X-ray fluorescence analyzer

Abstract

Provided is an X-ray fluorescence analyzer that analyzes a sample at a high speed in consideration of geometric factors of an optical system in X-ray fluorescence analysis. A fluorescent X-ray analysis device (10) is provided with: an X-ray source (1) that irradiates a sample (3) with primary X-rays (2); a detector (5) (measurement means) for determining the measured intensity of the secondary X-ray (4); a control unit (6) (theoretical intensity calculation means) that calculates the theoretical intensity of the secondary X-ray (4) on the basis of the assumed composition; and a control unit (6) (calculation means) that sequentially and approximately corrects and calculates the assumed composition so that the measured intensity matches the theoretical intensity, the control unit (6) multiplies the detection efficiency of the fluorescent X-ray corresponding to the sample depth from the surface of the sample (3) irradiated with the primary X-ray (2) to the point within the sample (3) at which the secondary X-ray (4) is emitted, and calculates the composition by multiplying the detection efficiency of the fluorescent X-ray corresponding to the sample depth from the surface of the sample (3) irradiated with the primary X-ray (2) to the point within the sample (3) at which the secondary X-ray (4) is emitted. And calculating the theoretical strength.

Description

Technical Field

[0001] This invention relates to a fluorescence X-ray analysis apparatus for analyzing the composition and area density of a sample using the fundamental parameter method (FP method). Background Technology

[0002] To determine the elemental composition of a sample, the FP method is known. In this method, the theoretical intensity of secondary X-rays calculated based on the assumed elemental composition is compared with the measured intensity to bring the assumed composition to converge. The theoretical intensity is calculated, for example, by using the sample size and the intensity and angle of incidence of primary X-rays irradiating various locations on the sample surface as parameters. To account for the geometric factors of the optical system, the theoretical intensity is sometimes calculated by simulating the theoretical intensity of secondary X-rays along each optical path (see, for example, Patent Document 1).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2006-292399 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] The simulations used to determine the theoretical intensities described above are performed for each X-ray path and repeated to bring the assumed composition to convergence. Therefore, conventional fluorescence X-ray analysis apparatuses have consumed a considerable amount of analysis time.

[0008] The present invention was made in view of the above aspects, and its object is to enable the analysis of samples at high speed.

[0009] means for solving problems

[0010] In order to achieve the above objectives,

[0011] The present invention is a fluorescence X-ray analysis apparatus for analyzing a sample, characterized in that it comprises: an X-ray source that irradiates the sample with a single X-ray; a measuring unit that measures the intensity of a second X-ray emitted from the sample to determine the measured intensity; a theoretical intensity calculation unit that calculates the theoretical intensity of the second X-ray emitted from each element in the sample based on an assumed composition; and a calculation unit that successively approximates the assumed composition by performing a corrective calculation to make the measured intensity consistent with the theoretical intensity, thereby calculating the composition of the sample. The theoretical intensity calculation unit calculates the theoretical intensity by multiplying the detection efficiency of the fluorescence X-ray corresponding to the sample depth, wherein the sample depth is the distance from the surface of the sample irradiated with a single X-ray to the point inside the sample from which the second X-ray is emitted.

[0012] Therefore, high-precision theoretical strength can be obtained quickly without Monte Carlo-based simulations, enabling analysis of the sample.

[0013] The effects of the invention

[0014] In this invention, sample analysis can be performed at high speed. Attached Figure Description

[0015] Figure 1 This is a schematic diagram illustrating the structure of a fluorescence X-ray analysis device.

[0016] Figure 2 This is a flowchart illustrating an example of an analysis action.

[0017] Figure 3 This is a graph illustrating an example of the relationship between sample depth and detection efficiency.

[0018] Figure 4 This is an explanatory diagram showing a measurement example prepared in advance. Detailed Implementation

[0019] (Simplified structure of a fluorescence X-ray analysis device)

[0020] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0021] like Figure 1 As shown, the fluorescence X-ray analysis apparatus 10 includes: an X-ray source 1 such as an X-ray tube that irradiates the sample 3 with primary X-rays 2; a detector 5 (measurement unit) that measures the intensity of secondary X-rays 4, such as fluorescence X-rays and scattered rays generated from the sample 3, to determine the measured intensity; and a control unit 6 (theoretical intensity calculation unit, calculation unit) that performs calculations and processing on the elemental composition of the sample 3. In this fluorescence X-ray analysis apparatus 10, the sample 3 is analyzed, for example, in the following manner.

[0022] (Analysis of actions: preparation beforehand)

[0023] First, such as Figure 2 As shown, the following procedures are performed as preparation.

[0024] (S1) Calculate the distance from the surface of the sample 3 irradiated by the first X-ray 2 to the point inside the sample 3 where the second X-ray 4 is emitted, i.e., the sample depth (sample height) z, and the detection efficiency dΩ of the fluorescent X-ray. d The relationship between (z), for example, Figure 3 The relationship is shown. Specifically, the above relationship is determined through simulation or experimental measurement, which will be described later.

[0025] (S2) As an approximation corresponding to the above relationship, for example, the exponential function shown in (Equation 1) and the polynomial shown in (Equation 2) can be derived. Here, Ω in (Equation 1) and (Equation 2) ∞ Ω0, α0, etc. are adjustment coefficients.

[0026] [Formula 1]

[0027]

[0028] [Formula 2]

[0029] dΩ d (z)=a0+a1*z+a2*z 2 +…

[0030] Such prior preparations can be performed only once, for example, when the fluorescence X-ray analysis device 10 is introduced and used for the first time. That is, the detection efficiency of the fluorescence X-rays can be determined in advance and stored for use in the analysis of multiple samples.

[0031] (Analysis action: Quantitative calculation action)

[0032] The quantitative calculation process itself is the same as the usual FP method, but the calculations performed here are as follows, thus enabling high-speed analysis.

[0033] (S3) First, for sample 3, the intensity of two X-ray measurements was measured.

[0034] (S4) Furthermore, the composition of sample 3 is assumed in the same way as in the usual FP method.

[0035] (S5) Calculate the theoretical intensity of the two X-rays based on the assumed sample composition. Specifically, perform the following calculations.

[0036] Here, typically, the detection efficiency dΩ of the fluorescence X-rays corresponding to the sample depth z is not considered. dThe intensity I of the fluorescent X-ray at that time is expressed by the following (Equation 3). In Equation 3, E is the energy of the incident X-ray, ρ is the density of the sample, t is the thickness of the sample, μ(E) is an X-ray physical parameter (mass absorption coefficient for the energy of the incident X-ray), μ(Ei) is an X-ray physical parameter (mass absorption coefficient for the energy of the generated fluorescent X-ray), and ψ... 1 ψ 2 These are the incident and exit angles of the X-rays relative to sample 3, respectively. I0(E) is the intensity of the incident X-rays (first-order X-rays), and Q... i (E) represents the fluorescence X-ray generation efficiency of a quantitative element.

[0037] [Formula 3]

[0038] I i (E)∝I0(E)×Q i (E)×∫0 t exp(-ρχ(E)z)dz (3)

[0039] here,

[0040] Here, the term in (Equation 3) that depends on the sample depth is set as g(E) as in (Equation 4).

[0041] [Formula 4]

[0042] g(E)=∫0 t exp{-ρχ(E)z}dz (4)

[0043] Regarding the term g(E) which depends on the sample depth, in this embodiment, as shown below (Equation 5), the detection efficiency dΩ is used. d The formula g(E)' is corrected by multiplication.

[0044] [Formula 5]

[0045] g(E)'=∫0 t exp{-ρχ(E)z}dΩ d (z)dz (5)

[0046] In this (Equation 5), the depth z of the specimen is calculated using a numerical integration method such as the trapezoidal method or Simpson's method with appropriate step sizes, thereby obtaining a highly accurate theoretical strength.

[0047] Furthermore, in the above (Equation 5) dΩ d As described above (Equation 1), when expressed as an exponential function of the sample depth z, we can obtain the integral g(E)' as shown below (Equation 6).

[0048] [Formula 6]

[0049]

[0050] Furthermore, in the above (Equation 5) dΩ d In the case where the sample depth z is expressed as a polynomial as in Equation 2 above, we can obtain the integral g(E)' as shown in Equation 7 below.

[0051] [Formula 7]

[0052] g(E)'=a0*I0+a1*I1+a2*I2 (7)

[0053] Here, I0, I1, and I2 in the above (Equation 7) are the following (Equations 8) to (Equations 10).

[0054] [Formula 8]

[0055]

[0056] [Formula 9]

[0057]

[0058] [Formula 10]

[0059]

[0060] By using an algebraic expression with integral expansion to derive the theoretical strength, a high-precision theoretical strength that takes into account the detection efficiency based on the sample depth z can be obtained quickly, compared to performing Monte Carlo-based simulations.

[0061] (S6) Compare the theoretical strength with the measured strength, and successively correct the sample composition to make the theoretical strength consistent with the measured strength. Repeat the process after (S3).

[0062] (Specific example of prior preparation 1)

[0063] This indicates that the results were obtained through Monte Carlo simulation. Figure 3 Such a sample depth z and fluorescence X-ray detection efficiency dΩ d An example of the relationship between (z) is that the sample depth z is the distance from the surface of sample 3 to the point inside sample 3 from which two X-rays 4 are emitted.

[0064] For the irradiation area of ​​the first X-ray generated by the tube of X-ray source 1, the detection area that can be observed by detector 5 (where the second X-ray can enter detector 5), and the observable area where the two areas overlap, at each surface of the sample depth z at a predetermined interval (step size), the position and azimuth angle of the second X-ray are determined using random numbers. If the second X-ray enters the detection window of detector 5 and can be observed, a count is performed. The determination of the position and the counting are repeated a sufficient predetermined number of times, and the total count is calculated. Furthermore, the above process is repeated for each sample depth z according to the step size scale.

[0065] Therefore, we can find Figure 3 The relationship between sample depth (sample height) and detection efficiency (detector solid angle) is shown.

[0066] (Specific example of prior preparation 2)

[0067] Sample depth z and detection efficiency dΩ of fluorescent X-rays d The relationship between (z) can also be determined through actual measurement. For example, Figure 4 As shown, a spacer 7 or similar element is provided between the fluorescence X-ray analysis apparatus 10 and the sample 3. The spacer between the fluorescence X-ray analysis apparatus 10 and the surface of the sample 3 is changed by a predetermined step size each time, and the intensity of secondary X-rays incident on the detector 5 is measured for each of the sample depths z. Here, although the sample 3 may differ from the actual sample being analyzed, it is preferably an element with a high X-ray absorption coefficient, such as copper (Cu) or zinc (Zn), because this makes it easier to primarily measure secondary X-rays from the surface of the sample 3 (a shorter analysis depth). Furthermore, the fluorescence X-rays selected should have energy that can ignore air absorption.

[0068] Through such actual measurements, it is also possible to determine... Figure 3 The relationship between sample depth (sample height) and detection efficiency (detector solid angle) is shown.

[0069] The simulation described above can be performed only once for the fluorescence X-ray analysis device 10, without the need for analysis of each actual sample 3. Therefore, it is easy to achieve high-speed analysis.

[0070] Explanation of reference numerals in the attached figures

[0071] 1X-ray source

[0072] 2 X-rays

[0073] 3 samples

[0074] 4.2 X-rays

[0075] 5 detectors

[0076] 6 Control Department

[0077] 7 spacers

[0078] 10 Fluorescence X-ray Analysis Device

Claims

1. A fluorescence X-ray analysis device for analyzing samples, characterized in that, The fluorescence X-ray analysis device includes: An X-ray source that irradiates the sample with X-rays once; A unit for measuring the intensity of two X-rays generated from the sample; The theoretical intensity calculation unit calculates the theoretical intensity of secondary X-rays generated from each element in the sample based on the assumed composition. as well as The calculation unit successively approximates the assumed composition by recalculating to ensure that the measured intensities of the two X-rays match the theoretical intensities, thereby calculating the composition of the sample. The theoretical intensity calculation unit calculates the theoretical intensity based on the product of the detection efficiency of the fluorescent X-rays corresponding to the sample depth, the intensity of the first X-ray, and the X-ray generation efficiency of the quantitative element. The sample depth is the distance from the surface of the sample irradiated with the first X-ray to the point inside the sample where the second X-ray is emitted. The detection efficiency of the fluorescent X-rays is pre-determined and stored for use in multiple sample analyses.

2. The fluorescence X-ray analysis apparatus according to claim 1, characterized in that, The detection efficiency is approximated as an exponential function or polynomial. The theoretical intensity is calculated by solving the integral of the approximate exponential function or polynomial, the intensity of the first-order X-ray, and the X-ray generation efficiency of the quantitative element.

3. The fluorescence X-ray analysis apparatus according to claim 1, characterized in that, The theoretical intensity is determined by calculating the integral of the product of the detection efficiency of the fluorescent X-ray, the intensity of the first X-ray, and the X-ray generation efficiency of the quantitative element relative to the sample depth using the numerical integration method.

4. The fluorescence X-ray analysis apparatus according to any one of claims 1 to 3, characterized in that, The detection efficiency is determined based on the intensity of fluorescent X-rays emitted from various points inside the sample, calculated using Monte Carlo simulations or by actual measurements.

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