JP3982732B2 - X-ray fluorescence measurement equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fluorescent X-ray measuring apparatus that detects fluorescent X-rays generated from a sample and measures the types of elements present in the sample based on the fluorescent X-rays.
[0002]
[Prior art]
The phenomenon that occurs when the sample is irradiated with X-rays includes 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 by the crystal lattice plane of the sample that satisfy a specific condition, the so-called Bragg diffraction condition, and the others that disappear from each other and are not observed. X-ray. This diffracted X-ray is generated in relation to the arrangement structure of elements such as crystals.
[0003]
On the other hand, each element constituting the sample has a unique shell electron order. When such materials are irradiated with radiation such as X-rays, γ-rays, electron beams, etc., X-rays having characteristics peculiar to elements, usually characteristic X-rays, are generated from the materials. This X-ray is usually called fluorescent X-ray. This fluorescent X-ray is generated regardless of the crystal structure of the sample and related to the type and amount of elements present in the sample.
[0004]
If the fluorescent X-ray generated from the sample is detected and the energy distribution or wavelength distribution of the fluorescent X-ray is obtained, the type and content of the element contained in the sample can be known. An apparatus used for performing such a measurement is a fluorescent X-ray measurement apparatus. The 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 that combines a spectroscopic crystal and a slit based on the principle of X-ray diffraction. On the other hand, in the energy dispersion type, for example, an X-ray is directly detected using an SSD (Solid-state Detector), and the output of the SSD is introduced into, for example, an MCA (Multi-Channel Pulse Height Analyzer). To sort by energy.
[0006]
The wavelength dispersion type fluorescent X-ray measurement apparatus has an advantage that the apparatus can be formed at low cost because an expensive SSD is not used. Further, the SSD has a problem that the diameter of the SSD cannot be increased so as to maintain the energy resolution, and thus the X-ray dose that can be taken in is limited. However, the wavelength dispersion type fluorescent X-ray measurement apparatus that does not use the SSD. There is no such problem, and there is an advantage that fluorescent X-rays can be detected from a wide range without omission by setting the aperture of the X-ray detection means large.
[0007]
Considering a wavelength dispersion type fluorescent X-ray measurement apparatus, the conventional configuration is as shown in FIG. Briefly explaining, X-rays generated from the X-ray source F are irradiated onto the sample S, and the fluorescent X-rays generated at the sample S at that time are shaped into a parallel X-ray beam by the solar slit 56a to be spectrally separated. Incident on the crystal 53. The fluorescent X-rays are dispersed in accordance with the incident angle θ with respect to the spectral crystal 53, the fluorescent X-rays having a specific wavelength are extracted on the output side, and the extracted fluorescent X-rays are taken into the X-ray counter 54 through the solar slit 56b. . The X-ray intensity calculation circuit 59 connected to the output terminal of the X-ray counter 54 determines the intensity of the fluorescent X-ray.
[0008]
[Problems to be solved by the invention]
However, the conventional fluorescent X-ray measurement apparatus has a structure in which X-rays are irradiated onto a wide surface of the sample S and fluorescent X-rays generated from the wide surface are taken into the X-ray counter 54. There has been a problem that it is impossible to obtain fluorescent X-ray information about a small region of S.
[0009]
The present invention has been made in view of the above-described problems in the conventional fluorescent X-ray measurement apparatus, and can reliably and accurately obtain fluorescent X-ray information from a minute region of a sample. An object is to provide a fluorescent X-ray measurement apparatus.
[0010]
[Means for Solving the Problems]
(1) In order to achieve the above object, an X-ray fluorescence measurement apparatus according to the present invention is an X-ray fluorescence measurement apparatus that measures fluorescence X-rays generated from a sample. A ray source, a capillary optical element in which an X-ray incident port is disposed at a position where fluorescent X-rays generated and radiated from the sample are taken in, and X-rays emitted from the X-ray exit port of the capillary optical element are incident A plate-shaped spectroscopic crystal disposed at a position; an X-ray detection means for detecting X-rays dispersed by the spectroscopic crystal through an X-ray inlet; and a wave height analysis provided in the X-ray detection means With a bowl. The capillary optical element is formed by bundling a plurality of capillary tubes, and the X-ray entrance port of the capillary optical element is larger than the X-ray exit port of the capillary optical element so as to allow for a minute region of the sample. The X-ray exit port of the capillary optical element is smaller than the X-ray entrance region of the flat plate-shaped spectral crystal, and the capillary optical element exits the X-ray exit from the X-ray entrance port. extend curved to mouth, emits parallel X-rays from the X-ray emitting window, the size of the X-ray intake port before Symbol X-ray detecting means as compared to the X-ray emission region of the spectral crystal of said flat plate It is getting bigger.
[0011]
According to this fluorescent X-ray measuring apparatus, when X-rays radiated from an X-ray source are incident on the sample, fluorescent X-rays are generated from the sample, and the fluorescent X-rays are taken in by the capillary optical element to form a spectral crystal. The wavelength components separated by the spectral crystal are counted by the X-ray detection means. The X-ray detection means used here does not need to use an X-ray detection means with its own energy resolution such as SSD, but a PC (Proportional Counter) or SC (Scintillation) which is a counter with low energy resolution. Counter: scintillation counter) can be used.
[0012]
According to the fluorescent X-ray measurement apparatus of the present invention, since the X-ray entrance port of the capillary optical element is formed smaller than the X-ray exit port, the capillary optical element can be arranged so as to allow a minute region of the sample. It is possible to measure fluorescent X-ray information relating to a minute region of a sample or a minute sample. Further, since the fluorescent X-rays generated from the sample are collimated and then separated by a spectroscopic crystal, the measurement can be performed with higher resolution than when the fluorescent X-rays are subjected to energy decomposition using SSD. it can.
[0013]
Further, since the X-ray detection means itself having a low resolution can be used, the X-ray intake port of the X-ray detection means can be set to a large diameter. Then, by setting the X-ray intake port of the X-ray detection means to a large diameter in accordance with the diameter of the X-ray output port of the capillary optical element, it is possible to reliably capture fluorescent X-rays without omission, that is, increase detection efficiency. Can do.
[0014]
(2) In the fluorescent X-ray measurement apparatus having the above configuration, the size of the X-ray intake port of the X-ray detection means can be set equal to or larger than the X-ray emission port of the capillary optical element. By doing so, fluorescent X-rays with higher intensity can be taken into the X-ray detection means, and as a result, highly reliable measurement can be performed.
[0015]
(3) In the fluorescent X-ray measurement apparatus having the above-described configuration, it is desirable that the capillary optical element, the spectroscopic crystal, and the X-ray detection means are configured so as to be relatively movable relative to the sample in an integrated state. According to this configuration, the microscopic region on the sample that is expected by the capillary optical element can be changed as desired, so that fluorescent X-ray information at various positions in the sample, that is, so-called mapping measurement is performed. Is possible.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an embodiment of a fluorescent X-ray measurement apparatus according to the present invention. This fluorescent X-ray measurement apparatus includes an X-ray including an X-ray focal point F as an X-ray source that generates a X-ray source for irradiating the sample S with a sample stage 1 for supporting the sample S as a measurement object. It has a tube 2 and an optical bench 7. The X-ray focal point F is set to a size of 2 mm × 2 mm, for example. The distance D0 between the X-ray focal point F and the sample S is set to about several mm.
[0017]
The optical bench 7 is provided with an X-ray optical system moving device 8. The optical bench 7 is driven by the X-ray optical system moving device 8 and is moved in three directions perpendicular to the X, Y and Z directions indicated by arrows. The optical stage 7 can be moved in any direction three-dimensionally or spatially with respect to the sample S, and can be stopped at that position.
[0018]
Such an X-ray optical system moving device 8 combines, for example, slide tables that move in three orthogonal directions of X, Y, and Z, and drives those slide tables by a pulse motor as a drive source. Can be configured by structure.
[0019]
On the optical table 7 as described above, a goniometer 17 configured to include the θ-rotation table 14 and the 2θ-rotation table 16 is installed. The θ turntable 14 is driven by a θ rotation driving device 18 and rotates around the crystal axis Z1. The 2θ rotating table 16 is driven by a 2θ rotation driving device 19 and rotates about the crystal axis Z1. During normal measurement, the 2θ rotating table 16 rotates in the same direction at an angular velocity twice that of the θ rotating table 14.
[0020]
The θ rotation driving device 18 and the 2θ rotation driving device 19 operate according to a command from the computer 11. Although the specific structure of these drive 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.
[0021]
A spectroscopic crystal 3 for spectroscopically analyzing fluorescent X-rays generated from the sample S is mounted on the θ rotation table 14. An X-ray detector 4 that detects X-rays separated by the spectroscopic crystal 3 is mounted on the counter arm 21 extending from the 2θ rotating table 16. 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 positioned between the sample S and the spectral crystal 3.
[0022]
The spectral crystal 3 is formed into a flat plate shape with an appropriate substance such as graphite, PET (polyethylene terephthalate), LiF (lithium fluoride), etc., depending on the wavelength of the X-ray to be extracted. Further, the X-ray detector 4 itself does not require high energy resolution in the case of the present embodiment, and therefore, this X-ray detector 4 uses, for example, a PC (Proportional Counter), an SC (Scintillation Counter), or the like. Can be configured.
[0023]
The capillary optical element 6 is formed by bundling a plurality of capillary tubes 10, and emits X-rays taken from the X-ray incident port 6a from the X-ray emission port 6b. Each capillary tube 10 transmits X-rays by total reflection. Even when X-rays enter the X-ray entrance 6a from all directions, a parallel X-ray beam is taken out from the X-ray exit 6b. Can do.
[0024]
Further, the diameter of the X-ray entrance 6a of the capillary optical element 6 used in the present embodiment is formed smaller than the diameter of the X-ray exit 6b. For example, the X-ray entrance 6a is formed with a diameter of about 10 mm × 10 mm to 20 mm × 20 mm, and the X-ray exit 6b is formed with a diameter of about 13 mm × 13 mm to 25 mm × 25 mm.
[0025]
Since the X-ray entrance 6a of the capillary optical element 6 is formed to be smaller than the X-ray exit 6b in this way, the capillary optical element 6 of the apparatus according to the present embodiment expects a minute region A in the sample S. Can be placed. That is, the capillary optical element 6 takes in the fluorescent X-rays generated only from the minute region A of the sample S from the X-ray incident port 6a, shapes it into a parallel X-ray beam having a large cross-sectional area, and forms the X-ray exit port. 6b can be supplied to the spectroscopic crystal 3.
[0026]
The individual capillary tubes 10 may have a uniform diameter from the X-ray entrance 6a to the X-ray exit 6b, or the diameter gradually increases from the X-ray entrance 6a to the X-ray exit 6b. A tapered capillary tube that becomes larger 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 bundled at a high density at the X-ray entrance 6a. In 6b, the arrangement density of the individual capillary tubes 10 is lowered by the increase in the diameter of the capillary optical element 6.
[0027]
Next, the aperture of the X-ray detector 4 is set to be equal to or larger than the aperture of the X-ray exit 6b of the capillary optical element 6. In this way, the X-rays emitted from the capillary optical element 6 and dispersed by the spectroscopic crystal 3 can be efficiently taken into the X-ray detector 4 without any leakage.
[0028]
In addition, an X-ray intensity calculation circuit 9 including a pulse height analyzer (PHA) is connected to the output terminal of the X-ray detector 4. 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 obtains the obtained fluorescent X-ray. Is displayed as an image on the display 12 or printed on paper by the printer 13.
[0029]
Since the fluorescent X-ray measurement apparatus of the present embodiment is configured as described above, the X-rays emitted from the X-ray focal point F are applied to a wide surface of the sample S. At this time, fluorescent X-rays are emitted from the surface. appear. Fluorescent X-rays generated from a minute region A expected by the capillary optical element 6 in the sample surface irradiated with X-rays are taken in by the capillary optical element 6 and formed into a parallel X-ray beam, and then to the spectral crystal 3. Supplied. Fluorescent X-rays generated from areas 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 area A expected by the capillary optical element 6 is the measurement area.
[0030]
While the fluorescent X-rays from the sample S are being supplied to the spectral crystal 3 as described above, the rotation angle of the spectral crystal 3 with respect to the fluorescent X-rays, that is, the θ angle, is gradually changed to change the fluorescent X-rays to the spectral crystal 3. Change the incident angle of the line. At the same time, the rotation angle of the X-ray detector 4, that is, the 2θ angle, is changed by twice the θ angle. Then, X-rays having a wavelength corresponding to the θ angle are separated from the fluorescent X-rays at each θ angle of the spectral crystal 3, and the spectral characteristic X-rays are taken in by the X-ray detector 4. The X-ray intensity is obtained by the X-ray intensity calculation circuit 9. This process is performed for each different 2θ angle of the X-ray detector 4, and as a result, the X-rays of various wavelengths contained in the fluorescent X-rays generated from the sample S, that is, the intensities of various characteristic X-rays. Desired.
[0031]
FIG. 2 shows an example of a fluorescent X-ray spectrum for the sample S obtained as described above. From this figure, it is understood that characteristic X-rays a, b, c,... With different wavelengths are detected at different 2θ angles, and that the intensity of these characteristic X-rays is indicated by the peak height. Is done. Since these characteristic X-rays a, b, c,... Correspond to the elements contained in the sample S and their contents, the sample S is observed by observing the peak appearing in the fluorescent X-ray spectrum. It is possible to know the types of elements contained in and their contents.
[0032]
As described above, according to the present embodiment, the fluorescent X-ray measurement can be performed only for the minute region A expected by the capillary optical element 6 in the sample S. Since the fluorescent X-rays generated from the sample S are collimated and then separated by the spectroscopic crystal 3, the measurement is performed with a higher resolution than when the fluorescent X-rays are subjected to energy decomposition using SSD. be able to.
[0033]
Furthermore, since the resolution of the X-ray detector 4 used in this embodiment is lower than that of SSD or the like, the X-ray intake port 4a of the X-ray detector 4 can be set to a large diameter. As a result, the fluorescent X-rays separated by the spectroscopic crystal 3 can be reliably taken in, that is, the detection efficiency can be increased, and as a result, a highly reliable measurement result can be obtained.
[0034]
In the present embodiment, the optical bench 7 on which the capillary optical element 6 and the goniometer 17 are mounted can be translated in three dimensions relative to the sample S by the X-ray optical system moving device 8. The expected area A of the sample S by the optical element 6 can be moved to an arbitrary location on the surface of the sample S, and the fluorescent X-ray can be measured on the area after the movement. If such measurement is performed on a plurality of different microregions of the sample S, a fluorescent X-ray spectrum relating to the plurality of different microregions of the sample S can be obtained, that is, mapping measurement can be performed.
[0035]
The present invention has been described with reference to the preferred embodiments. However, the present invention is not limited to the embodiments, and various modifications can be made 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 fluorescent X-ray measurement. However, the fluorescent X-ray measurement apparatus according to the present invention is different from such a general measurement method in that X The present invention can also be applied to XAFS measurement, which is an elemental analysis technique that uses line absorption. Since this XAFS measurement itself is a well-known measurement method, a detailed description thereof will be omitted, but this will be briefly described as follows.
[0036]
That is, generally, the energy of X-rays irradiated to a sample is gradually changed, and the intensity (Io) of X-rays incident on the sample and the intensity (If) of fluorescent X-rays generated on the sample for each energy. When the ratio (If / Io) is obtained, the absorption coefficient is calculated based on the ratio, and plotted on a graph, an X-ray absorption diagram as shown in FIG. 3 is obtained. In this figure, the horizontal axis indicates the photoelectron energy emitted from the inner core of the element when the energy at the absorption edge is zero.
[0037]
In this X-ray absorption diagram, the absorption edge fine structure appearing in a narrow region of about 50 eV on the high energy side from an arbitrary absorption edge is usually called XANES (X-Ray Absorption Near Edge Structure). Further, the vibration structure of the X-ray intensity ratio that appears in a wide region of about 1000 eV on the energy side higher than XANES, that is, the vibration structure of the absorption coefficient is called EXAFS (Extended X-Ray Absorption Fine Structure). The measurement performed to obtain these XANES and EXAFS is called XAFS measurement.
[0038]
These XANES and EXAFS contain 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, if an X-ray absorption diagram as shown in FIG. 3 is obtained for an unknown sample, the structure analysis of the unknown sample can be performed based on the X-ray absorption diagram. The X-ray fluorescence measurement apparatus according to the present invention can be used for performing such XAFS measurement. In particular, in this case, XAFS measurement is performed using fluorescent X-rays generated in a sample. Sometimes called XAFS measurement.
[0039]
【The invention's effect】
According to the fluorescent X-ray measurement apparatus of the present invention, the capillary optical element can be arranged so as to allow for a minute region of the sample because the X-ray entrance opening of the capillary optical element is made smaller than the X-ray exit opening. , X-ray fluorescence information relating to a micro region or a micro sample can be measured.
[0040]
Further, since the fluorescent X-rays generated from the sample are collimated and then separated by a spectroscopic crystal, the measurement can be performed with higher resolution than when the fluorescent X-rays are subjected to energy decomposition using SSD. it can.
[0041]
Further, since the X-ray detection means itself having a low resolution can be used, the X-ray intake port of the X-ray detection means can be set to a large diameter. For this reason, if the X-ray intake port of the X-ray detection means is set to a large diameter in accordance with the diameter of the X-ray emission port of the capillary optical element, the X-ray fluorescence can be reliably captured without leaking, that is, the detection efficiency can be increased. Can do.
[Brief description of the drawings]
FIG. 1 is a plan view showing an embodiment of an X-ray fluorescence measurement apparatus according to the present invention.
FIG. 2 is a graph showing an example of the result of fluorescent X-ray measurement performed using the apparatus of FIG.
FIG. 3 is a graph showing an example of the result of fluorescent XAFS measurement performed using the fluorescent X-ray measurement apparatus according to the present invention.
FIG. 4 is a plan view schematically showing an example of a conventional fluorescent X-ray measurement apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Sample stand 2 X-ray tube 3 Spectroscopic crystal 4 X-ray detector 6 Capillary optical element 6a X-ray entrance port 6b X-ray exit port 7 Optical stand 10 Capillary tube 12 Display 14 Theta turntable 16 The 2theta turntable 17 Goniometer 21 Counter arm A Micro area F X-ray focus (X-ray source)
S Sample Z1 Crystal axis

Claims (4)

In a fluorescent X-ray measuring apparatus for measuring fluorescent X-rays generated from a sample,
An X-ray source for generating X-rays for irradiating the sample;
A capillary optical element in which an X-ray entrance is disposed at a position where fluorescent X-rays generated from the sample and diverges are taken in;
A plate-shaped spectral crystal disposed at a position where X-rays emitted from the X-ray emission port of the capillary optical element are incident;
X-ray detection means for taking in and detecting X-rays separated by the spectral crystal from an X-ray inlet;
A wave height analyzer provided in the X-ray detection means,
The capillary optical element is formed by bundling a plurality of capillary tubes,
The X-ray entrance port of the capillary optical element is smaller than the X-ray exit port of the capillary optical element so as to allow for a minute region of the sample,
The X-ray exit of the capillary optical element is smaller than the X-ray incident area of the flat plate-shaped spectral crystal,
The capillary optical element is curvedly extended from the X-ray entrance to the X-ray exit, and emits parallel X-rays from the X-ray exit ,
X-ray fluorescence measurement device the size of the X-ray intake port is characterized in that is larger than the X-ray emission region of the analyzing crystal of the flat plate shape before Symbol X-ray detector.   2. The fluorescent X-ray measurement apparatus according to claim 1, wherein a size of an X-ray intake port of the X-ray detection means is equal to or larger than an X-ray emission port of the capillary optical element.   3. The fluorescent X-ray measurement apparatus according to claim 1, wherein the capillary optical element, the spectroscopic crystal, and the X-ray detection means are integrally movable relative to the sample in an integrated state. . And have you to any one of claims 1 to claim 3, each of the plurality of capillary tubes fluorescent X-ray measuring apparatus characterized by transmitting the X-rays by total internal reflection.

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