Particle beam imaging device and particle beam imaging method

Abstract

Provided is a particle beam imaging technology which makes it possible to irradiate the structure of a substance by means of a simple configuration. The particle beam imaging device comprises: a pin hole through which a particle beam from a particle source passes; a first detector which is disposed on the opposite side of the pin hole with a specimen-to-be-imaged interposed between the first detector and the pin hole, and detects the particle beam that penetrates through the specimen after having passed through the pin hole; a driving mechanism which changes the relative positions of the specimen and the pin hole; and a processor which obtains, on the basis of the output of the first detector, the intensity of the particle beam, which is scattered and refracted by the specimen, at each of the plurality of relative positions changed by the driving mechanism.

Description

Particle beam imaging device and particle beam imaging method

[0001] The present disclosure relates to a particle beam imaging apparatus and a particle beam imaging method, and more particularly to a particle beam imaging technique that can investigate the structure of a substance with a simple configuration.

[0002] The structure of materials contained in a sample can be investigated by irradiating the sample with particle beams such as neutrons, electrons, protons, and heavy particles, and analyzing the scattering and diffraction of the irradiated particle beams by the sample. Among particle beams, neutrons interact with atomic nuclei through nuclear forces, so their sensitivity is not simply proportional to the atomic number (number of electrons), and they have high sensitivity even for light elements. Hydrogen in particular exhibits an extraordinary scattering cross section, most of which is incoherent. They also have high material permeability, making them useful for non-destructive testing.

[0003] As a measurement method using particle beams, a small-angle neutron scattering method has been disclosed in which a sample is irradiated with a neutron beam and neutron beams scattered by the sample, of which those with small scattering angles, are detected by a two-dimensional detector (see, for example, Non-Patent Documents 1 and 2).

[0004] Shigehisa Endo et al., "Measurement of Powder and Porous Materials and Data Interpretation / Usage," S&T Publishing, June 2015, pp. 195-211. Satoshi Koizumi, "Polymers illuminated by quantum beams - Use of neutrons in polymer science, nuclear reactors and accelerators," Polymer, Vol. 58, October 2009, pp. 733-736.

[0005] However, the methods of Non-Patent Documents 1 and 2 require two-dimensional detectors to be arranged over a wide area in order to detect scattered neutrons, which increases the size of the device and complicates its configuration. In addition, the control of the two-dimensional detectors arranged over a wide area, such as adjusting their sensitivity, becomes complicated.

[0006] An object of the present disclosure is to provide a particle beam imaging technique that can investigate the structure of a substance using a simple configuration.

[0007] A particle beam imaging device according to an embodiment of the present disclosure includes a pinhole that allows a particle beam from a particle source to pass through, a first detector that is positioned on the opposite side of the pinhole across a sample to be imaged and detects the particle beam that has passed through the pinhole and then transmitted through the sample, a drive mechanism that changes the relative position between the sample and the pinhole, and a processor that calculates the intensity of the particle beam scattered and diffracted by the sample for each of a plurality of relative positions changed by the drive mechanism based on the output of the first detector.

[0008] This invention is based on the results of the "FY2021 Ibaraki Prefecture, Ibaraki Prefecture Neutron Beamline Operation, Maintenance, and User Support Commissioned Project."

[0009] According to the present disclosure, it is possible to provide a particle beam imaging technique that can investigate the structure of a substance with a simple configuration.

[0010] 6A . FIG. 6B is a diagram illustrating an example of the configuration of a neutron imaging device according to the first embodiment. FIG. 6C is a diagram explaining a pulsed neutron time-of-flight method. FIG. 6D is a diagram illustrating an example of the relationship between the wavelength of a neutron beam and the detection wavenumber range of a first detector. FIG. 6E is a diagram illustrating an example of the relationship between transmitted beam intensity and transmittance and the wavelength of a scattered neutron beam. FIG. 6F is a diagram illustrating an example of the relationship between the neutron beam wavenumber and the scattering cross section and the scattered neutron beam intensity. FIG. 6G is a diagram illustrating an example of a sample. FIG. 6H is a diagram illustrating an example of the imaging result of region D in FIG. 6A . FIG. 6H is a diagram explaining a first modified example of the neutron imaging device according to the first embodiment. FIG. 6I is a diagram explaining a second modified example of the neutron imaging device according to the first embodiment. FIG. 6I is a diagram illustrating an example of the configuration of a neutron imaging device according to the second embodiment. FIG. 6I is an overall diagram of a neutron imaging device according to the second embodiment. FIG. 9A is a schematic diagram of a neutron beam condenser used in FIG. 9A . FIG. 9I is a schematic diagram of small-angle scattering at a ring focus. FIG. 9I is a schematic diagram showing small-angle scattering at a point focus and a line focus for comparison. FIG. 9I is a diagram illustrating transmittance analysis at a ring focus. FIG. 9I is a diagram explaining quantification of small-angle scattering in the second embodiment. FIG. 9I is a diagram illustrating an example of the configuration of a neutron imaging device according to the third embodiment. FIG. 9I is a diagram illustrating an example of the configuration of a neutron imaging device according to the fourth embodiment.

[0011] A particle beam imaging device and a particle beam imaging technique according to an embodiment of the present disclosure will be described in detail with reference to the drawings. However, the following embodiments are merely examples of particle beam imaging devices and particle beam imaging techniques for realizing the technical concept of the present embodiment, and are not limited to the following.

[0012] Unless otherwise specified, the dimensions, materials, shapes, relative positions, etc. of components described in the embodiments are not intended to limit the scope of the present disclosure, but are merely illustrative examples. The sizes, positional relationships, etc. of components shown in each drawing may be exaggerated for clarity. In the following description, the same names and symbols indicate the same or similar components, and detailed descriptions will be omitted as appropriate.

[0013] In this specification, a neutron imaging device will be described as an example of a particle beam imaging device. The neutron beam used in the neutron imaging device is an example of a particle beam.

[0014] 1 is a diagram showing an example of the configuration of a neutron imaging device 100 according to Embodiment 1. The neutron imaging device 100 has a first pinhole 1, a second pinhole 2, a first detector 3, a drive mechanism 4, and a processor 5.

[0015] The neutron imaging device 100 causes a pulsed neutron beam N0 from a surface neutron source 9 that has passed through a first pinhole 1 and a second pinhole 2 to be incident on a sample 20 that is the target of imaging. The transmitted beam N1 that has passed through the sample 20 is attenuated according to the wavelength of the neutron beam N0 as a result of a portion of the neutron beam N0 being scattered and diffracted by the sample 20. The attenuation of this neutron beam N0 is expressed as an apparent scattering cross section Σs(λ) by the following equation (1):

[0016] The scattering cross section is the value obtained by integrating the intensity of the scattered neutrons of the neutron beam N0 by the sample 20 over the entire solid angle. In the formula (1) which is effective for samples having an isotropic microstructure, λ is the wavelength, π is the ratio of the circumference to the diameter of a circle, q is the wave number, and I(q) is the intensity of the neutrons as a function of the wave number q. ｍｉｎ If (λ) is the minimum wave number and the scattering angle of the neutron beam is α, then the minimum wave number q ｍｉｎ (λ) is expressed by the following equation (2).

[0017]

[0018] The neutron imaging device 100 detects the transmitted beam N1 attenuated by passing through the sample 20 using the first detector 3, and the processor 5 calculates the transmittance of the neutron beam attenuated by scattering and diffraction in the sample 20 based on the output E of the first detector 3. Focusing on the wavelength dependence of this transmittance, the small-angle scattering intensity I(q) is calculated according to the formula described below. The first detector 3 is approximately equal to or larger in size than the second pinhole 2 provided in the second shielding plate 21 that generates the incident beam to the sample 20, and is installed coaxially with the direction of propagation of the neutron beam N0 and on the side of the sample 20 where it has passed through. The neutron imaging device 100 also changes the relative position of the sample 20 with the first and second pinholes 1 and 2 using the drive mechanism 4, and outputs two-dimensional mapping results of the neutron beam intensities calculated for each of the multiple relative positions to an external device such as a display. The neutron imaging device 100 can visualize the internal state of the sample 20 using this two-dimensional mapping.

[0019] In FIG. 1 , scattered neutron beam N2 represents neutron beams that are incident on the detection surface of the first detector 3, among the neutron beams N2 scattered by the sample 20. Scattering angle 2α represents the angle (scattering angle) formed by a line connecting the outer frame of the light-receiving window of the first detector 3 and the sample. Intensity distribution 50 is a schematic representation of the distribution of intensities I(q) of neutron beams scattered and diffracted by the sample 20. Region a1 represents the region where the intensity distribution of neutron beams scattered at small angles by the sample 20 is mainly obtained. Region a2 represents the region where the intensity distribution of neutron beams diffracted by the sample 20 is mainly obtained. Distance L1 represents the distance from the exit surface of the neutron beam N0 on the surface neutron source 9 to the entrance surface of the neutron beam N0 on the sample 20. Distance L2 represents the distance from the exit surface of the transmitted beam N1 on the sample 20 to the entrance surface of the transmitted beam N1 on the first detector 3. The thickness d represents the thickness of the sample 20 .

[0020] The surface neutron source 9 emits thermal neutrons from a large area compared to the exit of a neutron guide tube in a large accelerator. By using the surface neutron source 9, it becomes possible to measure and analyze the structure of materials at the laboratory level without using a large-scale research facility equipped with a large accelerator.

[0021] The surface neutron source 9 scatters and slows down fast neutrons generated by colliding a proton beam with a Be thin film target 91 using a moderator block 92 made of polyethylene or the like, and emits thermal neutrons from the entire surface of the moderator block 92. The intensity of the neutron beam emitted from the surface neutron source 9 is about 1 / 1000 of the intensity of a neutron beam obtained from a large accelerator. Instead of a configuration in which a proton beam is collided with a Be thin film target 91, fast neutrons may be generated by colliding an accelerated electron beam with a Pb target.

[0022] The first pinhole 1 and the second pinhole 2 are both examples of pinholes that allow the neutron beam N0 from the surface neutron source 9 serving as a particle source to pass through. The first pinhole 1 is formed in a first shielding plate 11 located between the surface neutron source 9 and the second pinhole 2. The second pinhole 2 is formed in a second shielding plate 21 located between the first pinhole 1 and the incident surface of the sample 20. The first pinhole 1 and the second pinhole 2 reduce the diameter of the neutron beam N0 so that the cross-sectional area of ​​the neutron beam N0 in a direction perpendicular to the traveling direction of the neutron beam N0 is approximately the same as or smaller than the area of ​​the detection surface of the first detector 3. The neutron imaging device 100 may have only one of the first pinhole 1 or the second pinhole 2, or may have three or more pinholes.

[0023] The first detector 3 is disposed on the opposite side of the sample 20 from the first pinhole 1 and the second pinhole 2, and detects a transmitted beam N1 that has passed through the sample 20 or less after passing through the first pinhole 1 and the second pinhole 2. The area of ​​the detection surface of the first detector 3 is, for example, 1 cm ２ In this embodiment, the first detector 3 outputs one electrical signal corresponding to the intensity of the transmitted beam N1 to the processor 5 as an output E at each predetermined sampling period. The processor 5 receives the output E.

[0024] The first detector 3 may be filled with a gas that interacts with neutrons (nuclear reaction). 3 In addition to the He detector filled with He gas (helium gas), 6 A detector containing neutrons (including Li, etc.) as a neutron detecting material (including boron B, etc.) can be used. For example, a Gas Electron Multiplier Detector (GEM), which is a type of Micro Pattern Gas Detector (MPGD), may be used. From the viewpoint of reducing neutron count losses, the first detector 3 may contain helium gas as a sealed gas, and the number of molecules (gas pressure) of the helium gas or additives such as a quench gas may be optimized.

[0025] The driving mechanism 4 changes the relative position of the sample 20 with respect to the first pinhole 1 and the second pinhole 2. In this embodiment, the driving mechanism 4 changes the relative position by moving the sample 20 placed on the placement surface in the X and Y directions indicated by the arrows. The X and Y directions are each perpendicular to the direction of travel of the neutron beam N0. The X direction is also perpendicular to the Y direction. The driving mechanism 4 may also change the relative position of the sample 20 with respect to the first and second pinholes 1 and 2 in the thickness direction of the sample 20, i.e., in directions perpendicular to the X and Y directions.

[0026] The processor 5 calculates the intensity of the neutron radiation scattered and diffracted at small angles by the sample 20 as a function of wave number based on the output E of the first detector 3 .

[0027] <Example of Imaging Method Using Neutron Imaging Device 100> An imaging method using the neutron imaging device 100 will be described with reference to Figures 2 to 5. First, Figure 2 is a diagram illustrating the pulsed neutron time-of-flight method used in the neutron imaging device 100. The neutron time-of-flight method is a method of distinguishing wavelengths based on the time it takes for neutrons to reach the first detector 3 after being emitted from the surface neutron source 9.

[0028] The horizontal axis of Fig. 2 represents the time of flight t of the neutron beam N0. As an example, Fig. 2 shows four pulsed neutron beams N0-1, N0-2, N0-3, and N0-4 emitted at each period t0. For example, the surface neutron source 9 emits the pulsed neutron beam N0 at a frequency of 25 Hz, i.e., with a period t0 of 40 ms.

[0029] The vertical axis of Fig. 2 represents the flight distance L of the neutron beam N0. Fig. 2 shows, as an example, how a neutron beam emitted from the emission surface of the surface neutron source 9 is separated into three neutron beams according to wavelength before passing through the sample 20 and reaching the entrance surface of the first detector 3. Specifically, the neutron beam N0-1 is separated into a transmitted beam N1-1 (λ1) of wavelength λ1, a transmitted beam N1-1 (λ2) of wavelength λ2, and a transmitted beam N1-1 (λ3) of wavelength λ3. The neutron beam N0-2 is separated into a transmitted beam N1-2 (λ1) of wavelength λ1, a transmitted beam N1-2 (λ2) of wavelength λ2, and a transmitted beam N1-2 (λ3) of wavelength λ3. The neutron beam N0-3 is separated into a transmitted beam N1-3 (λ1) of wavelength λ1, a transmitted beam N1-3 (λ2) of wavelength λ2, and a transmitted beam N1-3 (λ3) of wavelength λ3. For example, the wavelength λ1 is 1 Å, the wavelength λ2 is 5 Å, and the wavelength λ3 is 10 Å.

[0030] The transmitted beams N1-1 (λ1), N1-1 (λ2), and N1-1 (λ3) arrive at the incident surface of the first detector 3 at the latest times in this order. The first detector 3 can output the output E of the transmitted beam N1-2, which has a different wavelength depending on the time, to the processor 5. This is also true for the transmitted beams N1-2 (λ1), N1-2 (λ2), and N1-2 (λ3) and the transmitted beams N1-3 (λ1), N1-3 (λ2), and N1-3 (λ3).

[0031] Next, Fig. 3 is a diagram showing an example of the relationship between the wavelength of a neutron beam and the range of wave numbers detected by the first detector 3. Fig. 3 shows the relationship between the wavelength of a neutron beam and the range of wave numbers detected by the first detector 3. ｍｉｎ The figure shows how (λ) varies depending on the wavelength of the scattered neutron beam N2. The minimum observable wave number indicates the lower limit of the scattered components that are not captured by the detector. The minimum wave number q at the edge of the detection light receiving surface ｍｉｎ (λ) is defined. Alternatively, the scattered component that enters the detection light receiving surface is considered as a direct beam and is related to the increase or decrease in transmittance. The minimum wave number q ｍｉｎ (λ1) represents the minimum wave number of the scattered neutron ray N2(λ1) of wavelength λ1. ｍｉｎ(λ10) represents the minimum wave number of the scattered neutron ray N2 (λ10) of wavelength λ10. The wavelength of the scattered neutron ray N2 includes a plurality of wavelengths in addition to the wavelength λ1 and the wavelength λ10.

[0032] According to actual measurements, the minimum wave number q ｍｉｎ The intensity of the transmitted beam N1 detected by the first detector 3 varies depending on the minimum wave number q ｍｉｎ The wavenumber range 0 to qmin detected by the first detector 3, i.e., the integration range in equation (1), differs depending on (λ). In other words, wavelength dependency occurs in the transmittance T of the sample 20. The intensity I(q) in Fig. 3 indicates the intensity distribution of the scattered neutron beam N2 depending on the wavenumber q.

[0033] The transmittance T(λ) of the sample 20 depending on the wavelength is expressed by the following equation (3).

[0034]

[0035] By modifying equation (3), the following equation (4) is obtained.

[0036]

[0037] FIG. 4 is a diagram showing an example of the relationship between the intensity S and transmittance T of the transmitted beam N1 and the wavelength λ of the scattered neutron beam N2. The horizontal axis of FIG. 4 represents wavelength λ (unit: Å). The left vertical axis of FIG. 4 represents the intensity S of the transmitted beam N1. The right vertical axis of FIG. 4 represents the transmittance T of the sample 20. A solid line graph 401 represents the transmittance T(λ). A dashed-dotted line graph 402 represents the intensity S1(λ) of the transmitted beam N1 of the sample 20. A two-dot dashed line graph 403 represents the intensity S2(λ) of the transmitted beam N1 when the sample 20 is not installed in the neutron imaging device 100. The intensities S1(λ) and S2(λ) are obtained based on the output E of the first detector 3. The transmittance T(λ) is obtained by dividing the intensity S1(λ) by the intensity S2(λ).

[0038] 5 is a diagram showing an example of the relationship between the wave number q of a neutron beam, the scattering cross section Σs(λ), and the intensity of the scattered neutron beam N2. The horizontal axis of FIG. 5 represents the wave number q of the neutron beam (unit: Å). －１) The vertical axis of FIG. 5 represents the relative value of the cross-sectional intensity, including the scattering intensity. Graph 51 represents the scattering cross-section Σs(λ) of the sample 20, which is obtained using equation (4) from the transmittance T(λ) of FIG. 4. Graph 52 is a profile obtained by subtracting the intensity S2(λ) from the scattering cross-section Σs(λ) of the sample 20, thereby subtracting the background noise from the scattering cross-section Σs(λ).

[0039] The differential amount of Σs(λ) according to wavelength, dif[Σs(λ)], is expressed by the following equation (5).

[0040]

[0041] 1 can calculate dif[Σs(λ)] using the following equations (6) and (7). Furthermore, based on dif[Σs(λ)], the processor 5 can calculate the intensity I(q) of the neutron beam scattered and diffracted by the sample 20 as a function of the wave number q using equation (8). Graph 53 in FIG. 5 represents the intensity I(q).

[0042]

[0043]

[0044]

[0045] <Example of Imaging Result by Neutron Imaging Device 100> An example of an imaging result by the neutron imaging device 100 will be described with reference to Figures 6A and 6B. Figure 6A is a diagram showing an example of the sample 20. Figure 6B is a diagram showing an example of the imaging result of region D in Figure 6A. Figures 6A and 6B show the imaging result of the internal state of polymer concrete, which is an example of the sample 20, by the neutron imaging device 100.

[0046] The neutron imaging device 100 determines the intensity of the neutron beam scattered and diffracted by the sample 20 at each of a plurality of relative positions changed by the driving mechanism 4 (FIG. 1). The imaging result in FIG. 6B is a two-dimensional mapping of the neutron beam intensity at each of a plurality of relative positions changed by the driving mechanism 4 by the processor 5. The neutron imaging device 100 calculates the integral scattering intensity Inv, A from the neutron beam intensity I(q) by the processor 5. ２ (correlation length of phase separation), A ３ (incoherent scattering proportional to the number density of hydrogen), Δb and φ1 are calculated. The neutron imaging device 100 maps these to each pixel of the image data of the sample 20, thereby visualizing the internal structure of the sample 20. The internal state of the polymer concrete corresponds to the distribution of water content contained in the sample 20.

[0047] As shown in Figure 6A, the sample 20 includes a dry region 61, a wet region 62, and a corroded region 63. A crack 64 has occurred between the dry region 61 and the wet region 62. As shown in Figure 6B, imaging results were obtained in which the amount of moisture increased in the order of the dry region 61, the wet region 62, and the corroded region 63. Furthermore, an imaging result corresponding to the crack 64 was obtained between the dry region 61 and the wet region 62. In this way, it was found that the internal state of the sample 20 can be imaged and visualized using the neutron imaging device 100.

[0048] <Major effects of neutron imaging device 100> As described above, the neutron imaging device 100 (particle beam imaging device) shown in Figure 1 calculates, by the processor 5, the intensity I(q) of the neutron beam scattered and diffracted by the sample 20 for each of a plurality of relative positions changed by the drive mechanism 4, based on the output E from the first detector 3 of the transmitted beam N1 that has passed through the sample 20.

[0049] For example, to detect neutron beams scattered and diffracted over a wide wavenumber (q) range, detectors must be arranged over a wide area, which increases the size of the neutron imaging device, the device configuration, and the device costs. Furthermore, control of the two-dimensional detectors arranged over a wide area becomes complicated. In this embodiment, the intensity of small-angle scattered and diffracted neutron beams is calculated based on the detection results of the transmitted beam N1 through the sample 20, so there is no need to arrange detectors over a wide area. This allows the neutron imaging device 100 to be made smaller, the device configuration to be simplified, and the device costs to be reduced. Furthermore, control of the first detector 3 can be simplified. As a result, this embodiment provides a particle beam imaging technology (neutron imaging technology) that can investigate the structure of a substance with a simple configuration. The particle beam imaging technology includes a particle beam imaging device and a particle beam imaging method.

[0050] Furthermore, since the intensity of small-angle scattered and diffracted neutron beams is weak, the signal-to-noise ratio (S / N ratio) may decrease, and the detection resolution may decrease. In this embodiment, since I(q) is detected from the transmitted beam N1 of the sample 20 and its attenuation, a high intensity of the neutron beam can be ensured, and a high signal-to-noise ratio (S / N ratio) and detection resolution can be ensured.

[0051] <First Modification> Various modifications are possible to the neutron imaging device 100. For example, the neutron imaging device 100 can detect scattered neutrons at a scattering angle (2α) corresponding to the area of ​​the detection surface of the first detector 3, and therefore can perform ultra-small angle scattering at a scattering angle that is very narrow compared to conventional small angle scattering methods.

[0052] 7A is a diagram illustrating an example of application of the neutron imaging device 100 to an ultra-small angle scattering method as a first modified example. Fig. 7 shows how the neutron beam N2 scattered by the sample 20 is detected by the first detector 3 of the neutron imaging device 100.

[0053] In Fig. 7A, for example, if the distance L2 is 5000 mm and the length δ of the first detector 3 in the direction perpendicular to the traveling direction of the neutron beam is 2 mm, the scattering angle 2α is 2 / 5000 = 0.02 (°), and the scattering angle α is 0.01 (°). ｍｉｎ is 0.00022 Å for a neutron beam with a wavelength λ of 10 Å. －１ The first detector 3 can detect scattered neutrons N2 that have passed through the first pinhole 1 and the second pinhole 2 and are scattered by the sample 20 at an angle of 0.02° or less. As a result, it is possible to perform ultra-small angle scattering, which applies small angle scattering to a very narrow scattering angle range compared to the scattering angle range of conventional small angle scattering methods.

[0054] <Second Modification> Fig. 7B is a diagram illustrating a second modification of the neutron imaging device 100. As shown in Fig. 7B, the neutron imaging device 100 may have a planar neutron spin filter 200 arranged to sandwich the sample 20 in order to separately observe incoherent scattering due to hydrogen and coherent scattering due to structure. The planar neutron spin filter 200 may be only an upstream portion of the sample 20. The neutron spin filter 200 may be a mirror made of a multilayer film or a type in which a glass container is filled with helium gas. In order to maintain the polarized state of the neutrons, an induced magnetic field of about several gauss may be installed in the space where the neutron spin filter 200 and the sample 20 are placed.

[0055] 7B, the neutron imaging device 100 may have a planar neutron energy filter sandwiching the sample 20 in order to observe the molecular motion of polymers and water molecules that make up the sample 20. The neutron energy filter is made of a single crystal such as a silicon wafer or pyrotic graphite (PG), and utilizes the diffraction phenomenon of neutron beams to reflect only the elastically scattered neutrons and guide them to detector D3 or detector D1. The observed elastic scattering is analyzed by processor 5 to calculate the mean square displacement of hydrogen atoms, which serves as an index of molecular motion.

[0056] Second Embodiment Next, a neutron imaging device according to a second embodiment will be described. Note that the same names and symbols as those in the first embodiment indicate the same or equivalent members, and detailed descriptions thereof will be omitted as appropriate.

[0057] <Configuration Example of Neutron Imaging Device 100a> Fig. 8 is a diagram showing an example of the configuration of a neutron imaging device 100a according to the second embodiment. The neutron imaging device 100a has an annular slit 103, a second detector 30, and a processor 5a.

[0058] The annular slit 103 is arranged on the exit surface side of the surface neutron source 9. In this embodiment, the annular slit 103 is formed in the first shielding plate 11 together with the first pinhole 1. The annular slit 103 and the first pinhole 1 form an aperture 101. The annular slit 103, the first pinhole 1, the second pinhole 2, and the third pinhole 113 form a neutron beam aperture 10. The annular slit 103 shapes the neutrons extracted from the surface neutron source 9 into a neutron beam N0a including an annular neutron beam. By this beam shaping, of the neutrons extracted from the surface of the surface neutron source 9, neutron fluxes with a relatively small divergence angle are sorted into a central spot and a surrounding annular spot.

[0059] The second detector 30 detects the small-angle scattering and direct beam of the annular neutron beam that has passed through the sample 20. The second detector 30 is disposed on the transmission side of the sample 20. Of the neutron beam N0a shaped by the annular slit 103, neutron flux other than the neutron beam that passes through the second pinhole 2 is blocked by the second shielding plate 21. Only neutrons that have been small-angle scattered by the sample 20 are incident on the second detector 30, and a bright small-angle scattering image 301 that has passed through the sample 20 is obtained with high contrast against a dark background. This allows the annular small-angle scattering to be detected. In the second embodiment, either the annular small-angle scattering or the annular transmitted light may be analyzed.

[0060] The processor 5a receives and processes the detection results of small-angle scattering by the second detector 30. The processor 5a determines the intensity of neutron beams scattered and diffracted by the sample 20 for each of a plurality of relative positions changed by the drive mechanism 4, based on the output of the first detector 3 and the output of the second detector 30. For example, the processor 5a determines the intensity of annular small-angle scattering as a function of wavenumber q for each of a plurality of relative positions between the sample 20 and the second pinhole 2. The neutron imaging device 100a can visualize the internal state of the sample 20 by using the processor 5a to map the intensity of annular small-angle scattering for each relative position on the sample 20.

[0061] Fig. 9A is a diagram showing an example of the overall configuration of a neutron imaging device 100a. Fig. 9B is a schematic diagram of a neutron beam condenser 115 used in Fig. 9A. In addition to the first detector 3, the neutron imaging device 100a may include a second detector 30 (denoted as "D1" in the figure) that detects coherent small-angle scattering, a third detector 13 (denoted as "D2" in the figure) that detects incoherent scattering, or a fourth detector 14 (denoted as "D3" in the figure) that detects coherent diffraction.

[0062] The third detector 13 is disposed between the sample 20 and the neutron beam aperture 10. The third detector 13 is sensitive to incoherent scattering and detects incoherently scattered neutrons from the sample 20. The output of the third detector 13 is connected to the input of the processor 5a. Based on the detection results of the third detector 13, information related to hydrogen, which has a very large scattering cross section, such as the number density of hydrogen and the distribution of water in the sample 20, can be obtained.

[0063] In order to detect incoherent scattering from the sample 20 in a dark field by the third detector 13, a third pinhole 113 is provided between the second pinhole 2 and the third detector 13. The third pinhole 113 is formed in a third shielding plate 112 and has a smaller diameter than the second pinhole 2. Neutron flux other than the annular neutron beam passing through the third pinhole 113 is blocked by the third shielding plate 112, and only an image of incoherent scattering from the sample 20 is incident on the detection surface of the third detector 13.

[0064] 9B , the neutron beam aperture 10 may have, in order from the side of the surface neutron source 9, an annular slit 103, a second pinhole 2, and a third pinhole 113. A part or the whole of the neutron beam aperture 10 may be placed inside a vacuum chamber 106, or may be placed in air. By keeping the neutron beam aperture 10 in a vacuum, attenuation of the annular neutron beam can be suppressed. However, the vacuum chamber 106 is not essential.

[0065] The second pinhole 2 and the third pinhole 113 are coaxial and are arranged so that the annular neutron beam is focused at the center in the thickness direction of the sample 20. The second pinhole 2 and the third pinhole 113 form a neutron beam condenser 115, and the outer diameter of the annular neutron beam at the focusing point F is narrowed to about several millimeters. The sample 20 is moved relative to the third pinhole 113 by the driving mechanism 4.

[0066] A fourth detector 14 may be provided between the sample 20 and the second detector 30. The fourth detector 14 is sensitive to coherent diffraction and detects neutrons, over a wide angle, that are diffracted by particles of additive material contained in the sample 20 and transmitted through the sample 20. The output of the fourth detector 14 is connected to the input of the processor 5a. The fourth detector 14 can detect the crystal polymorphism and distribution of the base material in the sample 20.

[0067] A fourth shielding plate 122 having a fourth pinhole 123 formed therein is disposed on the exit side of the fourth detector 14 to guide small-angle scattered neutrons from the sample 20 to the second detector 30. The small-angle scattered neutrons that have passed through the fourth pinhole 123 pass through the vacuum chamber 40 and enter the second detector 30. The vacuum chamber 40 may be formed of a plurality of chambers. In the example of FIG. 2A , a first chamber 41, a second chamber 42, and a third chamber 43 are connected in series. Windows 413, 423, and 433 made of a material transparent to the neutron beam may be provided at the boundaries of each chamber and on the exit surface of the vacuum chamber 40.

[0068] 10 is a schematic diagram of small-angle scattering when a sample 20 is irradiated with an annular neutron beam 6 that has passed through an annular slit 103 and a collimated neutron beam 7 that has passed through a first pinhole 1. Irradiation of the sample 20 with the annular neutron beam 6 that has been focused by a neutron beam aperture 10 is called a "ring focus." Each point P included in the annular neutron beam 6 is the spectral center of the neutron beam 6. The circles extending from each point P are the small-angle scattering spectra SS. For ease of explanation, the small-angle scattering spectra SS are shown as double circles.

[0069] For comparison, Figure 11 shows a schematic diagram of small-angle scattering with a point focus and a line focus. In the case of a point focus in Figure 11(A), the cross-sectional shape of a beam 71 incident on a sample is circular. A small-angle scattering spectrum SS is obtained around a center point P of the beam 71. In the case of a line focus in Figure 11(B), a beam 72 shaped into a line is irradiated onto the sample. A small-angle scattering spectrum SS is obtained for each center point P along the major axis of the beam 72.

[0070] Returning to Fig. 10, in the case of a ring focus, compared to a point focus or a line focus, the small-angle scattering spectrum SS spreads along the annulus of the neutron beam 6. The data may become unclear as the small-angle scattering spectrum SS generated in a single irradiation increases, but from the viewpoint of ensuring the intensity of the neutron beam irradiating the sample 20, focusing by the annular slit 103 and the second pinhole 2 is desirable. Therefore, an analytical method is devised to extract the scattering intensity as a function of the wave number q from the small-angle scattering spectrum SS in Fig. 10.

[0071] The extraction analysis method may be either annular small-angle scattering or annular transmitted light, and the analysis of annular transmitted light is the same as in the second embodiment.

[0072] FIG. 11B is a diagram showing transmittance analysis in a ring focus. As shown in FIG. 11B, annular bands of ΔR are set on the inside and outside of a ring of radius R, and the intensity inside the bands is integrated. The conversion formula for the width of ΔR into the viewing angle α is as follows: sin α=ΔR / (2L ２) Using α in the above equation, qmin can be calculated according to equation (2). qmin can be changed by changing various parameters on the computer that analyzes ΔR. The observable q range of I(q) becomes variable.

[0073] FIG. 12 is a diagram for explaining the quantification of small-angle scattering according to the second embodiment. This quantification is performed by the processor 5a. The incident plane of the annular neutron beam 6 and the detection plane of the detector are considered in terms of x and y coordinates. Each point (x ｉ , y ｉ ) for each small-angle scattering spectrum intensity I ｔｏｔａｌ (x, y) is found and integrated over the entire circular region.

[0074] The smearing effect of small angle scattering for an annular or ring-shaped incident beam can be described by the following equation (9):

[0075]

[0076] The intensity I of the small-angle scattering spectrum observed by the second detector 30 ｔｏｔａｌ is expressed in the convolution form of equation (9), where w ｉ (x, y) is a weighting function indicating the xy distribution (shape) of the intensity of the annular neutron beam 6 incident on the sample 20, I ｍ (x, y) is the scattering function due to the microstructure inside the sample 20. Equation (9) gives the intensity of the entire small-angle scattering spectrum around the beam center (0, 0) of the circular neutron beam 6.

[0077] Weight function w ｉ (x, y) is determined by observing the ring-shaped neutron beam 6 with the second detector 30 without placing the sample 20. ｉ , y ｉ The apparent wave number q of

[0078]

[0079] The scattering function due to the internal microstructure of the sample 20 is expressed as follows:

[0080] Here, if we use a Debye-Buch type function as the scattering function, Since it is the square of the modified formula 10, the scattering function Im(q) can be expressed by the following formula (10).

[0081] Here, A １ is the intensity of the scattering function, A ２ is the correlation length when the internal structure of the sample 20 is separated into two phases, the first phase and the second phase, A ３ is the incoherent scattering proportional to the number density of hydrogen.

[0082] Coefficient A １ , A ２ and A ３ is calculated by the processor 5a. The processor 5a calculates I from the equation (9). ｔｏｔａｌ (x, y) and compare it with the actual small-angle scattering obtained by the second detector 30 and the third detector 13, １ , A ２ , A ３ Determine.

[0083] The processor 5a also calculates the integrated scattering intensity Inv (invariant) according to the following equation (11): This gives the integrated scattering intensity Inv as a function of the wavenumber q.

[0084]

[0085] The integrated scattering intensity Inv is expressed by the difference Δb in scattering length density between the two phase-separated domains 1 and 2 and the volume fraction φ1 of the first phase (domain 1) using equation (12). The difference Δb in scattering length density between the phase-separated domains represents the structural contrast.

[0086] The calculations according to equations (9) to (12) are repeated for each of a plurality of relative positions on the sample 20 .

[0087] The processor 5a photographs the sample 20 with a digital camera and stores the image data in an internal memory. Alternatively, the image data may be acquired from an external device. The processor 5a calculates the integrated scattering intensity Inv, A ２ (correlation length of phase separation), A ３The internal structure of the sample 20 is visualized by mapping Δb (incoherent scattering proportional to the number density of hydrogen), Δb, and φ1 to each pixel of the image data of the sample 20. The pixel resolution of the image data and the spatial resolution of the annular neutron beam scan may be the same or different. If the pixel resolution is higher, the scattering intensity obtained at a certain scanning point may be mapped to multiple pixels.

[0088] The processor 5a may map the output results of the first detector 3, the fourth detector 14, or both the first detector 3 and the fourth detector 14 onto image data. The output of the first detector 3 corresponds to the transmittance T. The output of the fourth detector 14 corresponds to the wide-angle diffraction result. The detection result of the diffracted neutrons by the fourth detector 14 makes it possible to visualize the crystalline polymorphism of particles of additive material such as a reinforcing material contained in the sample 20, as well as the crystalline polymorphism, distribution orientation, and density of the matrix.

[0089] [Third Embodiment] Figure 13 is a diagram showing an example of the configuration of a neutron imaging device 100b according to the third embodiment. The neutron imaging device 100b is capable of performing multi-point simultaneous measurement of small-angle scattering. Multi-point simultaneous measurement of small-angle scattering is an alternative to the method shown in the second embodiment, i.e., the method of mapping by attaching a focusing point to the sample position and moving the sample using a movement mechanism. As shown in Figure 13, the neutron imaging device 100b has a first pinhole array 114 arranged on the surface neutron source 9 side of the sample 20, and a second pinhole array 44 arranged on the second detector 30 side of the sample 20.

[0090] The first pinhole array 114 has a plurality of pinholes arranged in an array. The first pinhole array 114 guides neutron beams emitted from each point of the surface neutron source 9 through each pinhole to the sample 20. The second pinhole array 44 performs multi-point simultaneous measurement of small-angle scattering using the neutron beams that have passed through the sample 20. This configuration significantly reduces the range over which the sample is moved by the movement mechanism, thereby shortening the measurement time. Note that in order to fill in the dead zones between adjacent pinholes, it is sufficient to move the sample by a distance approximately equal to the distance between the pinholes.

[0091] 14 is a diagram showing an example of the configuration of a neutron imaging device 100c according to the fourth embodiment. The neutron imaging device 100c has a first multi-pinhole 81, a second multi-pinhole 82, a third multi-pinhole 83, and a neutron radiography camera 84.

[0092] The first multi-pinhole 81, the second multi-pinhole 82, and the third multi-pinhole 83 each have a plurality of pinholes arranged in an array. The first multi-pinhole 81 is arranged on the surface neutron source 9 side of the sample 20. The second multi-pinhole 82 is arranged between the sample 20 and the neutron radiography camera 84. The third multi-pinhole 83 is arranged on the second detector 30 side of the neutron radiography camera 84.

[0093] The neutron radiography camera 84 includes a scintillator 85, an optical mirror 86, an imaging intensifier 87, and a CMOS (Complementary Metal Oxide Semiconductor) camera 88. The CMOS camera 88 may be a CCD (Charge Coupled Device) camera.

[0094] In the neutron imaging device 100c, it is preferable to make the scintillator 85 as thin as possible so as not to attenuate small-angle scattering. It is also preferable to select a highly transparent material (pure aluminum, silicon wafer, etc.) for the optical mirror 86.

[0095] Although the preferred embodiments have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the claims.

[0096] Small-angle scattering is generally suitable for analyzing fine structures such as the tissue structure of polymer alloys and alloys, the structure of biomolecules (the position of hydrogen molecules in proteins), and inorganic crystalline structures. However, by using the neutron imaging devices according to the first and second embodiments described above, it is possible to visualize everything from internal deterioration to water distribution in industrial composite materials such as polymer concrete and tires.

[0097] The above-described embodiments can also be applied to imaging using particle beams other than neutron beams, such as electron beams, proton beams, and heavy particle beams.

[0098] This application claims priority based on Japanese Patent Application No. 2023-034010 filed with the Japan Patent Office on March 6, 2023, and includes the entire contents of this Japanese patent application.

[0099] 1 First pinhole 11 First shielding plate 2 Second pinhole 21 Second shielding plate 3 First detector 4 Drive mechanism 5, 5a Processor 6 Annular neutron beam 7 Parallel neutron beam 9 Planar neutron source 91 Be thin film target 92 Moderator block 10 Neutron beam aperture 101 Ring aperture 103 Annular slit 112 Third shielding plate 113 Third pinhole 115 Neutron beam condenser 13 Third detector 14 Fourth detector 20 Sample 30 Second detector 40 Vacuum chamber 41 First chamber 42 Second chamber 43 Third chamber 100 Neutron imaging device 51, 52, 53, 401, 402, 403 Graph 61 Dry region 62 Wet region 63 Corrosion region 64 Crack 301 Small angle scattering image d Thickness E Output L1, L2 Distance N0 Neutron beam N1 Transmitted beam N2 Scattered neutron ray α Scattering angle I(q) Intensity δ Length

Claims

1. a pinhole through which a particle beam from a particle source passes; a first detector that is disposed on the opposite side of the pinhole across the sample to be imaged, and that detects the particle beam that has passed through the pinhole and then transmitted through the sample; a driving mechanism for changing the relative position between the sample and the pinhole; a processor that determines, based on the output of the first detector, the intensity of the particle beam attenuated according to the wavelength of the particle beam by being scattered and diffracted by the sample at each of a plurality of relative positions changed by the driving mechanism; The processor calculates the intensity I(q) based on the following formula, where λ is the wavelength, T(λ) is the transmittance of the sample, d is the sample thickness, q is the wave number, and I(q) is the intensity of the particle beam by the sample: I(q)=dif[-1n{T(λ)} / d] / q ２ , particle beam imaging device.

2. The particle beam imaging apparatus according to claim 1 , wherein the processor two-dimensionally maps the intensity of the particle beam at each of a plurality of relative positions changed by the driving mechanism.

3. (delete)

4. 3. The particle beam imaging device according to claim 1, wherein the first detector detects the particle beam that has passed through the pinhole and then been scattered by the sample at an angle of 0.02[deg.] or less.

5. an annular slit disposed on the emission surface side of the particle source; a second detector that detects small-angle scattering of the particle beam by the sample; 3. The particle beam imaging device according to claim 1, wherein the processor determines an intensity of the particle beam scattered and diffracted by the sample for each of a plurality of relative positions changed by the driving mechanism, further based on an output of the second detector.

6. the particle beam is a neutron beam, 3. The particle beam imaging apparatus according to claim 1, wherein the first detector contains helium gas as a filler gas.

7. A particle beam imaging method using a particle beam imaging device, comprising: The particle beam imaging device comprises: The pinhole allows the particle beam from the particle source to pass through, a detector disposed on the opposite side of the pinhole across the sample to be imaged detects the particle beam that has passed through the pinhole and then transmitted through the sample; a driving mechanism for changing the relative position between the sample and the pinhole; a processor, based on the output of the detector, for each of a plurality of relative positions changed by the driving mechanism, determining the intensity of the particle beam attenuated according to the wavelength of the particle beam by being scattered and diffracted by the sample; The processor calculates the intensity I(q) based on the following formula, where λ is the wavelength, T(λ) is the transmittance of the sample, d is the sample thickness, q is the wave number, and I(q) is the intensity of the particle beam by the sample: I(q)=dif[-1n{T(λ)} / d] / q ２ ,Particle beam imaging method.