X-ray monochromatization method and device of a full-focusing hyperbolic bending crystal

Abstract

The application discloses an X-ray monochromatization method and device of a full-focusing hyperbolic bending crystal, and the method comprises the following steps: firstly, a matching model is established through the position and geometric relation of the bending crystal and the light pipe; the incident angle of the X-ray and the control voltage are changed according to the monochromatization requirement to generate the optimal incident X-ray intensity; the X-ray emitted by the hyperbolic bending crystal diffraction X-ray tube is diffracted, and the diffraction light meeting the Bragg law is focused together to generate the X-ray with high diffraction intensity through the hyperbolic bending crystal diffraction method; and the X-ray monochromatic performance evaluation method is used to evaluate the monochromatic performance. The application can greatly improve the X-ray monochromatization performance, and solve the bottleneck problems of the insufficient light element ratio and the insufficient low element detection limit of the X-ray spectrometer.

Description

Technical Field

[0001] This invention relates to the field of X-ray fluorescence (XRF) spectroscopy analysis, and in particular to XRF spectrometers with insufficient light element fractionation and insufficient element detection limits. Background Technology

[0002] X-ray fluorescence spectrometry is suitable for the analysis of material composition, and can directly perform multi-element simultaneous analysis of major and trace elements in solid (bulk or powder) and liquid samples. With the development of analytical technology and the improvement of scientific research, the analytical field is paying more and more attention to the characteristics of complex and low-content components, which places higher demands on the instruments themselves.

[0003] The detection accuracy of X-ray fluorescence spectrometers is related to the intensity of fluorescent X-rays, which in turn is affected by the diffraction intensity of the X-rays incident on the sample. Therefore, the monochromaticity of the incident X-rays has a crucial impact on the spectrometer's performance. To improve the monochromaticity of X-ray fluorescence spectrometers, extensive research and improvements have been made to spectroscopic crystal monochromators.

[0004] The most common monochromatic spectroscopic crystal is the planar spectroscopic crystal. Its optical path system and fabrication process are relatively simple, but planar crystals also have significant drawbacks. First, they are only suitable for large-area surface light sources. For point sources or micro-area sample analysis, the effective diffraction area of ​​the spectroscopic crystal is very small, resulting in low efficiency, making planar crystal spectrometry unsuitable. Second, the optical path system requires front and rear collimation, leading to a complex structure and significant attenuation of X-ray fluorescence. Third, planar crystal spectrometry has low efficiency; some light elements cannot be accurately analyzed using planar crystal spectrometry.

[0005] To overcome the drawbacks of planar crystals, researchers began studying curved crystals, such as semi-focusing curved crystals. These are created by bending a planar crystal into a cylinder with a radius of curvature R, where the center point of the arc is tangent to a circle with a radius of R / 2. This circle is called the focusing circle, or Rowland's circle. Light emitted from a point source on this circle is diffracted by the crystal and converges at a symmetrical point on the circumference. If an extended surface source is located on the circle, different image points on the circumference correspond to monochromatic light of different wavelengths. The effective area and diffraction efficiency of the crystal surface participating in diffraction are far greater than those of planar crystals. Combined with its excellent focusing effect, theoretically, the spectral line intensities obtained can be tens of times higher than those of Bragg planar crystals. However, compared to semi-focusing curved crystals, fully focusing curved crystals have even higher diffraction efficiency. For line sources, the effective area of ​​the crystal surface participating in diffraction is theoretically 100%, and the optical path is relatively simple, requiring no collimator, giving it a significant advantage over other spectroscopic crystals.

[0006] Therefore, this invention proposes an X-ray monochromaticization method and apparatus for fully focused hyperbolic curved crystals, which significantly improves X-ray diffraction intensity and solves the bottleneck problems of insufficient light element fractionation and insufficient element detection limit in XRF spectrometers. Summary of the Invention

[0007] This invention provides a fully focused hyperbolic curved crystal monochromatic method, characterized by comprising: an X-ray generation method consisting of a high-voltage power supply and an X-ray tube, capable of generating X-rays with high diffraction intensity; a hyperbolic curved crystal spectrometry method, which uses the X-rays emitted by the hyperbolic curved crystal diffraction X-ray tube and focuses the diffracted light that conforms to Bragg's law together; and an X-ray monochromatic performance evaluation method, which uses a detector to receive X-rays and processes the received monochromatic X-rays after hyperbolic curved crystal diffraction using a peak-to-background ratio optimization method to evaluate their monochromatic performance.

[0008] As described in the background section of this patent, the planar spectroscopic crystal optical path system is simple and intuitive in design; the crystal manufacturing process is simple, and the crystal yield is high, making it a common spectroscopic element for monochromators. However, the focusing characteristics of planar crystals are insufficient, causing many X-rays to be dispersed, resulting in insufficient X-ray intensity. The fully focusing hyperbolic curved crystal X-ray monochromator disclosed in this invention, based on the X-ray generation method, matching model, and monochromatization requirements, generates high-energy electrons powered by a high-voltage power supply within the X-ray tube. These high-energy electrons bombard the target material in the X-ray tube, generating corresponding X-ray excitation light. According to the hyperbolic curved crystal dispersion method, the excited X-rays pass through the hyperbolic curved crystal-based monochromator. X-rays conforming to Bragg's law are focused onto the Rowland circle after hyperbolic curved crystal diffraction, achieving monochromatization. Subsequently, the sample in the sample cell is irradiated, and the elements within the sample are irradiated by the monochromated X-rays, exciting characteristic X-ray fluorescence. According to the X-ray monochromatic performance evaluation method, the X-rays are received using a detector, and the received monochromatic X-rays after hyperbolic curved crystal diffraction are processed using a peak-to-background ratio optimization method to evaluate their monochromatic performance. If the monochromatic performance is unsatisfactory, the incident X-ray angle and intensity are adjusted according to the matching model and feedback information.

[0009] Existing monochromators using planar crystals suffer from low diffraction efficiency, resulting in insufficient X-ray intensity. The X-ray monochromator device of this invention, employing a fully focusing hyperbolic curved crystal as the spectroscopic crystal in the monochromator module, can focus X-ray excitation light incident at the Bragg angle onto a Rowland circle after reflection, exhibiting excellent focusing characteristics. This significantly improves the diffraction intensity compared to planar crystal diffraction, greatly enhancing the X-ray monochromatic efficiency. Furthermore, the peak-to-background ratio optimization method within the monochromatic evaluation module can remove background noise generated during photoelectric signal transmission, accurately evaluating the system's monochromatic performance.

[0010] The fully focusing hyperbolic curved crystal X-ray monochromatic device disclosed in this invention includes an X-ray generating module composed of a high-voltage power supply and an X-ray tube. The module generates high-energy electrons powered by the high-voltage power supply, which bombard the target material in the X-ray tube to generate corresponding X-ray excitation light. The incident angle and intensity of the X-rays generated by the X-ray generating module can be dynamically adjusted based on a matching model. It also includes a hyperbolic curved crystal spectrometer module, which diffracts the excited X-rays through the monochromator module, focusing the X-rays that conform to Bragg's law onto the Rowland circle to achieve X-ray monochromaticity. Finally, it includes an X-ray monochromaticity evaluation module, which consists of a detection module and an analysis module. The detection module receives the characteristic X-ray fluorescence emitted after the sample is irradiated and converts it into an electrical signal. The analysis module contains a peak-to-background ratio optimization method that processes the electrical signal output by the detection module, evaluates its monochromatic performance, and provides corresponding feedback.

[0011] In addition, the fully focused hyperbolic curved crystal X-ray monochromaticization method and apparatus disclosed in this invention also have the following additional technical features:

[0012] Furthermore, the monochromator uses a Cr target as the target material for the X-ray tube. A matching model is established based on the positional geometric relationship between the bent crystal and the tube. Based on the matching model, the bracket is adjusted to change the incident angle of the X-rays according to the monochromatic requirements. The voltage and current input of the high-voltage power supply are controlled by the controlled variable method to obtain the optimal incident X-ray intensity.

[0013] Furthermore, the monochromator constructs a matching model between the curvature radius of the hyperbolic curved crystal and the diffraction intensity. Incident X-rays are incident on the cylindrical curved surface of the hyperbolic curved crystal, greatly increasing the effective area of ​​the diffracting crystal surface. The incident light source is adjusted according to the curvature radius to ensure that the incident X-rays are parallel to the crystal cylinder on the focusing circle. Utilizing the Bragg spectroscopy principle, each incident ray satisfies the Bragg condition. Based on the symmetry of the Rowland focusing circle, each diffracted ray converges on a line parallel to the cylinder on the other side of the focusing circle, improving the hyperbolic curved crystal diffraction intensity. Employing two-dimensional hyperbolic crystal technology, by adjusting the curvature radius of the crystal in two different directions, the point source is diffracted and focused into a point-like spot that enters the detector window. When the crystal size is increased, it is not limited by the area of ​​the detector's incident window, and the diffraction intensity is proportional to the increase in crystal area.

[0014] Furthermore, the monochromator utilizes an efficient wavelet denoising algorithm to process noise, optimize the peak-to-background ratio, eliminate interference peaks, and better reflect the monochromatic performance of X-rays. Specifically, this includes: first, expanding the noisy spectral signal into a wavelet series using wavelet transform; calculating the processing threshold of the wavelet coefficients based on the wavelet coefficients; then, extracting important wavelet coefficients based on the threshold; and finally, reconstructing the denoised signal from the threshold-processed wavelet coefficients using inverse wavelet transform.

[0015] Furthermore, the monochromator establishes a fully focused hyperbolic curved crystal theoretical model. By calculating the crystal's curvature and X-ray diffraction intensity, a curvature radius conforming to the Rowland circle radius requirement is obtained. Cylindrical wafers of suitable size and thickness are obtained through two grinding processes. The ground crystal is then placed in a furnace for high-temperature hot bending, and the convex and concave dies and the crystal are quenched together in cold water. Finally, the bent wafer is glued to a copper or aluminum template to obtain a hyperbolic curved crystal with a suitable radius.

[0016] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0017] The accompanying drawings, which are included to provide a further understanding of the invention, form part of this invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute a limitation thereof.

[0018] In the attached diagram:

[0019] Figure 1 This is a flowchart of the fully focused hyperbolic curved crystal X-ray monochromator in this invention.

[0020] Figure 2 This is a block diagram of the fully focused hyperbolic curved crystal X-ray monochromator in this invention. Detailed Implementation

[0021] Referring to the accompanying drawings, the foregoing and other features of the present invention will become apparent from the following description. These embodiments are merely exemplary and not intended to limit the invention. To enable those skilled in the art to readily understand the principles and implementation methods of the invention, embodiments of the present invention are provided below. Figure 1 The working principle of the present invention will be explained using the fully focused hyperbolic curved crystal X-ray monochromator shown as an example.

[0022] Example 1:

[0023] In a fully focused hyperbolic curved crystal X-ray monochromator, as follows: Figure 1 The workflow shown includes the following steps:

[0024] High-energy electrons generated by a high-voltage power supply bombard the Cr target inside the X-ray tube, causing the Cr target to produce X-ray excitation light. The intensity of the excitation light is determined by a pre-established matching model.

[0025] The generated X-ray excitation light is incident on a fully focusing hyperboloid crystal. The X-rays diffract on the surface of the spectroscopic crystal, and the monochromatic X-rays that match the Bragg angle are focused on the Rowland circle. The incident angle of the excitation light is determined by a pre-established matching model.

[0026] The sample cell is placed into the optical path, and the sample is irradiated by focused monochromatic X-rays, causing the elements in the sample to emit characteristic X-ray fluorescence.

[0027] The excited characteristic X-ray fluorescence is received by the detection module in the monochromatization evaluation module and converted into an electrical signal, which is then transmitted to the analysis module. The analysis module extracts the spectral information through the built-in peak-to-background ratio optimization method and evaluates the monochromatization.

[0028] Determine if the monochromatic performance meets the standard. If the monochromatic performance does not meet the standard, the information is fed back to the matching model to adjust the intensity and incident angle of the X-ray excitation light; if the monochromatic performance meets the standard, the spectral information and count rate data are output.

[0029] The working principle of the present invention is further explained using the crystal bending process as an example, including the following steps:

[0030] Grind both sides. Take a crystal of appropriate thickness and grind it into a cylindrical sheet of uniform thickness on a convex and concave mold with radii of 2R and 2R+△R (△R is the crystal thickness). Then bend it into a cylindrical surface with a radius of R. The curvature of the lattice surface is 1 / 2R.

[0031] Grind one side of the planar crystal into a concave cylindrical surface with a radius of 2R. Then place the other side (the plane) in a concave mold with a radius of ZR+ΔR and bend it to make the plane bend into a curved surface. The curvature of the diffraction surface of the crystal is l / R, while the curvature of the lattice surface is 1 / 2R. Since the crystal is thick at both ends and thin in the middle, bending is relatively difficult and it is only suitable for short dimensions.

[0032] The polished cylindrical wafer is placed on a die of known radius and placed in a furnace at room temperature along with a punch and a load. It is then heated to 500°C at a rate of 150-200°C / hour.

[0033] Gently place the punch on the wafer, keep it at a constant temperature for half an hour, then add a load of 1-2 kg, and then keep it at a constant temperature for another 2-3 hours to make the curvature of the wafer match the die.

[0034] The furnace temperature is reduced at a rate of 30°C / hour. When the furnace temperature drops to 100°C, the punch and die and the crystal are placed together in cold water for quenching.

[0035] Use 502 glue to attach the bent wafer to a copper or aluminum template; otherwise, the bent wafer will tend to recover after a few weeks.

Claims

1. A method for X-ray monochromaticization of a fully focused hyperbolic curved crystal, characterized in that, include: Using a Cr target as the target material for the X-ray tube, a matching model is established based on the positional geometric relationship between the bent crystal and the tube. Based on the matching model, the support is adjusted to change the incident angle of the X-rays according to the monochromatic requirements. The voltage and current input of the high-voltage power supply are controlled by the controlled variable method to obtain the optimal X-ray intensity. X-rays emitted by a hyperbolic curved crystal diffraction X-ray tube are focused together, conforming to Bragg's law. A matching model between the curvature radius of the hyperbolic curved crystal and the diffraction intensity is constructed. X-rays are incident on the columnar curved surface of the hyperbolic curved crystal, greatly increasing the effective area of ​​the diffraction on the crystal surface. The incident light source is adjusted according to the curvature radius so that the X-rays are parallel to the crystal columnar surface on the focusing circle. Using the Bragg principle, each incident line satisfies the Bragg condition. Based on the symmetry of the Rowland focusing circle, each diffracted line converges on a line parallel to the columnar surface on the other side of the focusing circle, improving the diffraction intensity of the hyperbolic curved crystal. Using two-dimensional hyperbolic crystal technology, by adjusting the curvature radius of the crystal in two different directions, the point source is diffracted and focused into a point spot that enters the detector window. When the crystal size is increased, it is not limited by the area of ​​the detector incident window, and the diffraction intensity is proportional to the increase of the crystal area. X-rays are received using a detection module, and the monochromatic X-rays after hyperbolic crystal diffraction are processed by a peak-to-background ratio optimization method to evaluate their monochromatic performance. The method utilizes an efficient wavelet denoising algorithm to process noise, optimize the peak-to-background ratio, and eliminate interference peaks. Specifically, it involves: first, expanding the noisy spectral signal into wavelet coefficients through wavelet transform; then, calculating the processing threshold of the wavelet coefficients based on the wavelet coefficients; finally, extracting important wavelet coefficients based on the threshold; and then reconstructing the denoised signal from the threshold-processed wavelet coefficients through inverse wavelet transform.

2. A fully focused hyperbolic curved crystal X-ray monochromatic device based on the fully focused hyperbolic curved crystal X-ray monochromatic method of claim 1, characterized in that, include: The X-ray generating module, consisting of a high-voltage power supply and an X-ray tube, is used to generate X-rays with high diffraction intensity; the hyperbolic crystal diffraction module is used to diffract the X-rays emitted by the X-ray tube and focus the diffracted light that conforms to Bragg's law; the X-ray monochromatic evaluation module is mainly used to receive the monochromatic X-rays after hyperbolic crystal diffraction and then evaluate their monochromatic performance.

3. The fully focused hyperbolic curved crystal X-ray monochromatic device according to claim 2, characterized in that, A theoretical model for a fully focused hyperbolic curved crystal was established. By calculating the curvature of the crystal and the X-ray diffraction intensity, the radius of curvature that meets the requirements of the Rowland circle was obtained. Cylindrical wafers of different sizes and thicknesses were obtained through two grinding processes. The ground crystals were then placed in a furnace for high-temperature hot bending. The convex and concave dies and the crystals were quenched together in cold water. Finally, the bent wafers were glued to a copper or aluminum template to obtain a hyperbolic curved crystal spectrometer with a suitable radius.

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