JP2000206061A - Fluorescent x-ray measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fluorescent X-ray measuring device for reliably obtaining fluorescent X-ray information from the small region of a sample with high resolution and without any leakage. SOLUTION: A device is provided with an X-ray source F for generating X rays that are applied to a sample S, a capillary optical element 6 that is arranged at a position for taking in fluorescent X rays being generated from the sample S, a spectral crystal 3 that is arranged at a position where X rays being emitted from the capillary optical element 6 enter, and an X-ray detector 4 for detecting X rays being dispersed by the spectral crystal 3. The capillary optical element 6 is formed by bundling a plurality of capillary tubes 10, and its X-ray incidence port 6a is formed to be smaller than an X-ray emission port 6b so that it anticipates the small region of the sample S.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluorescent X-ray measuring apparatus for detecting fluorescent X-rays generated from a sample and measuring the types of elements present inside the sample based on the fluorescent X-rays.

[0002]

2. Description of the Related Art Phenomena that occur when a sample is irradiated with X-rays include the generation of diffracted X-rays and the generation of fluorescent X-rays.
Diffracted X-rays are generated by increasing the number of X-rays reflected on the crystal lattice plane of the sample that meet specific conditions, so-called Bragg's diffraction conditions, and the other ones cancel each other out and are no longer observed. X-ray. This diffracted X-ray is generated in association with the arrangement of elements such as crystals.

On the other hand, the elements constituting the sample have their own shell electron ranks. X-ray,
When irradiated with radiation such as γ-rays and electron beams, the substance generates X-rays having properties peculiar to the element, usually characteristic X-rays. This X-ray is generally called fluorescent X-ray. This fluorescent X-ray is generated irrespective of the crystal structure of the sample, but in relation to the type and amount of elements present inside the sample.

[0004] By detecting the fluorescent X-rays generated from the sample and obtaining the energy distribution or wavelength distribution of the fluorescent X-rays, it is possible to know the types and contents of the elements contained in the sample. An apparatus used for performing such a measurement is an X-ray fluorescence measuring apparatus. This apparatus is roughly classified into two types, a wavelength dispersion type and an energy dispersion type.

[0005] In the wavelength dispersion type, the wavelength is selected using an X-ray spectrometer combining a spectral crystal and a slit based on the principle of X-ray diffraction. On the other hand, the energy dispersive type directly detects X-rays using, for example, an SSD (Solid-state Detector: semiconductor detector) and introduces the output of the SSD into, for example, an MCA (Multi-Channel Pulse Height Analyzer). And sort by energy.

The wavelength-dispersive X-ray fluorescence measuring apparatus has an advantage that the apparatus can be formed at low cost because an expensive SSD is not used. In addition, the SSD cannot increase its caliber to maintain the energy resolution, so that there is a problem that the amount of X-ray that can be captured is limited.
The wavelength-dispersive X-ray fluorescence measuring apparatus that does not use an SSD does not have such a problem, and has an advantage that X-ray fluorescence can be detected from a wide range without leakage by setting the aperture of the X-ray detection means large. .

[0007] Considering a wavelength-dispersive X-ray fluorescence measuring apparatus, it has been conventionally configured as shown in FIG. 4, for example. In brief, the X-rays generated from the X-ray source F are applied to the sample S, and at that time, the fluorescent X-rays generated from the sample S are shaped into parallel X-ray beams by the solar slit 56a and spectrally separated. The light enters the crystal 53. The fluorescent X-rays are separated according to the incident angle θ with respect to the spectral crystal 53, and fluorescent X-rays of a specific wavelength are extracted on the output side, and the extracted fluorescent X-rays are captured by the X-ray counter 54 through the solar slit 56b. . Then, the X-ray counter 54
The intensity of the fluorescent X-rays is obtained by an X-ray intensity calculation circuit 59 connected to the output terminal of (1).

[0008]

However, with respect to the above-mentioned conventional fluorescent X-ray measuring apparatus, the X-ray
Since the X-ray counter 54 has a structure in which the X-rays are irradiated and the fluorescent X-rays generated from a wide surface thereof are taken in by the X-ray counter 54, there is a problem that the fluorescent X-ray information on the minute area of the sample S cannot be obtained. .

The present invention has been made in view of the above-mentioned problems in the conventional X-ray fluorescence measuring apparatus, and obtains X-ray fluorescence information from a minute area of a sample without fail and with high resolution. It is an object of the present invention to provide a fluorescent X-ray measuring device capable of performing the above-mentioned.

[0010]

Means for Solving the Problems (1) In order to achieve the above-mentioned object, an X-ray fluorescence measuring apparatus according to the present invention is an X-ray fluorescence measuring apparatus for measuring X-ray fluorescence generated from a sample. An X-ray source for generating X-rays to be irradiated, a capillary optical element disposed at a position for capturing fluorescent X-rays generated from a sample, and an X-ray emitted from the capillary optical element
It has a dispersive crystal arranged at a position where a line is incident, and X-ray detection means for detecting X-rays separated by the dispersive crystal. The capillary optical element is formed by bundling a plurality of capillary tubes, and the X-ray entrance is smaller than the X-ray exit so as to look at the minute area of the sample.

According to this fluorescent X-ray measuring apparatus, when X-rays emitted from an X-ray source are incident on a sample, the sample generates fluorescent X-rays, which are captured by a capillary optical element. The light is guided to the spectral crystal by the X-ray detector, and the wavelength component of the wavelength component separated by the spectral crystal is counted by the X-ray detector. The X-ray detection means used here does not need to use an X-ray detection means having its own energy resolution such as an SSD, and a PC (Proportional Counter: proportional counter) or SC which is a low energy resolution counter is used.
(Scintillation Counter) can be used.

According to the fluorescent X-ray measuring apparatus of the present invention, the X-ray entrance of the capillary optical element is formed to be smaller than the X-ray exit, so that the capillary optical element can be arranged so as to see a minute area of the sample. Therefore, it is possible to measure the fluorescent X-ray information on the minute region of the sample or the minute sample. In addition, since the structure is such that the fluorescent X-rays generated from the sample are collimated and then separated by a spectral crystal, the measurement can be performed with higher resolution than when the fluorescent X-rays are energy-decomposed using an SSD. it can.

Furthermore, since the X-ray detecting means itself can be of low resolution, the X-ray inlet of the X-ray detecting means can be set to a large diameter. By setting the X-ray inlet of the X-ray detection means to a large diameter in accordance with the diameter of the X-ray emission port of the capillary optical element, it is possible to reliably capture the fluorescent X-ray without leakage, that is, to increase the detection efficiency. Can be.

(2) In the X-ray fluorescence measuring apparatus having the above structure, the size of the X-ray intake of the X-ray detecting means can be set to be equal to or larger than the X-ray exit of the capillary optical element. . In this case, the fluorescent X-rays having higher intensity can be taken into the X-ray detecting means, and as a result, highly reliable measurement can be performed.

(3) In the X-ray fluorescence measuring apparatus having the above-mentioned configuration, the capillary optical element, the spectral crystal, and the X-ray detecting means may be integrally movable relative to the sample in an integrated state. desirable. According to this configuration, it is possible to change the minute area on the sample to be viewed by the capillary optical element as desired, so that it is possible to measure the fluorescent X-ray information at various positions in the sample, that is, perform so-called mapping measurement. Becomes possible.

[0016]

FIG. 1 shows an embodiment of an X-ray fluorescence measuring apparatus according to the present invention. The X-ray fluorescence measurement apparatus includes an X-ray including a sample table 1 for supporting a sample S which is an object to be measured, and an X-ray focus F as an X-ray source for generating X-rays for irradiating the sample S. It has a tube 2 and an optical bench 7. The X-ray focal point F is set to, for example, a size of 2 mm × 2 mm. The distance D0 between the X-ray focal point F and the sample S is set to about several mm.

The optical table 7 is provided with an X-ray optical system moving device 8 which is driven by the X-ray optical system moving device 8 to make a right angle in the X, Y and Z directions indicated by arrows. The optical table 7 can move three-dimensionally, that is, spatially in all directions with respect to the sample S, and can stop at that position.

Such an X-ray optical system moving device 8 combines, for example, slide tables that move in each of three orthogonal directions of X, Y, and Z, and uses the slide tables by a pulse motor as a driving source. It can be constituted by a structure of driving.

A goniometer 17 including a θ turntable 14 and a 2θ turntable 16 is installed on the optical table 7 as described above. rotating table 14 is the .theta.
8 to rotate about the crystal axis Z1. The 2θ rotation table 16 is driven by a 2θ rotation drive device 19 to rotate about the crystal axis Z1. During the normal measurement, the 2θ turntable 16 is
Rotate in the same direction at twice the angular velocity with respect to the angular velocity.

The θ rotation driving device 18 and the 2θ rotation driving device 19 operate in accordance with a command from the computer 11.
The specific structure of these driving devices is not limited to a specific structure. For example, a structure in which the power of the pulse motor is transmitted via a power transmission mechanism including a worm and a worm wheel can be employed.

A dispersive crystal 3 for dispersing fluorescent X-rays generated from the sample S is mounted on the θ-turntable 14. The counter arm 2 extending from the 2θ turntable 16
On top of X, X for detecting X-rays separated by the
The line detector 4 is attached. Further, a capillary optical element 6 for guiding fluorescent X-rays from the sample S to the spectral crystal 3
Is disposed on the optical bench 7 so as to be located between the sample S and the spectral crystal 3.

The spectral crystal 3 is formed in a flat plate shape from an appropriate substance such as graphite, PET (polyethylene terephthalate), LiF (lithium fluoride) or the like according to the wavelength of the X-ray to be extracted. In the case of the present embodiment, the X-ray detector 4 itself does not require a high energy resolution. Therefore, this X-ray detector 4 is, for example, a PC (Proportional Counter), S
It can be configured using C (Scintillation Counter) or the like.

The capillary optical element 6 is formed by bundling a plurality of capillary tubes 10, and its X
The X-rays taken in from the line entrance 6a are emitted from the X-ray exit 6b. The individual capillary tubes 10 transmit X-rays by total internal reflection. Even when X-rays enter the X-ray entrance 6a from all directions, a parallel X-ray beam can be extracted from the X-ray exit 6b. Can be.

The diameter of the X-ray entrance 6a of the capillary optical element 6 used in the present embodiment is smaller than the diameter of the X-ray exit 6b. For example, if the X-ray entrance 6a is 1
It is formed to a diameter of about 0 mm × 10 mm to 20 mm × 20 mm, and the X-ray emission port 6 b is 13 mm × 13 mm to
It has a diameter of about 25 mm x 25 mm.

As described above, since the X-ray entrance 6a of the capillary optical element 6 is formed smaller than the X-ray exit 6b, the capillary optical element 6 of the apparatus of the present embodiment has the sample S
Can be arranged so as to allow for the micro area A. That is, the capillary optical element 6 takes in the fluorescent X-rays generated only from the minute area A of the sample S from the X-ray entrance 6a, shapes it into a parallel X-ray beam having a wide cross-sectional area, and forms the X-ray.
The light can be supplied to the spectral crystal 3 from the line emission port 6b.

Each of the capillary tubes 10 has an X
A uniform diameter can be used from the X-ray entrance 6a to the X-ray exit 6b, or the X-ray entrance 6
A tapered capillary tube whose diameter gradually increases from a to the X-ray emission port 6b can also be used. Here, when a capillary tube having a uniform diameter is used from the X-ray entrance 6a to the X-ray exit 6b, the capillary tube 10 is provided at the X-ray entrance 6a.
Are bundled at a high density. On the other hand, in the X-ray emission port 6b, the arrangement density of the individual capillary tubes 10 decreases as the diameter of the capillary optical element 6 increases.

Next, the diameter of the X-ray inlet 4a of the X-ray detector 4 is formed to be equal to or larger than the diameter of the X-ray emission port 6b of the capillary optical element 6. In this way, the X-rays that have exited from the capillary optical element 6 and have been separated by the spectral crystal 3 can be efficiently taken into the X-ray detector 4 without leakage.

An output terminal of the X-ray detector 4 is connected to an X-ray intensity calculation circuit 9 including a pulse height analyzer (PHA). The X-ray intensity calculation circuit 9 calculates the intensity of the fluorescent X-ray based on the output signal of the X-ray detector 4 and outputs the calculation result to the computer 11.
The computer 11 displays the obtained fluorescent X-ray intensity information as an image on the display 12 or prints it on paper by the printer 13.

Since the X-ray fluorescence measuring apparatus of the present embodiment is configured as described above, the X-ray radiated from the X-ray focus F
The line is irradiated on a wide surface of the sample S, and at this time, fluorescent X-rays are generated from the surface. X-ray fluorescence X-rays generated from the microscopic region A that can be seen by the capillary optical element 6 on the sample surface are captured by the capillary optical element 6 and shaped into a parallel X-ray beam. Supplied. The fluorescent X-rays generated from the area other than the minute area A are not taken into the capillary optical element 6 and are not used for measurement. That is, in the present embodiment, only the minute region A expected by the capillary optical element 6 is a measurement region.

As described above, while the fluorescent X-rays from the sample S are supplied to the spectral crystal 3, the rotation angle of the spectral crystal 3, that is, the θ angle with respect to the fluorescent X-rays is gradually changed to the spectral crystal 3. The incident angle of the fluorescent X-ray is changed. At the same time, the rotation angle of the X-ray detector 4, ie, 2
The θ angle is changed at twice the angle of the θ angle. Then, at each θ angle of the dispersive crystal 3, X-rays having a wavelength corresponding to the θ angle are separated from the fluorescent X-rays, and the separated characteristic X-rays are taken in by the X-ray detector 4, and the characteristic X-rays are further extracted. The X-ray intensity is obtained by the X-ray intensity calculation circuit 9. This processing is performed for each of the different 2θ angles of the X-ray detector 4, and as a result, the X-rays of various wavelengths included in the fluorescent X-rays generated from the sample S, that is, the intensities of various characteristic X-rays, Desired.

FIG. 2 shows an example of a fluorescent X-ray spectrum of the sample S obtained as described above. According to this figure, the characteristic X of the different wavelength at the place where the 2θ angle is different is shown.
It is understood that the lines a, b, c,... Are detected, and that the intensity of their characteristic X-rays is indicated by the peak height. These characteristic X-rays a, b, c,
... correspond to the elements contained in the sample S and their contents. By observing the peaks appearing in the fluorescent X-ray spectrum, the types of the elements contained in the sample S and their contents are determined. You can know.

As described above, according to the present embodiment, the fluorescent X-ray measurement can be performed only on the minute area A of the sample S which can be seen by the capillary optical element 6.
Since the structure is such that the fluorescent X-rays generated from the sample S are collimated and then separated by the spectral crystal 3, the measurement is performed with higher resolution than in the case where the fluorescent X-rays are energy-decomposed using the SSD. be able to.

Further, the X-ray detector 4 used in this embodiment
Since the resolution is lower than that of an SSD or the like, the X-ray inlet 4a of the X-ray detector 4 can be set to a large diameter. As a result, it is possible to reliably capture the fluorescent X-rays separated by the spectral crystal 3 without leakage, that is, to increase the detection efficiency, and as a result, to obtain a highly reliable measurement result.

In the present embodiment, the optical table 7 on which the capillary optical element 6 and the goniometer 17 are mounted can be translated three-dimensionally relative to the sample S by the X-ray optical system moving device 8. Therefore, the expected area A of the sample S by the capillary optical element 6 can be moved to an arbitrary position on the surface of the sample S, and the X-ray fluorescence can be measured for the area after the movement. If such a measurement is performed for a plurality of different minute regions of the sample S, it is possible to obtain a fluorescent X-ray spectrum relating to the plurality of different minute regions of the sample S, that is, perform a mapping measurement.

As described above, the present invention has been described with reference to the preferred embodiments. However, the present invention is not limited to the embodiments, and can be variously modified within the scope of the invention described in the claims. For example, the above measurement performed using the optical system of FIG. 1 is a general X-ray fluorescence measurement, but the X-ray fluorescence measurement apparatus according to the present invention is different from such a general measurement method. XAFS, an elemental analysis method that uses X-ray absorption
It can be applied to (Safus) measurement. Since the XAFS measurement itself is a well-known measurement method, a detailed description thereof will be omitted, but a brief description thereof is as follows.

That is, generally, the energy of the X-ray radiated to the sample is gradually changed, and for each of the energies, the intensity (Io) of the X-ray incident on the sample and the intensity of the fluorescent X-ray generated in the sample (Io) If) and the ratio (If / Io) are calculated, the absorption coefficient is calculated based on the ratio, and plotted on a graph, to obtain an X-ray absorption diagram as shown in FIG. In this figure, the horizontal axis indicates the photoelectron energy emitted from the inner shell of the element when the energy at the absorption edge is set to 0.

In this X-ray absorption diagram, the absorption edge fine structure appearing in a narrow region of about 50 eV on the higher energy side than an arbitrary absorption edge is usually XANES (X-rays: X-rays).
Absorption Near Edge Structure). Further, the vibration structure of the X-ray intensity ratio, that is, the vibration structure of the absorption coefficient, which appears in a wide area of about 1000 eV to the energy side higher than XANES, is EXAFS (Extephs: ExteX
It is called “nded X-Ray Absorption Fine Structure”. The measurement performed to determine these XANES and EXAFS is called XAFS measurement.

These XANES and EXAFS include:
It contains information on the chemical bond between the X-ray absorbing atom and the surrounding atoms, the three-dimensional structure of the molecule, the interatomic distance, or the atomic coordination. Therefore, FIG.
If an X-ray absorption diagram as shown in FIG. 1 is obtained, the structure of the unknown sample can be analyzed based on the X-ray absorption diagram. The fluorescent X-ray measuring apparatus according to the present invention can be used for performing such XAFS measurement. In particular, in this case, since the XAFS measurement is performed using fluorescent X-rays generated in a sample, the fluorescent X-ray measuring apparatus is used. Sometimes called XAFS measurement.

[0039]

According to the fluorescent X-ray measuring apparatus of the present invention, the X-ray entrance of the capillary optical element is formed smaller than the X-ray exit, so that the capillary optical element can see a small area of the sample. Therefore, X-ray fluorescence information on a small region or a small sample of the sample can be measured.

Also, since the structure is such that the fluorescent X-rays generated from the sample are collimated and then separated by a spectral crystal, the measurement can be performed with higher resolution than in the case where the fluorescent X-rays are energy-resolved using an SSD. It can be carried out.

Furthermore, since the X-ray detecting means itself can be of low resolution, the X-ray inlet of the X-ray detecting means can be set to a large diameter. Therefore, if the X-ray inlet of the X-ray detecting means is set to a large diameter in accordance with the diameter of the X-ray emission port of the capillary optical element, the fluorescent X-rays can be reliably captured without leakage, that is, the detection efficiency can be increased. Can be.

[Brief description of the drawings]

FIG. 1 is a plan view showing an embodiment of an X-ray fluorescence measuring apparatus according to the present invention.

FIG. 2 is a graph showing an example of a result of a fluorescent X-ray measurement performed using the apparatus of FIG.

FIG. 3 is a graph showing an example of a result of a fluorescent XAFS measurement performed using the fluorescent X-ray measuring apparatus according to the present invention.

FIG. 4 is a plan view schematically showing an example of a conventional fluorescent X-ray measuring device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sample stand 2 X-ray tube 3 Dispersion crystal 4 X-ray detector 6 Capillary optical element 6a X-ray entrance 6b X-ray exit 7 Optical table 10 Capillary tube 12 Display 14 θ turntable 16 2θ turntable 17 Goniometer 21 Counter arm A Micro area F X-ray focal point (X-ray source) S Sample Z1 Crystal axis

Claims (3)

[Claims] 1. An X-ray fluorescence measuring apparatus for measuring X-ray fluorescence generated from a sample, comprising: an X-ray source for generating X-rays for irradiating the sample; and a position for capturing X-ray fluorescence generated from the sample. A capillary optical element, a spectral crystal disposed at a position where X-rays emitted from the capillary optical element are incident, and X-ray detection means for detecting X-rays spectrally separated by the spectral crystal, The above-mentioned capillary optical element is formed by bundling a plurality of capillary tubes, and an X-ray entrance thereof is smaller than an X-ray exit so as to see a minute area of the sample. . 2. The apparatus according to claim 1, wherein the size of the X-ray inlet of the X-ray detection means is smaller than the size of the capillary optical element.
An X-ray fluorescence spectrometer characterized by being equal to or larger than the radiation exit. 3. The apparatus according to claim 1, wherein the capillary optical element, the dispersive crystal, and the X-ray detection unit are relatively movable in parallel with respect to the sample in an integrated state. X-ray fluorescence measurement device.