JP3860641B2 - X-ray fluorescence analyzer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention includes a secondary target device that is excited by X-rays generated from an X-ray source and generates fluorescent X-rays including characteristic X-rays, and irradiates the sample with fluorescent X-rays generated from the secondary target device. The present invention relates to a fluorescent X-ray analyzer for analyzing fluorescent X-rays generated from a sample.
[0002]
[Prior art]
FIG. 5A is a configuration diagram showing an example of a direct irradiation method in fluorescent X-ray analysis. An X-ray A1 is generated from the X-ray tube 1 and directly irradiated onto the sample S, and the fluorescent X-ray AS generated from the sample S is analyzed using an X-ray detector such as a semiconductor detector. The direct irradiation method is suitable for searching for unknown trace elements because it can analyze a wide element range at a time.
[0003]
When analyzing a specific trace element in a sample with high sensitivity, excitation X-rays irradiating the sample, fluorescent X-rays from the sample matrix, and fluorescent X-rays from the trace element are detected simultaneously, so excitation X The narrower the line spectrum and the smaller the background spectrum, that is, the monochromatic color, the more the detection limit of trace elements can be improved.
[0004]
Techniques such as a secondary target method and a spectral crystal method are known for monochromatic excitation X-rays.
[0005]
In the secondary target method, a secondary target made of a material different from the anode target of the X-ray tube is prepared, and the secondary target is irradiated with X-rays generated from the X-ray tube once. In this method, the sample is made almost monochromatic by generating fluorescent X-rays including the characteristic X-rays, and the sample is irradiated with the fluorescent X-rays. The wavelength switching of the excitation X-ray can be easily realized by exchanging the secondary target material.
[0006]
FIG.5 (b) is a block diagram which shows an example of the secondary target method in a fluorescent X ray analysis. The X-ray A1 from the X-ray tube 1 is once irradiated to the secondary target 2, the fluorescent X-ray A2 specific to the target material is generated from the secondary target 2, and the sample S is irradiated with the fluorescent X-ray A2. The generated fluorescent X-ray AS is analyzed using an X-ray detector such as a semiconductor detector.
[0007]
Next, the spectroscopic crystal method is a method in which X-rays generated from an X-ray tube are once irradiated onto the spectroscopic crystal, and are monochromatized by X-ray diffraction by the spectroscopic crystal, and the sample is irradiated with the diffracted fluorescent X-rays. Due to X-ray diffraction, the wavelength purity is increased, but the X-ray intensity is considerably reduced. Specifically, it is necessary to arrange a spectroscopic crystal instead of the secondary target 2 shown in FIG. 5B and finely adjust the positional relationship between the X-ray tube 1 and the sample S to satisfy the diffraction conditions. is there.
[0008]
[Problems to be solved by the invention]
The secondary target method has an advantage that the X-ray optical system can be easily adjusted and the obtained measured X-ray intensity is high as compared with the spectroscopic crystal method.
[0009]
However, as shown in FIG. 5B, since the optical axis of the X-ray is bent at the position of the secondary target, in order to realize the direct irradiation method and the secondary target method with the same apparatus, A moving mechanism such as rotation becomes indispensable, and the entire apparatus becomes large. Moreover, since the X-ray irradiation conditions (angle, irradiation position, etc.) by the direct irradiation method do not necessarily match the X-ray irradiation conditions by the secondary target method, the correspondence between the measurement data of both becomes inaccurate.
[0011]
An object of the present invention is to generate a fluorescent X-ray for measurement in the same direction as the X-ray optical axis from the X-ray source, thereby switching the X-ray irradiation optical axis when switching between the direct irradiation method and the secondary target method. It is an object of the present invention to provide a fluorescent X-ray analyzer that does not require an adjustment mechanism and can match both X-ray irradiation conditions.
[0012]
[Means for Solving the Problems]
The present invention comprises an X-ray source that generates X-rays;
A secondary target device that is excited by X-rays from an X-ray source and generates fluorescent X-rays for measurement;
An X-ray detector that irradiates a sample with fluorescent X-rays for measurement and detects fluorescent X-rays generated from the sample;
The secondary target device is formed of an X-ray shielding material and has a hollow portion that spatially connects the X-ray entrance opening and the X-ray exit opening, and the X-ray entrance opening and the X-ray exit opening are formed concentrically. A target body,
A target layer formed on the inner surface facing the hollow portion of the target body and excited by incident X-rays to generate fluorescent X-rays for measurement;
An X-ray blocking member that is made of an X-ray shielding material and partially blocks incident X-rays so that incident X-rays that pass through the X-ray incident aperture do not pass through the X-ray exit aperture as they are;
The direction of the optical axis of the incident X-ray is the same as the direction of the optical axis of the fluorescent X-ray for measurement.
[0013]
According to the present invention, when X-rays from the X-ray source enter the X-ray entrance opening and reach the target layer, fluorescent X-rays for measurement are generated from the target layer and emitted from the X-ray exit opening. On the other hand, since the X-ray blocking member and the target body are made of an X-ray shielding material, incident X-rays cannot reach the rear side of the target. Therefore, it is possible to generate measurement fluorescent X-rays that are substantially monochromatic along the same direction as the X-ray optical axis on the incident side.
Therefore, when the direct irradiation method is performed by moving or removing the secondary target device, the angle adjustment of the X-ray source is not necessary, and the X-ray irradiation conditions, for example, X-rays between the direct irradiation method and the secondary target method are eliminated. The irradiation angle and the irradiation position can be made almost coincident.
[0014]
In the invention, it is preferable that the inner surface is formed in a tapered shape that gradually decreases from the X-ray entrance opening toward the X-ray exit opening.
[0015]
According to the present invention, since the solid angle of the inner surface viewed from incident X-rays can be increased, the conversion efficiency and intensity of fluorescent X-rays for measurement can be improved.
[0016]
Further, the present invention is characterized in that an X-ray filter for monochromaticizing the fluorescent X-ray for measurement is provided in the X-ray exit opening.
[0017]
According to the present invention, not only characteristic X-rays specific to the main material of the target layer but also characteristic X-rays of impurities and atmospheric elements, or scattered X-rays of incident X-rays are superimposed and emitted from the X-ray emission aperture. Therefore, by providing an X-ray filter having a low-pass filter characteristic or a band-pass filter characteristic in the X-ray spectrum, the measurement fluorescent X-ray can be made more monochromatic.
[0021]
The present invention also provides a collimator device for directly irradiating a sample by focusing X-rays from an X-ray source into a beam shape,
A moving mechanism for selectively using the collimator device and the secondary target device is provided.
[0022]
According to the present invention, the spatial resolution in the direct irradiation method can be improved by narrowing the X-rays into a beam using a collimator device. In addition, switching between the direct irradiation method using the collimator device and the secondary target method using the secondary target device is facilitated, and the reproducibility of the measurement conditions is improved by employing both moving mechanisms.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a configuration diagram showing an embodiment of a fluorescent X-ray analyzer according to the present invention. The secondary target device 20 includes a target body 21 formed in a hollow shape, a target layer 22 formed on the inner surface of the target body 21, an X-ray blocking plate 23 that partially blocks incident X-rays, and the like. The
[0024]
The target body 21 is formed of an X-ray shielding material such as Pb, and an X-ray incident opening 21a and an X-ray emission opening 21b are formed concentrically on the front and back surfaces, and these openings 21a and 21b are spatially connected. Thus, a tapered hollow portion is formed.
[0025]
The target layer 22 is made of a material corresponding to a desired characteristic X-ray, for example, Al, Cu, Ge, Y, Sn, etc., and is formed on the inner surface of the hollow portion by adhesion or vapor deposition. The target layer 22 is excited by the X-ray A1 from the X-ray tube 10 and generates measurement fluorescent X-rays including characteristic X-rays specific to the layer material.
[0026]
The X-ray blocking plate 23 is made of an X-ray shielding material such as Pb, and viewed from the divergence point of the X-ray A1 so that the X-ray A1 that has passed through the X-ray incident opening 21a does not pass through the X-ray exit opening 21b as it is. The solid angle is larger than the solid angle of the X-ray emission opening 21b and smaller than the X-ray incident opening 21a, for example, a disk shape.
[0027]
The X-ray tube 10 includes a heater 11 that emits thermoelectrons, an anode target 12 that generates X-rays A1 by the collision of the thermoelectrons, and the like. The anode target 12 is formed of a material such as Cu, Mo, or W.
[0028]
Next, the operation will be described. The X-ray A1 generated from the X-ray tube 10 spreads conically around the optical axis k1 and enters the X-ray incident opening 21a. Of the incident X-rays A1, those reaching the target body 21 and the X-ray blocking plate 23 are blocked, and the remaining X-rays A1 reach the target layer 22. The target layer 22 generates a fluorescent X-ray A2 for measurement by X-ray excitation. The fluorescent X-ray A2 spreads in a conical shape with the optical axis k2 in the same direction as the optical axis k1 as the center, and reaches the sample S.
[0029]
In this way, the measurement fluorescent X-ray A2 that is substantially monochromatic can be generated along the optical axis k2 that is the same direction as the incident optical axis k1, without the incident X-ray A1 leaking to the sample S side.
[0030]
Here, the target layer 22 is preferably formed in a tapered shape that becomes gradually narrower from the X-ray incident opening 21a toward the X-ray emitting opening 21b, so that a large irradiation area of the incident X-ray A1 can be secured, and the measurement fluorescence can be secured. The conversion efficiency and intensity of X-ray A2 can be improved.
[0031]
FIG. 2 is a perspective view showing various shapes of the target main body 21. In FIG. 2A, the target body 21 is formed in a donut shape having a circular X-ray incident opening 21a having a large opening area and a circular X-ray emitting opening 21b having a small opening area. A tapered hollow portion connecting 21b is formed.
[0032]
In FIG. 2B, the target body 21 is formed in a rectangular donut shape having a square X-ray incident opening 21a having a large opening area and a square X-ray emitting opening 21b having a small opening area. , 21b are connected to form a truncated pyramid-shaped hollow portion.
[0033]
In FIG. 2 (c), the target body 21 has a rectangular shape having two wedge-shaped plate members opposed to each other, each plate member held between holders 24, and having a large opening area on the lower surface. An X-ray incident opening 21a and a rectangular X-ray exit opening 21b having a small opening area are formed on the upper surface.
[0034]
In addition, the shapes of the X-ray incident opening 21a and the X-ray exit opening 21b may be elliptical or polygonal.
[0035]
FIG. 3 is a block diagram showing an embodiment of the fluorescent X-ray analyzer according to the present invention. The X-ray fluorescence analyzer includes an X-ray tube 10 that generates X-rays, the secondary target device 20 shown in FIG. 1, an X-ray detector 15 that detects fluorescent X-ray AS generated from a sample S, and a direct It comprises a pinhole collimator 25 for the irradiation method, a moving table 30 that supports the secondary target device 20 and the pinhole collimator 25, and the like.
[0036]
This apparatus is configured so that the secondary target method and the direct irradiation method can be selectively performed. By the horizontal positioning of the moving table 30, the secondary target device 20 and the direct irradiation method can be used in the secondary target method. When the pinhole collimator 25 is selected.
[0037]
The X-ray tube 10 is fixed so that X-rays A1 are generated along the same optical axis k1 in the secondary target method and the direct irradiation method.
[0038]
When the X-ray A1 from the X-ray tube 10 is incident, the secondary target device 20 generates fluorescent X-rays A2 including characteristic X-rays specific to the material of the target layer 22 along the optical axis k2.
[0039]
The pinhole collimator 25 is supported by a cylindrical holder 26 formed of an X-ray shielding material, and irradiates the sample S directly by focusing the X-ray A1 from the X-ray tube 10 into a beam shape.
[0040]
The X-ray detector 15 is composed of a semiconductor detector, a scintillation counter, or the like, and outputs an electric signal corresponding to the intensity of the fluorescent X-ray.
[0041]
Next, the operation will be described. First, in the secondary target method, the X-ray A1 generated from the X-ray tube 10 spreads conically around the optical axis k1 and enters the X-ray incident opening 21a. Of the incident X-rays A1, those reaching the target body 21 and the X-ray blocking plate 23 are blocked, and the remaining X-rays A1 reach the target layer 22. The target layer 22 generates a fluorescent X-ray A2 for measurement by X-ray excitation. The fluorescent X-ray A2 spreads in a conical shape with the optical axis k2 in the same direction as the optical axis k1 as the center, and reaches the sample S. The sample S is excited by the fluorescent X-ray A2, generates the fluorescent X-ray AS corresponding to the composition material, and is detected by the X-ray detector 15.
[0042]
Next, in the direct irradiation method, the moving table 30 is moved so that the optical axes k1 and k2 coincide with the optical axis of the pinhole collimator 25. Next, the X-ray A1 generated from the X-ray tube 10 travels in a conical shape centering on the optical axis k1, is shaped into a beam by the pinhole collimator 25, and reaches the sample S as it is. The sample S is directly excited by the X-ray A1 from the X-ray tube 10, generates a fluorescent X-ray AS corresponding to the composition material, and is detected by the X-ray detector 15.
[0043]
By using the hollow secondary target device 20 in this way, the measurement is made substantially monochromatic along the optical axis k2 which is the same direction as the incident optical axis k1 without the incident X-ray A1 leaking to the sample S side. Fluorescent X-ray A2 can be generated. Therefore, it is not necessary to adjust the angle of the X-ray tube 10 in switching between the secondary target method and the direct irradiation method, and the X-ray irradiation conditions such as the X-ray irradiation angle and the irradiation between the secondary target method and the direct irradiation method are eliminated. The positions can be almost matched.
[0044]
FIG. 4 is a block diagram showing another embodiment of the present invention. In the vicinity of the exit of the X-ray emission opening 21b of the secondary target device 20, an X-ray filter 27 for monochromaticizing the measurement fluorescent X-rays is provided.
[0045]
The X-ray filter 27 is formed of a material having a low-pass filter characteristic that absorbs a shorter wavelength than the X-ray absorption edge and a band-pass filter characteristic that passes only a specific wavelength region, and the measurement fluorescence generated in the target layer 22. By passing only specific characteristic X-rays among the X-rays, the measurement fluorescent X-rays can be made more monochromatic. Such an X-ray filter 27 can be similarly used in the fluorescent X-ray analysis apparatus shown in FIG.
[0046]
As described above in detail, according to the present invention, it is possible to generate measurement fluorescent X-rays that are substantially monochromatic along the same direction as the X-ray optical axis on the incident side, which facilitates incorporation into an X-ray optical system. .
In addition, according to the present invention, since the measurement fluorescent X-ray substantially monochromatic along the same direction as the incident X-ray optical axis can be generated, the direct irradiation method and the secondary target method can be selectively performed. In this case, it is not necessary to adjust the angle of the X-ray source, and the X-ray irradiation conditions can be substantially matched.
[0047]
Further, by forming the inner surface of the target body in a tapered shape, the solid angle of the inner surface viewed from incident X-rays can be increased, so that the conversion efficiency and intensity of the measurement fluorescent X-rays can be improved.
[0048]
Further, by providing an X-ray filter for monochromaticizing the measurement fluorescent X-rays at the X-ray exit aperture, the measurement fluorescent X-rays can be made monochromatic.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an embodiment of an X-ray fluorescence analyzer according to the present invention.
2 is a perspective view showing various shapes of a target body 21. FIG.
FIG. 3 is a configuration diagram showing an embodiment of an X-ray fluorescence analyzer according to the present invention.
FIG. 4 is a configuration diagram showing another embodiment of the present invention.
FIG. 5 is a configuration diagram showing a direct irradiation method and a secondary target method in a conventional fluorescent X-ray analysis.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 X-ray tube 15 X-ray detector 20 Secondary target apparatus 21 Target main body 21a X-ray entrance opening 21b X-ray exit opening 22 Target layer 23 X-ray blocking plate 24 Holder 25 Pinhole collimator 27 X-ray filter 30 Moving table

Claims (4)

An X-ray source generating X-rays;
A secondary target device that is excited by X-rays from an X-ray source and generates fluorescent X-rays for measurement;
An X-ray detector for irradiating the sample with fluorescent X-rays for measurement and detecting the fluorescent X-rays generated from the sample;
The secondary target device is formed of an X-ray shielding material, and has a hollow portion that spatially connects the X-ray entrance opening and the X-ray exit opening, and the X-ray entrance opening and the X-ray exit opening are formed concentrically. A target body,
A target layer that is formed on the inner surface facing the hollow portion of the target body and is excited by incident X-rays to generate fluorescent X-rays for measurement;
An X-ray blocking member that is formed of an X-ray shielding material and partially blocks incident X-rays so that incident X-rays that pass through the X-ray incident aperture do not pass through the X-ray exit aperture as they are;
The direction of the optical axis of the incident X-ray is the same as the direction of the optical axis of the fluorescent X-ray for measurement. 2. The fluorescent X-ray analyzer according to claim 1, wherein the inner surface is formed in a tapered shape that gradually decreases from the X-ray incident opening toward the X-ray exit opening. The X-ray exit opening, X-ray fluorescence analyzer according to claim 1 or 2, wherein the X-ray filter for monochromatic measuring fluorescent X-rays is provided. A collimator device for directly irradiating a sample by focusing X-rays from an X-ray source into a beam;
The fluorescent X-ray analyzer according to claim 1, further comprising a moving mechanism for selectively using the collimator device and the secondary target device.

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