A nested full toroidal quasi-ellipsoidal focusing system based on neutron super-mirror and a design method thereof

Abstract

The application discloses a nested full-ring quasi-ellipsoid focusing system based on a neutron super mirror and a design method, which comprises an object plane light source, a focusing mirror arranged on one side of the object plane light source, a sample diaphragm arranged on one side of the focusing mirror, a sample arranged in the sample diaphragm and an image plane detector arranged on one side of the sample diaphragm. The focusing mirror comprises a core shaft and a plurality of mirror surface assemblies uniformly fixed on a circle of the outer surface of the core shaft, and each mirror surface assembly is arranged at intervals. A boron carbide light shielding plate is arranged on the side of the focusing mirror close to the object plane light source, and the focusing mirror improves the signal-to-noise ratio of the system through the boron carbide light shielding plate. According to the application, high gain and high resolution are simultaneously realized, and the designed novel focusing system can meet the application requirement of a small-angle neutron scattering spectrometer of a small accelerator neutron source.

Description

Technical Field

[0001] This invention relates to the technical field of neutron optical instruments, and in particular to a nested full-ring quasi-ellipsoidal focusing system based on a neutron supermirror and its design method. Background Technology

[0002] Small-angle neutron scattering (SANS) spectrometers are mature and stable devices that utilize elastic neutron small-angle scattering (SANS) technology to characterize the nanoscale to mesoscale structures of materials. Considering the safety management and technical challenges of spallation sources, reactor neutron sources, and other neutron sources, the development and widespread application of neutron scattering technology based on large sources have been significantly limited. Therefore, in recent years, small accelerator neutron sources have received widespread attention and development to meet the needs of small-angle neutron scattering experiments in materials science, chemistry, biology, condensed matter physics, and other fields.

[0003] Neutron flux is closely related to the effective focusing area, which consists of the geometric focusing area and the specular reflectivity. Increasing the geometric focusing area is usually achieved through structural optimization design of different focusing devices, mainly in the form of multi-channel conduit focusing, multi-segment connected conduit focusing, and nested focusing. Improving the specular reflectivity is usually achieved by depositing a neutron super mirror coating on the substrate, mainly in the form of nickel film, nickel-iron film, and nickel-titanium film. Related inventions and articles at home and abroad include—Patent 1: A high-throughput small-focal-spot neutron focusing system (Application No.: CN202211030012.X), which discloses a high-throughput small-focal-spot neutron focusing system. Eight Montel-type neutron super mirrors coated with nickel-titanium multilayer films with a super mirror coefficient m≥3 and a critical reflectivity Rc≥90% are arranged in a ring, with precise alignment of the common focal points, allowing different objects to have a common image. However, the double reflection and insufficient expansion of the geometric focusing area still result in a low neutron gain. Patent 2: A neutron conduit (CN201921767208.0) discloses a neutron conduit, which is a multi-segment neutron supermirror conduit. These segments, each coated with a nickel-iron film, are sequentially connected to form the conduit body. However, its single-channel light-gathering capability is insufficient, and the connection method is complex. Article 1: Gubarev et al. (link: https: / / doi.org / 10.1016 / j.nimb.2007.09.041) achieved high light gathering at neutron wavelengths by plating nickel onto nested Wolter mirrors. While achieving a gain of at least 8 times, the nested structure increased the geometric light-gathering area, but the lack of a neutron super mirror with a higher m-value resulted in insufficient neutron gain. Furthermore, none of the aforementioned inventions and articles optimized their structural design based on a surface light source and broad spectrum consistent with actual neutron beamlines, and they failed to couple neutron focusing gain with spectrometer accuracy, preventing the focusing system from achieving theoretical optimization. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a nested, fully annular quasi-ellipsoidal focusing system and its design method based on a neutron supermirror, achieving both high gain and high resolution. The novel focusing system can meet the application requirements of small-angle neutron scattering spectrometers in small accelerator neutron sources. To achieve the above-mentioned objectives and other advantages of the present invention, a nested, fully annular quasi-ellipsoidal focusing system based on a neutron supermirror is provided, comprising:

[0005] An object light source, a focusing lens disposed on one side of the object light source, a sample aperture disposed on one side of the focusing lens, a sample disposed in the sample aperture, and an image detector disposed on one side of the sample aperture.

[0006] The focusing lens includes a core shaft and multiple mirror components uniformly fixed in a ring around the outer surface of the core shaft, with each mirror component spaced apart from the others.

[0007] A boron carbide light-shielding plate is provided on the side of the focusing lens closest to the object light source. The focusing lens improves the signal-to-noise ratio of the system through the boron carbide light-shielding plate.

[0008] Preferably, the mirror assembly includes a multi-layered, fully annular, six-sector, four-segment conical mirror spliced ​​together, with multiple ellipsoidal mirrors supported by five graphite strips and fixed with epoxy resin.

[0009] A design method for a nested, fully annular quasi-ellipsoidal focusing system based on a neutron supermirror includes the following steps:

[0010] S1. Based on the construction requirements and focusing composite structure of the small-angle scattering spectrometer, determine the optimizable parameters and external input conditions of the spectrometer focusing system;

[0011] S2. Establish a geometric model of the spectrometer focusing system, add the geometric modeling parameters to the corresponding positions of the geometric model, and obtain an optimizable basic model of the spectrometer focusing system.

[0012] S3. Based on the existing basic model, the neutron flux data corresponding to different parameter groups of the focusing lens under different system input parameters are calculated by deriving the focal spot formula and optimizing the magnification based on the principles of tight nesting and high signal-to-noise ratio structure.

[0013] S4. Find the parameter set corresponding to the maximum neutron flux intensity and the corresponding optimal system input parameters, light source radius S1 and magnification M, as the design parameters of the small-angle neutron scattering spectrometer.

[0014] S5. Establish a complete model of the spectrometer focusing system based on the optimal parameters, and use the ray tracing method to simulate the performance of the focusing system to characterize its high gain and high resolution features.

[0015] Preferably, the optimizable parameters in step S1 include object-image distance, magnification, incident neutron spectrum, mirror coating material and critical reflectivity, light source size, divergence angle, minimum wave vector transfer, mirror radius, number of nested layers, mirror length and shading area ratio. The external input conditions are determined for the establishment of the basic model of the focusing system, and the optimizable parameters are determined for multi-parameter optimization.

[0016] Preferably, the parameter traversal calculation process in step S3 further includes the following steps: determining the outermost radius R1m of the focusing lens, deriving the parameters of each layer sequentially from the outside to the inside, the selection range of R1m is determined by the grazing incidence angle, and the range of R1m includes receiving the maximum wavelength neutrons from the farthest off-axis light source point to receiving all neutrons of any wavelength from any light source point; based on the object surface light source, for any light source radius S1, adjacent layers should be as close as possible and completely not block the incident and reflected neutrons on the ellipsoidal mirror, and some neutrons will pass directly through the nested layers without reflection; the sample aperture connected to the sample aperture completely blocks these directly penetrating neutrons, that is, the sample aperture and the sample axial position need to be closer to the image plane detector than the axial intersection point of the innermost layer directly penetrating neutron beam and the outermost layer reflected neutron beam; obtaining all neutron flux numbers corresponding to the closely nested high signal-to-noise ratio focusing lens composed of parameter groups of different outermost mirror radii R1m and nested layer number N under the optimal magnification M for any light source radius S1 and optimal magnification M.

[0017] Preferably, the relatively independent parameter magnification M in the system is obtained by establishing a single-wavelength single-layer quasi-ellipsoidal mirror structure. For different light source radii S1, the minimum wave vector transfer amount Qmin required by the spectrometer is used to constrain the position of the focusing mirror, i.e., the magnification M, to obtain the optimal focusing position corresponding to different light source radii S1. The focusing mirror position is determined preferentially according to the spectrometer requirements.

[0018] Preferably, a structural design of tightly nested high signal-to-noise ratio focusing mirrors is achieved by using a variable-sized object surface light source and a movable sample aperture to maximize the neutron flux at the sample. The adjacent ellipsoidal mirrors in the focusing mirror are close to each other and do not block the incident and reflected neutrons on the ellipsoidal mirrors at all, ensuring that neutrons passing through each layer of ellipsoidal mirrors do not incident on the sample 4.

[0019] Compared with the prior art, the beneficial effects of this invention are: (1) It fully combines the neutron supermirror magnetron sputtering technology and the thin cylindrical glass substrate integration assembly technology, and proposes and realizes a composite focusing structure of high-precision lightweight metal core 11-conical approximately thin lens 8 coated with neutron supermirror-high viscosity epoxy resin adhesive 9-high precision graphite strip 10, so that the large m-value supermirror and multi-layer nested coupling system can be used for efficient neutron focusing, laying the foundation for small-angle scattering spectrometers based on small sources to simultaneously meet high gain and high resolution; (2) Under the premise of meeting the spectrometer accuracy, the focusing structure is optimized after fully considering the variable size light source 1 and wide spectrum in the actual application conditions of the spectrometer, which can maximize the neutron flux intensity at 4 points of the sample, making up for the shortcomings of traditional The shortcomings of ideal point source and single-energy neutron system design are addressed by focusing structure that simultaneously satisfies tight nesting and high signal-to-noise ratio; (3) It provides the theoretical radius formula of the focal spot of the cone-shaped approximate quasi-ellipsoidal mirror composed of optimizable parameters and external input conditions and its derivation ideas. By optimizing the relationship between system magnification and focusing mirror position, it provides the design ideas for the optimal focusing mirror position required by the spectrometer, providing a complete new design method for neutron optical system design; (4) It uses the ray tracing method to simulate the intensity distribution of the focused neutron beam on the focal plane under point source and surface source conditions with high precision. At the same time, for the design results based on surface source, it simulates the energy spectrum gain of the focusing mirror under the optimal source size, providing a more complete performance simulation and evaluation system for neutron focusing system. Attached Figure Description

[0020] Figure 1 This is a schematic diagram illustrating the system principle and design of the nested full-ring quasi-ellipsoidal focusing system based on a neutron supermirror according to the present invention.

[0021] Figure 2 The diagram shows the structure of the nested full-ring quasi-ellipsoidal focusing system based on the neutron supermirror according to the present invention.

[0022] Figure 3 A flowchart illustrating the design method of the nested full-ring quasi-ellipsoidal focusing system based on the neutron supermirror according to the present invention.

[0023] Figure 4 The figure shows the minimum wave vector transfer Qmin required by the CPHS small-angle neutron scattering spectrometer based on the nested full-ring quasi-ellipsoidal focusing system of the neutron super mirror according to the present invention under different modes and different light source sizes.

[0024] Figure 5 The measured CPHS spectrum at 240W in May 2021 is the result of the nested full-ring quasi-ellipsoidal focusing system based on the neutron super mirror according to the present invention.

[0025] Figure 6The diagram shows the ideal approximate reflectivity curve of an m=3Ni / Ti super mirror deposited using magnetron sputtering technology with a nested full-ring quasi-ellipsoidal focusing system based on a neutron super mirror according to the present invention.

[0026] Figure 7 To constrain the focusing mirror position L1 of the CPHS spectrometer based on the nested full-ring quasi-ellipsoidal focusing system of the neutron super mirror according to the present invention under different light source radii by the required minimum wave vector transfer amount Qmin, the focusing mirror position when the single-wavelength single-layer conical surface approximate quasi-ellipsoidal mirror reaches the maximum current intensity, and the optimal position L1 selected by the focusing mirror of the CPHS spectrometer.

[0027] Figure 8 To illustrate the focal spot intensity distribution and its encircling energy ratio of the nested full-ring quasi-ellipsoidal focusing system based on a neutron supermirror according to the present invention, which has an ideal mirror surface shape when focusing based on a point source, the three dashed circles in the focal spot diagram correspond to the encircling energy diagrams of 100%, 90%, and 50%, respectively.

[0028] Figure 9 The image shows the intensity distribution of the focal spot and the radius of the focal spot with the ideal mirror shape when focusing on a nested full-ring quasi-ellipsoidal focusing system based on a neutron supermirror according to the present invention, based on a surface light source (S1 = 1, 2.5, 5, 10, 15, 20 mm).

[0029] Figure 10 The left figure of the nested full-ring quasi-ellipsoidal focusing system based on the neutron supermirror according to the present invention shows the current intensity If and the corresponding gain with and without the focusing mirror at different light source radii; the right figure shows the focusing mirror Qmin curve and whether it satisfies a specific Qmin curve at different light source radii.

[0030] Figure 11 This paper presents the neutron flux If and corresponding gain diagrams for the nested full-ring quasi-ellipsoidal focusing system based on a neutron supermirror according to the present invention, with the light source radius at the optimal value (S1 = 15 mm), for different neutron wavelengths with and without a focusing mirror. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] The small-angle neutron scattering spectrometer relies on the Tsinghua University Micro Pulse Hadron Source, which features a variable-size surface source and a wide spectrum. characteristic.

[0033] Reference Figure 1-11 A nested, fully annular quasi-ellipsoidal focusing system based on a neutron supermirror includes: an object light source 1, a focusing mirror 2 disposed on one side of the object light source 1, a sample aperture 3 disposed on one side of the focusing mirror 2, a sample 4 disposed in the sample aperture 3, and an image detector 5 disposed on one side of the sample aperture 3; the focusing mirror 2 includes a core shaft 11 and multiple mirror components uniformly fixed in a ring around the outer surface of the core shaft 11, with each mirror component spaced apart; for example... Figures 1-2 As shown, the neutron beam 6 emitted by the light source 1 is focused by the focusing mirror 2 coated with a neutron super mirror and the unreflected neutrons are blocked by the sample aperture 3. The ring-shaped sample scattering signal after the neutron beam 6 hits the sample 4 and small-angle neutron scattering is received by the image plane detector 5. The neutrons that have not been scattered form a focused spot 7. A boron carbide shield 12 is provided on the side of the focusing mirror 2 near the object surface light source 1. The focusing mirror 2 improves the signal-to-noise ratio of the system through the boron carbide shield 12.

[0034] Furthermore, the mirror assembly includes a multi-layered, fully annular, six-sector, four-segment conical splicing quasi-ellipsoidal mirror 8, with multiple quasi-ellipsoidal mirrors 8 supported by five graphite strips 10 and fixed with epoxy resin adhesive 9.

[0035] A design method for a nested, fully annular quasi-ellipsoidal focusing system based on a neutron supermirror includes the following steps:

[0036] S1. Based on the construction requirements and focusing composite structure of the small-angle scattering spectrometer, determine the optimizable parameters and external input conditions of the spectrometer focusing system;

[0037] S2. Establish the geometric model of the spectrometer focusing system, add the geometric modeling parameters to the corresponding positions of the geometric model, and obtain the basic model of the spectrometer focusing system that can be optimized; add the parameters from the geometric modeling parameter table in Table 1 to the corresponding positions of the geometric model, and obtain the basic model of the spectrometer focusing system that can be optimized.

[0038] Table 1 Geometric Modeling Parameters

[0039]

[0040]

[0041] Among them, a, b, xni, These represent the semi-major axis and semi-minor axis of the ellipsoid, the position of the axial intersection point between the innermost direct-penetrating neutron beam and the outermost reflected neutron beam, and the number of neutrons emitted per unit wavelength per unit solid angle per unit time per unit area of ​​the light source.

[0042] S3. Based on the existing basic model, the focal spot formula is derived and the magnification is optimized. Based on the principle of tight nesting and high signal-to-noise ratio structure, the total neutron flux data corresponding to different parameter groups of focusing mirror 2 under different system input parameters are calculated through multi-parameter traversal.

[0043] S4. Find the parameter set corresponding to the maximum neutron flux and the corresponding optimal system input parameters: source radius S1 and magnification M. These will be used as the design parameters for the small-angle neutron scattering spectrometer. Table 2 shows the design parameters of the CPHS spectrometer focusing system, which will then be used as the design parameters for the CPHS small-angle neutron scattering spectrometer, forming... Figure 2 A ten-layer nested, fully annular, six-sector, four-segment conical, approximately quasi-ellipsoidal focusing lens coated with an m=3Ni / Ti super mirror;

[0044] Table 2. Design parameters of the CPHS spectrometer focusing lens system.

[0045]

[0046] S5. Establish a complete model of the spectrometer focusing system based on the optimal parameters, and use the ray tracing method to simulate the performance of the focusing system to characterize its high gain and high resolution features.

[0047] Furthermore, the optimizable parameters in step S1 include object-image distance, magnification, incident neutron spectrum, mirror coating material and critical reflectivity, light source size, divergence angle, minimum wave vector transfer, mirror radius, number of nested layers, mirror length and shading area ratio. The external input conditions are determined for establishing the basic model of the focusing system, and the optimizable parameters are determined for multi-parameter optimization.

[0048] Furthermore, in step S3, within the system of surface light source 1-conical approximate quasi-ellipsoidal mirror 2-image plane 5, a random light source exit point (x1, S1) is defined to be incident at an angle θ1 onto the random mirror reflection point (x1, S1). 1p ,R 1p The grazing incidence and grazing exit angles are θ. in and θ out Given the lens tilt angle θ2, the relationship between the image plane detection point (x2, P1) and the magnification M, the light source radius S1, and the lens parameters can be obtained using geometric optics as follows:

[0049]

[0050] Where L 1p L 2p R 1r R 1f Let be the axial distance from the reflection point to the object plane and the image plane, respectively, and be the radius of the front and rear ends of the mirror. The function f can be further simplified using the difference in slope between the ellipsoid and the cone, yielding the approximate formula P1.

[0051] This formula is entirely determined by the optimizable parameters and external input conditions;

[0052] In a nested coaxial confocal system, the magnification M is a relatively independent parameter. By establishing a simplified model of a single-wavelength, single-layer conical quasi-ellipsoidal mirror structure, the current intensity formula is used.

[0053] and Figure 4 The focusing mirror position L1 (i.e., magnification M) of the medium-wavelength spectrometer in different modes is constrained by the required minimum wave vector transfer Qmin. In other words, it is the position where the single-wavelength, single-layer conical quasi-ellipsoidal mirror reaches its maximum current intensity, provided that the Qmin of the mirror structure does not exceed the required Qmin. Figure 7 As shown, the optimal position L1 selected by the focusing lens 2 of the CPHS spectrometer is 4000mm, that is, the focusing lens 2 is located in the center of the image, which provides the prerequisite for subsequent multi-parameter traversal calculations.

[0054] In the multi-parameter traversal calculation process, the outermost radius R1m of the focusing lens is first determined, and the parameters of each layer are derived sequentially from the outside to the inside. 1m The selected range is determined by the grazing incidence angle θ (θ = θc = mλ). This range includes all neutrons from the farthest off-axis source point (receiving only the maximum wavelength neutrons) to the point of receiving any wavelength neutrons from any source point. For the CPHS spectrometer, most fast neutrons cannot be reflected by the mirrors. The above neutrons are more widely used. If S1 is 5mm, then R1m≈60mm–194mm. Since the influence of the light source radius S1 is taken into account, in order to make full use of the incident neutrons and suppress unreflected neutrons, two structural principles need to be followed on the basis of the surface light source 1. First, for any light source radius S1, adjacent layers should be as close as possible and should not block the incident and reflected neutrons on the reflector 8. At this time, some neutrons will pass directly through the nested layers without being reflected. Therefore, the second principle is that the sample aperture 3 connected to the sample 4 completely blocks these directly penetrating neutrons. That is, the axial position of the sample aperture 3 and the sample 4 needs to be closer to the detector 5 than the axial intersection point xni of the innermost layer of the directly penetrating neutron beam and the outermost layer of the reflected neutron beam, so as to ensure that the directly penetrating neutrons do not incident on the sample 4 and reduce the signal-to-noise ratio. The position of the sample aperture 3 is also affected by the influence of the light source radius S1. Figure 4 The constraint of minimum wave vector transfer Qmin allows us to determine the maximum number of nested layers N that meets the spectrometer accuracy requirements, using the formulas for light-gathering area and current intensity:

[0055]

[0056]

[0057] For small-angle neutron scattering spectrometers, R Q(Q) is usually used to represent the reflectivity of neutrons of different wavelengths at a certain grazing incidence angle θ, R Q (Q) Cannot be directly converted to R λ (λ), therefore the normalized density distribution function D(θ) is introduced, R λ (λ) can be expressed as

[0058]

[0059] Where D(θ)·dθ represents the proportion of incident neutrons within the grazing incidence angle θ to θ+dθ, and thus the outermost mirror radius R can be obtained under the optimal magnification M and arbitrary source radius S1. 1m All neutron flux intensity data corresponding to the tightly nested high signal-to-noise ratio focusing lens 1, which consists of a nested parameter group with N nesting levels.

[0060] Furthermore, the relatively independent parameter magnification M in the system is obtained by establishing a single-wavelength, single-layer quasi-ellipsoidal mirror structure. For different light source radii S1, the minimum wave vector transfer amount Qmin required by the spectrometer is used to constrain the position of the focusing mirror, i.e., the magnification M, to obtain the optimal focusing position corresponding to different light source radii S1. The focusing mirror position is determined preferentially according to the spectrometer requirements.

[0061] Furthermore, the structure of the tightly nested high signal-to-noise ratio focusing mirror 2, which maximizes the neutron flux at sample 4, is achieved through the variable-size object surface light source 1 and the movable sample aperture 3. The adjacent ellipsoidal mirrors 8 in the focusing mirror 2 are close to each other and do not block the incident and reflected neutrons on the ellipsoidal mirrors 8 at all, ensuring that the neutrons passing through each layer of ellipsoidal mirrors 8 do not incident on sample 4.

[0062] The intensity distribution of the focal spot can reflect the focusing quality. In this embodiment, a relatively simple code was developed to mount all lenses 8 on top of each graphite strip 10 with perfect radius and angle. By establishing a virtual source (point source or surface source) that diverges uniformly at a small angle, approximately 576,000 rays are used to trace the entire focusing lens 2 to obtain the focal spot pattern. Point source focusing evaluated the low-to-mid frequency error of the conical approximation and the future mirror surface shape, thus determining the optical resolution. Surface source focusing has guiding and evaluative value for the experiment. In this embodiment, the ray tracing is all based on an ideal mirror surface shape. Half-power diameter (HPD) is a commonly used parameter characterizing optical resolution. A large number of ray-traced dot plots can obtain diameters with different ingress energies, such as... Figure 8As shown, based on the point light source, the ideal resolution HPD of the focusing lens 2 in this embodiment is 1.354 mm. Compared with the spatial resolution and large field of view of a typical 3He tube detector, this resolution is acceptable. The boron carbide shield 12 blocks the graphite strip 10 and the gaps between each sector. Therefore, this embodiment does not perform ray tracing on the blocked area, resulting in a vacuum region in the intensity distribution, such as... Figure 9 As shown, based on the surface light source 1 (S1 = 1, 2.5, 5, 10, 15, 20 mm), the 100% in-circle energy radius of the focusing lens 2 in this embodiment changes linearly with S1, conforming to the theoretical formula of P1. When S1 < 2.5 mm, the proportions of 50%, 90%, and 100% in-circle energy radii increase (i.e., the relative intensity tends to be distributed outwards). When introducing actual surface shape errors caused by radial mismatch and torsion, this trend in the focal spot intensity distribution of a small light source will amplify the focal spot deformation ratio. In addition, the light emitted from the off-axis light source point can be reflected to... Figure 8 The vacuum region forms a complete circular focal spot 7;

[0063] Neutron flux intensity If is a decisive evaluation indicator characterizing the efficiency of the SANS device. With the use of boron carbide shield 12, the geometric collecting area of ​​focusing mirror 2 is approximately 219 cm², significantly improving neutron collection efficiency. The focusing capability is illustrated by comparing If with and without focusing mirror 2 in the same detection area. Figure 10 As shown in the left figure, the gain decreases as S1 increases. When S1 < 6mm (Low-Q and transition modes), If increases by more than 100 times. When 6mm ≤ S1 < 15mm (partial transition modes), the If gain reaches 23-100 times. When 15mm ≤ S1 ≤ 20mm (Mid-Q mode), the If gain is only 13-23 times. Figure 10 The right figure shows the actual Qmin of focusing lens 2 under different S1 values. When S1>15mm, focusing lens 2 cannot meet the specific Qmin, thus sacrificing detection accuracy. To meet the specific Qmin, sample 4 and sample aperture 3 need to be moved towards the light source 1 (i.e., increase L3). However, sample aperture 3 needs to block all the direct beams, thus inevitably blocking part of the outer reflected neutron beam. In other words, to ensure detection accuracy, neutron flux intensity needs to be sacrificed.

[0064] The energy spectrum gain reflects the focusing capability for a wide CPHS spectrum. In this embodiment, with S1 at its optimal value of 15mm, the If and corresponding gains with and without focusing lens 2 were simulated. It should be noted that... Figure 11 The absolute value of If depends on the wavelength interval step size. Figure 11(For better comparison, the If without focusing lens 2 in the figure is magnified 10 times.) This shows that focusing lens 2 in this embodiment can effectively suppress fast neutrons, achieve a high signal-to-noise ratio, reflect more cold neutrons, and achieve high gain. When the gain reaches saturation, cold neutrons can be completely reflected. In this embodiment, the neutron wavelength is... The effective light-gathering area is approximately 186 cm², achieving a current gain of 83 times, demonstrating excellent neutron focusing capability.

[0065] The number of devices and processing scale described herein are for the purpose of simplifying the description of the invention, and applications, modifications and variations thereof will be apparent to those skilled in the art.

[0066] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A nested, fully annular quasi-ellipsoidal focusing system based on a neutron supermirror, characterized in that, include: Object surface light source (1), focusing lens (2) set on one side of object surface light source (1), sample aperture (3) set on one side of focusing lens (2), sample (4) set in sample aperture (3) and image detector (5) set on one side of sample aperture (3); The focusing lens (2) includes a core shaft (11) and multiple mirror components uniformly fixed to a ring around the outer surface of the core shaft (11), with each mirror component spaced apart. A boron carbide shield (12) is provided on the side of the focusing lens (2) close to the object light source (1). The focusing lens (2) improves the signal-to-noise ratio of the system through the boron carbide shield (12). Based on the existing basic model, the focal spot formula is derived and the magnification is optimized. Based on the principle of tight nesting and high signal-to-noise ratio structure, the multi-parameter traversal calculation is performed to calculate all neutron flux data corresponding to different parameter groups of the focusing lens (2) under different system input parameters. The parameter traversal calculation process includes the following steps: determine the outermost radius R1m of the focusing lens, derive the parameters of each layer from the outside to the inside, the selection range of R1m is determined by the grazing incidence angle, and the range of R1m includes the maximum wavelength neutrons received only from the farthest off-axis light source point to all neutrons received from any light source point of any wavelength; based on the object surface light source (1), for any light source radius S1, adjacent layers should be as close as possible and completely not block the incident and reflected neutrons on the ellipsoidal mirror (8). Some neutrons will pass directly through the nested layers without being reflected. The sample aperture (3) connected to the sample aperture completely blocks these through neutrons. That is, the axial position of the sample aperture (3) and the sample (4) should be closer to the image detector (5) than the axial intersection point of the innermost through neutron beam and the outermost reflected neutron beam. All neutron flux numbers corresponding to the tightly nested high signal-to-noise ratio focusing mirror (2) with different outermost mirror radii R1m and nested layer number N under the parameter group of arbitrary light source radius S1 and optimal magnification M are obtained. The relatively independent parameter magnification M in the system is obtained by establishing a single-wavelength single-layer quasi-ellipsoidal mirror structure. For different light source radii S1, the minimum wave vector transfer amount Qmin required by the spectrometer is used to constrain the position of the focusing mirror, i.e., the magnification M, to obtain the optimal focusing position corresponding to different light source radii S1. The focusing mirror position is determined first according to the spectrometer requirements. The structure design of the tightly nested high signal-to-noise ratio focusing lens (2) under the maximum neutron flux intensity at the sample (4) is achieved by using a variable-size object surface light source (1) and a movable sample aperture (3). The adjacent ellipsoidal mirrors (8) in the focusing lens (2) are close to each other and do not block the incident and reflected neutrons on the ellipsoidal mirrors (8), ensuring that the neutrons passing through each layer of ellipsoidal mirrors (8) do not incident on the sample (4). The mirror assembly includes a multi-layered, fully annular, six-sector, four-segment conical splicing quasi-ellipsoidal mirror (8), with multiple quasi-ellipsoidal mirrors (8) supported by five graphite strips (10) and fixed with epoxy resin glue (9).

2. The design method for a nested full-ring quasi-ellipsoidal focusing system based on a neutron supermirror as described in claim 1, characterized in that, Includes the following steps: S1. Based on the construction requirements and focusing composite structure of the small-angle scattering spectrometer, determine the optimizable parameters and external input conditions of the spectrometer focusing system; S2. Establish a geometric model of the spectrometer focusing system, add the geometric modeling parameters to the corresponding positions of the geometric model, and obtain an optimizable basic model of the spectrometer focusing system. S3. Based on the existing basic model, the focal spot formula is derived and the magnification is optimized. Based on the principle of tight nesting and high signal-to-noise ratio structure, the multi-parameter traversal is used to calculate all the neutron flux data corresponding to different parameter groups of the focusing lens (2) under different system input parameters. S4. Find the parameter set corresponding to the maximum neutron flux intensity and the corresponding optimal system input parameters, light source radius S1 and magnification M, as the design parameters of the small-angle neutron scattering spectrometer. S5. Establish a complete model of the spectrometer focusing system based on the optimal parameters, and use the ray tracing method to simulate the performance of the focusing system to characterize its high gain and high resolution features.

3. The design method for a nested full-ring quasi-ellipsoidal focusing system based on a neutron supermirror as described in claim 2, characterized in that, The optimizable parameters in step S1 include object-image distance, magnification, incident neutron spectrum, mirror coating material and critical reflectivity, light source size, divergence angle, minimum wave vector transfer, mirror radius, number of nested layers, mirror length and shading area ratio. The external input conditions are determined for the establishment of the basic model of the focusing system, and the optimizable parameters are determined for multi-parameter optimization.

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