Element distribution measuring device and element distribution measuring method

Abstract

To provide an apparatus and a method capable of easily measuring a distribution of a content rate of each element contained in a sample to be measured with an inexpensive configuration.SOLUTION: An element distribution measuring apparatus 1 is an apparatus for measuring a distribution of a content rate of each element contained in a sample 4 to be measured, and includes a measurement unit 2 and a computing unit 3. The measurement unit 2 causes radiation of a plurality of spectra within a band including X-rays and γ-rays to be made incident on the sample 4 to be measured to obtain projection data. The computing unit 3 obtains a distribution of a content rate of each element contained in the sample to be measured based on a distribution of linear attenuation coefficients of the sample to be measured obtained for each of the plurality of spectra based on the projection data acquired by the measurement unit 2 and based on a linear attenuation coefficient formula for each of the plurality of spectra expressed using the value of a mass attenuation coefficient of each element, the value of an atomic weight of each element, the variable of the content rate of each element, and the variable of the density of the sample to be measured.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an apparatus and method for measuring the distribution of the content of each element contained in a sample to be measured. [Background technology]

[0002] Known techniques for measuring the content of each element contained in a sample include wavelength-dispersive X-ray spectroscopy, energy-dispersive X-ray spectroscopy, and unmixing method (see Non-Patent Document 1). These techniques use a spectroscope (including a detector for dispersing light) that disperses the light output from the sample when light is incident on the sample. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Masahiko Hirano and Kazuji Matsumoto, "Fluorescence imaging using unmixing method - Application to live cell imaging," Instrumentation and Control, Vol. 45, No. 11, pp. 977-981 (2006). Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned conventional techniques, since it is necessary to use a spectrometer, the apparatus becomes expensive, and it is not easy to adjust the optical system including the spectrometer. The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide an apparatus and method that can easily measure the distribution of the content of each element contained in a sample to be measured with an inexpensive configuration. [Means for solving the problem]

[0005] The element distribution measuring device of the first embodiment of the present invention is a device for measuring the distribution of the content of each element contained in a measured sample, and includes: (1) a measuring unit that irradiates each of a plurality of monochromatic spectra in a band including X-rays and gamma rays onto the measured sample to obtain projection data; and (2) a calculation unit that calculates the distribution of the content of each element contained in the measured sample based on the distribution of the linear attenuation coefficient of the measured sample calculated for each of the plurality of monochromatic spectra based on the projection data obtained by the measuring unit, and a formula for the linear attenuation coefficient expressed for each of the plurality of monochromatic spectra using the value of the mass attenuation coefficient of each element, the value of the atomic weight of each element, a variable for the content of each element, and a variable for the density of the measured sample.

[0006] An element distribution measuring device of a second aspect of the present invention is a device for measuring the distribution of the content of each element contained in a measured sample, and includes: (1) a measuring unit that irradiates each of a plurality of polychromatic spectra in a band including X-rays and gamma rays onto the measured sample to obtain projection data; and (2) a calculation unit that calculates the distribution of the content of each element contained in the measured sample based on the distribution of the effective linear attenuation coefficient of the measured sample calculated for each of the plurality of polychromatic spectra based on the projection data obtained by the measuring unit, and a formula for the effective linear attenuation coefficient for each of the plurality of polychromatic spectra expressed using the value of the effective mass attenuation coefficient of each element, the value of the atomic weight of each element, variables for the content of each element, and variables for the density of the measured sample.

[0007] An element distribution measuring device of a third aspect of the present invention is a device for measuring the distribution of the content of each element contained in a measured sample, and includes: (1) a measuring unit that irradiates each of a plurality of polychromatic spectra, including at least one of a plurality of monochromatic spectra in a band including X-rays and gamma rays, onto the measured sample to obtain projection data; and (2) a calculation unit that calculates the distribution of the content of each element contained in the measured sample based on the distribution of the linear attenuation coefficient of the measured sample calculated for each of the plurality of monochromatic spectra based on the projection data obtained by the measuring unit, and on a formula for the linear attenuation coefficient expressed for each of the plurality of monochromatic spectra using the value of the mass attenuation coefficient of each element, the value of the atomic weight of each element, a variable for the content of each element, and a variable for the density of the measured sample.

[0008] The element distribution measurement method of the first aspect of the present invention is a method for measuring the distribution of the content of each element contained in a measured sample, and includes: (1) a measurement step of irradiating each of a plurality of monochromatic spectra in a band including X-rays and gamma rays onto the measured sample to obtain projection data; and (2) a calculation step of calculating the distribution of the content of each element contained in the measured sample based on the distribution of the linear attenuation coefficient of the measured sample calculated for each of the plurality of monochromatic spectra based on the projection data obtained in the measurement step, and a mathematical formula for the linear attenuation coefficient expressed for each of the plurality of monochromatic spectra using the value of the mass attenuation coefficient of each element, the value of the atomic weight of each element, a variable for the content of each element, and a variable for the density of the measured sample.

[0009] An element distribution measurement method according to a second aspect of the present invention is a method for measuring the distribution of the content of each element contained in a measured sample, and includes: (1) a measurement step of irradiating each of a plurality of polychromatic spectra in a band including X-rays and gamma rays onto the measured sample to obtain projection data; and (2) a calculation step of calculating the distribution of the content of each element contained in the measured sample based on the distribution of the effective linear attenuation coefficient of the measured sample calculated for each of the plurality of polychromatic spectra based on the projection data obtained in the measurement step, and a formula for the effective linear attenuation coefficient expressed for each of the plurality of polychromatic spectra using the value of the effective mass attenuation coefficient of each element, the value of the atomic weight of each element, variables for the content of each element, and variables for the density of the measured sample.

[0010] An element distribution measurement method according to a third aspect of the present invention is a method for measuring the distribution of the content of each element contained in a measured sample, and includes: (1) a measurement step of irradiating each of a plurality of polychromatic spectra, including at least one of a plurality of monochromatic spectra in a band including X-rays and gamma rays, onto the measured sample to obtain projection data; and (2) a calculation step of calculating the distribution of the content of each element contained in the measured sample based on the distribution of the linear attenuation coefficient of the measured sample calculated for each of the plurality of monochromatic spectra on the basis of the projection data obtained in the measurement step, and on the basis of an equation for the linear attenuation coefficient expressed for each of the plurality of monochromatic spectra using the value of the mass attenuation coefficient of each element, the value of the atomic weight of each element, a variable for the content of each element, and a variable for the density of the measured sample. Effect of the Invention

[0011] According to the present invention, the distribution of the content of each element contained in a sample to be measured can be easily measured with an inexpensive configuration. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram showing the configuration of an element distribution measuring device 1. [Diagram 2] FIG. 2 is a diagram showing the configuration of a modified element distribution measuring apparatus 1A. [Diagram 3] FIG. 3 is a diagram showing a first configuration example of the irradiation unit 11. As shown in FIG. [Figure 4] FIG. 4 is a diagram showing a second configuration example of the irradiation unit 11. As shown in FIG. [Diagram 5] FIG. 5 is a diagram showing a third configuration example of the irradiation unit 11. As shown in FIG. [Figure 6] FIG. 6 is a flow chart showing a first embodiment of the element distribution measuring method. [Figure 7] FIG. 7 is a flowchart showing a second embodiment of the element distribution measuring method. [Figure 8] FIG. 8 is a flowchart showing a third embodiment of the element distribution measuring method. [Figure 9] FIG. 9 is a diagram showing a cross-sectional structure of the sample 4 to be measured that was assumed in the simulation. [Figure 10] Fig. 10(a) is a diagram showing a projection image obtained by the imaging unit 12 when the measured sample 4 is irradiated with the X-ray of the 0th polychromatic spectrum. Fig. 10(b) is a diagram showing a projection image obtained by the imaging unit 12 when the measured sample 4 is irradiated with the X-ray of the first polychromatic spectrum. [Figure 11] FIG. 11 is a diagram showing a profile of a projected image. [Figure 12] Fig. 12(a) is a diagram showing the distribution of effective linear attenuation coefficients obtained when the measured sample 4 is irradiated with the X-ray of the 0th polychromatic spectrum, and Fig. 12(b) is a diagram showing the distribution of effective linear attenuation coefficients obtained when the measured sample 4 is irradiated with the X-ray of the 1st polychromatic spectrum. [Figure 13] FIG. 13 is a diagram showing the density distribution of the sample 4 to be measured. [Figure 14] FIG. 14 is a diagram showing the density distribution of the sample 4 to be measured. [Figure 15] FIG. 15 is a diagram showing the distribution of the content of each element in the measurement sample 4. As shown in FIG. [Figure 16] FIG. 16 is a diagram showing the distribution of the content of each element in the measurement sample 4. As shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, the embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are given the same reference numerals, and duplicated descriptions are omitted. The present invention is not limited to these examples, but is indicated by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0014] 1 is a diagram showing the configuration of an element distribution measuring device 1. The element distribution measuring device 1 is a device that measures the distribution of the content of each element contained in a measured sample 4, and includes a measurement unit 2 and a calculation unit 3. The measurement unit 2 acquires projection data by irradiating each of a plurality of spectra of radiation in a band including X-rays and gamma rays onto the measured sample 4, and includes an irradiation unit 11, an imaging unit 12, and a holding unit 13. The calculation unit 3 performs a predetermined calculation using the projection data acquired by the measurement unit 2, etc., to obtain the distribution of the content of each element contained in the measured sample 4. The following describes the case where X-rays are used as the radiation.

[0015] The irradiation unit 11 outputs X-rays to be irradiated onto the measured sample 4. The irradiation unit 11 selects one of a plurality of spectra, outputs X-rays of the selected spectrum, and irradiates the measured sample 4. The spectrum of the X-rays output by the irradiation unit 11 preferably includes characteristic X-rays, and may be either a monochromatic spectrum or a polychromatic spectrum.

[0016] The imaging unit 12 receives the X-rays output from the irradiation unit 11 and transmitted through the measured sample 4, and obtains projection data by imaging the X-ray intensity distribution at the time of receiving the X-rays. The imaging unit 12 obtains projection data for each of the multiple spectra output from the irradiation unit 11. The imaging unit 12 may be any device capable of obtaining an X-ray image. The imaging unit 12 may be an X-ray CCD camera or an X-ray CMOS camera that is sensitive to X-rays. The imaging unit 12 may also be configured to include a scintillator that generates scintillation light when X-rays are incident thereon, and a CCD camera or a CMOS camera that images the distribution of scintillation light generated in the scintillator.

[0017] The holder 13 holds the sample 4 to be measured and places the sample 4 on the X-ray propagation path from the irradiation unit 11 to the imaging unit 12. The holder 13 can rotate the sample 4 to be measured around a central axis perpendicular to the X-ray propagation direction. In addition, the holder 13 is preferably capable of translating the sample 4 to a direction parallel to the central axis, and is also preferably capable of translating the sample 4 to another direction.

[0018] The calculation unit 3 calculates the distribution of the content of each element contained in the measured sample 4 based on the distribution of the linear attenuation coefficient (or effective linear attenuation coefficient) of the measured sample calculated for each of the multiple spectra based on the projection data acquired by the measurement unit 2, and on the formula of the linear attenuation coefficient (or effective linear attenuation coefficient) expressed for each of the multiple spectra. The calculation unit 3 can also calculate the distribution of the density of the measured sample 4. The details of the calculation will be described later.

[0019] The calculation unit 3 includes a CPU that performs various calculations and other processes, a program required for the calculations, a memory (RAM, ROM, hard disk drive, etc.) that stores the projection data and calculation results, a display that displays the projection data, calculation results, etc. The calculation unit 3 may be a computer.

[0020] Fig. 2 is a diagram showing the configuration of a modified element distribution measuring apparatus 1A. Compared to the configuration of the element distribution measuring apparatus 1 (Fig. 1), the configuration of the element distribution measuring apparatus 1A (Fig. 2) differs in that a measuring unit 2A is provided instead of the measuring unit 2. In addition to the irradiation unit 11, the imaging unit 12, and the holding unit 13, the measuring unit 2A further includes a focusing optical system 14 and an imaging optical system 15.

[0021] The focusing optical system 14 is provided on the X-ray propagation path from the irradiation unit 11 to the measured sample 4. The focusing optical system 14 converges (or reduces the divergence angle of) the divergent X-rays output from the irradiation unit 11, thereby enabling the X-rays to be efficiently irradiated onto the measured sample 4. The imaging optical system 15 is provided on the X-ray propagation path from the measured sample 4 to the imaging unit 12. The imaging optical system 15 can image the X-rays output after passing through the measured sample 4 on the imaging plane of the imaging unit 12.

[0022] Next, configuration examples of the irradiation unit 11 will be described with reference to Fig. 3 to Fig. 5. In any configuration example, the irradiation unit 11 can select any spectrum from among a plurality of spectra, and output X-rays of the selected spectrum.

[0023] The irradiation unit 11A of the first configuration example shown in Fig. 3 includes a plurality of (three in this figure) X-ray tubes 21-23 that output X-rays with different spectra. The X-ray tubes 21-23 may have different tube voltages, may include targets made of different materials, and may include filters with different transmission characteristics. The irradiation unit 11A selects one of the plurality of X-ray tubes 21-23, and irradiates the measured sample 4 with X-rays output from the selected X-ray tube.

[0024] 4 includes one X-ray tube 20 and a plurality of (three in this figure) filters 31-33 having different transmission characteristics. The irradiation unit 11B selects one of the plurality of filters 31-33, and irradiates the measured sample 4 with X-rays that have been output from the X-ray tube 20 and transmitted through the selected filter.

[0025] 5 includes one electron beam generating unit 40 and a plurality of targets 51-53 (three in this figure) made of different materials. The irradiating unit 11C selects one of the plurality of targets 51-53, irradiates the selected target with an electron beam from the electron beam generating unit 40, and irradiates the measured sample 4 with X-rays generated by the selected target.

[0026] Any two or more of the switching of the X-ray tube described in Fig. 3, the switching of the filter described in Fig. 4, and the switching of the target described in Fig. 5 may be combined, thereby making it possible to output X-rays with more types of spectra.

[0027] The element distribution measuring method is a method for measuring the distribution of the content rate of each element contained in the measured sample 4, and includes a measuring step and a calculating step. In the measuring step, radiation (X-rays) of a plurality of spectra in a band including X-rays and gamma rays is incident on the measured sample 4 to obtain projection data. The measuring step may be executed by the measuring unit 2 (or the measuring unit 2A). In the calculating step, a predetermined calculation is performed using the projection data obtained in the measuring step, etc., to obtain the distribution of the content rate of each element contained in the measured sample 4. The calculating step may be executed by the calculating unit 3. Next, the operation of the element distribution measuring device and the flow of the element distribution measuring method will be described.

[0028] 6 is a flowchart showing a first aspect of the element distribution measuring method. The first aspect of the element distribution measuring method includes steps S11 to S14. Step S11 is included in the measurement step executed by the measurement unit 2 (or the measurement unit 2A). Steps S12 to S14 are included in the calculation step executed by the calculation unit 3. Note that steps S11, S12, and S14 are executed in this order, but step S13 may be executed before step S14.

[0029] In step S11, radiation (X-rays) of each of the multiple monochromatic spectra is incident on the measured sample 4 to obtain projection data. Specifically, the process is as follows. The X-rays output from the irradiation unit 11 are irradiated onto the measured sample 4, and the X-rays that have passed through the measured sample 4 are received by the imaging unit 12 to obtain projection data. At this time, the X-rays of each of the multiple monochromatic spectra are output sequentially from the irradiation unit 11, and projection data is obtained for each of the multiple monochromatic spectra. In addition, the measured sample 4 is rotated by the holding unit 13 around a central axis perpendicular to the X-ray propagation direction, and X-rays are incident on the measured sample 4 from various directions to obtain projection data.

[0030] When the X-rays are parallel beams, the sample 4 to be measured may be rotated within a range of 180°. When the X-rays are fan beams or cone beams, the sample 4 to be measured may be rotated within an angle range according to the divergence angle or convergence angle of the X-rays.

[0031] In step S12, based on the projection data acquired in step S11, image reconstruction processing is performed for each of the multiple monochromatic spectra to obtain the distribution of the linear attenuation coefficient of the measured sample 4. Specifically, the process is as follows. When X-rays of any one of the multiple monochromatic spectra are incident on the measured sample 4, the incident X-ray intensity is defined as A, and the i-th measurement value among the measurements taken by the imaging unit 12 is defined as I. i Let us assume that.

[0032] The subscript i is used to distinguish both the pixel number on the imaging surface of the imaging unit 12 and the orientation of the measured sample 4. For example, it can be expressed as i = (pixel number) + (total number of pixels) x (numeric value representing the orientation). If the orientation of the measured sample 4 during rotation is incremented by δ, the numerical value representing the orientation of the measured sample 4 may be set to 0 with respect to the reference orientation, and the angle changed from the reference orientation due to rotation may be divided by δ.

[0033] The measured sample 4 is spatially discretized and divided into a plurality of voxels, and the linear attenuation coefficient of the jth voxel for the incident X-ray is μ j Let I be the i-th measured value. iLet L be the distance that the X-ray passes through the jth voxel to obtain ij In this case, I i is expressed by the following formula (1). By transforming this, the following formula (2) is obtained. L ij is known, and the right-hand side of equation (2) is also known.

[0034]

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[0035]

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[0036] In step S13, for each of the multiple monochromatic spectra, the linear attenuation coefficient is expressed by a formula using the value of the mass attenuation coefficient of each element, the value of the atomic weight of each element, a variable of the content of each element, and a variable of the density of the measured sample 4. Specifically, the formula is as follows. The atomic weight of the i-th element among the multiple elements for which the content is to be calculated is M i The content of the i-th element is α i The elements for which the content ratio is to be determined may be any of the 88 elements that exist in nature, or any elements that are assumed to be contained in the sample 4 to be measured.

[0037] The mass attenuation coefficient of the i-th element for the k-th monochromatic spectrum among multiple monochromatic spectra is ν kiThe density of the sample 4 to be measured is ρ. Among these, the atomic weight M of the i-th element is i and the mass attenuation coefficient ν ki is a known value, and the content α of the i-th element i and the density ρ of the sample 4 are unknown variables. k is expressed by the following equation (3).

[0038]

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[0044] 7 is a flowchart showing a second aspect of the element distribution measuring method. The second aspect of the element distribution measuring method includes steps S21 to S24. Step S21 is included in the measurement step executed by the measurement unit 2 (or the measurement unit 2A). Steps S22 to S24 are included in the calculation step executed by the calculation unit 3. Note that steps S21, S22, and S24 are executed in this order, but step S23 may be executed before step S24.

[0045] In step S21, radiation (X-rays) of multiple polychromatic spectra are each incident on the measured sample 4 to obtain projection data. Specifically, the process is as follows. The measured sample 4 is irradiated with X-rays output from the irradiation unit 11, and the X-rays transmitted through the measured sample 4 are received by the imaging unit 12 to obtain projection data. At this time, it is assumed that each of the multiple polychromatic spectra includes at least one of multiple monochromatic spectra (characteristic X-rays). The multiple polychromatic spectra X-rays are each output from the irradiation unit 11 in sequence to obtain projection data for each of the multiple polychromatic spectra. In addition, the measured sample 4 is rotated around a central axis perpendicular to the X-ray propagation direction by the holding unit 13, and X-rays are incident on the measured sample 4 from various directions to obtain projection data.

[0046] In step S22, based on the projection data acquired in step S21, image reconstruction processing is performed for each of the multiple polychromatic spectra to obtain the distribution of the effective linear attenuation coefficient of the measured sample 4. Specifically, the process is as follows. When X-rays of any one of the multiple polychromatic spectra are incident on the measured sample 4, the X-ray intensity of the kth monochromatic spectrum of the incident X-rays is expressed as A k The i-th measurement value among the measurements taken by the imaging unit 12 is I i Let us assume that.

[0047] The measured sample 4 is spatially discretized and divided into a plurality of voxels, and the linear attenuation coefficient of the jth voxel for the kth monochromatic spectrum X-ray among the incident X-rays is calculated as μ kj Let I be the i-th measured value. i Let L be the distance that the X-ray passes through the jth voxel to obtain ij In this case, I i is expressed by the following equation (9).

[0048]

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[0052] In step S23, for each of the multiple polychromatic spectra, the effective linear attenuation coefficient is expressed by a formula using the value of the effective mass attenuation coefficient of each element, the value of the atomic weight of each element, a variable of the content of each element, and a variable of the density of the measured sample 4. Specifically, the formula is as follows. The atomic weight of the i-th element among the multiple elements for which the content is to be calculated is M i The content of the i-th element is α i Let us assume that.

[0053] Let ν be the effective mass attenuation coefficient of the i-th element for the p-th polychromatic spectrum among the multiple polychromatic spectra. eff pi The effective mass attenuation coefficient ν eff pi is the mass attenuation coefficient ν of the i-th element for the k-th monochromatic spectrum ki The density of the sample 4 to be measured is expressed by the following formula (13). Among these, the atomic weight M of the i-th element is i and the effective mass attenuation coefficient ν eff pi is a known value, and the content α of the i-th element i and the density ρ of the measured sample 4 are unknown variables. eff p is expressed by the following equation (14).

[0054]

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[0058] In the second embodiment, the number of polychromatic spectra is preferably equal to or greater than the number of elements whose content is to be determined. When the number of polychromatic spectra is equal to the number of elements, the content α of each element contained in the sample 4 can be calculated by the above-mentioned calculation. i The distribution of the density ρ of the measured sample 4 and the distribution of the density ρ of the measured sample 4 can be obtained. When the number of multi-color spectra is greater than the number of types of elements, the content α of each element contained in the measured sample 4 can be calculated by the least squares method or the like. i and the distribution of density ρ of the measured sample 4 can be obtained.

[0059] 8 is a flowchart showing a third aspect of the element distribution measuring method. The third aspect of the element distribution measuring method includes steps S31 to S34. Step S31 is included in the measurement step executed by the measurement unit 2 (or the measurement unit 2A). Steps S32 to S34 are included in the calculation step executed by the calculation unit 3. Note that steps S31, S32, and S34 are executed in this order, but step S33 may be executed before step S34.

[0060] In step S31, radiation (X-rays) of multiple polychromatic spectra are each incident on the measured sample 4 to obtain projection data. Specifically, the process is as follows. The measured sample 4 is irradiated with X-rays output from the irradiation unit 11, and the X-rays transmitted through the measured sample 4 are received by the imaging unit 12 to obtain projection data. At this time, it is assumed that each of the multiple polychromatic spectra includes at least one of multiple monochromatic spectra (characteristic X-rays). The multiple polychromatic spectra X-rays are each output from the irradiation unit 11 in sequence to obtain projection data for each of the multiple polychromatic spectra. In addition, the measured sample 4 is rotated around a central axis perpendicular to the X-ray propagation direction by the holding unit 13, and X-rays are incident on the measured sample 4 from various directions to obtain projection data.

[0061] In step S32, based on the projection data acquired in step S31, image reconstruction processing is performed for each of the multiple monochromatic spectra to obtain the distribution of the linear attenuation coefficient of the measured sample 4. Specifically, the process is as follows. When X-rays of the p-th polychromatic spectrum among the multiple polychromatic spectra are incident on the measured sample 4, the X-ray intensity of the k-th monochromatic spectrum among the incident X-rays is expressed as A pk The i-th measurement value among the measurements taken by the imaging unit 12 is I pi Let us assume that.

[0062] The measured sample 4 is spatially discretized and divided into a plurality of voxels, and the linear attenuation coefficient of the jth voxel for the kth monochromatic spectrum X-ray among the incident X-rays is calculated as μ kj Let I be the i-th measured value. pi Let L be the distance that the X-ray passes through the jth voxel to obtain ij In this case, I pi is expressed by the following equation (17).

[0063]

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[0064]

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[0065]

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[0066] In this way, in the third embodiment, it is possible to obtain a three-dimensional distribution of the linear attenuation coefficient μ of the measured sample 4 for each of the multiple monochromatic spectra based on the projection data acquired by irradiating each of the multiple polychromatic spectra onto the measured sample 4. This is called monochromatization processing.

[0067] In step S33, for each of the multiple monochromatic spectra, the linear attenuation coefficient is expressed by a formula using the mass attenuation coefficient value of each element, the atomic weight value of each element, variables of the content of each element, and variables of the density of the measured sample 4. The specific process of step S33 in the third embodiment is the same as step S13 in the first embodiment.

[0068] In step S34, the distribution of the content of each element contained in the measured sample 4 is obtained based on the distribution of the linear attenuation coefficient of the measured sample 4 obtained in step S32 and the formula for the linear attenuation coefficient expressed in step S33. The specific process of step S34 in the third aspect is the same as step S14 in the first aspect.

[0069] In the third embodiment, the number of polychromatic spectra is preferably equal to or greater than the number of elements whose content is to be determined. When the number of polychromatic spectra is equal to the number of elements, the content α of each element contained in the sample 4 can be calculated by the above-mentioned calculation. i The distribution of the density ρ of the measured sample 4 and the distribution of the density ρ of the measured sample 4 can be obtained. When the number of multi-color spectra is greater than the number of types of elements, the content α of each element contained in the measured sample 4 can be calculated by the least squares method or the like. i and the distribution of density ρ of the measured sample 4 can be obtained.

[0070] In the third aspect, the number of polychromatic spectra is preferably equal to or greater than the number of monochromatic spectra (monochromatic X-rays) included in any one of the polychromatic spectra. When the number of polychromatic spectra is equal to the number of monochromatic spectra, the above formulas (17) to (19) can be calculated. When the number of polychromatic spectra is greater than the number of monochromatic spectra, the least squares method or the like can be used.

[0071] Next, the results of the simulation will be described. Although some of the parameters appearing in the conditions and results of the simulation described below originally have units, the simulation was performed without adding units here.

[0072] FIG. 9 is a diagram showing a cross-sectional structure of the measured sample 4 assumed in the simulation. The assumed measured sample 4 was a sphere 4a with a diameter of 10 and a spherical shell 4b with an outer diameter of 20 and an inner diameter of 18, which were arranged concentrically. Both the sphere 4a and the spherical shell 4b contained two elements A and B. The atomic weight M0 of the element A was set to 1, and the atomic weight M1 of the element B was set to 2. In the sphere 4a, the content α0 of the element A was set to 0.6, the content α1 of the element B was set to 0.4, and the density ρ was set to 0.2. In the spherical shell 4b, the content α0 of the element A was set to 0.4, the content α1 of the element B was set to 0.6, and the density ρ was set to 0.1.

[0073] The X-rays of two kinds of polychromatic spectra were irradiated as parallel beams from the irradiation unit 11 onto the measured sample 4. Each of the two kinds of polychromatic spectra included a zeroth monochromatic spectrum and a first monochromatic spectrum. The zeroth polychromatic spectrum had an intensity A 00 The 0th monochromatic spectrum with a value of 0.1 and an intensity A 01 The first polychromatic spectrum had an intensity A of 0.9. 10 The 0th monochromatic spectrum with a value of 0.9 and an intensity A 11 The mass attenuation coefficient v of element A for the 0th monochromatic spectrum is 0.1. 00 is set to 0.053, and the mass attenuation coefficient ν 01 was set to 0.021. The mass attenuation coefficient ν of element A for the first monochromatic spectrum 10 is set to 0.016, and the mass attenuation coefficient ν 11 was set to 0.063. The orientation when rotating the measured sample 4 by the holding unit 13 was set to 0.5° increments. The pixel size of the imaging surface of the imaging unit 12 was set to 0.1.

[0074] Fig. 10(a) is a diagram showing a projection image obtained by the imaging unit 12 when the measured sample 4 is irradiated with X-rays of the 0th polychromatic spectrum. Fig. 10(b) is a diagram showing a projection image obtained by the imaging unit 12 when the measured sample 4 is irradiated with X-rays of the first polychromatic spectrum. As shown in this figure, the projection images of the sphere 4a and the spherical shell 4b differ slightly depending on the polychromatic spectrum used.

[0075] 11 is a diagram showing the profile of a projection image. This diagram shows the profile of a projection image of a monochromatic spectrum obtained by irradiating a measured sample 4 with an X-ray having a polychromatic spectrum and performing a monochromatic processing in the third embodiment of the element distribution measuring method, and the profile of a projection image (true monochromatic profile) obtained when the measured sample 4 is irradiated with an X-ray having a monochromatic spectrum. These profiles show the X-ray intensity at each position on a line passing through the center of the measured sample 4. As shown in this diagram, both profiles are in good agreement.

[0076] Fig. 12(a) is a diagram showing the distribution of effective linear attenuation coefficients obtained when the measured sample 4 is irradiated with X-rays of the 0th polychromatic spectrum. Fig. 12(b) is a diagram showing the distribution of effective linear attenuation coefficients obtained when the measured sample 4 is irradiated with X-rays of the 1st polychromatic spectrum. These were obtained in step S22 of the element distribution measuring method of the second aspect, and show the effective linear attenuation coefficients at each position on a plane passing through the center of the measured sample 4.

[0077] 13 and 14 are diagrams showing the density distribution of the measured sample 4. These diagrams were obtained in step S24 of the second aspect of the element distribution measuring method. FIG. 13 shows the density ρ at each position on a plane passing through the center of the measured sample 4 by shading. FIG. 14 shows the density ρ at each position on a line passing through the center of the measured sample 4. As shown in these diagrams, the distribution of density ρ as initially expected is obtained with high accuracy.

[0078] 15 and 16 are diagrams showing the distribution of the content of each element in the measured sample 4. These diagrams were obtained in step S24 of the second embodiment of the element distribution measuring method. FIG. 15 shows the content ratio (α1 / α0) at each position on a plane passing through the center of the measured sample 4 by shading. FIG. 16 shows the content ratio (α1 / α0) at each position on a line passing through the center of the measured sample 4. However, in the region where ρ<<0.1, the content ratio (α1 / α0) is displayed as -1. As shown in this diagram, the content ratios α0 and α1 of each element are obtained with high accuracy as initially expected.

[0079] As described above, according to the present embodiment, since it is not necessary to use a spectrometer, it is possible to provide an inexpensive device configuration and to easily adjust the optical system. According to the present embodiment, it is possible to easily measure the distribution of the content of each element contained in the measurement sample with an inexpensive configuration.

[0080] The element distribution measuring device or element distribution measuring method of this embodiment can be applied to observation of the morphology of a material, and measurement of the composition distribution and density distribution. Specific examples include observation of the morphology, composition distribution and density distribution of a composite material, and composition distribution (impurity) and density distribution (single crystal, polycrystal) of a semiconductor material.

[0081] The element distribution measuring device or the element distribution measuring method of the present embodiment can be applied to the chemical field (for example, measurement of chemical reactions such as oxidation-reduction reactions, and measurement of composition distribution by adsorption). Specific examples include measurement of chemical reactions in lithium ion batteries and measurement of adsorbed substances in catalysts (exhaust gas, hydrogen).

[0082] The element distribution measuring device or the element distribution measuring method of the present embodiment can also be applied to the medical field, for example, hair testing (mineral analysis) and bone density and cancer density distribution measurement. [Explanation of symbols]

[0083] 1,1A...element distribution measuring device, 2,2A...measurement section, 3...calculation section, 4...sample to be measured, 11,11A,11B,11C...irradiation section, 12...imaging section, 13...holding section, 14...light-collecting optical system, 15...imaging optical system, 20-23...X-ray tube, 31-33...filter, 40...electron beam generating section, 51-53...target.

Claims

1. An apparatus for measuring the distribution of the content of each element contained in a sample to be measured, comprising: a measurement unit for acquiring projection data by irradiating a sample with each of a plurality of monochromatic spectrum radiations in a band including X-rays and gamma rays; a calculation unit that calculates a distribution of the linear attenuation coefficient of the measured sample for each of the plurality of monochromatic spectra based on the projection data acquired by the measurement unit, and a mathematical formula for the linear attenuation coefficient expressed for each of the plurality of monochromatic spectra using a value of the mass attenuation coefficient of each element, a value of the atomic weight of each element, a variable of the content of each element, and a variable of the density of the measured sample; and An element distribution measuring device comprising:

2. An apparatus for measuring the distribution of the content of each element contained in a sample to be measured, comprising: a measurement unit for irradiating a plurality of polychromatic spectrum radiations in a band including X-rays and gamma rays onto the sample to obtain projection data; a calculation unit that calculates a distribution of the effective linear attenuation coefficient of the measured sample calculated for each of the plurality of polychromatic spectra based on the projection data acquired by the measurement unit, and a mathematical expression for the effective linear attenuation coefficient expressed for each of the plurality of polychromatic spectra using the value of the effective mass attenuation coefficient of each element, the value of the atomic weight of each element, a variable of the content of each element, and a variable of the density of the measured sample; An element distribution measuring device comprising:

3. An apparatus for measuring the distribution of the content of each element contained in a sample to be measured, comprising: a measurement unit that causes radiation of a plurality of polychromatic spectra, including at least one of a plurality of monochromatic spectra in a band including X-rays and gamma rays, to be incident on the sample to be measured and acquires projection data; a calculation unit that calculates a distribution of the linear attenuation coefficient of the measured sample for each of the plurality of monochromatic spectra based on the projection data acquired by the measurement unit, and a mathematical formula for the linear attenuation coefficient expressed for each of the plurality of monochromatic spectra using a value of the mass attenuation coefficient of each element, a value of the atomic weight of each element, a variable of the content of each element, and a variable of the density of the measured sample; and An element distribution measuring device comprising:

4. A method for measuring a distribution of the content of each element contained in a sample to be measured, comprising the steps of: a measurement step of irradiating each of a plurality of monochromatic spectrum radiations in a band including X-rays and gamma rays onto the sample to acquire projection data; a calculation step of calculating a distribution of the linear attenuation coefficient of the measured sample calculated for each of the plurality of monochromatic spectra based on the projection data acquired in the measurement step, and a distribution of the content of each element contained in the measured sample based on a mathematical formula for the linear attenuation coefficient expressed for each of the plurality of monochromatic spectra using a value of the mass attenuation coefficient of each element, a value of the atomic weight of each element, a variable of the content of each element, and a variable of the density of the measured sample; The element distribution measuring method includes:

5. A method for measuring a distribution of the content of each element contained in a sample to be measured, comprising the steps of: a measurement step of irradiating each of a plurality of polychromatic spectrum radiations in a band including X-rays and gamma rays onto the sample to obtain projection data; a calculation step of calculating a distribution of the effective linear attenuation coefficient of the measured sample calculated for each of the plurality of polychromatic spectra based on the projection data acquired in the measurement step, and a mathematical expression of the effective linear attenuation coefficient expressed for each of the plurality of polychromatic spectra using the value of the effective mass attenuation coefficient of each element, the value of the atomic weight of each element, a variable of the content of each element, and a variable of the density of the measured sample; The element distribution measuring method includes:

6. A method for measuring a distribution of the content of each element contained in a sample to be measured, comprising the steps of: a measurement step of irradiating radiation of a plurality of polychromatic spectra, including at least one of a plurality of monochromatic spectra in a band including X-rays and gamma rays, onto the sample to be measured and acquiring projection data; a calculation step of calculating a distribution of the linear attenuation coefficient of the measured sample calculated for each of the plurality of monochromatic spectra based on the projection data acquired in the measurement step, and a distribution of the content of each element contained in the measured sample based on a mathematical formula for the linear attenuation coefficient expressed for each of the plurality of monochromatic spectra using a value of the mass attenuation coefficient of each element, a value of the atomic weight of each element, a variable of the content of each element, and a variable of the density of the measured sample; The element distribution measuring method includes:

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