CN112927834B - Diaphragm structure and micro-angle neutron scattering spectrometer - Google Patents
Diaphragm structure and micro-angle neutron scattering spectrometer Download PDFInfo
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- CN112927834B CN112927834B CN202110112691.4A CN202110112691A CN112927834B CN 112927834 B CN112927834 B CN 112927834B CN 202110112691 A CN202110112691 A CN 202110112691A CN 112927834 B CN112927834 B CN 112927834B
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- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21K—TECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
- G21K1/00—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating
- G21K1/02—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating using diaphragms, collimators
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
- G01N23/20—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by using diffraction of the radiation by the materials, e.g. for investigating crystal structure; by using scattering of the radiation by the materials, e.g. for investigating non-crystalline materials; by using reflection of the radiation by the materials
- G01N23/20008—Constructional details of analysers, e.g. characterised by X-ray source, detector or optical system; Accessories therefor; Preparing specimens therefor
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
- G01N23/20—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by using diffraction of the radiation by the materials, e.g. for investigating crystal structure; by using scattering of the radiation by the materials, e.g. for investigating non-crystalline materials; by using reflection of the radiation by the materials
- G01N23/201—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by using diffraction of the radiation by the materials, e.g. for investigating crystal structure; by using scattering of the radiation by the materials, e.g. for investigating non-crystalline materials; by using reflection of the radiation by the materials by measuring small-angle scattering
- G01N23/202—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by using diffraction of the radiation by the materials, e.g. for investigating crystal structure; by using scattering of the radiation by the materials, e.g. for investigating non-crystalline materials; by using reflection of the radiation by the materials by measuring small-angle scattering using neutrons
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2223/00—Investigating materials by wave or particle radiation
- G01N2223/05—Investigating materials by wave or particle radiation by diffraction, scatter or reflection
- G01N2223/054—Investigating materials by wave or particle radiation by diffraction, scatter or reflection small angle scatter
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2223/00—Investigating materials by wave or particle radiation
- G01N2223/10—Different kinds of radiation or particles
- G01N2223/106—Different kinds of radiation or particles neutrons
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E30/00—Energy generation of nuclear origin
- Y02E30/30—Nuclear fission reactors
Abstract
The embodiment of the invention discloses a diaphragm structure and a micro-angle neutron scattering spectrometer. The diaphragm structure is used for realizing the focusing of a plurality of neutron beams and comprises a plurality of diaphragms which are arranged in sequence along the propagation direction of the neutron beams and share the same optical axis; the diaphragm comprises a first neutron absorption layer, a second neutron absorption layer and a supporting layer which are sequentially stacked, wherein the first neutron absorption layer is positioned on one side of the diaphragm close to the neutron source; the diaphragm structure comprises a plurality of slits, and the width of the incident end of each slit is larger than that of the emergent end; wherein the width direction of the slit is perpendicular to the optical axis. According to the technical scheme of the embodiment of the invention, a plurality of beams of neutrons can be transmitted to the surface of a detector without crosstalk, meanwhile, the stray neutrons generated by reflection and parasitic scattering at the edge of the collimator are reduced as much as possible, the method can be applied to a high-precision neutron optical path structure of a small-angle neutron scattering spectrometer, and the sample size range which can be represented by the conventional small-angle neutron scattering spectrometer is expanded from nano-scale to submicron-scale.
Description
Technical Field
The embodiment of the invention relates to a small-angle neutron scattering technology, in particular to a diaphragm structure and a micro-angle neutron scattering spectrometer.
Background
Since the discovery of neutrons by chard-weck in 1932, scientists have been investigating neutrons as probes for exploring secrets within matter. After 1945, a large number of fission reactors were built, and scientific experiments were conducted to extract neutrons produced by the reactors. The american scientist Shull and canadian scientist Brockhouse collectively honor the 1994 nobel prize in physics by studying the structure and movement of internal atoms of matter using reactor-derived neutrons.
With the development of the research, scientists have increasingly demanded neutron sources and neutron spectrometers, which require high resolution in addition to high neutron flux. Reactor neutron sources are limited by heat dissipation limits and the use of internationally highly enriched uranium, neutron flux has reached a limit, and spallation neutron sources are becoming a new favorite of scientists with the high resolution of their pulsed neutron sources and the neutron flux constantly refreshed by new technologies. Since the eighties of the last century, each of the major countries develops its own spallation neutron source technology. The four major spallation neutron sources currently in operation comprise an English spallation neutron source (ISIS), an American Spallation Neutron Source (SNS), a Japanese spallation neutron source (J-PARC) and a Chinese Spallation Neutron Source (CSNS), wherein the Chinese spallation neutron source is from formal start-up construction in 10 months in 2010, and the national acceptance is completed in 23 months in 8 months in 2018, so that the four spallation neutron sources are the first pulse type neutron sources in China. Currently, europe is building the world's largest pulsed spallation neutron source-european spallation neutron source (ESS), which is expected to be completed in 2025. Compared with a synchrotron radiation X-ray source, the brightness of a neutron source is very limited, and the neutron source is also very expensive, so that the brightness is more technically and budgetedly challenging. Therefore, it is the most economical and efficient means to improve the neutron optical design in the beam line of the neutron scatterometer and maximize the utilization of each neutron that is not easy to come. The new optical path design can break through the limit of the traditional spectrometer and provide new possibility for discovering new physics and better serving the industrial field.
The small-angle neutron scattering technology is one of the most commonly used scattering technologies in the neutron scattering technology, and can be used for characterizing materials with the characteristic dimension of 1-100 nanometers. The method is widely applied to characterization of internal structures of biomacromolecules, macromolecules, metal precipitated phases, carbon fibers and the like in the aspects of new energy, new materials and the like. Conventional small-angle neutron scattering spectrometers (SANS) typically employ a pinhole tableIt features that a source diaphragm and a sample diaphragm are used to collimate incident light, but the diameter of diaphragm is usually in cm order due to the brightness limitation of neutron source, the minimum scattering angle is limited, and its minimum scattering vector Q is min (
Wherein theta is min At minimum scattering angle, λ max The longest neutron wavelength) or the largest measurable sample size d max 
May be limited to a certain range. Therefore, it is necessary to develop an optical path structure having a good neutron beam focusing effect.
Disclosure of Invention
The embodiment of the invention provides a diaphragm structure and a micro-angle neutron scattering spectrometer, wherein the diaphragm structure is used for focusing a plurality of neutron beams, transmitting the plurality of neutrons to the surface of a detector without crosstalk, reducing the stray neutrons generated by reflection and parasitic scattering at the edge of a collimator as much as possible, and can be applied to a high-precision neutron optical path structure of the micro-angle neutron scattering spectrometer, so that the sample size range which can be represented by the conventional small-angle neutron scattering spectrometer is expanded from the nanometer level (1-100 nanometers) to the submicron level (1-1000 nanometers).
In a first aspect, an embodiment of the present invention provides a diaphragm structure, configured to implement focusing of a plurality of neutron beams, including a plurality of diaphragms that share an optical axis and are sequentially arranged along a propagation direction of the neutron beams;
the diaphragm comprises a first neutron absorption layer, a second neutron absorption layer and a supporting layer which are sequentially stacked, wherein the first neutron absorption layer is positioned on one side of the diaphragm close to the neutron source;
the diaphragm comprises a plurality of slits, and the width of the incident end of each slit is larger than that of the emergent end of each slit;
wherein the width direction of the slit is perpendicular to the optical axis.
Optionally, the first neutron absorption layer includes boron-aluminum alloy, the second neutron absorption layer includes cadmium or gadolinium, and the support layer includes aluminum alloy.
Optionally, the position relationship of each diaphragm satisfies:
the width of the incident end of the slit of each diaphragm satisfies the following conditions:
wherein the content of the first and second substances,
r represents the ratio of the width of a shielding area of the diaphragm to the width of an incident end of the slit, p represents the ratio of the width of the shielding area of the next diaphragm to the width of the shielding area after the slit of the previous diaphragm is penetrated, p is a certain value between 0 and 1, D represents the position of the diaphragm, O represents the width of the incident end of the slit, subscripts of O and D are the serial numbers of the diaphragms, the diaphragm closest to the neutron source is the 0 th diaphragm, the diaphragm farthest from the neutron source is the 1 st diaphragm, the serial numbers of the diaphragms are sequentially increased along the direction that the 1 st diaphragm points to the 0 th diaphragm, and n and j are positive integers.
Optionally, the positional relationship of each diaphragm satisfies:
the width of the incident end of the slit of each diaphragm satisfies the following conditions:
wherein the content of the first and second substances,
r represents the ratio of the width of the shielding area of the diaphragm to the width of the incident end of the slit, D represents the position of the diaphragm, O represents the width of the incident end of the slit, B represents the width of the shielding area of the diaphragm, subscripts of O, D, K and p are the numbers of the diaphragms, the diaphragm closest to a neutron source is a 0 th diaphragm, the diaphragm farthest from the neutron source is a 1 st diaphragm, the numbers of the diaphragms are sequentially increased along the direction that the 1 st diaphragm points to the 0 th diaphragm, and p is sequentially increased n Represents the ratio of the width of the shielding region of the nth diaphragm to the width of the shielding region after passing through the slit of the (n + 1) th diaphragm, and p n *B n And n and j are positive integers and are constant values.
Optionally, the number of the diaphragms is greater than 3, and along the propagation direction of the neutron beam, the thicknesses of the first neutron absorption layers in the first diaphragm to the third diaphragm are 2.5mm to 3mm, and the thicknesses of the first neutron absorption layers in the other diaphragms are 1.5mm to 2mm.
Optionally, the thickness of the second neutron absorption layer is 0.5mm to 1mm, and the thickness of the support layer is 2mm to 3mm.
Optionally, the projection shapes of the slits of the first neutron absorption layer and the second neutron absorption layer on a first plane are trapezoidal, and the first plane is perpendicular to the plane where the diaphragm is located;
the included angle between the trapezoid waist and the optical axis direction is 3-5 degrees.
Optionally, the number of the diaphragms is 10 to 15.
In a second aspect, an embodiment of the present invention further provides a micro-angle neutron scattering spectrometer, including a neutron source arranged along a common optical axis, any one of the above diaphragm structures, a sample to be detected, and a detector.
Optionally, the neutron source comprises a spallation neutron source or a reactor neutron source.
The diaphragm structure provided by the embodiment of the invention is used for realizing the focusing of a plurality of neutron beams, and comprises a plurality of diaphragms which are arranged in sequence along the propagation direction of the neutron beams and share a common optical axis; the diaphragm comprises a first neutron absorption layer, a second neutron absorption layer and a supporting layer which are sequentially stacked, wherein the first neutron absorption layer is positioned on one side of the diaphragm close to the neutron source; the diaphragm comprises a plurality of slits, and the width of the incident end of each slit is larger than that of the emergent end; wherein, the width direction of the slit is vertical to the optical axis. By arranging a plurality of diaphragms, a plurality of neutron beams are focused on the surface of a detector without crosstalk, and stray neutrons generated by reflection and parasitic scattering at the edge of a collimator are reduced as much as possible; by designing the multi-slit diaphragm with a high-precision sandwich structure of the first neutron absorption layer, the second neutron absorption layer and the supporting layer, the edge scattering of neutrons is greatly reduced; by reasonably designing the gap width of the multi-slit diaphragms, the proportion of the blocking width to the gap width and the position of each multi-slit diaphragm, the maximum neutron flux is realized by using the minimum number of diaphragms, and meanwhile, even if certain installation errors exist, crosstalk cannot occur between all the beams, so that the method is applied to a high-precision neutron optical path structure of a micro-angle neutron scattering spectrometer, and the sample size range which can be represented by the conventional small-angle neutron scattering spectrometer is expanded from the nanometer level (1-100 nanometers) to the submicron level (1-1000 nanometers).
Drawings
Fig. 1 is a schematic structural diagram of a diaphragm structure according to an embodiment of the present invention;
FIG. 2 is a schematic enlarged partial structural view of a dashed-line frame region in FIG. 1;
FIG. 3 is a schematic diagram of neutron transmittance in boron-aluminum (B-Al) alloy;
FIG. 4 is a graph showing the neutron transmittance in cadmium (Cd);
FIG. 5 is a schematic view of a slit edge profile provided in an embodiment of the present invention;
fig. 6 is a schematic position diagram of a diaphragm structure according to an embodiment of the present invention;
FIG. 7 is a schematic illustration of the position of another diaphragm structure provided in an embodiment of the present invention;
FIGS. 8 and 9 are schematic diagrams of arrangement of diaphragms obtained by using a Barker algorithm and an optimized Barker algorithm, respectively;
FIGS. 10 and 11 are schematic diagrams of neutron trajectory simulations obtained using the Barker algorithm and the optimized Barker algorithm, respectively;
FIG. 12 is a schematic diagram of the position distribution of the neutron flux after eight neutron beams are focused on the surface of the detector obtained by simulation by the Monte-Carlo method;
FIG. 13 is a schematic diagram of the horizontal distribution of neutron count rates at the sample location after the last three diaphragms have been removed;
fig. 14 is a schematic structural diagram of a micro-angle neutron scattering spectrometer according to an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not to be construed as limiting the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.
The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. It should be noted that the terms "upper", "lower", "left", "right", and the like used in the description of the embodiments of the present invention are used in the angle shown in the drawings, and should not be construed as limiting the embodiments of the present invention. In addition, in this context, it will also be understood that when an element is referred to as being "on" or "under" another element, it can be directly formed on "or" under "the other element or be indirectly formed on" or "under" the other element through intervening elements. The terms "first," "second," and the like, are used for descriptive purposes only and not for purposes of limitation, and do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The specific meanings of the above terms in the present invention can be understood according to specific situations by those of ordinary skill in the art.
The sample size that can be measured by conventional small angle neutron scattering spectrometers is typically in the range of 1nm to 100 nm. To extend the characterization scale range of conventional small-angle neutron scattering spectrometers to the sub-micron scale of 100-1000nm, various neutron focusing techniques, the so-called micro-angle neutron scattering spectrometer (VSANS) technique, have been tried, which can be generally classified into the following categories: 1) Very long spectrometer technology; 2) The compound lens focusing technology comprises a wolter toroidal mirror and ellipsoidal focusing; 3) Magnetic lens focusing techniques; 4) Reflective focusing mirror technology; 5) Multi-slit and multi-aperture collimating diaphragm techniques. However, the first three techniques are generally only suitable for reactor neutron sources using neutrons of a single wavelength, and lens focusing is currently only applied to reactor neutron sources in ulishi, germany due to the technical difficulty and difficulty in integrating with a spectrometer for scattering neutron sources. There have been several attempts at multi-slit and multi-aperture focusing diaphragms in reactor neutron sources, such as the VSANS spectrometer of the berlin research heap of the helmholtz research union of germany and the VSANS spectrometer of the Sacalay research heap of french. The cold neutrons are in parabolic motion under the action of gravity, so that the focusing of the multi-aperture focusing diaphragm is not suitable for a spallation neutron source. Based on the above analysis, a multi-slit diaphragm is the best choice for the current VSANS spectrometer based on a spallation neutron source. The adoption of a multi-slit diaphragm to collimate the neutron beam has three problems, namely, the selection of a proper material can reduce the edge parasitic scattering and the gamma background generated by the neutron captured by the material to the maximum limit; secondly, selecting a proper processing technology on the basis of material selection to ensure the processing precision of micron level; thirdly, designing and optimizing a layout algorithm of the diaphragms, and realizing the maximum neutron flux at the sample position with the minimum diaphragm quantity. The above three problems are the basis for achieving high-flux, low-background, slight angular neutron scattering.
Therefore, an embodiment of the present invention provides a diaphragm structure suitable for a micro-angle neutron scattering spectrometer, fig. 1 is a schematic structural diagram of the diaphragm structure provided in the embodiment of the present invention, and fig. 2 is a schematic partial enlarged structural diagram of a dashed-line frame region in fig. 1. Referring to fig. 1 and 2, the diaphragm structure provided in this embodiment is used for focusing a plurality of neutron beams, and includes a plurality of diaphragms 10 that share an optical axis and are sequentially arranged along a propagation direction of the neutron beams; the diaphragm 10 comprises a first neutron absorption layer 11, a second neutron absorption layer 12 and a support layer 13 which are sequentially stacked, wherein the first neutron absorption layer 11 is positioned on one side of the diaphragm 10 close to the neutron source; the diaphragm 10 comprisesA plurality of slits 14, a width d of an incident end of the slits 14 1 Is greater than the width d of the emergent end 2 (ii) a Wherein the width direction of the slit 14 is perpendicular to the optical axis.
The first neutron absorption layer 11 and the second neutron absorption layer 12 are used for absorbing neutrons, the slit 14 is used for transmitting neutrons, and it is very critical that the material selection of the first neutron absorption layer 11 and the second neutron absorption layer 12 and the signal-to-noise ratio of parasitic scattering at the edge of the slit 14 can reach the theoretical minimum scattering vector. The elements for absorbing neutrons usually include lithium, boron, cadmium and gadolinium, wherein Li-6 in the lithium element is an effective isotope for absorbing neutrons, and generates a helium nucleus and a tritium without gamma rays after absorbing neutrons, but lithium is too active and is usually dispersed in rubber and resin in the form of compounds to form neutron absorbing materials, boron generates gamma rays of about 400keV after absorbing neutrons, and is relatively easy to shield, cadmium and gadolinium are easy to process, neutron absorbing cross sections are as much as one order of magnitude higher than that of boron, but cadmium and gadolinium can generate high-energy gamma rays of about 80MeV after absorbing neutrons. Based on the above facts, optionally, the first neutron absorption layer 11 includes a boron-aluminum alloy, the second neutron absorption layer 12 includes cadmium or gadolinium, and the support layer 13 includes an aluminum alloy. The diaphragm 10 is to be a sandwich structure, the foremost layer may be boron-aluminum alloy with a boron content of 30wt%, the middle layer may be cadmium or gadolinium with an edge accurately cut to reduce parasitic scattering at the edge, and the last layer is aluminum alloy for fixing cadmium or gadolinium which is easy to deform in the middle. If the edge of the diaphragm is cut very smoothly, neutrons are reflected to cause a background, and optionally, referring to fig. 2, the projection shapes of the slits 14 of the first neutron absorbing layer 11 and the second neutron absorbing layer 12 on a first plane are trapezoidal, and the first plane is perpendicular to the plane of the diaphragm; the angle between the trapezoid waist and the optical axis direction is 5 deg. I.e. bevelling the edge of the diaphragm 10 by 5 deg. is usually a good option. In particular implementations, it is quite challenging to cut three layers of diaphragm material with micron-scale precision, and embodiments of the present invention determine to use three layers of conductive material to form the slits 14 using a spark slow wire cutting (WEDM) process. The first layer is made of boron aluminum alloy, the second layer is made of cadmium or gadolinium, and the third layer is made of aluminum alloy to ensure that the cadmium or gadolinium with poor hardness cannot deform. The gadolinium has the largest absorption cross section for cold neutrons, but a practical result of a large number of slow-running wire cutting shows that, because the gadolinium has low conductivity, molybdenum wires are easy to break in the wire cutting process, and the precision of the cut diaphragm is not high, cadmium is preferably used as the material of the second neutron absorption layer 12 in the embodiment.
Optionally, the number of the diaphragms is greater than 3, and along the propagation direction of the neutron beam, the thickness of the first neutron absorption layer in the first diaphragm to the third diaphragm is 2.5mm to 3mm, and the thickness of the first neutron absorption layer in the other diaphragms is 1.5mm to 2mm. Optionally, the thickness of the second neutron absorption layer is 0.5mm to 1mm, and the thickness of the support layer is 2mm to 3mm.
The boron content of the currently commercialized boron-aluminum alloy can reach 30wt% at most, and the transmittance of a diaphragm to neutrons is calculated below to verify that the thickness of the selected neutron absorbing material is enough to absorb 1E9 (10) generated by a spallation neutron source 9 ) neutron flux of the order of n/s.
The formula of the neutron transmittance of the material is as follows:
wherein N represents that N isotopes exist in the material, sigma (i) is a macroscopic neutron absorption section of the ith isotope, sigma (i) is a microscopic neutron absorption section of the ith element, rho (i) is the density of the ith isotope in the system, and d is the thickness of the absorption material.
The isotopic neutron cross-sectional Data (https:// www-nds. Iaea. Org/for/ENDF. Htm) using the above transmittance formula (1) and the online database (Evaluated Nuclear Data File ENDF) are shown in fig. 3, which is a graph showing the transmittance of neutrons in boron-aluminum alloy (B-Al), and fig. 4, which is a graph showing the transmittance of neutrons in cadmium (Cd). The density of the B-Al alloy used in the calculation was 2.5g/cm 3 The density of Cd was 7.99g/cm 3 Boron in the B-Al alloy in an amount of 30wt%, an isotope 10 The abundance of B in natural boron is 19.9%, 113 the abundance ratio of Cd isotope in natural cadmium is 12.36%,and the absorption of neutrons by other isotopes of cadmium is neglected.
2mm of B-Al alloy pair with reference to FIG. 3
Neutron transmission of 1.0E5, and 3mm B-Al alloy pair
Has a neutron transmittance of 3.5e8. The first three diaphragms will absorb most of the neutrons coming out of the conduit, so it is necessary to take the thickness of the B-Al alloy to 2.5mm to 3mm. For other diaphragms, a B-Al alloy of 1.5mm to 2mm may be sufficient. By using 10 The thickness of the B-Al alloy and the B-Al alloy layer can be reduced to about 1/4 of that of the natural B-Al alloy, but the cost is higher. Cadmium mainly serves to reduce edge parasitic scattering, and the thickness of cadmium can be thinner.
FIG. 5 is a schematic view showing the shape of a slit edge according to an embodiment of the present invention, referring to FIG. 5,3mm B-Al alloy, 0.5mm Cd and 5 ° chamfer angle, the chamfer portion forming a triangle having a height of about 0.3mm, wherein FIG. 5 does not show an aluminum alloy layer as a support layer. At the edge position, the thickness of B-Al alloy can be thinner, at this moment mainly rely on Cd to absorb the neutron, because metal Cd can cut very level and smooth, can prevent effectively that edge burr from producing edge parasitic scattering simultaneously.
According to the technical scheme of the embodiment, a plurality of diaphragms are arranged, so that a plurality of neutron beams are focused on the surface of a detector without crosstalk, and stray neutrons generated by reflection and parasitic scattering at the edge of a collimator are reduced as much as possible; by designing the multi-slit diaphragm with a high-precision sandwich structure of the first neutron absorption layer, the second neutron absorption layer and the supporting layer, the edge scattering of neutrons is greatly reduced; by reasonably designing the gap width of the multi-slit diaphragms, the proportion of the blocking width to the gap width and the position of each multi-slit diaphragm, the maximum neutron flux is realized by using the minimum number of diaphragms, and meanwhile, even if certain installation errors exist, crosstalk cannot occur between all the beams, so that the method is applied to a high-precision neutron optical path structure of a micro-angle neutron scattering spectrometer, and the sample size range which can be represented by the conventional small-angle neutron scattering spectrometer is expanded from the nanometer level (1-100 nanometers) to the submicron level (1-1000 nanometers).
On the basis of the above technical solution, optionally, the position relationship of each diaphragm satisfies:
the width of the incident end of the slit of each diaphragm satisfies the following conditions:
wherein the content of the first and second substances,
r represents the ratio of the width of the shielding area of the diaphragm to the width of the incident end of the slit, p represents the ratio of the width of the shielding area of the next diaphragm to the width of the shielding area after the slit of the previous diaphragm is transmitted, and p is a certain value between 0 and 1, D represents the position of the diaphragm, O represents the width of the incident end of the slit, subscripts of O and D are the serial numbers of the diaphragms, the diaphragm closest to the neutron source is the 0 th diaphragm, the diaphragm farthest from the neutron source is the 1 st diaphragm, the direction of pointing to the 0 th diaphragm along the 1 st diaphragm, the serial numbers of the diaphragms are sequentially increased, and n and j are positive integers.
It will be appreciated that the arrangement of the diaphragms is designed to deliver the most neutrons from the source diaphragm (the diaphragm closest to the neutron source) to the detector surface, and that the number of diaphragms is minimized to achieve a plurality of neutron beams without crosstalk.
Fig. 6 is a schematic diagram of positions of a diaphragm structure provided in an embodiment of the present invention, where the positions of the diaphragms are derived from a set of algorithms based on John Barker of neutron scattering center in the national bureau of standards, specifically as follows:
referring to FIG. 6, assume that the width of the opening at the source aperture is O 0 The distance source diaphragm D can be calculated by focusing multiple neutrons on a point on the detector surface of the distance source diaphragm D 1 Position of sample diaphragm opening width O 1 . First, a block aperture ratio (ratio of the width of the shielding region of the diaphragm to the width of the entrance end of the slit) is defined
The basic geometry of multi-aperture focusing is thus determined by the source and sample apertures (the apertures closest to the sample to be measured), the multi-slit between the source and sample apertures being primarily to prevent cross-talk between the neutron beams. The design of the multi-slit diaphragm is mainly to determine the position D of the middle slit 2 、D 3 …D n 。
The basic design concept of the Barker algorithm is that the intermediate diaphragms are arranged backwards one by one from the one closest to the sample diaphragm, D 2 Is arranged at a position to ensure that the neutron beam can only irradiate 0.5B 1 Position of (D), D 3 Is arranged at a position to ensure that the neutron beam can only irradiate 0.5B 2 Position, D n Is arranged at a position to ensure that the neutron beam can only irradiate 0.5B n-1 Position of (3) or pB n-1 Where p is a real number between 0 and 1.
Referring to fig. 6, the diaphragms are numbered one by one according to the determination sequence of the diaphragm positions, the diaphragm closest to the neutron source is the 0 th diaphragm, the diaphragm closest to the sample is the 1 st diaphragm, the diaphragm next to the sample is the 2 nd diaphragm, and so on. According to the geometrical relationship:
wherein the ratio of the blocking opening
n =1,2,3 \8230pis the safety margin ratio, a real number between 0 and 1, and usually between 0.1 and 0.5 is appropriate,
a general formula for the diaphragm position can be found from equation (2):
wherein n =1,2,3 \ 8230, j =1,2,3 \ 8230;
the geometrical relationship according to fig. 6:
combining equations (2) and (4) yields:
the general formula for the central multiple diaphragm openings is:
wherein n =1,2,3 8230, j =1,2,3, 8230.
Known parameter O 0 、O 1 、D 1 R and p, the opening and position of all the intermediate diaphragms can be determined by the formulas (3) and (6), and n =1, j =1,2,3 \8230canbe set in specific implementation. Specifically, if n is 1,2,3,4,5 \8230canbe obtained by adding 1 to j, alternately using formula (6) and formula (3), and the opening widths and positions of all the diaphragms are obtained, and if n is equal to 2, then j is added 1 to obtain 3,4,5,6 \8230andthe opening widths and positions of the diaphragms.
In another embodiment, the method can be further improved on the basis of the Barker algorithm, crosstalk among neutron beams is prevented to a greater extent while the number of diaphragms is reduced by about 30%, and fewer diaphragms can reduce parasitic scattering caused by edge scattering and reduce the difficulty of collimation. OptimizedThe Barker algorithm is improved by 0.5B n-1 Or pB n-1 A constant value of m is used to ensure that no crosstalk between the neutron beams occurs as long as m is greater than the horizontal movement uncertainty of the multi-slit aperture because the horizontal uncertainty of each aperture is the same.
Optionally, the position relationship of each diaphragm satisfies:
the width of the incident end of the slit of each diaphragm satisfies the following conditions:
wherein the content of the first and second substances,
r represents the ratio of the width of the shielding area of the diaphragm to the width of the incident end of the slit, D represents the position of the diaphragm, O represents the width of the incident end of the slit, B represents the width of the shielding area of the diaphragm, subscripts of O, D, K and p are the serial numbers of the diaphragms, the diaphragm closest to the neutron source is the 0 th diaphragm, the diaphragm farthest from the neutron source is the 1 st diaphragm, the 1 st diaphragm points to the 0 th diaphragm along the direction in which the 1 st diaphragm points, the serial numbers of the diaphragms are sequentially increased, and p is n Represents the ratio of the width of the shielding region of the nth diaphragm to the width of the shielding region after passing through the slit of the (n + 1) th diaphragm, and p n *B n And n and j are positive integers and are constant values.
FIG. 7 is a schematic diagram showing the positions of another diaphragm structure provided by the embodiment of the present invention, the positions of the respective diaphragms are obtained by the optimized Barker algorithm, and the general equations (3) and (6) are still applied, when the boundary safety ratio p is changed to p n And K will become K n ：
Barrier opening ratio
n＝1，2，3…，j＝1，2，3……，
Known parameter O 0 、D、D 1 R and m, the openings and positions of all intermediate diaphragms can be determined one by one in an iterative manner using equations (7) and (8), which can be taken as n =1, j =1,2,3 \ 8230.
In specific implementation, the optimized Barker algorithm and the Barker algorithm should have the same straight light spot on the surface of the detector, but the optimized Barker algorithm has better capability of resisting crosstalk under the condition of the same number of diaphragms.
For example, fig. 8 and 9 are schematic diagrams of the arrangement of the diaphragm obtained by the Barker algorithm and the optimized Barker algorithm, respectively, where O is 0 、D、D 1 Initial values of r, p and m were 2.554mm, 25500mm,12320mm,0.535,0.396 and
in order to ensure the fairness of comparison, the number of the diaphragms used in the two algorithms is the same, and is 12.
In order to further verify the advantages of the optimization algorithm, neutron trajectory tracking software McStas is used for establishing a model for the arrangement of the diaphragms obtained by the two algorithms, and the distribution situation of neutrons in the horizontal direction after the neutrons penetrate through the diaphragms is simulated. Fig. 10 and 11 are schematic diagrams showing neutron trajectory simulation by using the Barker algorithm and the optimized Barker algorithm, respectively, and it can be known from comparison between fig. 10 and 11 that the crosstalk between neutron beams can be better suppressed by the optimization algorithm than the Barker algorithm under the condition of using the same number of slits and multiple slits. Fig. 12 is a schematic diagram showing the position distribution of the neutron flux after eight neutron beams are focused on the surface of the detector by the Monte-Carlo method simulation, in this case, the results obtained by the two algorithms are the same, and the neutron flux is distributed in a triangular shape in the horizontal direction. If the three diaphragms closest to the sample are removed, FIG. 13 is a schematic diagram showing the horizontal distribution of neutron counting rates at the sample position after the last three diaphragms are removed, as can be seen from FIG. 13, crosstalk between neutron beams occurs in the diaphragm arrangement obtained by the Barker algorithm, and the result of Monte-Carlo simulation verifies the conclusion.
Optionally, the number of the diaphragms 10 is 10 to 15, which may be selected according to actual situations in specific implementation, and this is not limited in the embodiment of the present invention.
Fig. 14 is a schematic structural diagram of a micro-angle neutron scattering spectrometer according to an embodiment of the present invention, and referring to fig. 14, the micro-angle neutron scattering spectrometer includes a neutron source 1, any one of the diaphragm structures 2 provided in the foregoing embodiments, a sample 3 to be detected, and a detector 4, which are arranged on a common optical axis.
Optionally, the neutron source comprises a spallation neutron source or a reactor neutron source.
For a conventional small-angle neutron scattering spectrometer, the collimation length is set to be L 1 ＝L 2 =12m, diameter of the source diaphragm is phi source =30mm, sample diaphragm diameter phi sample =15mm, maximum wavelength
Minimum scattering vector:
the result of the calculation is
If the micro-angle neutron scattering spectrometer provided by the embodiment is adopted, source lightDiaphragm width of 3mm, sample diaphragm width of 1.5mm, maximum wavelength
The minimum scattering vector calculation result according to the formula (9) is
The characteristic size range of the sample which can be characterized is increased by an order of magnitude compared with the conventional small-angle neutron scattering. If the neutron conduit has a width of 40mm and 8 neutron beams are used, the barrier/opening width is (40-3 × 8)/3 × 8=0.667. The spallation neutron source adopts multi-wavelength pulse neutrons to carry out a scattering experiment, so that a very wide scattering vector range can be measured at one time, and thus, data of a tiny angle can be connected with scattering data of a conventional small-angle spectrometer, and the characterization of the characteristic dimension of a sample from 1 nanometer to 1 micrometer is realized.
For a multi-slit diaphragm focusing tiny angle neutron scattering experiment based on a reactor neutron source, the diaphragm material and the processing technology are also applicable, and the optimization algorithm is also applicable. The reactor neutron source generally uses a monochromator or a speed selector to monochromate incident neutrons, and for the monochromated neutrons, the neutrons can be focused not only in the horizontal direction but also in the vertical direction.
It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in some detail by the above embodiments, the invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the invention, and the scope of the invention is determined by the scope of the appended claims.
Claims (8)
1. A diaphragm structure is characterized by being used for realizing the focusing of a plurality of neutron beams and comprising a plurality of diaphragms which are arranged in sequence along the propagation direction of the neutron beams and share an optical axis;
the diaphragm comprises a first neutron absorption layer, a second neutron absorption layer and a supporting layer which are sequentially stacked, wherein the first neutron absorption layer is positioned on one side, close to a neutron source, of the diaphragm;
the diaphragm comprises a plurality of slits, and the width of the incident end of each slit is larger than that of the emergent end of each slit;
wherein the width direction of the slit is perpendicular to the optical axis;
the slit is formed by adopting an electric spark slow wire cutting process;
the first neutron absorption layer comprises boron-aluminum alloy, the second neutron absorption layer comprises cadmium or gadolinium, and the support layer comprises aluminum alloy;
the projection shapes of the slits of the first neutron absorption layer and the second neutron absorption layer on a first plane are trapezoids, and the first plane is perpendicular to the plane where the diaphragm is located;
the included angle between the trapezoid waist and the optical axis direction is 3-5 degrees.
2. The diaphragm structure according to claim 1, wherein the positional relationship of each diaphragm satisfies:
the width of the incident end of the slit of each diaphragm satisfies the following conditions:
wherein the content of the first and second substances,
r represents the ratio of the width of the shielding area of the diaphragm to the width of the incident end of the slit, p represents the ratio of the width of the shielding area of the next diaphragm to the width of the shielding area after the slit of the previous diaphragm passes through, p is a certain value between 0 and 1, D represents the position of the diaphragm, O represents the width of the incident end of the slit, subscripts of O and D are the serial numbers of the diaphragms, the diaphragm closest to the neutron source is the 0 th diaphragm, the diaphragm farthest from the neutron source is the 1 st diaphragm, the serial numbers of the diaphragms are sequentially increased along the direction that the 1 st diaphragm points to the 0 th diaphragm, and n and j are positive integers.
3. The diaphragm structure according to claim 1, wherein the positional relationship of each diaphragm satisfies:
the width of the incident end of the slit of each diaphragm satisfies the following conditions:
wherein, the first and the second end of the pipe are connected with each other,
r represents the ratio of the width of the shielding area of the diaphragm to the width of the incident end of the slit, D represents the position of the diaphragm, O represents the width of the incident end of the slit, subscripts of O, D, K and p are the number of the diaphragm, the diaphragm closest to the neutron source is the 0 th diaphragm, the diaphragm farthest from the neutron source is the 1 st diaphragm, the number of the diaphragms is increased in sequence along the direction that the 1 st diaphragm points to the 0 th diaphragm, and p is the same as the number of the diaphragm n The ratio of the width of the shielding area of the nth diaphragm to the width of the shielding area after the slit of the (n + 1) th diaphragm is penetrated is shown, and n and j are positive integers.
4. The diaphragm structure of claim 1, wherein the number of the diaphragms is more than 3, and the thickness of the first neutron absorption layer in the first to third diaphragms is 2.5mm to 3mm, and the thickness of the first neutron absorption layer in the other diaphragms is 1.5mm to 2mm along the propagation direction of the neutron beam.
5. The diaphragm structure of claim 4, wherein the thickness of the second neutron absorption layer is 0.5mm to 1mm, and the thickness of the support layer is 2mm to 3mm.
6. The diaphragm structure of claim 1, wherein the number of diaphragms is 10 to 15.
7. A micro-angle neutron scattering spectrometer is characterized by comprising a neutron source, the diaphragm structure of any one of claims 1 to 6, a sample to be detected and a detector which are arranged on a common optical axis.
8. The micro angular neutron scattering spectrometer of claim 7, wherein the neutron source comprises a spallation neutron source or a reactor neutron source.
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Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH01312043A (en) * | 1988-06-09 | 1989-12-15 | Hitachi Zosen Corp | Manufacture of boron-containing aluminum alloy |
| US5016267A (en) * | 1986-08-15 | 1991-05-14 | Commonwealth Scientific And Industrial Research | Instrumentation for conditioning X-ray or neutron beams |
| CN102290113A (en) * | 2011-07-18 | 2011-12-21 | 中国原子能科学研究院 | Neutron Absorbing Layer Carrier Stretching Device |
| CN203422938U (en) * | 2012-11-20 | 2014-02-05 | 中国工程物理研究院核物理与化学研究所 | Neutron radial collimator |
| CN105729937A (en) * | 2016-01-29 | 2016-07-06 | 南京航空航天大学 | Novel neutron shielding super-hybrid laminate composite material for spent fuel storage and preparation method thereof |
| CN109671513A (en) * | 2018-12-27 | 2019-04-23 | 中国原子能科学研究院 | The continuously adjustable neutron howitzer structure of the angle of divergence and its scaling method |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE10239691B4 (en) * | 2002-08-25 | 2004-06-09 | Hahn-Meitner-Institut Berlin Gmbh | Neutron optical component for neutron small angle scattering measurement technology |
| JP3757199B2 (en) * | 2002-09-03 | 2006-03-22 | 株式会社リガク | X-ray small angle scattering optical system |
| DE102017223228B3 (en) * | 2017-12-19 | 2018-12-27 | Bruker Axs Gmbh | Setup for spatially resolved measurement with a wavelength-dispersive X-ray spectrometer |
-
2021
- 2021-01-27 CN CN202110112691.4A patent/CN112927834B/en active Active
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5016267A (en) * | 1986-08-15 | 1991-05-14 | Commonwealth Scientific And Industrial Research | Instrumentation for conditioning X-ray or neutron beams |
| JPH01312043A (en) * | 1988-06-09 | 1989-12-15 | Hitachi Zosen Corp | Manufacture of boron-containing aluminum alloy |
| CN102290113A (en) * | 2011-07-18 | 2011-12-21 | 中国原子能科学研究院 | Neutron Absorbing Layer Carrier Stretching Device |
| CN203422938U (en) * | 2012-11-20 | 2014-02-05 | 中国工程物理研究院核物理与化学研究所 | Neutron radial collimator |
| CN105729937A (en) * | 2016-01-29 | 2016-07-06 | 南京航空航天大学 | Novel neutron shielding super-hybrid laminate composite material for spent fuel storage and preparation method thereof |
| CN109671513A (en) * | 2018-12-27 | 2019-04-23 | 中国原子能科学研究院 | The continuously adjustable neutron howitzer structure of the angle of divergence and its scaling method |
Non-Patent Citations (2)
| Title |
|---|
| On the design and experimental realization of a multislit-based very small angle neutron scattering instrument at the European Spallation Source;Sohrab Abbas et al;《JOURNAL OF APPLIED CRYSTALLOGRAPGY》;20151231;第48卷;第1244-1245页、第1251-1252页 * |
| Sohrab Abbas et al.On the design and experimental realization of a multislit-based very small angle neutron scattering instrument at the European Spallation Source.《JOURNAL OF APPLIED CRYSTALLOGRAPGY》.2015,第48卷 * |
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