A system and method for calibrating photon energy of synchrotron radiation beam line

Abstract

The present invention relates to a system for calibrating the photon energy of a synchrotron radiation beam line, comprising a double-crystal monochromator and a spectroscopic crystal arranged in sequence along the direction of the optical path, wherein the spectroscopic crystal is arranged on a precision turntable, wherein the precision turntable is connected to a vertical translation stage and a horizontal translation stage in sequence, wherein a first detector is provided directly in front of the spectroscopic crystal, and a second detector is provided directly above the spectroscopic crystal. The present invention utilizes the intrinsic diffraction of crystals under dispersion conditions to achieve the requirements for high-precision calibration of X-beam photon energy. According to the Bragg crystal diffraction formula and utilizing a family of crystal diffraction surfaces, the present invention can realize the calibration of multiple X-photon energies, thus realizing multiple uses of one crystal. In addition, the mechanical structure of the present invention is easy to realize, and the spectroscopic crystal structure is cleverly designed, which can accurately realize the switching between single crystal diffraction and double crystal diffraction, thereby realizing rapid and high-precision calibration of X-beam photon energy.

Description

Technical Field

[0001] The present invention relates to the technical field of synchrotron radiation beam lines, and more specifically to a system and method for calibrating photon energy of synchrotron radiation beam lines. Background Art

[0002] Synchrotron radiation facilities use high-quality electron beams to generate highly collimated, high-brightness photon beams ranging from infrared to X-ray spectra. The hard X-band beamline uses a crystal monochromator as a beam modulation device, and the diffracted beam of its spectroscopic crystal is monochromatic light that meets the requirements of scientific experiments. In synchrotron radiation spectroscopy and diffraction experimental methods, the beam energy is used as a benchmark to test the structure and performance of the sample. Therefore, the calibration of photon energy is crucial, and an efficient photon energy calibration method needs to be established.

[0003] At present, the most commonly used method for calibrating X-ray photon energy is to measure the K absorption edge of a specific element. When the photon energy of X-rays is close to the binding energy of K-shell electrons, photons can excite electrons from low bound states, and under this condition, the absorption coefficient of the element suddenly increases; when the photon energy of X-rays is greater than the K absorption edge, the absorption coefficient of the element suddenly decreases. The sudden change in the absorption coefficient near the K edge of an element corresponds to a specific energy, so measuring the K absorption edge of a specific element can be used for photon energy calibration.

[0004] However, the absorption edge of an element has a natural width. For example, the natural width of the K edge of the commonly used Cu element is about 1.55 eV. Therefore, there is a certain deviation in calibrating the photon energy using the absorption edge of the element. This method cannot meet the requirements of experiments with high accuracy in photon energy calibration. Summary of the invention

[0005] In order to solve the above problems in the prior art, the present invention provides a system and method for calibrating the photon energy of a synchrotron radiation beam line, which uses the diffraction characteristics of a spectroscopic crystal for calibration and has a simple structure and high precision.

[0006] The present invention provides a system for calibrating photon energy of a synchrotron radiation beam line, comprising a double-crystal monochromator and a spectroscopic crystal arranged in sequence along an optical path, wherein the spectroscopic crystal is arranged on a precision turntable, which is connected in sequence to a vertical translation stage and a horizontal translation stage, a first detector is provided directly in front of the spectroscopic crystal, and a second detector is provided directly above the spectroscopic crystal.

[0007] Furthermore, the spectroscopic crystal has a first diffraction surface and a second diffraction surface which are perpendicular to each other, and a through light outlet is provided at the connection between the top surface of the spectroscopic crystal and the second diffraction surface.

[0008] Furthermore, the first detector is arranged above the light outlet to receive the light beam emitted from the light outlet; and the second detector is arranged in front of the second diffraction surface to receive the light beam emitted from the second diffraction surface.

[0009] Furthermore, both the first detector and the second detector are photodiode detectors.

[0010] Furthermore, the precision of the precision turntable is 0.01 arcsec, and the precision of the vertical translation stage and the horizontal translation stage is 2 μm.

[0011] The present invention also provides a method for calibrating photon energy of a synchrotron radiation beam line, comprising:

[0012] Step S1, providing the above-mentioned system for calibrating photon energy of a synchrotron radiation beam line, and adjusting the Bragg angle of a double-crystal monochromator according to the Bragg diffraction law so as to make the energy of an outgoing light beam of the double-crystal monochromator close to the photon energy to be calibrated;

[0013] Step S2, using a vertical translation stage and a horizontal translation stage to adjust the position of the spectroscopic crystal, so that the output light beam of the double-crystal monochromator is irradiated to the first diffraction surface of the spectroscopic crystal, a primary diffraction is generated on the first diffraction surface, and the primary diffracted light beam is incident on the first detector from the light outlet;

[0014] Step S3, the first detector scans the primary diffraction light beam to obtain the primary diffraction rocking curve, and simultaneously rotates the precision turntable to adjust the Bragg angle of the spectroscopic crystal to the peak of the primary diffraction rocking curve;

[0015] Step S4, using the horizontal translation stage to adjust the horizontal position of the spectroscopic crystal so that the outgoing light beam of the double-crystal monochromator is irradiated to the first diffraction surface and emitted from the second diffraction surface to generate two diffractions, and the two diffracted light beams are incident on the second detector;

[0016] Step S5, the second detector scans the twice diffracted light beams to obtain the twice diffracted rocking curves, and simultaneously rotates the precision turntable to record the peak values ​​of the twice diffracted rocking curves;

[0017] Step S6, adjusting the Bragg angle of the double-crystal monochromator, and rotating the precision turntable in the same direction to change the energy of the output light beam of the double-crystal monochromator by 0.1 eV, and simultaneously acquiring the rocking curves of the two diffractions, and recording the peak values ​​of the rocking curves of the two diffractions;

[0018] Step S7, repeating step S6 until the Bragg angle of the double-crystal monochromator corresponding to the maximum peak of the rocking curve of the two diffractions is found, so as to achieve high-precision calibration of the photon energy of the synchrotron radiation beam line.

[0019] The present invention utilizes the intrinsic diffraction of the crystal under dispersion conditions to achieve the requirement of high-precision (0.1 eV) calibration of the X-beam photon energy. According to the Bragg crystal diffraction formula and by utilizing the crystal diffraction surface family, the present invention can realize the calibration of multiple X-photon energies, thus achieving multiple uses of one crystal. In addition, the mechanical structure of the present invention is easy to realize, and the design of the spectroscopic crystal structure is ingenious, which can accurately realize the switching between single crystal diffraction and double crystal diffraction, thus achieving rapid and high-precision calibration of the X-beam photon energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the structure of a system for calibrating photon energy of a synchrotron radiation beam line according to the present invention.

[0021] Figure 2 yes Figure 1 Schematic diagram of the structure of the medium-spectral splitter crystal.

[0022] Figure 3 yes Figure 2 Side view of the spectroscopic crystal. DETAILED DESCRIPTION

[0023] The preferred embodiments of the present invention are given below in conjunction with the accompanying drawings and described in detail.

[0024] like Figure 1 As shown, the system for calibrating photon energy of synchrotron radiation beam line provided by the present invention comprises a double-crystal monochromator 1 and a spectroscopic crystal 2 arranged in sequence along the optical path, wherein the spectroscopic crystal 2 is arranged on a precision turntable 3, and the precision turntable 3 is connected to a vertical translation stage 4 and a horizontal translation stage 5 in sequence, a first detector 61 is provided directly in front of the spectroscopic crystal 2, and a second detector 62 is provided directly above the spectroscopic crystal 2.

[0025] like Figure 2 and Figure 3 As shown, the spectroscopic crystal 2 is cut from a complete piece of single crystal silicon, and has a first diffraction surface 21 and a second diffraction surface 22 that are perpendicular to each other. A through light outlet 23 is provided at the connection between the top surface of the spectroscopic crystal 2 and the second diffraction surface 22. In addition, a first detector 61 is arranged above the light outlet 23 to receive the light beam emitted from the light outlet 23; and a second detector 62 is arranged in front of the second diffraction surface 22 to receive the light beam emitted from the second diffraction surface 22. It should be noted that the first detector 61 and the second detector 62 are of the same model and do not block the incident light beam. In this embodiment, the first detector 61 and the second detector 62 are both photodiode detectors.

[0026] Due to the structure of the spectroscopic crystal 2, the position of the spectroscopic crystal 2 is changed by using the vertical displacement stage 4 and the horizontal displacement stage 5, so that the synchrotron radiation beam line can be diffracted once on the first diffraction surface 21, and the light beam diffracted once is incident on the first detector 61 through the light outlet 23, and the first detector 61 detects the photocurrent generated by the single diffraction in real time; the synchrotron radiation beam line can also be diffracted twice through the first diffraction surface 21 and the second diffraction surface 22, and the light beam diffracted twice is incident on the second detector 62, and the second detector 62 detects the photocurrent generated by the double diffraction in real time, so as to calibrate the photon energy of the incident synchrotron radiation beam line.

[0027] Considering the crystal structure, manufacturing process and photon energy range, the surface crystal orientation of the spectroscopic crystal 2 can be 400, 800, 220, 440, 880, and the corresponding photon energies to be calibrated are 6.457keV, 12.914keV, 4.566keV, 9.132keV, and 18.263keV, respectively. In this embodiment, the precision of the precision turntable 3 is 0.01arcsec, and the precision of the vertical displacement stage 4 and the horizontal displacement stage 5 is 2μm to ensure mechanical precision. It should be noted that the photon energy to be calibrated is required by the synchrotron radiation line station experiment and is a known quantity. The purpose of the present invention is to achieve photon energy calibration with an accuracy better than 0.1eV.

[0028] The spectroscopic crystal 2 of the present invention uses a first diffraction surface 21 and a second diffraction surface 22 that are perpendicular to each other to form a dispersion configuration, and the diffraction of the high index surface ensures the accuracy of the calibrated photon energy. Since the primary diffraction does not require high photon energy, the range of photon energy can be preliminarily calibrated through the primary diffraction of the crystal, thereby improving the operational efficiency of photon energy calibration.

[0029] Therefore, the present invention also provides a method for calibrating photon energy of a synchrotron radiation beam line, the method comprising the following steps:

[0030] Step S1, providing the above-mentioned system for calibrating the photon energy of a synchrotron radiation beam line, adjusting the Bragg angle of the double-crystal monochromator 1 according to the Bragg diffraction law, so as to make the energy of the output light beam of the double-crystal monochromator 1 close to the photon energy to be calibrated. At this time, the photon energy of the output light beam of the double-crystal monochromator 1 easily satisfies the first diffraction of the crystal.

[0031] Step S2, using the vertical translation stage 4 and the horizontal translation stage 5 to adjust the position of the spectroscopic crystal 2, so that the outgoing light beam of the double crystal monochromator 1 is irradiated to the first diffraction surface 21 of the spectroscopic crystal 2, and a first diffraction is generated on the first diffraction surface 21, and the first diffracted light beam is incident on the first detector 61 from the light outlet 23.

[0032] In step S3, the first detector 61 scans the first diffraction light beam to obtain the rocking curve of the first diffraction of the spectroscopic crystal 2, and then rotates the precision turntable 3 to adjust the Bragg angle of the spectroscopic crystal 2 (i.e., the angle between the outgoing light beam of the double-crystal monochromator 1 and the first diffraction surface 21) to the peak value of the rocking curve of the first diffraction, thereby preliminarily locking the range of the photon energy to be calibrated.

[0033] Step S4, using the horizontal displacement stage 5 to adjust the horizontal position of the spectroscopic crystal 2, so that the outgoing light beam of the double crystal monochromator 1 is irradiated to the first diffraction surface 21 and emitted from the second diffraction surface 22 to generate two diffractions, and the two diffracted light beams are incident on the second detector 62.

[0034] It should be noted that the diffraction angles of the first diffraction and the second diffraction are both 45° to ensure horizontal incidence and horizontal emission of the light beam, and there is a certain height difference to avoid blocking the incident light beam, which is beneficial to the detection of photon signals.

[0035] Step S5 , the second detector 62 scans the twice diffracted light beams to obtain the rocking curves of the twice diffracted light beams of the spectroscopic crystal 2 , and simultaneously rotates the precision turntable 3 to record the peak values ​​of the twice diffracted rocking curves.

[0036] Step S6, adjust the Bragg angle of the double crystal monochromator 1, and rotate the double crystal monochromator 1 in the same direction to change the energy of its output light beam by 0.1 eV, and at the same time obtain the rocking curves of the two diffractions of the spectroscopic crystal 2, and record the peak values ​​of the rocking curves of the two diffractions. In this way, the influence of the mechanical return difference can be eliminated.

[0037] Step S7, repeat step S6 until the Bragg angle of the double crystal monochromator 1 corresponding to the maximum peak of the rocking curve of the two diffractions is found, so as to realize the high-precision calibration of the photon energy of the synchrotron radiation beam line. Specifically, repeat step S6 5 to 10 times to find the maximum peak of the rocking curve of the two diffractions of the spectroscopic crystal. At this time, the photon energy of the light beam emitted at the angle of the double crystal monochromator 1 is the photon energy to be calibrated, so as to realize the high-precision calibration of the photon energy of the synchrotron radiation beam line.

[0038] The diffraction of X-ray beams can be divided into achromatic and dispersive arrangements. The dispersive arrangement means that the diffraction surfaces are not arranged in parallel, and the incident angles of the light on the central axis of the incident beam are equal on the two crystals, while the incident angles of the incident light beam deviating from the central axis on the two diffraction surfaces are unequal. The bandwidth of the outgoing light beam in the crystal dispersive arrangement is equivalent to the intrinsic Darwin bandwidth of the crystal, ensuring the accuracy of the outgoing photon energy. The spectroscopic crystal diffraction of the present invention has extremely strict requirements on the incident photon energy (within 0.1eV error). The maximum peak value of the rocking curve means that the incident photon energy reaches the optimal diffraction condition, thereby realizing high-precision photon energy calibration.

[0039] The present invention has the following beneficial effects:

[0040] 1) The present invention uses naturally mutually perpendicular crystal planes as diffraction planes, and utilizes the principle of crystal intrinsic diffraction and crystal plane dispersion configuration, so that the bandwidth of the output light after two diffractions approaches the intrinsic Darwin bandwidth, ensuring the high accuracy of X-beam photon energy calibration;

[0041] 2) The present invention can pre-lock the X-beam photon energy range through a crystal diffraction through the design of the light outlet, and then perform more precise calibration, which is convenient for practical operation;

[0042] 3) The present invention can realize the calibration of various X-beam photon energies by using the crystal diffraction surface family based on the Bragg crystal diffraction formula;

[0043] 4) The mechanical structure of the present invention is easy to implement, and includes a rotating table and two translation tables. By adjusting the translation tables, the switching between single crystal diffraction and double crystal diffraction can be accurately realized, thereby realizing the calibration of X-beam photon energy.

[0044] The above is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. The above embodiment of the present invention can also be modified in various ways. That is, all simple, equivalent changes and modifications made according to the claims and the description of the present invention fall within the scope of protection of the claims of the present invention. The contents not described in detail in the present invention are all conventional technical contents.

Claims

1. A system for calibrating photon energy of synchrotron radiation beamline, characterized in that: It includes a double-crystal monochromator and a spectroscopic crystal arranged in sequence along the optical path, the spectroscopic crystal is arranged on a precision turntable, the precision turntable is connected to a vertical displacement stage and a horizontal displacement stage in sequence, a first detector is arranged in front of the spectroscopic crystal, and a second detector is arranged above the spectroscopic crystal; The spectroscopic crystal has a first diffraction surface and a second diffraction surface which are perpendicular to each other, and a through light outlet is provided at the connection between the top surface of the spectroscopic crystal and the second diffraction surface; The first detector is arranged above the light outlet to receive the light beam emitted from the light outlet; the second detector is arranged in front of the second diffraction surface to receive the light beam emitted from the second diffraction surface.

2. The system for synchrotron radiation beamline photon energy calibration according to claim 1, characterized in that: The first detector and the second detector are both photodiode detectors.

3. The system for synchrotron radiation beamline photon energy calibration according to claim 1, characterized in that: The precision of the precision turntable is 0.01 arcsec, and the precision of the vertical translation stage and the horizontal translation stage is 2 μm.

4. A method for calibrating photon energy of a synchrotron radiation beamline, characterized in that: include: Step S1, providing a system for calibrating photon energy of a synchrotron radiation beam line as described in any one of claims 1 to 3, and adjusting the Bragg angle of a double-crystal monochromator according to the Bragg diffraction law so as to make the energy of an output light beam of the double-crystal monochromator close to the photon energy to be calibrated; Step S2, using a vertical translation stage and a horizontal translation stage to adjust the position of the spectroscopic crystal, so that the output light beam of the double-crystal monochromator is irradiated to the first diffraction surface of the spectroscopic crystal, a primary diffraction is generated on the first diffraction surface, and the primary diffracted light beam is incident on the first detector from the light outlet; Step S3, the first detector scans the primary diffraction light beam to obtain the primary diffraction rocking curve, and simultaneously rotates the precision turntable to adjust the Bragg angle of the spectroscopic crystal to the peak of the primary diffraction rocking curve; Step S4, using the horizontal translation stage to adjust the horizontal position of the spectroscopic crystal so that the outgoing light beam of the double-crystal monochromator is irradiated to the first diffraction surface and emitted from the second diffraction surface to generate two diffractions, and the two diffracted light beams are incident on the second detector; Step S5, the second detector scans the twice diffracted light beams to obtain the twice diffracted rocking curves, and simultaneously rotates the precision turntable to record the peak values ​​of the twice diffracted rocking curves; Step S6, adjusting the Bragg angle of the double-crystal monochromator, and rotating the precision turntable in the same direction to change the energy of the output light beam of the double-crystal monochromator by 0.1 eV, and simultaneously acquiring the rocking curves of the two diffractions, and recording the peak values ​​of the rocking curves of the two diffractions; Step S7, repeating step S6 until the Bragg angle of the double-crystal monochromator corresponding to the maximum peak of the rocking curve of the two diffractions is found, so as to achieve high-precision calibration of the photon energy of the synchrotron radiation beam line.

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