CN111650226B - Medium energy X-ray absorption spectrometer based on laboratory X-ray source - Google Patents
Medium energy X-ray absorption spectrometer based on laboratory X-ray source Download PDFInfo
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Abstract
The invention provides a middle energy X-ray absorption spectrometer based on a laboratory X-ray source, which comprises an X-ray source, a bending crystal, a detector, a sample stage, a motion adjusting mechanism and a vacuum cavity, wherein the X-ray source, the bending crystal and the detector are positioned on a movable Roland circle with a constant radius; the motion adjusting mechanism is arranged to drive the bending crystal and the detector to move and adjust, and the X-ray source, the bending crystal and the detector are always positioned on the Roland circle; the bending crystal, the detector, the sample table and the motion adjusting mechanism are all arranged in the vacuum cavity, and the X-ray source is arranged on the outer side of the vacuum cavity and fixedly connected with the vacuum cavity. The invention arranges the bending crystal, the detector, the sample stage and the motion adjusting mechanism in the vacuum cavity to ensure that the optical path is in a vacuum condition, reduce the attenuation of the air absorption on the optical path to the X-rays and the back-bottom scattering in the air, improve the final counting rate of the spectrometer, and build the medium-energy X-ray absorption spectrometer with sub-eV energy resolution.
Description
Technical Field
The invention relates to an X-ray absorption spectrometer, in particular to a high-resolution medium-energy X-ray absorption spectrometer based on a laboratory X-ray source. A medium energy X-ray absorption spectrometer based on a laboratory X-ray source.
Description of the background
The X-ray absorption spectrum is an experimental technology which matures along with the development of a synchrotron radiation device, is one of important methods for researching a substance structure, can research an atomic neighbor local structure under various conditions such as solid state, liquid state and the like, and is widely applied to various fields such as materials, biology, chemistry, environment, geology and the like. The near-edge X-ray absorption spectrum (XANES) has higher requirement on energy resolution, which is generally smaller than the natural bandwidth of the absorption edge of the element to be detected, and the energy resolution required by the extended-edge X-ray absorption spectrum (EXAFS) is equivalent to the natural bandwidth of the specific absorption edge of the element. The energy resolution and the counting rate of the spectrometer are important indexes for spectrometer development.
The early X-ray absorption spectrometers based on laboratory light sources are basically EXAFS spectrometers with low energy resolution, and the applicable energy ranges of the X-ray absorption spectrometers are all 5-20keV in the hard X-ray band, and mainly comprise a planar crystal EXAFS spectrometer, a bent crystal EXAFS spectrometer, a total reflection EXAFS spectrometer, a dispersion EXAFS spectrometer and the like. Planar crystals have low diffraction efficiency, although they have high energy resolution.
Currently, the X-ray curved crystal spectrometers mainly comprise Rowland circle type, vonHamos type, johann type and Johansson type crystal spectrometers.
The Von-Hamos type spectrometer does not need to move any optical element during energy scanning, can obtain higher energy resolution, but has lower detection efficiency due to smaller collected solid angle and poorer signal-to-noise ratio of a large background signal. Johansson-type flexural spectroscopy is theoretically capable of achieving higher energy resolution, but the processing of the crystal limits its final performance.
With the development of micro-focusing X-ray source and the improvement of bending crystal process, G.T.Seidler of university of Washington in 2014 is designed and built with a set of hard X-ray wave band (5-12 keV) XAS spectrometer based on laboratory light source, johann type bending crystal, "point-to-point energy scanning" and sub eV energy resolution, the energy resolution is higher, and the counting rate of 100W X-ray source at the detector can reach 50kcps. The solid angle collected by the Johann type bent crystal spectrometer is larger, so that high detection efficiency can be obtained, compared with a Von-Hamos type bent crystal spectrometer, the higher signal-to-noise ratio can be achieved, but the higher energy resolution can be achieved only in a back scattering geometric configuration, and the requirement on mechanical optical calibration is higher because crystals and detectors are required to carry out linkage scanning during energy scanning.
The rowland circle imaging principle is a theoretical basis of a high-resolution X-ray absorption spectrometer, as shown in fig. 1, the diameter of a rowland circle 101 is equal to the curvature radius of a curved crystal 102, incident light is placed on the rowland circle 101, a limiting slit 105 is arranged between an X-ray source 103 and the curved crystal 102, X-rays of the X-ray source 103 are subjected to energy monochromatization through the crystal, namely spectral lines of various wavelengths generated after the diffraction of the crystal can be focused in the meridian plane direction (meridian plane, i.e., rowland circle plane, and a vector plane is perpendicular to the rowland circle), and focuses (i.e., detectors 104) are arranged at different positions of the rowland circle according to the magnitude of different bragg angles θ, so that energy selection is performed.
Although there are many X-ray absorption spectrometers based on the rowland circle principle in laboratories and synchrotron radiation, medium energy X-ray (2-5 keV) absorption spectrometers (Laboratory Tender X Ray Absorption Spectrometer, lab-TXAS) based on conventional laboratory X-ray sources have not been reported, and the greatest difficulty of medium energy X-ray spectrometers compared to existing hard X-ray band spectrometers is: the photon count of the laboratory light source in the medium energy section is too low, so that the measurement signal is too weak and the resolution is low.
Disclosure of Invention
The invention aims to provide a medium energy X-ray absorption spectrometer based on a laboratory X-ray source so as to improve the resolution ratio.
In order to achieve the above-mentioned object, the present invention provides a laboratory X-ray source-based medium energy X-ray absorption spectrometer for X-ray absorption spectrum testing of a sample to be tested, comprising an X-ray source, a curved crystal and a detector, a sample stage disposed between the curved crystal and the detector, a motion adjusting mechanism, and a vacuum chamber, wherein the X-ray source, the curved crystal and the detector are located on a movable and constant radius Roland circle; the motion adjusting mechanism is arranged to drive the bending crystal and the detector to move and adjust along multiple dimension directions, and the X-ray source, the bending crystal and the detector are always positioned on the Roland circle with constant radius; the bending crystal, the detector, the sample stage and the motion adjusting mechanism are all arranged in the vacuum cavity, and the X-ray source is arranged on the outer side of the vacuum cavity and fixedly connected with the vacuum cavity.
A limiting slit is arranged between the X-ray source and the bent crystal.
The X-ray source has a source window in its direction facing the curved crystal, the source window being arranged close to the focal spot of the X-ray source, the source window having a thickness of 50 μm.
The source window is a Be window with a thickness of 50 μm.
The focal spot of the X-ray source is located on the rowland circle, the focal spot having a diameter of at most 50 μm.
The curved crystal is a Johann type spherical curved crystal.
The detector is a silicon drift detector that can be used in vacuum.
The sample to be tested is plated on the sample table by adopting a magnetron sputtering process.
The bending crystal and the detector are both arranged on an optical platform through the motion adjusting mechanism, the X-ray source is directly fixed on the optical platform, and the sample stage and the detector are connected and fixed with each other.
The motion adjusting mechanism comprises a stepping motor, a crystal multidimensional adjusting mechanism and a detector multidimensional adjusting mechanism, wherein the crystal multidimensional adjusting mechanism is connected with the stepping motor, a first translation table, a lifting table, a first rotary table, a pitching adjusting device and a second translation table are sequentially arranged from bottom to top, and the bent crystal is fixed on the second translation table; the detector multidimensional adjusting mechanism comprises a third translation table, a fourth translation table and a second rotation table which are sequentially arranged from bottom to top, and the detector is fixed on the second rotation table.
According to the invention, the bending crystal, the detector, the sample stage and the motion adjusting mechanism are arranged in the vacuum cavity, so that the optical path is ensured to be in a vacuum condition, the attenuation of air absorption on the optical path to X-rays and the back scattering in the air are reduced, the final counting rate of the spectrometer is improved, and the medium-energy X-ray absorption spectrometer with sub-eV energy resolution is built, so that the medium-energy X-ray absorption spectrometer based on the laboratory X-ray source has sub-eV energy resolution, and the X-ray absorption spectrum test of the energy range of 2-5keV can be performed. In addition, the laboratory X-ray source-based medium energy X-ray absorption spectrometer of the invention reduces the absorption of window materials by adopting an X-ray window with the thickness of 50 mu m, thereby improving the intensity of the X-ray source 1; and the sample to be measured is plated on the sample table by adopting a magnetron sputtering process, so that the thickness of the sample to be measured can be controlled and the absorption of a carrier can be reduced.
Drawings
Fig. 1 is a schematic diagram of a typical rowland circular spectrometer.
FIG. 2 is a system diagram of a laboratory X-ray source-based medium energy X-ray absorption spectrometer in accordance with one embodiment of the invention
Fig. 3 is a schematic diagram of a laboratory X-ray source-based medium energy X-ray absorption spectrometer after removal of the vacuum cavity, in accordance with one embodiment of the present invention.
Fig. 4 is a schematic diagram of the installation of a crystal multidimensional adjustment mechanism and a detector multidimensional adjustment mechanism of a laboratory X-ray source-based medium energy X-ray absorption spectrometer according to one embodiment of the invention.
Fig. 5 is a schematic diagram of the motion pattern of the motion adjustment mechanism of the laboratory X-ray source-based medium energy X-ray absorption spectrometer of the present invention.
Fig. 6 is a schematic diagram of an assembly of an X-ray source, a motion adjustment mechanism and a vacuum chamber of a laboratory X-ray source-based medium energy X-ray absorption spectrometer according to one embodiment of the invention.
Detailed Description
The invention will be further illustrated with reference to specific examples. It should be understood that the following examples are illustrative of the present invention and are not intended to limit the scope of the present invention.
Fig. 2-3 show a laboratory X-ray source-based medium energy X-ray absorption spectrometer for X-ray absorption spectroscopy of a sample to be tested (e.g. a radioactive actinide) according to one embodiment of the invention, comprising an X-ray source 1, a curved crystal 2 and a detector 3, a sample stage 4 arranged between the curved crystal 2 and the detector 3, a motion adjustment mechanism 5 and a vacuum chamber 6, which are located on a movable and radius-constant rowland circle. A limiting slit is provided between the X-ray source 1 and the curved crystal 2 to reduce the acceptance angle of the curved crystal 2, thereby improving the energy resolution.
Wherein the X-ray source 1 is arranged to output a bremsstrahlung white light and form a focal spot. The X-ray source 1 is preferably a medium power X-ray source with a power of 100-300W.
The X-ray source 1 has a source window (not shown) in a direction in which it faces the curved crystal 2 to transmit and emit X-rays well through the source window and vacuum-seal the inside of the X-ray source 1.
The absorptivity of the source window is one of the decisive factors influencing the performance of the laboratory-based mid-energy X-ray absorption spectrometer of the present invention. According to the calculation, the attenuation of air and common window materials such as Be, siC and the like to 2-5keV is serious. In this embodiment, the source window is of a material Be.
However, the Be window thickness is typically greater than 100 μm for existing commercial medium power X-ray sources (100-300W), which cannot meet the needs of the laboratory X-ray source-based medium energy X-ray absorption spectrometer of the present invention of 2-5 keV. The focal spot of the X-ray source 1 is thus located on the rowland circle, the diameter of which is at most 50 μm, thereby reducing the influence of the focal spot size on the energy resolution, and the source window is arranged close to the focal spot of the X-ray source 1, in this embodiment the distance between the source window and the focal spot being in the range of 15-20mm. Since the size of the source window is limited by the size of the divergence angle of the bremsstrahlung white light output by the X-ray source 1, and the closer the source window is to the focal spot under the condition of fixed divergence angle of the emergent light, the smaller the area of the source window, therefore, the focal spot passing through the X-ray source is positioned on the rowland circle, and the distance between the focal spot and the window is reduced, so that the area of the source window is reduced, and the thickness of the source window can be reduced. Finally, in the case of a power of 200W of the X-ray source 1, the thickness of the source window is 50 μm. The thinner the source window is, the better the thickness of the source window is, the thinner source window material can reduce the attenuation of X-rays, but certain intensity and radiation damage resistance are still maintained, the thinnest thickness of the source window can reach 50 mu m under the current power of 200W, and when the existing Be window with the thickness of 200 mu m is adopted, the energy 2keV transmittance is less than 10%, the final spectrometer counting rate is lower, and the requirements of the laboratory X-ray-based medium-energy X-ray absorption spectrometer with the 2-5keV can not Be met. The middle energy X-ray absorption spectrometer based on the laboratory X-ray source reduces the absorption of window materials by adopting an X-ray window with the thickness of 50 mu m, thereby improving the intensity of the X-ray source 1 and being applicable to the laboratory absorption spectrometer with the thickness of 2-5 keV.
The X-ray source 1 may be used as an X-ray system 100 of the laboratory X-ray source based medium energy X-ray absorption spectrometer of the present invention.
The curved crystal 2 is arranged to energy-select the incident bremsstrahlung light by bragg diffraction. Wherein, the bending crystal 2 is Johann type spherical bending crystal and can be purchased commercially. The curved crystal 2 can perform energy splitting and focusing on the incident X-rays in both a meridian direction (i.e., a direction of a plane where the rowland circle is located) and a sagittal direction, and can obtain higher diffraction efficiency than a cylindrical crystal. The conventional spherical bent crystal mainly comprises Johann type spherical bent crystal and Johansson type spherical bent crystal, and in theory, the latter can obtain higher energy resolution, but the limitation of the crystal processing technology is not ideal in practice, so in the embodiment, the selected bent crystal 2 is Johann type spherical bent crystal.
The curved crystal 2 is mounted on a crystal holder, and the curved crystal 2 and the crystal holder together form the crystal analyser 200 of the laboratory X-ray source based medium energy X-ray absorption spectrometer of the invention.
The detector 3 is arranged to collect "quasi-monochromatic" X-rays after diffraction by said curved crystal 2. The detector 3 is a silicon drift detector usable in vacuum with an energy resolution < 130eV, having a detector window (not shown) for sealing the interior of the detector 3 from ultra-high vacuum and allowing light to pass through. The detector window has a window thickness of 12.5 μm, a material of Be, and an effective area of 50m m2 The maximum photon counting rate is 1Mcps, and the higher harmonic content after the diffraction of the bent crystal can be effectively restrained.
The detector 3 described above may be used as a laboratory X-ray source-based medium energy X-ray absorption spectrometer detection system 300 of the present invention.
The sample stage 4 is plated with the sample to be measured. In this embodiment, the sample stage 4 is a 200nm silicon nitride window, and the sample to be measured is plated on the sample stage 4 by using a magnetron sputtering process, so that the thickness of the sample to be measured can be controlled and the absorption of the carrier can be reduced. The sample stage 4 is arranged at the end between the curved crystal 2 and the detector 3 near the detector 3. Specifically, the sample stage 4 is installed in a sample introduction chamber, and the bent crystal 2 and the detector 3 are fixed therebetween through the sample introduction chamber. The sample stage 4 and the sample introduction chamber together form a sample system 400 of the laboratory X-ray source based medium energy X-ray absorption spectrometer of the present invention.
The bending crystal 2 and the detector 3 are both arranged on an optical platform 7 through the motion adjusting mechanism 5, and the motion adjusting mechanism 5 is arranged to drive the bending crystal 2 and the detector 3 to move and adjust along multiple dimension directions, and the X-ray source 1, the bending crystal 2 and the detector 3 are always positioned on the Roland circle with constant radius so as to realize optical calibration and energy scanning. In this embodiment, the motion adjusting mechanism 5 includes a stepper motor (not shown) and a crystal multidimensional adjusting mechanism 51 and a detector multidimensional adjusting mechanism 52 connected to the stepper motor, and the stepper motor is a high-precision vacuum inner stepper motor, so as to improve the control precision of the optical element bending crystal 2 and the detector 3, and further improve the energy resolution.
In this embodiment, the X-ray source 1 is directly fixed on said optical stage 7 and the sample stage 4 and the detector 3 are fixed in connection with each other for a common movement.
Referring again to fig. 2, in other embodiments, in addition to the curved crystal 2 and detector 3, the X-ray source 1 and the sample stage 4 are also mounted on an optical stage 7 by the motion adjustment mechanism 5.
As shown in fig. 4, the crystal multidimensional adjusting mechanism 51 comprises a first translation stage 511, a lifting stage 512, a first rotation stage 513, a pitching adjusting device 514 and a second translation stage 515 which are sequentially arranged from bottom to top, and the curved crystal 2 is fixed on the second translation stage 515. The first translation stage 511 and the second translation stage 515 are both configured to drive the bending crystal 2 to translate along the linear movement direction X1, the lifting stage 512 is configured to drive the bending crystal 2 to move along the vertical movement direction Z, and the first rotation stage 513 is configured to drive the bending crystal 2 around its vertical axis (i.e., along the first rotation direction θ Z1 ) Rotation, pitchingThe adjusting means 514 is arranged to adjust the curved crystal 2 in the direction of arc θ y Is a pitch angle of (c). The detector multidimensional adjustment mechanism 52 comprises a third translation stage 521, a fourth translation stage 522 and a second rotation stage 523 which are sequentially arranged from bottom to top, and the detector 3 is fixed on the second rotation stage 523. The third 521 and fourth 522 translation stages are respectively arranged to drive the detector 3 in two horizontal directions X3 and Y perpendicular to each other, and the second 523 rotation stage is arranged to drive the detector 3 about its vertical axis (i.e. in the second direction of rotation θ) Z2 ) And (5) rotating. At the time of energy scanning, the curved crystal 2 needs to be translated in the linear movement direction X1 by the first translation stage 511 and in the first rotation direction θ by the first rotation stage 513 Z1 The detector is required to be translated in two horizontal directions X3 and Y perpendicular to each other by the first translation stage 511 and the second translation stage 515 and in a second rotational direction θ by the second rotation stage 523 Z2 The rotating, multi-dimensional adjustment mechanism 51 adjusts the other dimensional components for optical calibration.
Fig. 5 shows the movement of the movement control device 5, i.e. the movement of the movement control device 5 such that the X-ray source 1, the curved crystal 2 and the detector 3 are always maintained on a rowland circle with a constant radius. In this example, the Roland circle has a diameter of 0.5m. And establishing a two-dimensional coordinate system by taking the X-ray source 1 as an origin of the coordinate system and taking the horizontal movement direction of the bent crystal 2 as an X-axis, wherein the radius of the Rowland circle is R, the bent crystal 2 moves along an axis I, and the moving axis I is coincident with the axis of the X-ray source 1. During the energy scan, the position of the X-ray source 1 is fixed, the radius of the Rowland circle is kept constant, and the curved crystal 2 changes the Bragg angle θ by horizontal movement along the X-axis direction and rotation of the curved crystal 2 itself B The detector 3 determines its position according to the X-ray source 1, the position of the bent crystal 2 and the radius of the rowland circle, and performs data acquisition. Due to the linkage of the bending crystal 2 and the detector 3 and the change in the position of the rowland circle at the time of energy scanning, the coordinates (a x ，A y ) Coordinates of the detector 3 (D x ，D y ) And Bragg angle theta B The following relation needs to be satisfiedThe formula:
wherein A is x ，A y The abscissa and the ordinate of the curved crystal 2, respectively; d (D) x ，D y The abscissa and the ordinate of the detector 3, respectively; r is the radius of Rowland circle, θ B Is the bragg angle.
As shown in fig. 6, the curved crystal 2, the detector 3, the sample stage 4 and the motion adjusting mechanism 5 are disposed in the vacuum chamber 6, so as to ensure that the optical path is a vacuum condition, and avoid attenuation of X-rays by air on the optical path and back scattering in the air, thereby improving the final counting rate of the spectrometer, and being capable of performing X-ray absorption spectrum test in an energy range of 2-5 keV. The X-ray source 1 is arranged at the outer side of the vacuum cavity 6 and is fixedly connected with the vacuum cavity 6 through a flange.
Referring again to fig. 1, the vacuum chamber 6 described above may be used as a vacuum system 600 for a laboratory X-ray source-based medium energy X-ray absorption spectrometer of the present invention.
In addition, the laboratory X-ray source-based medium energy X-ray absorption spectrometer of the invention can further comprise a radiation protection system 700, a motion control system 800 and a data acquisition system 900, wherein the motion control system 800 is connected with the motion adjustment mechanism 5 to control the motion adjustment mechanism 5 to drive the X-ray source 1, the bending crystal 2, the detector 3 and the sample stage 4 to move and adjust along multiple dimension directions, and the data acquisition system is connected with the detector 3 to realize data acquisition of the detector.
The principle of the present invention, which is excellent in performance of a laboratory X-ray source-based medium energy X-ray absorption spectrometer, will be specifically described. The energy resolution and photon counting rate are key indicators of the final performance of the medium energy X-ray absorption spectrometer based on the laboratory X-ray source.
The main factors affecting the energy resolution of the spectrometer include: 1. the curved crystal 2 is the line broadening caused by non-ideal complete crystal; 2. absorption by a monochromator; 3. the natural bandwidth of the spectral lines 4. Divergence of the incident X-rays of the X-ray source 1; focal spot size of the x-ray source; 6. line broadening due to deviations of the optical element from the rowland circle geometry, etc. Wherein, the line broadening of the bending crystal 2 and the natural bandwidth of the line belong to inherent influencing factors, and the absorption of the monochromator is small in the medium-energy band and can be ignored.
The laboratory X-ray source-based medium energy X-ray absorption spectrometer 1) of the invention reduces the impact of the focal spot size of the X-ray source 1 on the energy resolution by using an X-ray source 1 with a focal spot diameter of 50 μm; 2) The receiving angle of the bent crystal 2 is reduced by adding a limiting slit between the X-ray source 1 and the bent crystal 2, so that the energy resolution is improved; 3) The invention adopts a high-precision vacuum internal stepping motor to improve the control precision of the optical element and further improve the energy resolution.
Factors affecting the final count rate of the spectrometer mainly include: the intensity of the X-ray source 1, the diffraction efficiency of the crystal, the quantum efficiency of the detector, the path transfer efficiency, etc. The diffraction efficiency of the crystal and the quantum efficiency of the detector are mainly limited by the processing technology, and are difficult to improve in a short period.
The middle energy X-ray absorption spectrometer based on the laboratory X-ray source reduces the absorption of window materials by adopting an X-ray window with the thickness of 50 mu m, thereby improving the intensity of the X-ray source 1; the bending crystal 2, the detector 3, the sample stage 4 and the motion adjusting mechanism 5 are arranged in the vacuum cavity 6, so that the optical path is a vacuum condition, the attenuation of air on the optical path to X-rays and the back scattering in the air are avoided, and the final counting rate of the spectrometer is improved, therefore, the medium-energy X-ray absorption spectrometer based on the laboratory X-ray source has sub-eV energy resolution, and the X-ray absorption spectrum test of the energy range of 2-5keV can be performed.
The design parameters of the high-resolution laboratory X-ray source-based medium energy X-ray absorption spectrometer are as follows:
1) Energy range of spectrometer: 2.3-7keV;
2) Energy resolution: 4X 10 -4 @2.3-7keV；
3) Roland circle diameter: 0.5m;
4) Bragg angle theta B Is defined in the following range: 60-80 degrees;
5) Crystal type: johann type spherical crystal.
Among them, the spectrometer of Roland circle of 0.5m and 1.0m is a more common choice, the invention adopts Roland circle of 0.5 meter diameter, the counting rate is high, but the resolution ratio is low; the crystal faces of the same material and different Bragg angles correspond to different energy ranges, the range of the Bragg angles is mainly limited by space, and the range of the Bragg angles of 60-80 degrees is unchanged compared with the prior art, wherein different crystal face indexes correspond to different crystal face intervals, and the conventional silicon and germanium crystal only has low crystal face index 111 220 311 400 440 and can carry out 2.3-7keV energy selection through Bragg diffraction.
The foregoing description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and various modifications can be made to the above-described embodiment of the present invention. All simple, equivalent changes and modifications made in accordance with the claims and the specification of the present application fall within the scope of the patent claims. The present invention is not described in detail in the conventional art.
Claims (6)
1. A laboratory X-ray source-based medium energy X-ray absorption spectrometer for X-ray absorption spectrum testing of a sample to be tested, which is characterized by comprising an X-ray source (1), a bending crystal (2) and a detector (3) which are positioned on a movable Roland circle with a constant radius, a sample stage (4) arranged between the bending crystal (2) and the detector (3), a motion adjusting mechanism (5) and a vacuum cavity (6); the motion adjusting mechanism (5) is used for driving the bending crystal (2) and the detector (3) to move and adjust along multiple dimension directions, and the X-ray source (1), the bending crystal (2) and the detector (3) are always positioned on the Roland circle with constant radius; the bending crystal (2), the detector (3), the sample stage (4) and the motion adjusting mechanism (5) are all arranged in the vacuum cavity (6), and the X-ray source (1) is arranged on the outer side of the vacuum cavity (6) and fixedly connected with the vacuum cavity (6);
the X-ray source (1) has a source window in its direction facing the curved crystal (2), the source window being arranged close to a focal spot of the X-ray source (1), the distance of the source window from the focal spot being in the range of 15-20mm, the power of the X-ray source (1) being 200W, the source window being a Be window with a thickness of 50 μm, the focal spot of the X-ray source (1) being located on the rowland circle, the focal spot having a diameter of at most 50 μm;
the laboratory X-ray source-based medium-energy X-ray absorption spectrometer has energy resolution of sub-eV level and can perform X-ray absorption spectrum test in an energy range of 2-5 keV;
establishing a two-dimensional coordinate system by taking an X-ray source (1) as an origin of a coordinate system and taking a horizontal movement direction of a bent crystal (2) as an X axis, wherein the position of the X-ray source (1) is fixed during energy scanning, the radius of a Rowland circle is kept unchanged, the bent crystal (2) moves along a moving axis (I), the moving axis (I) coincides with the axis of the X-ray source (1), and the Bragg angle theta of the bent crystal (2) is changed by horizontal movement along the X axis direction and rotation of the bent crystal (2) per se B The detector (3) determines the position of the X-ray source (1), the position of the bent crystal (2) and the radius of the Rowland circle according to the size of the X-ray source, the position of the bent crystal and the radius of the Rowland circle, and performs data acquisition;
coordinates (A) of the bent crystal (2) x ，A y ) And the coordinates (D) of the detector (3) x ，D y ) And Bragg angle theta B The following relation is satisfied:
A x ＝2R sinθ B
A y ＝0
D x ＝4R sinθ B cos 2 θ B
D y ＝4R sin 2 θ B cosθ B
wherein A is x ，A y The abscissa and the ordinate of the curved crystal (2), respectively; d (D) x ，D y The abscissa and the ordinate of the detector (3) are respectively; r is the radius of Rowland circle, θ B Is a cloth drawnGrid angles;
a limiting slit is arranged between the X-ray source (1) and the bending crystal (2).
2. Laboratory X-ray source based medium energy X-ray absorption spectrometer according to claim 1, wherein the curved crystal (2) is a Johann type spherical curved crystal.
3. Laboratory X-ray source based medium energy X-ray absorption spectrometer according to claim 1, wherein the detector (3) is a silicon drift detector usable in vacuum with an energy resolution of less than 130eV.
4. Laboratory X-ray source based medium energy X-ray absorption spectrometer according to claim 1, wherein the sample to be measured is plated on the sample stage (4) using a magnetron sputtering process.
5. Laboratory X-ray source based medium energy X-ray absorption spectrometer according to claim 1, wherein the curved crystal (2) and detector (3) are each mounted on an optical platform (7) by means of the motion adjustment mechanism (5), the X-ray source (1) is directly fixed on the optical platform (7), and the sample stage (4) and the detector (3) are connected and fixed to each other.
6. The laboratory X-ray source based medium energy X-ray absorption spectrometer according to claim 1, wherein the motion adjustment mechanism (5) comprises a stepper motor and a crystal multidimensional adjustment mechanism (51) and a detector multidimensional adjustment mechanism (52) connected to the stepper motor, the crystal multidimensional adjustment mechanism (51) comprises a first translation stage (511), a lifting stage (512), a first rotation stage (513), a pitch adjustment device (514) and a second translation stage (515) arranged in sequence from bottom to top, and the curved crystal (2) is fixed on the second translation stage (515); the detector multidimensional adjusting mechanism (52) comprises a third translation table (521), a fourth translation table (522) and a second rotation table (523) which are sequentially arranged from bottom to top, and the detector (3) is fixed on the second rotation table (523).
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