A high-resolution multi-channel curved crystal imaging system and its assembly method

Abstract

This invention discloses a high-resolution multi-channel curved crystal imaging system and its assembly and adjustment method, comprising: S1, using a beam-expanded and collimated visible light laser as a coherent light source, adjusting the multi-channel curved crystal device to the visible light laser reflection path, and adjusting the imaging element to the image plane position of the multi-channel curved crystal device; S2, placing periodic diffractors on the object plane, the coherent light source is diffracted and converted into light waves from different points on the plane of the light source after passing through the periodic diffractors, the light waves are reflected by the curved crystal and converge to the corresponding points on the image plane, forming the spatial spectrum of the periodic diffractors, and the spatial spectrum light waves form a diffractor image on the image plane through free space; S3, replacing the visible light laser with an X-ray tube based on the optimal object image position determined by Abbe imaging of the periodic object. This ensures the aiming accuracy of multiple imaging channels for the same object field of view, realizes precise control of different backlight field of view positions, and meets the need for high-precision adjustment of multi-channel precise object-image relationships.

Description

Technical Field

[0001] This invention relates to the field of X-ray imaging technology for laser plasma, and in particular to a high-resolution multi-channel bent crystal imaging system and its assembly method. Background Technology

[0002] In laser inertial confinement fusion research, X-rays emitted by the laser plasma contain rich physical information, which can be used to study the interaction between the laser and matter, as well as state parameters of the plasma such as electron temperature, density, and ionization. Among these, time-fractionated X-ray high-resolution imaging plays a crucial role in diagnosing the temporal evolution behavior of laser plasmas and is a key tool for studying important physical issues such as driving asymmetry, hydrodynamic instability growth, hot spot shape, and fuel mixing. X-ray imaging based on curved crystals has advantages such as good monochromaticity, high light-gathering efficiency, high spatial resolution, and a large effective field of view, and is widely used in laser plasma diagnostics.

[0003] Spherical curved crystals are widely used, but high-resolution imaging of spherical curved crystals requires near-normal X-ray incidence, which limits the choice of crystal materials, crystal orientations, diffraction orders, or operating energies. Toroidal curved crystal structures are an effective way to solve this bottleneck. By controlling different radii of curvature in the meridional and sagittal directions, astigmatism in both directions can be effectively eliminated, significantly expanding the working scenarios of curved crystal imaging. Especially when combined into multi-channel curved crystal imaging structures, and with framing cameras placed at the image plane, time-framing measurements can be further achieved under high monochromaticity and high spatial resolution conditions, thereby diagnosing the temporal evolution behavior of plasma information. For example, in 2000, Ingo Uschmann et al. designed a ten-channel Si-based imaging system for the self-luminescence imaging measurement of argon-doped Lyβ and Heβ lines in target pellets. <311> and Ge <311> The supertoroidal bent crystal operates at 4.2 keV, and its ten imaging channels are arranged on two microstrips (corresponding to two transient moments), achieving a spatial resolution better than 15 μm. In 2021, Jiang et al. developed a four-channel Ge array for Kα-line self-emission imaging of Ti (operating energy point 4.75 keV). <400> Supertoroidal bent crystals were obtained, and offline experimental results with a spatial resolution of approximately 4-10 μm were obtained.

[0004] For multi-channel bent crystal imaging systems with backlighting, it is crucial not only to ensure the aiming accuracy of multiple imaging channels towards the same object-side field of view but also to achieve precise control over the positions of different backlight fields of view. Current methods for adjusting bent crystal systems primarily use visible light lasers to establish the optical axis and further refine the object-image relationship in repeated offline X-ray experiments. However, this approach struggles to meet the high-precision adjustment requirements of multi-channel object-image relationships. Furthermore, while using ordinary X-ray tube targets as illumination sources can be used for offline X-ray fine-tuning of certain energy lines, it remains difficult to select suitable offline X-ray tube targets as the energy points for most of the interconnected lines commonly used in laser plasma diagnostics. Summary of the Invention

[0005] The purpose of this invention is to provide a high-resolution multi-channel bent crystal imaging system and its assembly and adjustment method. The imaging system achieves effective coupling between the multi-channel bent crystal and the imaging element through optimized arrangement of the bent crystal. Furthermore, by utilizing the Abbe imaging principle of periodic diffractors under laser, high-resolution imaging results of X-ray bent crystal reflective devices are obtained in the visible light band. Based on this, the optimal object-image relationship of bent crystal imaging is established, thereby achieving high-precision assembly and adjustment of the bent crystal system.

[0006] To achieve the above objectives, the present invention provides a method for assembling and adjusting a high-resolution multi-channel curved crystal imaging system, comprising the following steps:

[0007] S1. Using the expanded and collimated visible light laser as a coherent light source, the multi-channel bent crystal device is adjusted to the visible light laser reflection path, and the imaging element is adjusted to the image plane position of the multi-channel bent crystal device.

[0008] S2. Periodic diffractors are placed on the object plane as spatial resolution markers. After passing through the periodic diffractors, the coherent light source is diffracted and converted into light waves from different points on the plane where the light source is located. The light waves are reflected by the multi-channel bent crystal device and focused on the corresponding points on the image plane to form the spatial spectrum of the periodic diffractors. The spatial spectrum light waves pass through free space to form a diffractor image containing multiple orders on the image plane.

[0009] S3. Based on the optimal object-image position determined by Abbe imaging of periodic objects, replace the visible light laser with an X-ray tube to complete the system assembly and adjustment of the precise object-image relationship in X-ray curved crystal imaging.

[0010] Preferably, in step S1, when the structure of the curved crystal element is a focusing form, the relative positions of the periodic diffractometer, the multi-channel curved crystal device, and the imaging element satisfy the following in both the meridional and sagittal directions:

[0011]

[0012]

[0013] Where u is the distance from the laser plasma X-ray radiation source to the center of the curved crystal, v is the distance from the center of the curved crystal to the image plane, θ is the Bragg diffraction angle at the center of the curved crystal, and f is the distance from the laser plasma X-ray radiation source to the center of the curved crystal. m and f s These are the focal lengths in the meridional and sagittal directions, respectively; R m R is the radius of curvature in the direction of the sub-arc; s Let be the radius of curvature in the direction of the arc sagitta.

[0014] The present invention also provides a high-resolution multi-channel bent crystal imaging system, comprising a visible light laser, a periodic diffractometer, a multi-channel bent crystal device, and an imaging element arranged sequentially along the optical path direction. The multi-channel bent crystal device is provided with an overall attitude adjustment assembly connected to it in a transmission manner on its lower side, and the imaging element is provided with a first linear guide rail connected to it in a transmission manner on its lower side.

[0015] Preferably, the multi-channel bent crystal device includes multiple bent crystal elements arranged in parallel, and the bent crystal elements are one of the following shapes: spherical, toroidal, or elliptical.

[0016] Preferably, the overall attitude adjustment assembly includes a second linear guide rail and a horizontal moving base.

[0017] Therefore, the present invention employs the above-mentioned high-resolution multi-channel curved crystal imaging system and assembly method, and its technical effects are as follows:

[0018] (1) By utilizing the Abbe imaging principle of visible light laser, high-resolution imaging results of X-ray bent crystal reflective device are obtained, and the optimal object-image relationship of bent crystal imaging is established accordingly. This solves the problem of high-precision aiming of ideal object point position in offline assembly of multi-channel bent crystal system, ensures the spatial resolution of the system, and has the correct optical axis angle relationship to ensure the diffraction efficiency of imaging, thus realizing high-precision assembly and adjustment of bent crystal system.

[0019] (2) By coupling a multi-channel spatial resolution bent crystal imaging system with a framing camera, the bent crystal spectrometer has a multi-channel optical structure with spatial and spectral resolution, which can be used for diagnostic experiments of the multi-channel backlight imaging type, such as the measurement of the growth of hydrodynamic instability of the modulated target.

[0020] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure and assembly of the device in this invention;

[0022] Figure 2 (a) is a diagram showing the light path arrangement near the object surface; Figure 2 (b) is an image layout diagram showing the image plane position;

[0023] Figure 3 The image shows the effect of image distance deviation on visible light imaging using curved crystal meshes; among them... Figure 3 (a) is a deviation of +25mm; Figure 3 (b) represents the ideal position; Figure 3 (c) represents a deviation of -25mm;

[0024] Figure 4 The figure shows the effect of object-side field-of-view deviation on visible light imaging of curved crystal meshes; among them... Figure 4 (a) is the optimal field of view position; Figure 4 (b) indicates that the grid has been shifted 0.25 mm to the right; Figure 4 (c) indicates that the grid has been moved 0.5 mm to the right;

[0025] Figure 5 The image shows the mesh imaging results of the upper and lower channels of the toroidal curved crystal obtained by X-ray CCD; among them, Figure 5 (a) shows the grid imaging result of the upper channel; Figure 5 (b) shows the lower channel grid imaging results;

[0026] Figure 6 This is the spatial resolution map of the horizontal direction of the dual-channel toroidal bent crystal; among which... Figure 6 (a) represents the spatial resolution of the upper channel; Figure 6 (b) represents the spatial resolution of the lower channel;

[0027] Figure 7 This is a mechanical structure diagram of a dual-channel toroidal bent crystal system; among which... Figure 7 (a) is a dual-channel bent crystal mechanical structure; Figure 7 (b) is the curved crystal objective lens section;

[0028] Figure 8 The images show the 600-mesh grid imaging results of the upper and lower channels of the toroidal bent crystal; among them, Figure 8 (a) is the upper channel; Figure 8 (b) is the lower channel;

[0029] Figure 9 This is the spatial resolution map of the horizontal direction of the dual-channel toroidal bent crystal; among which... Figure 9 (a) represents the upper channel spatial resolution; Figure 9 (b) represents the spatial resolution of the lower channel.

[0030] Figure Labels

[0031] 1. Visible laser; 2. Periodic diffractometer; 3. Multi-channel bent crystal device; 4. Imaging element; 5. First linear guide rail; 6. Overall attitude adjustment assembly; 601. Horizontal moving base; 602. Second linear guide rail. Detailed Implementation

[0032] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0033] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0034] Example 1

[0035] like Figure 1 As shown, the structure of a high-resolution multi-channel bent crystal imaging system is illustrated, including a visible light laser 1, a periodic diffractometer 2, a multi-channel bent crystal device 3, and an imaging element 4 arranged sequentially along the optical path. An overall attitude adjustment assembly 6 is provided on the lower side of the multi-channel bent crystal device 3 and is connected to it through a transmission. A first linear guide rail 5 is provided on the lower side of the imaging element 4 and is connected to it through a transmission.

[0036] The multi-channel bent crystal device 3 includes multiple bent crystal elements arranged in parallel, and the bent crystal elements are one of the following shapes: spherical, toroidal, or elliptical.

[0037] The overall attitude adjustment component 6 includes a second linear guide rail 602 and a horizontal moving base 601.

[0038] Example 2

[0039] The invention is further illustrated by using a dual-channel toroidal curved crystal imaging system for high-resolution backlight dynamic diagnosis as an example. This imaging system is used for dynamic diagnosis of X-ray backlight imaging and achieves a spatial resolution of 5-10 μm. Based on the working energy point of Ti-like He line combination lines (4.727 keV), a quartz crystal was designed. <203> The supertoroidal bent crystal structure: X-rays emitted from the backlight irradiate the object to be diagnosed, and then are dispersed and focused by two supertoroidal bent crystals respectively. The distance between the two image points is controlled by adjusting the orientation of the two supertoroidal bent crystals, forming a monoenergetic image at two different positions on the image plane, which is received by the two microstrips of the framing camera, and finally the perspective images of the object evolving at two different times are obtained.

[0040] For each set of toroidal bent crystals, the radii of curvature R in the meridional and sagittal directions are... m and R s Conforms to R m / R s =sin 2 θ, so that its imaging in both the meridional and sagittal directions simultaneously satisfies the following formula:

[0041]

[0042]

[0043] Where u and v are the object distance and image distance, respectively, and fm and f s Here, θ represents the focal length in the meridional and sagittal directions, respectively, and θ is the Bragg angle. The actual working energy point was chosen as the helium-like line of Ti (4.727 keV), which exhibits relatively high excitation efficiency in laser plasma experiments and provides a suitable penetration depth for CH modulation targets diagnosed in hydrodynamic instability experiments. At this energy point, commonly used quartz was selected. <203> As a bent crystal material, its first-order diffraction corresponds to a Bragg angle θ of 72.536°. The final determined optical structure parameters of the dual-channel supertoroidal bent crystal are shown in Table 1.

[0044] Table 1 Optical structural parameters of dual-channel supertoroidal bent crystal

[0045]

[0046] The corresponding magnification is approximately 12x. Due to the large effective field of view of curved crystal imaging, overlap may occur when two channels are arranged together. Therefore, 32mm was chosen as the imaging spacing, corresponding to the center interval between the three microstrips of the framing camera. For dual-channel backlit curved crystal imaging, the curved crystal aperture significantly affects the effective illumination field of view and directly limits the minimum angle of divergence between the two channel observation axes. This invention selected a crystal aperture of Φ = 12mm and a super-toroidal mirror substrate aperture of Φ15mm, close to the crystal aperture, which minimizes the observation angle. Optical simulation software showed that the spatial resolution of this imaging system is better than 7μm.

[0047] Under multi-channel arrangement and single-energy backlight imaging of feature lines, high-precision aiming at the ideal object point position is a challenge that needs to be solved in the offline assembly of a bent crystal system. It is necessary to establish a precise object-image relationship in geometric imaging for the multi-channel bent crystal system to ensure spatial resolution, while also maintaining the correct optical axis angle relationship to guarantee diffraction efficiency in backlight feature line imaging. Due to the existence of diffraction effects, the traditional aiming method based on visible light laser reflection to establish the optical axis has limited accuracy and is even more difficult to apply to the precise adjustment of multi-object-image relationships in online laser devices for multi-channel bent crystal systems.

[0048] The following is combined with Figure 1 , 2The assembly details are as follows: The imaging system includes a visible light laser 1, spatial markers, a multi-channel bent crystal device 3, and an imaging element 4 (framing camera). Its overall attitude can be adjusted via an overall attitude adjustment assembly 6 (including a second linear guide 602; high-precision repeatability ensures 10-20 μm accuracy during disassembly; a horizontally movable base 601 is also mounted below the imaging system, which extends or compresses via a bellows). A 600-mesh metal grid (approximately 5 μm linewidth and 42 μm period) is used as the spatially resolved markers. The bent crystal element of the multi-channel bent crystal device 3 can be made of quartz. <203> Supertoroidal bent crystal. The specific workflow is as follows:

[0049] (1) A visible light laser 1 after beam expansion and collimation is used as a coherent illumination source to illuminate a 600-mesh metal grid placed on the object plane as a spatial resolution marker. The coherent light source undergoes Fraunhofer diffraction after passing through the metal grid.

[0050] (2) The light source undergoes Fraunhofer diffraction, and then the diffracted light spot, containing multiple diffraction orders (corresponding to high-frequency spatial information of the grid), is reflected and focused by the toroidal mirror to form a visible light image on the image plane. In such cases... Figure 2 (b) shows that within the mirror receiving area containing fourth or fifth order diffraction, visible light imaging can still contain sufficiently clear grid detail information;

[0051] (3) Based on the optimal object position for curved crystal imaging determined by Abbe imaging of the metal mesh, an X-ray tube was used to replace the visible light laser (1) to complete the system assembly and adjustment of the precise object-image relationship of the curved crystal for X-ray imaging.

[0052] To evaluate the impact of object-image distance and object-side field of view offset on spatial resolution, the visible light imaging of the grid was assessed under varying image distance and grid vertical axis movement. Figure 3 (a)-(c) show the visible light imaging of the grid when the image distance deviates from the theoretical image distance (1860mm) by +25mm, 0mm, and -25mm, respectively. Figure 5 As shown in b, the image is clearest when the grid is at the theoretical image distance position, while the sharpness of the grid lines is significantly reduced when the image distance deviation reaches ±25mm. Figure 4 (a)-(c) show the visible light imaging results at the optimal field of view position of the grid in the horizontal direction, and at rightward shifts of 0.25 mm and 0.50 mm, respectively. It can be seen that horizontal shift of the grid has no effect on the optimal field of view position; clear black grid lines are obtained near the same optimal field of view position A. However, the black grid lines become increasingly blurry the further away from the optimal field of view, and the resolution of the grid imaging gradually deteriorates. Figure 3 and Figure 4The results collectively demonstrate that by utilizing the Abbe imaging principle of periodic grids under laser light, high-resolution imaging results of X-ray bent crystal reflective devices can be obtained in the visible light band, and the optimal object-image relationship for bent crystal imaging can be established accordingly, thereby achieving high-precision assembly and adjustment of the bent crystal system.

[0053] Offline X-ray imaging experiments further verified the feasibility of this assembly method. Although there was no elemental Kα line with energy close to the Ti-type He line (4.727 keV) as an offline X-ray assembly energy point, we found that the Lα line of Pt is approximately twice its energy. Therefore, using a Pt target X-ray tube as the backlight, a Φ300 μm diameter Pb aperture was placed approximately 15 mm from the grid to simulate the backlight of the online experiment. Offline X-ray imaging of the grid verified the actual integration and assembly accuracy of this method. In the experiment, the operating voltage and current of the Pt target X-ray tube were set to 30 kV and 15 mA, respectively. The grid used was consistent with the visible light imaging experiment, still a 600-mesh grid. The X-ray grid imaging results of the two channels obtained on the image plane X-ray CCD detector are shown below. Figure 5 As shown. Using the distance corresponding to "80%-20%" of the change in light intensity peaks and valleys as the evaluation standard for spatial resolution, the calibrated spatial resolution is as follows: Figure 6 As shown, the effective illumination field of view is approximately 5-10 μm. By comparing the SEM measurement results of the grid period before and after imaging, it was found that the magnification of the upper and lower channels of the toroidal curved crystal in the meridional and sagittal directions are very close, at 12.64 and 12.43 times; and 12.91 and 12.72 times, respectively.

[0054] Online calibration experiments were conducted at the Shenguang III prototype device to verify the performance of dual-channel toroidal bent crystals. The rapid installation and deployment of the system on the Shenguang III prototype device is the foundation for the successful application of its physical experiments. The high repeatability and precision of the dual-simulation positioning ball method were used to simultaneously indicate the object point and image point positions of the toroidal bent crystal after the offline calibration experiment, realizing the rapid switching of the system from offline calibration experiments to laser device applications. Figure 7 (a) shows the final mechanical structure of the system assembled after offline calibration experiments, including the curved lens objective and its mounting tubing, and the position-adjustable image recording assembly. The curved lens section is shown below. Figure 7 As shown in (b), the system includes a Φ300μm diameter analog sphere for positioning the object point and the backlight, and a crosshair laser module with a linewidth of approximately 1mm for indicating the image point position. The specific workflow is as follows:

[0055] (1) After the offline calibration experiment, the point simulation sphere and the crosshair laser were adjusted to... Figure 7 The corresponding object's grid center and the X-ray CCD imaging center of the upper channel curved crystal;

[0056] (2) Then, the imaging optical path corresponding to the object point simulation sphere and the upper channel curved crystal center is defined by the optical axis of the internal focusing telescope.

[0057] (3) Finally, the center position of the backlight simulation sphere is adjusted to the optical axis of the internal focusing telescope, thereby finally determining the spatial relationship between "backlight source - object point - curved crystal - image point". The simulation positioning sphere and laser module are connected to the toroidal curved crystal through a high repeatability resettable linear guide (HIWIN, MGN15P) to achieve rapid installation and removal;

[0058] (4) After adjusting the image recording component to the image plane position indicated by the crosshair laser, the online imaging results of the curved crystal system were recorded by the X-ray framing camera.

[0059] Two laser beams (1 ns, 3 ω, 800 J) with a focal spot diameter of approximately 200 μm were used to irradiate a Ti foil at the simulated backlight sphere position in the upper channel and the expected backlight position in the lower channel, respectively, to generate helium-like lines. The resulting 600-mesh grid imaging results are shown below. Figure 8 As shown. Following the "80%-20%" evaluation standard, the final spatial resolution result of the bent crystal system is as follows. Figure 9 As shown, by Figure 9 Its spatial resolution is approximately 5-10 μm.

[0060] Therefore, this invention employs the aforementioned high-resolution multi-channel bent crystal imaging system and assembly method. This method utilizes the Abbe imaging principle of visible light lasers to obtain high-resolution imaging results of X-ray bent crystal reflective devices, and establishes the optimal object-image relationship for bent crystal imaging accordingly. This solves the problem of high-precision aiming at the ideal object point position during offline assembly of the multi-channel bent crystal system, ensuring the spatial resolution of the system. Simultaneously, it has the correct optical axis angle relationship to ensure the diffraction efficiency of imaging, achieving high-precision assembly and adjustment of the bent crystal system. By coupling the multi-channel spatial resolution bent crystal imaging system with a framing camera, the bent crystal spectrometer possesses a multi-channel optical structure with spatial and spectral resolution, which can be used for diagnostic experiments of multi-channel backlight imaging type, such as measuring the growth of hydrodynamic instability of a modulation target.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for assembling and adjusting a high-resolution multi-channel curved crystal imaging system, characterized in that, Includes the following steps: S1. Using the expanded and collimated visible light laser as a coherent light source, the multi-channel bent crystal device is adjusted to the visible light laser reflection path, and the imaging element is adjusted to the image plane position of the multi-channel bent crystal device. S2. Periodic diffractors are placed on the object plane as spatial resolution markers. After passing through the periodic diffractors, the coherent light source is diffracted and converted into light waves from different points on the plane where the light source is located. The light waves are reflected by the multi-channel bent crystal device and focused on the corresponding points on the image plane to form the spatial spectrum of the periodic diffractors. The spatial spectrum light waves pass through free space to form a diffractor image containing multiple orders on the image plane. S3. Based on the optimal object position determined by Abbe imaging of periodic objects, replace the visible light laser with an X-ray tube to complete the system assembly and adjustment of the precise object-image relationship of X-ray curved crystal imaging. In step S1, when the structure of the bent crystal element is a focusing form, the relative positions of the periodic diffractometer, the multi-channel bent crystal device, and the imaging element satisfy the following in both the meridional and sagittal directions: （1） （2） in, u This is the distance from the laser plasma X-ray radiation source to the center of the bent crystal. v This is the distance from the center of the curved crystal to the image plane. θ The Bragg diffraction angle at the center of the curved crystal. f m and f s These are the focal lengths in the meridional and sagittal directions, respectively; R m The radius of curvature is the radius along the meridian. R s Let be the radius of curvature in the direction of the arc sagitta.

2. A high-resolution multi-channel curved crystal imaging system, employing the assembly and adjustment method of the high-resolution multi-channel curved crystal imaging system as described in claim 1, characterized in that, It includes a visible light laser, a periodic diffractometer, a multi-channel bent crystal device, and an imaging element arranged sequentially along the optical path. The multi-channel bent crystal device has an overall attitude adjustment assembly connected to it for transmission on its lower side, and the imaging element has a first linear guide rail connected to it for transmission on its lower side.

3. The high-resolution multi-channel curved crystal imaging system according to claim 2, characterized in that, The multi-channel bent crystal device includes multiple bent crystal elements arranged in parallel, and the bent crystal elements are one of the following shapes: spherical, toroidal, or elliptical.

4. The high-resolution multi-channel curved crystal imaging system according to claim 3, characterized in that, The overall attitude adjustment assembly includes a second linear guide rail and a horizontal moving base.

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