpose of describing particular example embodiments only, and is not intended to be limiting. As used herein, the singular forms "a", "an" and "the" may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprises," "comprising," "including," and "having" are inclusive and therefore specify the presence of stated features, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order described or illustrated, unless specifically identified as an order of performance. It should also be understood that additional or alternative steps may be used.
For convenience of description, spatially relative terms, such as "inner", "outer", "lower", "upper", and the like, may be used herein to describe one element or feature's relationship to another element or feature as illustrated in the figures. Such spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures.
XAS can be generally divided into two parts according to XAS characteristics: (1) near-edge absorption spectrum (XANES-X-ray absorption near structure) and (2) Extended-edge absorption spectrum (EXAFS-Extended X-ray absorption fine structure). For XANES, the absorption coefficient of atoms for X-rays varies significantly with the energy of the incident X-ray, and the variation of the absorption coefficient jumps over a small energy range, typically less than 100eV, requiring higher energy resolution for XANES measurement. For the EXAFS, the scattering of surrounding atoms has a small influence on the atomic absorption coefficient, the EXAFS is characterized by smooth oscillation, and the X-ray energy deviates from the characteristic absorption peak by about a large amount, and the more smooth the oscillation, the more gradual the EXAFS spectral range can reach 1keV in general. The EXAFS measurement requires a higher X-ray flux because the X-ray absorption coefficient varies less in the EXAFS region.
As a non-limiting example shown in fig. 1, the present embodiment provides a multifunctional high-efficiency X-ray absorption spectrum measurement system, which includes:
the X-ray source 100 is configured to generate X-rays A by means of high-voltage electron beam targeting, and the target material can be pure metal or alloy. The sample 200 to be detected is arranged near the light outlet of the X-ray source 100, and the effective detection area of the X-ray source 100 is 201;
the X-ray crystal group 300 is an X-ray dispersion device, and diffracts the X-rays transmitted through the sample to be measured on the surface of the X-ray dispersion device. The X-ray crystal group 300 at least comprises two X-ray crystals which are different in type and can be switched to use, and the two X-ray crystals are vertical to the X-ray diffraction direction, so that XANES spectral measurement and EXAFS spectral measurement can be completed;
a detector array configured to detect diffraction signals of the set of X-ray crystals. The detector array comprises a first X-ray area array detector with high resolution and a second X-ray area array detector with high sensitivity, X-ray detection of XANES spectral measurement and EXAFS spectral measurement is realized, wherein detection surfaces of the first X-ray area array detector and the second X-ray area array detector are arranged orthogonally;
and the signal receiver 400 is configured to record and process the acquired X-ray signals of the detector array, so as to measure the X-ray absorption spectrum.
In some embodiments of the present invention, the X-ray source 100 is a "line source", i.e., the smallest cross-section of the X-ray beam has a finite dimension, typically less than 100 microns, in at least one dimension, and can be up to a millimeter in another dimension orthogonal thereto. The "linear light source" is parallel to the surface center axis 313 of the X-ray dispersive crystal 312 and perpendicular to the surface center axis 314 of the X-ray dispersive crystal 311.
Further, the "line light source" can be realized in two ways:
1. method for controlling angle between target surface and X-ray collection direction
The non-limiting embodiment shown in FIG. 2 provides a way to control the target surface and the X-ray collection direction angle. The angle 109 between the X-ray collection direction 107 and the X-ray generating target surface 103 is controlled to be in the range of 0.1 deg. -45 deg..
The electron gun 101 emits electrons 102 which act on the target surface 103, the actual region of action 104 of the electrons. The electrons 102 strike the target surface 104 and emit X-rays, which are not specifically directed and have a divergence angle of 4 pi. In the implementation of the present invention, only X-rays having a propagation direction within an effective collection angle 108 from the X-ray collection direction 107 can be effectively collected. In a plane perpendicular to the X-ray collection direction 107, the X-ray equivalent minimum beam spot 105 size can be much smaller than the electron actual region of action 104. The size of the X-ray equivalent minimum beam spot 105 is 1/5.7 of the actual region of action of the electrons, as in the case of a collection angle 108 and an included angle 109 of 5. The X-ray equivalent beam spot remains unchanged in the direction perpendicular to 105.
2. Linear electron beam spot system
The non-limiting embodiment shown in fig. 3 shows a linear electron beam spot pattern. In this embodiment, the electron beam and target surface active area are linear, and implementations include, but are not limited to:
(1) the X-ray micro-focus spot is scanned in a linear direction within a certain area 109 by increasing the electric or magnetic field 111;
(2) by increasing the electric field and the magnetic field, the X-ray beam spot is made linear. It should be noted here that the term "linear light source" when used in the present invention is characterized by a spot shape at the source point or effective X-ray spot minimum cross-section having a finite size in at least one dimension, typically less than 100 μm in size, to meet the X-ray absorption spectrum measurement resolution requirements; in another dimension orthogonal thereto, the dimensions are of the order of tens of micrometers to millimeters.
In some embodiments of the present invention, the X-ray crystal assembly 300 includes two dispersive components with different functions, including a low energy resolution X-ray dispersive crystal 311, for XANES spectral measurements; high energy resolution X-ray dispersive crystal 312 for EXAFS spectroscopy. The EXAFS signal is detected by the high sensitivity X-ray area array detector 500 and the XANES signal is detected by the high resolution X-ray area array detector 600.
The two X-ray dispersion crystals can be switched in position, and when an EXAFS spectrum is measured, the high-energy resolution X-ray dispersion crystal 312 is placed in an X-ray light path, and the low-energy resolution X-ray dispersion crystal 311 is moved out of the X-ray light path;
in XANES measurement, the low energy resolving X-ray dispersive crystal 311 is moved into the X-ray path and the high energy resolving X-ray dispersive crystal 312 is placed in the X-ray path and moved out of the X-ray path.
The plane of the X-ray path during the EXAFS measurement is orthogonal to the plane of the X-ray path during the XANES measurement. The X-ray dispersion crystal 311 may be a von Hamos type crystal or a planar crystal, and this is not limitative.
In some embodiments of the present invention, as shown in fig. 4, for the von Hamos crystal 312, the X-ray reflection surface is a cylindrical surface, the axis of symmetry 315 is located within the cylindrical surface and parallel to the cylindrical surface, and the distance between the equivalent linear X-ray beam spot and the axis of symmetry 315 is the same as the radius of curvature of the cylindrical surface. Incident X-rays have a certain divergence angle, and when the incident angle satisfies the Bragg diffraction condition, the X-rays are diffracted. Under the dispersive action of the von Hamos crystal 312, X-rays of different energies are imaged at different spatial positions on the image plane. The detector 500 is used to detect the intensity of the X-rays at different spatial locations, thereby obtaining an X-ray energy spectrum. Further, the angle between the detector 500 and the symmetry axis 315 of the von Hamos crystal can be adjusted appropriately to optimize the detection of the X-ray spectral range. In other implementations, the EXAFS measurement may also use a planar crystal. As a non-limiting example shown in FIG. 5, single energy X-rays are distributed in an arc on the detector 500. The crystal material used for the EXAFS measurement includes, but is not limited to, single crystal, mosaic crystal. Among all commonly used X-ray crystals, Ge111, HAPG/HOPG are the preferred crystals for the EXAFS measurement.
In some embodiments of the present invention, as shown in fig. 6, the crystal used for XANES spectral measurement is Johannson crystal 311 having a cylindrical structure. The Rowland circle is characterized in that: the point positions on the rowland circle correspond to the X-ray energy one by one, and for the X-ray with the wavelength of lambda _0, the cambered surface included in the Johannson crystal 311 can meet the Bragg diffraction condition. FIG. 6A is a schematic diagram of crystal versus X-ray dispersion using a point source and a light source on a Rowland circle. In this case, only X-rays of a single energy satisfy the bragg diffraction condition, and therefore the detector can detect only X-rays having a specific energy, and measurement of an X-ray spectrum cannot be achieved. Fig. 6B is a schematic diagram of the crystal versus X-ray dispersion when the point source is placed inside the rowland circle. In this case, X-rays of different energies may be spatially distributed on the detector 600, but the X-ray utilization efficiency is low. Fig. 6C is an X-ray path diagram when a "linear light source" is placed inside the rowland circle, which has the following advantages: for X-rays of a particular energy, X-rays in a wider range of divergence angles are effectively scatter imaged onto the detector surface.
In some embodiments of the present invention, the multifunctional high-efficiency X-ray absorption spectrum measuring system of the present embodiment further comprises an X-ray focusing mirror 700, which functions to collect and focus X-rays, as shown in fig. 7. The X-ray focusing optical system is a surface reflection type X-ray component, and the reflection surface has a central axis symmetry structure. The X-ray focusing optical system comprises two X-ray components with paraboloids or I-shaped Wolter profiles on the surfaces, wherein X-rays are converted into parallel light through the first paraboloid or the I-shaped Wolter profile and then are focused after being reflected through the second paraboloid or the second Wolter profile. The X-ray focusing may be performed by using an X-ray focusing apparatus having an elliptical surface, for example, without being limited thereto.
In some embodiments of the present invention, the multifunctional high-efficiency X-ray absorption spectroscopy measurement system of the present embodiment is further augmented with a fluorescent XAS measurement device, which, as a non-limiting embodiment shown in fig. 8, includes an X-ray collimating optics 800, an X-ray monochromatic optics 810, a thin film 820, a detector 830, and an X-ray detector 840.
The X-ray source position is unchanged and the X-ray a collected by X-ray is collimated using the X-ray collimating optics 800. The X-ray collimating optical train may be, but is not limited to, the following: an X-ray collimating capillary having an axisymmetric surface with a parabolic or type I Wolter profile or an X-ray collimating capillary having a composite structure. The collimated X-rays pass through the X-ray monochromatic optics 810 and become monochromatic light C, a small portion of which is scattered by the thin film 820 and detected by the detector 830. The detector 830 directly uses any one of the detectors 500 or 600 used in the transmission X-ray absorption spectrum measurement. Detector 830 is positioned adjacent to scattering film 820 to achieve a greater acceptance angle of the scattered X-ray signal. The detector 830 receives a signal as a reference intensity I _0 of the X-rays. Most of the monochromatic X-rays pass through the scattering film 820 and then act on the sample 200 to be measured. Under the excitation of the X-rays, the sample 200 to be measured emits X-ray fluorescence, the intensity (I _ f) of which is detected by the X-ray detector 840 with energy resolution. Preferably, the X-ray fluorescence intensity may be detected using a plurality of X-ray detectors 840 having energy resolution to increase the collection efficiency of the X-ray fluorescence signal. In fluorescent XAS measurements, monochromatic light C can be made to have different energies by rotating the angle of each crystal (811, 812, 813, 814) in the planar-to-X-ray monochromatic optical train 810, resulting in a measurement of the X-ray absorption spectrum. Preferably, the X-ray monochromatic optical system 810 may only include one group of planar crystal pairs, and may be set according to actual needs to meet the requirements of optical paths.
In some embodiments of the present invention, where the X-ray resolution required for the XANES measurement and the EXAFS measurement are different, the system may comprise two or more X-ray monochromatic optical trains having different crystal (or facet) planes. When the XANES signal is measured, the X-ray after being monochromated by the used X-ray monochromating optical system has smaller bandwidth so as to ensure the high resolution of the XANES signal; when the EXAFS signal is measured, the X-ray after being monochromatic by the X-ray monochromatic optical system has larger bandwidth so as to ensure the X-ray luminous flux required by the EXAFS measurement.
In some embodiments of the invention, for a system with a fluorescent XAS measurement device, only one X-ray dispersion element is allowed in the X-ray optical path during measurement of transmission XANES, transmission EXAFS, fluorescent XANES, and fluorescent EXAFS. Preferably, different X-ray dispersion components (including but not limited to 311, 312, 810) can be mounted on the mobile platform 900 with one-dimensional or two-dimensional adjustment function, so as to realize the switching of different X-ray dispersion components, as shown in fig. 9. In this embodiment, the X-ray focusing components in the X-ray optical train (700, 800) used for transmission XAS and fluorescent XAS measurements are different. Furthermore, the system can also comprise one or more movable platforms, and switching of different crystals in the X-ray crystal group and position adjustment of each X-ray component are realized in a translation or rotation mode. Switching can be facilitated, for example, by placing different types of X-ray focusing components 700, 800 on a moving platform 910 with one-dimensional or two-dimensional adjustment.
In some embodiments of the invention, simultaneous measurement of transmissive XAS and fluorescent XAS may also be achieved, as shown in fig. 10. The X-ray source 100 may have a plurality of X-ray exit holes, and a certain angle is formed between the two exit holes. One of the X-ray exit apertures is used for perspective XAS measurement, and the other is used for fluorescence yield XAS measurement.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: it is to be understood that modifications may be made to the above-described arrangements in the embodiments or equivalents may be substituted for some of the features of the embodiments without departing from the spirit or scope of the present invention.
Claims (10)
1. An X-ray absorption spectroscopy measurement system, comprising:
an X-ray source configured to generate X-rays by bombarding a target with an electron beam;
an X-ray crystal set comprising at least two X-ray crystals of different types and switchable use, the two X-ray crystals being perpendicular to an X-ray diffraction direction and configured to perform XANES spectral measurement or EXAFS spectral measurement;
the detector array comprises a first X-ray area array detector and a second X-ray area array detector and is configured to realize X-ray detection of XANES spectral measurement and EXAFS spectral measurement, wherein detection areas of the first X-ray area array detector and the second X-ray area array detector are arranged orthogonally;
a signal receiver configured to process the received detection signal to obtain an X-ray absorption spectrum measurement.
2. The X-ray absorption spectrum measuring system according to claim 1, wherein a sample to be measured is disposed near the light exit hole of the X-ray source, X-rays penetrate through the sample to be measured and then enter the X-ray crystal group, and the X-ray beam effectively collected is characterized as a "linear light source", that is, the minimum cross section of the X-ray beam has a finite size in at least one dimension direction and reaches a millimeter level in another dimension orthogonal to the X-ray beam.
3. The X-ray absorption spectroscopy system of claim 2, wherein the X-ray beam is generated in a "linear light source" fashion by controlling the target surface and X-ray collection direction angle or in a linear electron beam spot fashion.
4. The system according to claim 1, further comprising an X-ray focusing mirror disposed at the light-emitting position of the X-ray source and configured to collect X-rays radiated from the X-ray source and focus the X-rays on the surface of the sample to be measured.
5. The system according to claim 4, wherein the X-ray focusing mirror is a surface reflection type X-ray focusing device having an axisymmetric feature, the focal point and the X-ray source are in an object-image relationship, and the X-ray focusing mirror includes two types of X-ray optical devices: (1) an X-ray reflecting surface with a paraboloid or I-shaped Wolter profile; the X-ray is changed into parallel light after passing through the first reflecting surface, and the parallel light enters the second reflecting surface and is focused; (2) the surface is an X-ray reflecting surface of an ellipsoid, and X-rays are directly focused on the surface of a sample to be measured after being reflected by the ellipsoid.
6. The X-ray absorption spectroscopy measurement system of claim 1, further comprising a fluorescent XAS detection system comprising an X-ray collimator, an X-ray monochromating optical train, an X-ray scattering film, a detector, and an X-ray detector;
the X-ray source radiates X-rays and becomes parallel light after passing through the X-ray collimator, and the parallel light becomes monochromatic light after passing through the X-ray monochromatic optical system; the X-ray scattering film is arranged on the X-ray scattering film, the detector is close to the X-ray scattering film, a small part of monochromatic light is scattered by the X-ray scattering film and detected by the detector, signals received by the detector serve as reference intensity of X-rays, most of the monochromatic light penetrates through the X-ray scattering film and then acts on a sample to be detected, under the excitation action of the X-rays, the sample to be detected emits X-ray fluorescence, the intensity of the X-ray fluorescence is detected by an X-ray detector with energy resolution, and in the XAS spectrum measuring process, the angle of an X-ray incident angle is changed by rotating an X-ray monochromatic optical system, so that the XAS spectrum is measured in an energy scanning mode.
7. The X-ray absorption spectrum measurement system according to any one of claims 1 to 6, wherein the system further comprises one or more slits disposed in front of the X-ray beam spot and the detector for limiting the size of the X-ray beam and removing scattered X-rays to improve the signal-to-noise ratio of the detection signal.
8. The X-ray absorption spectrum measurement system according to any one of claims 1 to 6, wherein the X-ray source is provided with two X-ray exit apertures, and the exit apertures form an angle therebetween, wherein one of the X-ray exit apertures is used for perspective XAS measurement, and the other is used for fluorescence yield XAS measurement.
9. The X-ray absorption spectrum measurement system according to any one of claims 1 to 6, further comprising one or more movable platforms, wherein switching of different crystals in the X-ray crystal group and positional adjustment of each X-ray component are realized in a translational or rotational manner.
10. The X-ray absorption spectrum measurement system according to any one of claims 1 to 6, wherein the X-ray dispersive crystal is a von Hamos type crystal or a planar crystal at the time of the EXAFS measurement; the X-ray dispersive crystal used for XANES spectral measurement is a Johannson crystal with a cylindrical structure.
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