Monochromator preparation method and monochromator

Abstract

The invention discloses a monochromator preparation method and a monochromator, and belongs to the technical field of synchrotron radiation. The method comprises a crystal polishing step, a step of calibrating an intersection line of a crystal lattice surface and the crystal surface and cutting to enable the calibrated crystal lattice surface and the crystal surface to be approximately parallel, a step of polishing the crystal surface to enable the crystal surface to be completely parallel to the crystal lattice surface, a bonding step and a detection step, and the monochromator is prepared by using the method. According to the invention, a bonding technology of two crystals with perfect surface polishing and a high-precision polishing method of the crystals are utilized to prepare a bonding type channel-cut monochromator device capable of being used for perfect X-ray imaging, and the problems of stability and non-uniform light beam distribution in an existing monochromator are solved.

Description

Technical Field

[0001] The present invention relates to the field of synchrotron radiation technology, and in particular to a method for preparing a monochromator and a monochromator. Background Art

[0002] Synchrotron radiation is an X-ray source with high coherence and high energy characteristics. It has characteristics that traditional X-ray sources do not have, such as high penetration, high spatial resolution, and high contrast. Therefore, it is increasingly widely used in various scientific research fields and industrial applications. With the improvement of light source performance, synchrotron radiation also plays an important role in solving some scientific and technological problems.

[0003] In order to ensure the full utilization of coherent light sources, all downstream optical components must meet extremely demanding conditions, especially the most widely used crystal components, including monochromators, spectrometers, analytical crystals, etc. Compared with other components, the diffraction of crystal optical components has a more complex effect on beamline coherence. Previously, various light sources only considered the process use at the usage level, but the improvement of user research level and the high quality of the fourth-generation light source have put forward higher and more complex requirements for crystals, and also provided an opportunity for the study of the influence of crystals on optical properties.

[0004] Monochromator is one of the most common optical devices in synchrotron radiation. Crystal is the core component of monochromator. Its function is to separate monochromatic light of specific wavelength from the white light of synchrotron radiation. Generally, continuous diffraction of two crystals is used to keep the transmission direction of the outgoing light unchanged. Due to the high power of synchrotron radiation, the first crystal of the double crystal monochromator needs to be cooled. The mechanical vibration caused by the cooling fluid will change the parallelism between the two crystals, resulting in unstable intensity and position of the outgoing X-rays, which directly affects the quality of the experimental results.

[0005] When high-energy imaging is required in the fields of paleontology, medicine, biology, etc., crystals with higher index surfaces are used, which have higher resolution and are more susceptible to external influences. Although the current acquisition technology can ensure the high quality of each projected image, the phase difference and uneven distribution of light intensity caused by the unstable light intensity will make the quality of a group of projected images uneven, ultimately resulting in the degradation or even destruction of the reconstructed image quality. In addition, the high-energy monochromator used in ultra-high resolution experiments (such as inelastic and resonant scattering experiments) has higher requirements for the stability of the entire experimental system. In order to solve the problem of temperature differences and vibrations between different crystals, scientists often need a special mechanical system to connect the two crystals together. At the same time, the two crystals need to be kept at the same temperature for a long time before the experiment can be carried out, which greatly limits the efficiency of the experiment and increases the cost.

[0006] In order to meet the requirements of stability, the researchers designed an integrated slotted monochromator. A slotted monochromator (channel-cut) refers to a monochromator in which a channel is machined on the same crystal and the two side walls of the channel are used as parallel diffraction surfaces. Due to the integrated structure of the slotted monochromator, compared with the structure of the traditional double-flat crystal monochromator, it is less affected by the vibration of the cooling device and has obvious advantages in stability. Therefore, the slotted monochromator has been widely used in some conventional experiments. Although the slotted monochromator has a very obvious stability advantage, the quality of the crystal working surface prepared by chemical corrosion alone cannot meet the requirements of the experiment. Therefore, it is necessary to polish the inner working surface of the slotted monochromator crystal. Since the two parallel diffraction surfaces of the slotted monochromator are inside the crystal, conventional surface grinding methods cannot be applied and cannot guarantee that the diffraction surface has good quality. Especially for monochromators with a slotted crystal spacing of less than 5 mm, due to the narrow space, it is difficult for the working surface to move irregularly relative to the polishing material / fixture, and the required crystal processing accuracy cannot be achieved.

[0007] In addition, the two working surfaces of the grooved crystal are in perfect parallelism because they are on the same piece of crystal, which leads to the problem of high-order harmonics when diffraction occurs. This cannot meet the resolution requirements of high-resolution experiments. For this reason, an additional harmonic suppression mirror needs to be added, which makes the optical path more complicated and destroys the efficiency and quality of the experiment. Summary of the invention

[0008] 1. Technical problem to be solved by the invention

[0009] The existing monochromators cannot meet the high quality requirements of images under high resolution, while the grooved monochromators that can meet the high quality requirements are difficult to process and their application optical paths are complex, which cannot meet the existing use requirements of monochromators. The present invention provides a monochromator preparation method and a monochromator, which are used to manufacture a monochromator that combines the easy processing and simple optical path characteristics of traditional monochromators and the high stability characteristics of grooved monochromators.

[0010] 2. Technical solution

[0011] In order to achieve the above object, the technical solution provided by the present invention is:

[0012] The present invention provides a method for preparing a monochromator, the steps of which are:

[0013] Step 1: Perform stress-free crystal polishing on the monochromator crystal to obtain two monochromator crystals with high surface accuracy;

[0014] Step 2: measure the angle between the lattice plane and the crystal surface of each monochromator crystal, and calibrate the intersection line between the lattice plane and the crystal surface; and when the cutting device cuts the crystal, rotate the monochromator crystal at a certain angle for horizontal cutting, so that the lattice plane and the crystal surface are roughly parallel;

[0015] Step 3: further modify the crystal surface to make it completely parallel to the lattice plane;

[0016] Step 4: Bond the two monochromator crystals so that the lattice planes of the two monochromator crystals are parallel;

[0017] Step 5: Perform quality inspection on the grooved monochromator formed after bonding.

[0018] As a further improvement of the present invention, in the step 1, the mechanical cutting stress layer is firstly removed by etching with a mixture of HNO3 and HF, and then a plane is ground out using an abrasive and a grinding wheel to complete the flatness trimming of the crystal surface; then the surface roughness and flatness are optimized; and then the crystal surface is polished.

[0019] As a further improvement of the present invention, during polishing, X-ray diffraction technology is used to detect the diffraction situation to ensure that there is no processing stress on the surface of the crystal and a perfect image after the final polishing stage; finally, the magnification effect of the beveled crystal is used to perform a morphology test to detect the diffraction quality of the test crystal.

[0020] As a further improvement of the present invention, in the step 2, a composite detection method of x-ray diffraction and optical measurement is used to achieve angle measurement between the lattice plane and the surface at the arc second level, and the intersection line of the lattice plane and the crystal surface is calibrated; then, mutually perpendicular X and Y directions are determined on the crystal surface as reference axes, and according to the angle difference between the intersection line of the lattice plane and the crystal surface and the X direction, the monochromator crystal is rotated until the intersection line of the lattice plane and the crystal surface coincides with the X direction, and finally positioning cutting is performed along the X direction.

[0021] As a further improvement of the present invention, in the step three, a polishing disk is used to correct the crystal surface, and the crystal orientation deviation of the crystal is adjusted by uneven pressure; the pressure distribution on the crystal is adjusted by a counterweight to ensure that the pressure in the direction of the intersection line of the lattice plane and the crystal surface is evenly distributed, and the pressure in the direction perpendicular to it is gradient distributed; the Preston formula is used to calculate the processing rate and processing time for the final required surface angle accuracy.

[0022] As a further improvement of the present invention, in the step four, the pressure distribution at the bonding point under the condition of simulated clamp pressure is first analyzed and the clamp is made; then, with the help of pressure test paper, by applying different pressures, the pressure distribution data on the pressure test paper is read, the pressure size and distribution uniformity are observed, and the pressure size and temperature when the pressure is most uniform are selected.

[0023] As a further improvement of the present invention, in the step four, the crystal is bonded by a bonding method, the crystal is first pre-treated, and the crystal and the pillar are treated according to a standard semiconductor crystal cleaning process to remove organic impurities, particles and oxide layers on the surface to avoid contaminating the bonding surface; then, they are placed in deionized water and brought into a clean room for experiment, the crystal and the pillar are fixed with a special clamp and rinsed with distilled water, and then dried and sealed before entering the bonding mode.

[0024] As a further improvement of the present invention, stress isolation grooves are provided between the working surface of the crystal to be bonded and the bonding portion to prevent the stress caused by bonding from affecting the working surface of the crystal.

[0025] As a further improvement of the present invention, in the step five, a synchrotron radiation test optical path is constructed, and intensity detection devices are placed before and after the monochromator to test the reflectivity of the monochromator at different energies; the resolution of the monochromator is tested using an absorption target or a four-crystal monochromator method; a large-size digital CCD is selected for imaging to monitor the intensity distribution uniformity and stability of the monochromator output light spot.

[0026] The invention also provides a monochromator, which is prepared by the above method.

[0027] 3. Beneficial effects

[0028] Compared with the existing known technologies, the technical solution provided by the present invention has the following significant effects:

[0029] The monochromator preparation method and monochromator of the present invention utilize the bonding technology of two crystals with perfect surface polishing and the method of high-precision crystal polishing to prepare a bonded channel-cut monochromator device that can be used for perfect X-ray imaging, thereby solving the problems of stability and uneven beam distribution in the current monochromator. At the same time, the intersection line between the lattice plane and the crystal surface is calibrated by the method of precise measurement using the composite detection technology of visible light and X-rays, and the ultra-high precision matching between the lattice plane and the surface is achieved by the method of in-plane rotation of the crystal, thereby solving the problem that the current directional processing means cannot directly achieve the micro-radian directional accuracy required for synchrotron radiation. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the intersection line between the lattice plane and the crystal surface before the crystal is rotated in the present invention;

[0031] Figure 2 It is a schematic diagram of the intersection line between the lattice plane and the crystal surface after the crystal is rotated in the present invention;

[0032] Figure 3 Schematic diagram of crystal bonding in the present invention. DETAILED DESCRIPTION

[0033] In order to make the above-mentioned objects, features and advantages of the invention more obvious and understandable, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0034] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0035] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0036] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0037] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0038] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are for illustrative purposes only and are not intended to be the only implementation method.

[0039] Example

[0040] Combination Figure 1-Figure 3 , this embodiment provides a method for preparing a monochromator, the steps of which are:

[0041] Step 1: Perform stress-free crystal polishing on the monochromator crystal to obtain two monochromator crystals with high surface accuracy;

[0042] Taking the crystal surface of commonly used devices as an example, a 6-inch single crystal silicon rod was selected to cut a 20 mm thick round flat crystal, and the existing equipment in the laboratory was used for grinding and polishing: first, a mixture of HNO3 and HF was used to etch and remove the mechanical cutting stress layer to ensure that the surface layer would not have residual stress caused by cutting in the subsequent process; then a 20μm Al 2 O 3 Or SiC and other abrasives and cast iron grinding discs to grind out the plane, complete the flatness of the crystal surface trimming; use 9μm abrasive particles to continue to optimize the surface roughness and flatness; then replace the polyurethane polishing disc or asphalt ring polishing disc for polishing, and use 50nm alkaline SiO 2 The suspension is polished and the diffraction is detected using X-ray diffraction technology to ensure that there is no processing stress on the crystal surface and a perfect image after the final polishing stage.

[0043] Then, the magnification effect of the beveled crystal is used to perform morphology tests to test the diffraction quality of the test crystal: Taking the Si crystal plane as an example, there is a crystal plane at an angle of 29.5° (α) with the crystal surface. The energy of 7.5keV is selected to test the crystal plane. The Bragg angle of this energy is 30.3° (θ). The calculated bevel factor b is 62, which means that a 1.4mm spot can detect a 100mm long crystal. Small spot size and highly parallel output light can improve the measurement accuracy, and ultimately the internal morphology of the crystal can be tested in a relatively simple, convenient and high-precision manner.

[0044] Step 2: measure the angle between the lattice plane and the crystal surface of each monochromator crystal, and calibrate the intersection line between the lattice plane and the crystal surface; and when the cutting device cuts the crystal, rotate the monochromator crystal at a certain angle for horizontal cutting, so that the lattice plane and the crystal surface are roughly parallel;

[0045] Since the bonding accuracy of the two crystals depends on the crystal surface, and x-rays require parallelism between the lattice planes, the bonding of the channel-cut monochromator requires the lattice plane to maintain a high degree of parallelism with the crystal surface. A simple grinding process can only guarantee the flatness of the crystal, but the angle accuracy with the lattice plane cannot be guaranteed. If the two planes are not parallel, there must be an intersection line. If the direction of this intersection line on the crystal surface is measured, the direction of the surface can be corrected according to this direction to achieve the required parallelism of the two surfaces. This embodiment adopts a composite detection method of x-ray diffraction and optical measurement to achieve the angle measurement of the lattice plane and the surface at the arc second level, and calibrate the direction of the intersection line between the lattice plane and the crystal surface. Then, the mutually perpendicular X and Y directions are determined on the crystal surface as the reference axes. According to the angle difference between the intersection line of the lattice plane and the crystal surface and the X direction, the monochromator crystal is rotated until the intersection line of the lattice plane and the crystal surface coincides with the X direction, and finally the positioning cutting is performed along the X direction.

[0046] Step 3: further modify the crystal surface to make it completely parallel to the lattice plane;

[0047] In this embodiment, the crystal surface is corrected by using a laboratory polishing disc, the crystal orientation deviation is adjusted by uneven pressure, and the pressure distribution on the crystal is adjusted by weight to ensure that the pressure in the direction of the crystal intersection is evenly distributed and the pressure in the direction perpendicular to it is gradient distributed. The correction makes the crystal surface completely parallel to the lattice plane.

[0048] Step 4: Bond the two monochromator crystals so that the lattice planes of the two monochromator crystals are parallel;

[0049] First, ANSYS is used to analyze the pressure distribution of the bonding part when the clamp is pressurized, and the clamp is made. The actual pressure distribution of the clamp is detected by means of pressure test paper. At present, the most common method of high-pressure testing is to provide high pressure by screwing the bolts. In this embodiment, the pressure is adjusted by means of a preset torque wrench, different forces are applied, and the pressure distribution data on the pressure test paper are read respectively to observe the pressure and the uniformity of the distribution, and the pressure and temperature when the pressure is most uniform are selected.

[0050] Then the crystal is bonded by bonding method: the crystal is pre-processed, all crystal processing and bonding processes will be carried out in a Class 100 clean room, the crystal and the pillar are treated according to the standard semiconductor crystal cleaning process, and the organic impurities, particles and oxide layer on the surface are removed to avoid contaminating the bonding surface. After the crystal is cleaned, it is placed in deionized water and brought into the clean room for experiment. The crystal and the pillar are fixed with a special clamp and rinsed with distilled water. The number of bubbles that may appear is inversely proportional to the speed of the water flow, so the speed of the water flow can be increased as much as possible under the premise of safety and stability. After cleaning, the crystal and the pillar are dried with a spin dryer, and then sealed and entered into the bonding mode. During the crystal processing process, impurities on the surface will cause bubbles on the bonding surface, and the clean room environment cannot guarantee the absolute cleanliness of the surface. Therefore, it is necessary to use a laser measurement system to detect the crystal surface from time to time. When there are impurity particles, refer to the optical mirror wiping method to clean the surface and try to clean the crystal surface. This embodiment has support parts on both sides of the crystal working surface, which can obtain higher stability. At the same time, stress isolation grooves are set between the working surface of the crystal to be bonded and the bonding part to prevent the stress caused by bonding from affecting the working surface of the crystal. The middle support part is a finely polished silicon single crystal or quartz glass.

[0051] Step 5: Perform quality inspection on the grooved monochromator formed after bonding.

[0052] Cut the bonded monochromator into suitable sizes according to different functions. Use a synchrotron radiation device to detect the quality of the monochromator: build a synchrotron radiation test optical path, place intensity detection devices before and after the monochromator, and test the reflectivity of the monochromator at different energies. According to previous test experience, the reflectivity will be significantly reduced when there is an angle detuning between the two diffraction surfaces; use the absorption target or four-crystal monochromator method to test the resolution of the monochromator; select a large-size digital CCD for imaging, and monitor the intensity distribution uniformity and stability of the monochromator's output light spot.

[0053] This embodiment also provides a monochromator, which is prepared using the above method.

[0054] The present invention and its embodiments are described schematically above, and the description is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. Therefore, if a person skilled in the art is inspired by it and designs a structural method and an embodiment similar to the technical solution without creativity without departing from the purpose of the invention, they shall all fall within the protection scope of the present invention.

Claims

1. A method for preparing a monochromator, characterized in that: The steps are: Step 1: Perform stress-free crystal polishing on the monochromator crystal to obtain two monochromator crystals with high surface accuracy; Step 2: measure the angle between the lattice plane and the crystal surface of each monochromator crystal, and calibrate the intersection line between the lattice plane and the crystal surface; and when the cutting device cuts the crystal, rotate the monochromator crystal at a certain angle for horizontal cutting, so that the lattice plane and the crystal surface are roughly parallel; Step 3: further modify the crystal surface to make it completely parallel to the lattice plane; Step 4: Bond the two monochromator crystals so that the lattice planes of the two monochromator crystals are parallel; Step 5: Perform quality inspection on the grooved monochromator formed after bonding.

2. The method for preparing a monochromator according to claim 1, characterized in that: In the step 1, the mechanical cutting stress layer is firstly removed by etching with a mixture of HNO3 and HF, and then a plane is ground out using an abrasive and a grinding wheel to complete the flatness trimming of the crystal surface; then the surface roughness and flatness are optimized; and then the crystal surface is polished.

3. The method for preparing a monochromator according to claim 2, characterized in that: During polishing, X-ray diffraction technology is used to detect diffraction conditions to ensure that there is no processing stress on the surface of the crystal and a perfect image after the final polishing stage; finally, the magnification effect of the beveled crystal is used to perform morphology testing to detect the diffraction quality of the test crystal.

4. The method for preparing a monochromator according to claim 1, characterized in that: In the step 2, a composite detection method of x-ray diffraction and optical measurement is used to measure the angle between the lattice plane and the surface at the arc second level, and the intersection line between the lattice plane and the crystal surface is calibrated; then, mutually perpendicular X and Y directions are determined on the crystal surface as reference axes, and according to the angle difference between the intersection line of the lattice plane and the crystal surface and the X direction, the monochromator crystal is rotated until the intersection line of the lattice plane and the crystal surface coincides with the X direction, and finally positioning cutting is performed along the X direction.

5. The method for preparing a monochromator according to claim 1, characterized in that: In the step three, the crystal surface is corrected by a polishing disk, and the crystal orientation deviation of the crystal is adjusted by uneven pressure; the pressure distribution on the crystal is adjusted by counterweights to ensure that the pressure in the direction of the intersection line between the lattice plane and the crystal surface is evenly distributed, and the pressure in the direction perpendicular to it is gradient distributed.

6. The method for preparing a monochromator according to claim 1, characterized in that: In the step 4, the pressure distribution at the bonding point under the condition of simulated clamp pressure is first analyzed and the clamp is made; then, with the help of pressure test paper, different pressures are applied to read the pressure distribution data on the pressure test paper, observe the pressure size and distribution uniformity, and select the pressure size and temperature when the pressure is most uniform.

7. A method for preparing a monochromator according to claim 6, characterized in that: In the step 4, the crystal is bonded by a bonding method. The crystal is first pre-treated, and the crystal and the pillar are treated according to the standard semiconductor crystal cleaning process to remove organic impurities, particles and oxide layers on the surface to avoid contaminating the bonding surface; then, they are placed in deionized water and brought into a clean room for experiment. The crystal and the pillar are fixed with a special clamp and rinsed with distilled water, and then dried and sealed before entering the bonding mode.

8. A method for preparing a monochromator according to claim 7, characterized in that: Stress isolation grooves are provided between the working surface of the crystal to be bonded and the bonding part to prevent the stress caused by bonding from affecting the working surface of the crystal.

9. A method for preparing a monochromator according to claim 8, characterized in that: In the step five, a synchrotron radiation test optical path is constructed, and intensity detection devices are placed before and after the monochromator to test the reflectivity of the monochromator at different energies; the resolution of the monochromator is tested using an absorption target or a four-crystal monochromator method; a large-size digital CCD is selected for imaging to monitor the intensity distribution uniformity and stability of the monochromator output light spot.

10. A monochromator, characterized in that: The method according to any one of claims 1 to 9 is used for preparation.

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