Vacuum adsorption large-size spherical curved crystal monochromator and preparation method thereof

Abstract

The invention discloses a vacuum adsorption large-size spherical curved crystal monochromator and a preparation method thereof. The crystal diffraction unit comprises a polycarbonate sheet and a plurality of stripes obtained by cutting the crystal diffraction unit, all the strips are bonded to the polycarbonate sheet and cured, and a combined body is obtained; taking the surface with the strip as the upper surface of the assembly; the lower surface of the assembly is placed on the concave spherical surface of a porous ceramic plate, gas between the lower surface of the assembly and the concave spherical surface of the porous ceramic plate is removed through vacuum adsorption, and the assembly is bent to obtain the spherical curved crystal monochromator. According to the invention, the problem of non-uniform stress of the crystal in the bending process is solved, and the problems that the wafer is easy to break and generates microcracks when the germanium crystal is bent to the curvature radius of less than or equal to 0.5 m are avoided; and meanwhile, the problem that vacuum sealing is not easy due to large curvature is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of precision optical element manufacturing, and particularly relates to a method for manufacturing a large-sized spherical bent crystal monochromator by using a vacuum adsorption technique and a manufacturing method thereof, which is applicable to the manufacturing of a spherical germanium crystal monochromator for a Rowland circle configuration X-ray absorption and emission spectrometer. Background Technique

[0002] A bent crystal monochromator is a core optical element in an X-ray spectrometer. Its function is to select a specific wavelength (monochromatize) from broadband X-rays and achieve focusing or collimation of X-rays through the geometric characteristics of the bent crystal. It is widely used in synchrotron radiation light sources, X-ray absorption spectroscopy (XAS) and X-ray emission spectroscopy (XES) spectrometers. The bent crystal monochromator is based on Bragg's law. By adjusting the crystal angle (θ), X-rays of a specific wavelength can be selectively reflected to achieve monochromatization. By bending the crystal into a specific radius of curvature (such as a spherical surface or a cylindrical surface), the divergence of X-rays can be compensated by using the geometric focusing effect, improving the signal intensity and resolution. Common materials include silicon (Si): the most commonly used, suitable for medium and low energy X-rays (<20 keV), with high lattice integrity. Germanium (Ge): high atomic number, with high diffraction efficiency and infrared optical compatibility. Quartz (SiO2) belongs to a non-cubic crystal system and is suitable for the manufacture of high-energy resolution bent crystal monochromators with an energy resolution less than 10 - 50 meV.

[0003] There are two technical solutions for traditional bent crystal monochromators: One is the solution proposed by Evan P. Jahrman, which uses a flexible polyimide film to seal a vacuum housing. There is a concave spherical substrate support and a single crystal silicon wafer inside the housing. Under the action of atmospheric pressure, the flexible polyimide film bends and transfers the force to the silicon wafer, so that the crystal is bent and attached to the concave spherical substrate. The other solution is proposed by Ayman H. Said, which uses porous aluminum, combined with a vacuum housing and a thin borosilicate glass sheet for sealing; first, a single crystal silicon wafer is grown on the thin borosilicate glass sheet by anodic bonding. The borosilicate glass sheet seals the vacuum housing with multiple rubber rings. Porous aluminum is placed inside the housing to generate an adsorption force, so that the glass and silicon can be better adsorbed on the concave porous aluminum plate, and the rubber rings and the vacuum housing are used to achieve sealing.

[0004] In the solution proposed by Evan P. Jahrman mentioned above, since the crystal is behind the flexible polyimide film, there is a problem of X-ray absorption by the flexible polyimide film, especially in the interval of relatively low X-ray energy, such as the 4 - 6 keV interval, and this problem will be more serious. For the porous aluminum solution proposed by Ayman H. Said, based on borosilicate glass as a single crystal material substrate, when manufacturing a bent crystal monochromator with a relatively small radius of curvature, there are certain problems with vacuum sealing due to the lack of ductility of the glass. Summary of the Invention

[0005] Aiming at the problems existing in the prior art, the purpose of the present invention is to provide a vacuum adsorption large-size spherical bent crystal monochromator and its preparation method. The present invention uses vacuum adsorption technology to develop a 6-inch germanium spherical bent crystal monochromator, solves the problem of uneven stress during the bending process of the crystal, and avoids problems such as easy breakage of the wafer and generation of microcracks when the germanium crystal is bent to a curvature radius less than or equal to 0.5 meters (R≤500mm); at the same time, solves the problem of difficult vacuum sealing caused by a large curvature.

[0006] The technical solution of the present invention is as follows:

[0007] A vacuum adsorption large-size spherical bent crystal monochromator, characterized in that it includes a polycarbonate sheet and a plurality of strips obtained by cutting a crystal diffraction unit;

[0008] Bond each of the strips on the polycarbonate sheet and cure to obtain an assembly; use the side with the strips as the upper surface of the assembly;

[0009] By placing the lower surface of the assembly on the concave spherical surface of a porous ceramic plate, removing the gas between the lower surface of the assembly and the concave spherical surface of the porous ceramic plate by vacuum adsorption, and pressing the assembly to obtain a spherical bent crystal monochromator.

[0010] Further, the diameter of the crystal diffraction unit is smaller than the diameter of the porous ceramic plate, and the diameter of the polycarbonate sheet is larger than the diameter of the porous ceramic plate.

[0011] Further, the diameter of the diffraction unit is 150 mm, the diameter of the porous ceramic is 198 mm, and the diameter of the polycarbonate is 200 mm; polish a 160-mm-diameter central area on one side of the porous ceramic plate into a concave spherical surface with a radius R = 500 mm, and the width of the strip is 2-10 mm.

[0012] Further, the crystal diffraction unit is a germanium double-sided polished single crystal wafer with a thickness of 300-500 um, the thickness of the polycarbonate sheet is 200 um, and the thickness of the porous ceramic plate is 18 mm.

[0013] Further, the crystal diffraction unit is a silicon double-sided polished single crystal wafer, a quartz double-sided polished single crystal wafer, or a lithium niobate double-sided polished single crystal wafer.

[0014] A preparation method of a vacuum adsorption large-size spherical bent crystal monochromator, the steps of which include:

[0015] Step 1, select a crystal diffraction unit, a polycarbonate sheet, and a porous ceramic plate with comparable diameters; polish one side of the porous ceramic plate into a concave spherical surface;

[0016] Step 2: Cut the crystal diffraction unit into strips;

[0017] Step 3: Bond each strip onto the polycarbonate sheet and cure to obtain an assembly; Take the side with the strip as the upper surface of the assembly;

[0018] Step 4: Place the assembly on the porous ceramic plate; wherein, the lower surface of the assembly faces the concave spherical surface of the porous ceramic plate, and a sealing rubber ring is provided at the outer edge of the assembly;

[0019] Step 5: Place the structure obtained in Step 4 into a vacuum housing for evacuation to remove the gas between the lower surface of the assembly and the concave spherical surface of the porous ceramic plate, and press the assembly to be bent by vacuum pressure to obtain a spherical crystal monochromator.

[0020] Furthermore, the diameter of the crystal diffraction unit is smaller than the diameter of the porous ceramic plate, and the diameter of the polycarbonate sheet is larger than the diameter of the porous ceramic plate.

[0021] Furthermore, the crystal diffraction unit is a germanium double-sided polished single crystal wafer with a thickness of 300 - 500 μm, the thickness of the polycarbonate sheet is 200 μm, and the thickness of the porous ceramic plate is 18 mm; the diameter of the diffraction unit is 150 mm, the diameter of the porous ceramic is 198 mm, and the diameter of the polycarbonate is 200 mm; Polish a region with a central diameter of 160 mm on one side of the porous ceramic plate into a concave spherical surface with a radius R = 500 mm, and the width of the strip is 2 - 10 mm.

[0022] Furthermore, the vacuum housing includes an air extraction plate, a housing, and a bottom fixing ring; the upper end of the housing is open for the structure obtained in Step 4 to contact with air; the lower end of the housing is hermetically connected to the air extraction plate for fixing the structure obtained in Step 4 on the air extraction plate, wherein the porous ceramic plate faces the air extraction plate; the bottom fixing ring is hermetically connected to the air extraction plate, and the air extraction plate has a plurality of microchannel holes for communicating with the micropores in the porous ceramic plate; an air extraction port is provided at the bottom of the air extraction plate for connecting to a vacuum pump.

[0023] Furthermore, the crystal diffraction unit is a silicon double-sided polished single crystal wafer, a quartz double-sided polished single crystal wafer, or a lithium niobate double-sided polished single crystal wafer.

[0024] When fabricating a bent crystal monochromator with a small radius of curvature, there is a problem of large vertical bending deformation. Traditional glass substrates have problems of breakage and inability to seal in a vacuum due to lack of flexibility and ductility. The present invention uses flexible plastics such as polycarbonate as the crystal support unit and the sealing unit, and realizes a vacuum degree of the order of Pa through the flexibility and ductility of the polycarbonate sheet.

[0025] For the sealing of a small-curvature concave porous ceramic material, when the overall surface shape of the porous ceramic material is concave, there is a problem that it cannot be sealed with polycarbonate and rubber rings. This patent adopts a surface shaping method combining a partial concave surface and a flat surface, so that the contact sealing point is a flat surface, which is conducive to vacuum sealing.

[0026] The present invention uses single crystal materials such as germanium, silicon, quartz, and lithium niobate to fabricate a bent crystal monochromator with a size larger than 4 inches, and applies it to X-ray absorption and emission spectrometers.

[0027] The advantages of the present invention are as follows:

[0028] 1. The fabrication of a bent crystal monochromator with a radius of curvature of 250 - 500 mm can be realized by using the present invention.

[0029] 2. It has good material universality and vacuum sealing effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a front sealing diagram of a porous ceramic cooperating with a polycarbonate sheet.

[0031] Figure 2 It is an overall cross-sectional view of a germanium bent crystal monochromator. DETAILED DESCRIPTION OF THE INVENTION

[0032] The present invention will be further described in detail below with reference to the drawings. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0033] This invention patent uses a porous ceramic material with a specific structure in cooperation with a thin polycarbonate sheet with a certain ductility to complete crystal support and vacuum sealing. Taking the single crystal material germanium as an example, the specific scheme is described in detail as follows:

[0034] 1. Material preparation: Obtain a 6-inch germanium double-sided polished single crystal wafer with a thickness preferably of 300 - 500 um as the crystal diffraction unit. Select a polycarbonate sheet with a thickness preferably of 200 um. A porous ceramic plate with a thickness of 18 mm and a diameter of 198 mm, polish one side of the central area with a diameter of 160 mm into a concave spherical surface with a radius R = 500 mm, and the micropore diameter of the porous ceramic plate is 30 um. Among them, the diameter of the crystal diffraction unit is slightly smaller than the diameter of the porous ceramic plate, and the diameter of the polycarbonate sheet is slightly larger than the diameter of the porous ceramic plate; specifically, the diameter of the diffraction unit is 150 mm, the diameter of the porous ceramic is 198 mm, and the diameter of the polycarbonate is 200 mm.

[0035] 2. Cut the germanium wafer through and cut it into multiple strips with a width of 2 - 10 mm to release the stress generated during bending and reduce the risk of crystal breakage.

[0036] 3. Bond the grooved germanium wafer to the polycarbonate sheet and cure it. The curing temperature is 60 degrees and the time is 24 hours. Among them, the gap between adjacent strips is 100 microns, and the glue model is EPO-TEK353.

[0037] 4. Place the bonded germanium / polycarbonate combination on the porous ceramic plate and combine it with a rubber ring. The effect is as Figure 1 shown.

[0038] 5. Place the Figure 1 combination into the vacuum housing shown in Figure 2 , slowly evacuate the air and lock the screws. The vacuum housing includes an air extraction plate, a housing, and a bottom fixing ring; the upper end opening of the housing is used for the structure obtained in step 4 to contact the air, the lower end opening of the housing is hermetically connected to the air extraction plate for hermetically fixing the structure obtained in step 4 on the air extraction plate, where the porous ceramic plate faces the air extraction plate; the bottom fixing ring is hermetically connected to the air extraction plate; the air extraction plate has multiple microchannel holes for communicating with the micropores in the porous ceramic plate; the bottom of the air extraction plate is provided with an air extraction port for connecting to a vacuum pump. When the air extraction port is evacuated with a vacuum pump, the air inside the vacuum housing is pumped away, and the external atmospheric pressure acts on the crystal diffraction unit, causing it to bend and fit onto the porous ceramic material. The function of these microchannel holes is to connect the micropores in the porous ceramic, so that the gas in all the micropores of the porous ceramic plate can be discharged.

[0039] 6. The vacuum pressure will act on the single crystal germanium wafer and the polycarbonate sheet. Since the depth of the concave spherical surface of the porous ceramic plate is relatively deep, traditional glass cannot fit with the concave spherical surface. This patent uses polycarbonate with certain flexibility and ductility as the crystal substrate, which will fit with the concave spherical surface under the action of the vacuum pressure, and the edge rubber ring plays a role in fixing and sealing.

[0040] The present invention respectively uses single crystal materials such as germanium, silicon, quartz, and lithium niobate to fabricate a spherical bent crystal monochromator with a size larger than 4 inches.

[0041] The present invention also provides an X-ray absorption spectrometer based on the above spherical bent crystal monochromator, specifically a Rowland circle configuration X-ray absorption spectrometer.

[0042] The present invention also provides an X-ray emission spectrometer based on the above spherical bent crystal monochromator, which is used to obtain an X-ray emission spectrum, specifically a Rowland circle configuration X-ray emission spectrometer.

[0043] Although specific embodiments of the present invention are disclosed for illustrative purposes, which are intended to help understand the content of the present invention and implement it accordingly, those skilled in the art can understand that various substitutions, changes, 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 content disclosed in the best embodiments, and the scope of protection claimed by the present invention shall be defined by the scope defined in the claims.

Claims

1. A vacuum adsorption large-size spherical crystal monochromator, characterized in that It includes a polycarbonate sheet and a plurality of strips obtained by cutting a crystal diffraction unit; Bond each of the strips to the polycarbonate sheet and cure to obtain an assembly; Take the side with the strips as the upper surface of the assembly; By placing the lower surface of the assembly on the concave spherical surface of a porous ceramic plate, use vacuum adsorption to remove the gas between the lower surface of the assembly and the concave spherical surface of the porous ceramic plate, and bend the assembly to obtain a spherical crystal monochromator.

2. The vacuum adsorption large-size spherical crystal monochromator according to claim 1, characterized in that, The diameter of the crystal diffraction unit is smaller than the diameter of the porous ceramic plate, and the diameter of the polycarbonate sheet is larger than the diameter of the porous ceramic plate.

3. The vacuum adsorption large-size spherical bent crystal monochromator according to claim 1 or 2, characterized in that, The diameter of the diffraction unit is 150 mm, the diameter of the porous ceramic is 198 mm, and the diameter of the polycarbonate is 200 mm; Polish a region with a central diameter of 160 mm on one side of the porous ceramic plate into a concave spherical surface with a radius R = 500 mm, and the width of the strip is 2 - 10 mm.

4. The vacuum adsorption large-size spherical crystal monochromator according to claim 3, characterized in that, The crystal diffraction unit is a germanium double-sided polished single crystal wafer with a thickness of 300 - 500 um, the thickness of the polycarbonate sheet is 200 um, and the thickness of the porous ceramic plate is 18 mm.

5. The vacuum adsorption large-size spherical bent crystal monochromator according to claim 1, wherein The crystal diffraction unit is a silicon double-sided polished single crystal wafer, a quartz double-sided polished single crystal wafer, or a lithium niobate double-sided polished single crystal wafer.

6. A preparation method of a vacuum adsorption large-size spherical crystal monochromator, the steps of which include: Step 1, Select a crystal diffraction unit, a polycarbonate sheet, and a porous ceramic plate with comparable diameters; Polish one side of the porous ceramic plate into a concave spherical surface; Step 2, Cut the crystal diffraction unit into strips; Step 3, Bond each of the strips to the polycarbonate sheet and cure to obtain an assembly; Take the side with the strips as the upper surface of the assembly; Step 4, Place the assembly on the porous ceramic plate; wherein, the lower surface of the assembly faces the concave spherical surface of the porous ceramic plate, and a sealing rubber ring is provided at the outer edge of the assembly; Step 5, Install the structure obtained in Step 4 into a vacuum housing and evacuate to remove the gas between the lower surface of the assembly and the concave spherical surface of the porous ceramic plate, and bend the assembly by vacuum pressure to obtain a spherical crystal monochromator.

7. The method according to claim 6, wherein The diameter of the crystal diffraction unit is smaller than the diameter of the porous ceramic plate, and the diameter of the polycarbonate sheet is larger than the diameter of the porous ceramic plate.

8. The method according to claim 6 or 7, characterized in that, The crystal diffraction unit is a germanium double-sided polished single crystal wafer with a thickness of 300 - 500 um, the thickness of the polycarbonate sheet is 200 um, and the thickness of the porous ceramic plate is 18 mm; The diameter of the diffraction unit is 150 mm, the diameter of the porous ceramic is 198 mm, and the diameter of the polycarbonate is 200 mm; Polish a region with a central diameter of 160 mm on one side of the porous ceramic plate into a concave spherical surface with a radius R = 500 mm, and the width of the strip is 2 - 10 mm.

9. The method according to claim 6, wherein The vacuum housing includes an air extraction plate, a housing, and a bottom fixing ring; the upper end of the housing is open for the structure obtained in Step 4 to contact air; the lower end of the housing is hermetically connected to the air extraction plate for fixing the structure obtained in Step 4 on the air extraction plate, wherein the porous ceramic plate faces the air extraction plate; the bottom fixing ring is hermetically connected to the air extraction plate, and the air extraction plate has a plurality of micro-channel holes for communicating with the micropores in the porous ceramic plate; an air extraction port is provided at the bottom of the air extraction plate for connecting to a vacuum pump.

10. The method according to claim 6, characterized in that The crystal diffraction unit is a silicon double-sided polished single crystal wafer, a quartz double-sided polished single crystal wafer, or a lithium niobate double-sided polished single crystal wafer.

Images