X-ray beam preparation method and detector calibration method

Abstract

The invention discloses an X-ray beam preparation method and a detector calibration method. The X-ray beam preparation method comprises the following steps: 1) selecting an X-ray light tube of a corresponding target material according to the scale requirement of a detector; (2) preparing a multi-layer film element according to the energy of the selected X-ray light tube, wherein the multi-layer film element is used for diffracting X-rays output by the X-ray light tube; 3) placing the multilayer film element at a position which is a set distance away from the selected X-ray light tube, and adjusting the posture of the multilayer film element, so that the multilayer film element diffracts the X-rays output by the selected X-ray light tube; 4) moving the multilayer film element back and forth along the light beam direction, and determining the position with the largest diffraction spot and the strongest central spot as the final position of the multilayer film element; and 5) adjusting the roll angle and the swing angle of the multilayer film element, and taking the X-ray when the diffraction spot is strongest and maximum as the X-ray for detector scale calibration. The prepared X-ray beam is used for calibrating the detector, and the problems of scale and calibration of the advanced detector are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of synchrotron radiation and relates to an X-ray beam preparation method and a detector calibration method. Background Art

[0002] X-ray pixel array detectors are advanced detectors currently widely used in various X-ray diffraction, scattering and imaging. Before use, the threshold accuracy of each pixel and the consistency between pixels need to be calibrated. The prerequisite for successfully carrying out this work is to obtain a series of monochromatic lights with a single energy, a large area, a certain uniformity and a high flux.

[0003] In the past, three methods could be used: one was to directly use the monochromatic light generated by the synchrotron radiation source, the second was to directly use a conventional X-ray tube, and the third was to use a radioactive source.

[0004] As a major national scientific facility, synchrotron radiation sources are extremely limited and precious, primarily used to support cutting-edge scientific research or experiments requiring national significance, making them inconvenient to use. Furthermore, the synchrotron radiation beam has extremely low emittance and requires secondary beam expansion through scatterers. However, this beam spot cannot meet uniformity requirements, making it unsuitable for detector calibration.

[0005] Conventional X-ray tubes can emit a large-angle uniform beam, but this directly generated beam has the K α , K β In addition, there is a continuous background, which affects the quality of detector scale and calibration and is not suitable for detector calibration.

[0006] The intensity of the radiation source is too low and the spectrum has a certain structure, which makes it unsuitable for detector calibration. Summary of the Invention

[0007] In response to the problems existing in the prior art, the purpose of the present invention is to provide an X-ray beam preparation method and a detector calibration method. The present invention can obtain a large-area, uniform, single-energy and high-intensity X-ray beam to meet the calibration requirements of detectors such as X-ray two-dimensional pixel array detectors.

[0008] The technical solution of the present invention is:

[0009] A method for preparing an X-ray beam, comprising the steps of:

[0010] 1) Select the X-ray tube corresponding to the target material according to the detector calibration requirements;

[0011] 2) preparing a multilayer film element according to the energy of the selected X-ray tube, for diffracting the X-rays output by the selected X-ray tube;

[0012] 3) placing the multilayer film element at a set distance from the selected X-ray tube, and adjusting the posture of the multilayer film element according to the selected position so that the multilayer film element diffracts the X-rays output by the selected X-ray tube;

[0013] 4) moving the multilayer film element forward and backward along the direction of the light beam, and determining the position where the diffraction spot is the largest and the central spot is the strongest as the final position of the multilayer film element;

[0014] 5) Adjusting the roll angle and the swing angle of the multilayer film element, and using the X-ray when the diffraction spot is strongest and largest as the X-ray for detector calibration.

[0015] Furthermore, the method for preparing the multilayer membrane element is:

[0016] 21) Selecting the fluorescence characteristic peak of the target element of the X-ray tube to determine the target wavelength λ;

[0017] 22) Selecting materials for preparing multilayer film elements based on the target wavelength λ and the coating conditions;

[0018] 23) Determine the incident angle of each point on the incident plane of the multilayer film element based on the optical path geometry; then calculate the coating parameters at different positions of the multilayer film element based on the Bragg formula and the refraction-corrected Bragg equation;

[0019] 24) A multilayer film element is prepared according to the coating parameters.

[0020] Furthermore, the multilayer film element is formed by alternately plating materials with high and low atomic numbers.

[0021] Furthermore, according to the coating parameters, a magnetron sputtering coating device is used to prepare a gradient-distributed multilayer film element.

[0022] Furthermore, the position of the multilayer membrane element is adjusted by a posture adjustment mechanism, and the roll angle and the swing angle of the multilayer membrane element are adjusted.

[0023] A detector calibration method, comprising the steps of:

[0024] 1) placing the detector under beams of different energies to perform threshold scans, and obtaining threshold scan curves corresponding to the respective energies; the beams are the X-rays produced by the above method;

[0025] 2) Determining the optimal threshold value of each pixel at each energy in combination with the noise curve of each pixel in the detector, and generating a corresponding calibration table;

[0026] 3) Load the scale back into the detector to complete the calibration of the detector.

[0027] The present invention uses a conventional X-ray tube in combination with a multilayer film element, taking advantage of its monochromatic diffraction function, as well as its wide energy band and easy adjustment characteristics, to obtain monochromatic light with a single energy, a large area, a certain uniformity and a high flux, thereby making the calibration work of detectors such as X-ray two-dimensional pixel array detectors simple and easy.

[0028] The present invention utilizes gradient multilayer film elements in combination with a wide-angle X-ray machine to obtain a single-energy, wide-angle, uniform and high-intensity X-ray beam.

[0029] The present invention also provides a method for calibrating and calibrating a pixel array detector using a single energy, large angle, uniform and high intensity X-ray beam.

[0030] The advantages of the present invention are as follows:

[0031] Gradient multilayer film elements combined with large-angle emission X-ray machines can obtain single-energy, large-angle, uniform and high-intensity X-ray beams, thereby solving the problem of advanced detector scale and calibration. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a flow chart of the X-ray beam preparation method.

[0033] Figure 2 This is a design diagram of a multilayer membrane element using a parabolic substrate as an example. DETAILED DESCRIPTION

[0034] The present invention will be described in further detail below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0035] The X-ray beam preparation method of the present invention is as follows: Figure 1 As shown, the steps include:

[0036] 1. Selection of conventional X-ray tubes

[0037] According to the detector calibration requirements, select X-ray tubes with different target materials, such as chromium target tubes (the strongest characteristic energy is 5.41keV), copper target tubes (the strongest characteristic energy is 8.04keV), molybdenum target tubes (the strongest characteristic energy is 17.44keV), etc.

[0038] 2. Multilayer membrane element:

[0039] Based on the selected X-ray tube energy, a multilayer film element is designed and prepared to achieve a large emission angle and a uniform monochromatic beam. Taking a planar multilayer film element as an example, the specific design and preparation process is as follows:

[0040] Step 1: Based on the target element of the X-ray tube used, select its fluorescence characteristic peak as the target energy (wavelength λ).

[0041] Step 2: Based on the target energy and coating conditions, select the appropriate multilayer film component material, which is usually made by alternating the coating of two materials with different atomic numbers, high and low.

[0042] Step 3: Determine the incident angle of each point on the incident plane of the multilayer film element based on the optical path geometry. Calculate the coating parameters at different positions of the multilayer film element based on the Bragg formula and the refraction-corrected Bragg equation.

[0043] Step 4: Based on the design parameters, a magnetron sputtering coating device is used to precisely control the motion of the shielding plate (MASK) to ultimately obtain a multilayer film element with a gradient distribution.

[0044] If focusing is required, the multilayer film substrate is designed as an ellipsoid; if collimation is required, the multilayer film substrate is designed as a parabola. The design of the multilayer film needs to be adjusted accordingly based on the design of the substrate. Figure 2 As shown, taking the base as a parabola as an example, assuming point A is the light source, and points B, C, and D are the points of the multilayer film on the parabola. The gradient multilayer film is divided into several segments according to the requirements, and the period thickness of each segment is replaced by the period thickness calculated at a certain point on the segment. The following is the calculation method of the period thickness at a certain point:

[0045] First, calculate the angle between the line connecting the light source and each point on the multilayer film and the tangent line at that point, for example, the angle between line AB and the tangent line at point B. This angle is the angle of incidence at each point on the multilayer film. Substituting the calculated angle of incidence into the refractive index-corrected Bragg equation, the periodic thickness of the multilayer film at each point can be calculated. The calculated periodic thickness of each segment is then combined to form the designed periodic thickness of the focusing multilayer film.

[0046] The calculation method for focusing multilayer films is similar, except that the parabola is replaced by an ellipsoid.

[0047] 3. Calibration system construction:

[0048] Step 1: Place the multilayer film element at the selected design distance from the X-ray tube.

[0049] Step 2: Determine the zero angle of the multilayer film element, that is, the angle when the multilayer film surface is parallel to the center of the light beam.

[0050] Step 3: Rotate the multilayer film element to the specified Bragg diffraction angle position through the posture adjustment mechanism.

[0051] Step 4: Move the multi-layer film element forward and backward through the posture adjustment mechanism. The position where the light spot is the largest and the central light spot is the strongest is the final position of the multi-layer film element.

[0052] Step 5: Adjust the roll angle and swing angle of the multilayer film element in turn, iterate repeatedly, and finally obtain the strongest and largest light spot.

[0053] 4. Detector calibration:

[0054] Move the detector into a large, uniform, monochromatic beam and calibrate the detector according to conventional procedures.

[0055] Step 1: Place the detector under beams of different energies and perform threshold scanning to obtain the threshold scanning curves corresponding to each energy.

[0056] Step 2: Determine the optimal threshold for each pixel at each energy based on the noise curve of each pixel and generate the corresponding scale table.

[0057] Step 3: Load the scale back into the detector to complete the detector calibration.

[0058] While specific embodiments of the present invention have been disclosed for illustrative purposes, intended to facilitate understanding and implementation of the present invention, those skilled in the art will appreciate that various substitutions, variations, and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the present invention should not be limited to the disclosure of the preferred embodiments, and the scope of protection claimed in the present invention shall be determined by the scope of the claims.

Claims

1. A method for preparing an X-ray beam, comprising the steps of: 1) Select the X-ray tube corresponding to the target material according to the detector calibration requirements; 2) preparing a multilayer film element according to the energy of the selected X-ray tube, for diffracting the X-rays output by the selected X-ray tube; 3) placing the multilayer film element at a set distance from the selected X-ray tube, and adjusting the posture of the multilayer film element according to the selected position so that the multilayer film element diffracts the X-rays output by the selected X-ray tube; 4) moving the multilayer film element forward and backward along the direction of the light beam, and determining the position where the diffraction spot is the largest and the central spot is the strongest as the final position of the multilayer film element; 5) Adjusting the roll angle and the swing angle of the multilayer film element, and using the X-ray when the diffraction spot is strongest and largest as the X-ray for detector calibration.

2. The method according to claim 1, characterized in that The method for preparing the multilayer membrane element is: 21) Selecting the fluorescence characteristic peak of the target element of the X-ray tube to determine the target wavelength λ; 22) Selecting materials for preparing multilayer film elements based on the target wavelength λ and the coating conditions; 23) Determine the incident angle of each point on the incident plane of the multilayer film element based on the optical path geometry; then calculate the coating parameters at different positions of the multilayer film element based on the Bragg formula and the refraction-corrected Bragg equation; 24) A multilayer film element is prepared according to the coating parameters.

3. The method according to claim 2, characterized in that The multilayer film element is formed by alternately plating two materials with different atomic numbers, high and low.

4. The method according to claim 2 or 3, characterized in that According to the coating parameters, a magnetron sputtering coating device is used to prepare a gradient-distributed multilayer film element.

5. The method according to claim 1, 2 or 3, characterized in that: The position of the multilayer membrane element is adjusted by a posture adjustment mechanism, and the roll angle and the swing angle of the multilayer membrane element are adjusted.

6. A detector calibration method, comprising the steps of: 1) placing the detector under beams of different energies to perform threshold scans, respectively, to obtain threshold scan curves corresponding to the respective energies; the beams being the X-rays produced and output by the method of claim 1; 2) Determining the optimal threshold value of each pixel at each energy in combination with the noise curve of each pixel in the detector, and generating a corresponding calibration table; 3) Load the scale back into the detector to complete the calibration of the detector.

Images