JPH0933700A - X-ray monochromator and x-ray diffractor using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten an X-ray passing route from an X-ray source to a sample and make the whole dimension of an X-ray diffractor very small by generating X-ray beams being monochromatized and concurrently radiating with an X-ray monochromator. SOLUTION: An X-ray monochromator 1 is used to take out characteristic X rays Rt from continuous X rays Rr. The X-ray monochromator 1 has the first crystal 1a and the second crystal 1b. The first crystal 1a is placed in a position where the continuous X rays Rr enter and has a wide mosaic angle for diffracting radiating X rays. The second crystal 1b, which is placed virtually parallel to the first crystal 1a and where the X rays diffracted by it enter, has a wide mosaic angle for diffracting radiating X rays. Both crystals can be made of pyrolytic graphite with a mosaic angle width of about 0.3 deg. to 1.0 deg..

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray monochromator for extracting characteristic X-rays from continuous X-rays, that is, for converting continuous X-rays into a single color. Also, the present invention
The present invention relates to an X-ray diffractometer using the X-ray monochromator.

[0002]

2. Description of the Related Art In a general X-ray diffractometer, a sample is irradiated with X-rays generated from an X-ray source, and the X-rays diffracted by the sample are detected by an X-ray detector such as an X-ray counter. Then, various information regarding the sample is observed based on the detection result. Usually, continuous X-rays containing X-rays of various wavelengths are generated from the X-ray source. If this continuous X-ray is used as it is for X-ray diffraction measurement, the background of the X-ray image obtained by the X-ray detection means becomes too strong and the diffraction line image to be obtained may not be obtained clearly.

In order to remove this background,
There is known an X-ray optical system in which an X-ray monochromator is installed on the upstream side or the downstream side of a sample with respect to an X-ray traveling path from an X-ray source to an X-ray counter. X-ray monochromator
Usually, it is composed of a crystal, and only the X-ray of a specific wavelength is diffracted by the crystal lattice plane unique to the crystal. That is, if the X-ray monochromator is arranged on the upstream side of the sample, the X-rays emitted from the X-ray source and directed to the sample can be monochromatic, while if the X-ray monochromator is arranged on the downstream side of the sample, The X-rays diffracted by the sample can be monochromaticized and guided to the X-ray counter.

Conventionally, an apparatus as shown in FIG. 4 is known as an X-ray diffraction apparatus having a structure in which an X-ray monochromator is arranged on the upstream side of a sample. In this X-ray diffractometer, the continuous X-rays emitted from the X-ray source F are monochromaticized by the X-ray monochromator 51, that is, characteristic X-rays of a specific wavelength are extracted from the continuous X-rays. The characteristic X-rays extracted are
Once the light is focused on the focus point A, it diverges again, and then enters the sample 53 with its divergence being restricted by the divergence slit 52. When the incident X-ray satisfies a predetermined diffraction condition with respect to the crystal lattice plane of the sample 53, that is, the Bragg condition, the X-ray is diffracted in the sample 53.

The diffracted X-rays are focused on a focus point B, further pass through a light receiving slit 54 placed on the focus point B, and then are received by an X-ray counter 55 and attached to the X-ray counter 55. The intensity calculation circuit (not shown) determines the intensity of the diffracted X-ray. Center of sample 53
A circle C _G passing through the two X-ray focusing points A and B centering on is a goniometer circle. X for sample 53
When the X-ray source F, the sample 53, or the X-ray counter 55 is rotationally moved about the sample axis ω to change the line diffraction angle, the focus points A and B always exist on the gonio circle C _G.

[0006]

As described above, the conventional X
Since only one X-ray monochromator is used in the line diffractometer, the X-rays diffracted by the X-ray monochromator are focused on the focusing point A in the middle of the path. Therefore, the X-ray optical system after the divergence slit 52 could be installed only on the downstream side of the focusing point A. That is, in the conventional X-ray diffractometer using the X-ray monochromator, since the X-ray monochromator 51 is installed, the entire X-ray optical system from the X-ray source F to the X-ray counter 55 must be very large. Didn't get

The present invention has been made in order to solve the above-mentioned problems in the conventional X-ray monochromator and X-ray diffractometer, and the X-ray monochromator converts the monochromatic and divergent X-ray beam. The X-ray passing path from the X-ray source to the sample is shortened by forming
The purpose is to make the overall shape of the line diffraction device very small.

[0008]

In order to achieve the above object, an X-ray monochromator according to the present invention has a reference numeral 1 in FIG.
As shown in, the first crystal 1a having a wide mosaic angle width arranged at the position where the continuous X-ray Rr is incident and diffracting the X-ray in a divergent state, and substantially parallel to the first crystal 1a. And a second crystal 1b having a wide mosaic angle width, which is arranged at the position where X-rays diffracted by the first crystal 1a are incident and diffracts the X-ray in a divergent state. The term "substantially parallel" includes the case of being strictly parallel and the case of causing an error in the parallel state to the extent that it is practically acceptable for manufacturing reasons.

The wide mosaic angle width means that a crystal having a narrow mosaic angle width, for example, a complete single crystal such as germanium or silicon is excluded. As such a crystal having a wide mosaic angle width, for example, a pyrolitec graphite, that is, a crystal formed by graphite formed by thermal synthesis can be used.

The mosaic angle width represents the angular spread of the intensity of diffraction lines generated due to the so-called crystal mosaic structure. For example, X-ray measurement as schematically shown in FIG. It can be measured by the system. In this measurement system, the X-rays emitted from the X-ray source F are shaped into a parallel X-ray beam by the monochromator 57 and irradiated on the sample crystal 58, and the sample crystal 58 has a small angle ω around the sample axis ω. While rotating, the intensity of the diffraction line is measured by the X-ray counter 55. As shown in FIG. 6, the measurement result appears as a mountain-shaped diffraction line pattern on a graph having the ω rotation angle (ω) and the diffraction line intensity (I) as the orthogonal coordinate axes.

The width W of such a diffraction line pattern indicates the mosaic angle width. A perfect crystal, which is made up of one crystal, has almost no mosaic structure.
The mosaic angle width W becomes very narrow as W = W2.
On the other hand, in the case of a crystal formed by stacking a large number of minute crystal pieces into a mosaic shape like Pyrolithic graphite, the mosaic angle width W becomes wide as W = W1. Since the intensity of the X-ray diffracted by the crystal appears as the area of the diffraction pattern, that is, the integrated value, the crystal having a wide mosaic angle width W has a higher X-ray intensity than the crystal having a narrow mosaic angle width W.

When an X-ray monochromator is formed by using crystals, the divergence angle of the X-ray beam obtained from the X-ray monochromator is almost equal to the mosaic angle width of the crystals forming the monochromator. Pyrolytec graphite has a half-width of a mosaic angle of about 0.3 ° to 0.5 °, and about 1 ° including the hem (see FIG. 6).

In the X-ray monochromator 1 shown in FIG.
The first crystal 1a and the second crystal 1b were configured by using flat crystal. However, these crystals can also be configured using crystals having a curved X-ray reflecting surface as shown in FIG. More specifically, X of the first crystal 11a
The line incident surface is formed as a cylindrical concave surface, and the second crystal 11
The X-ray incidence surface of b is formed as a cylindrical convex surface. Then, the X-ray monochromator 11 is configured by arranging these crystals so as to face each other. If the first crystal 11a and the second crystal 11b are curved in this manner, the first crystal 1
Divergence angle θ of X-rays that can cause diffraction at 1a
2 can be made larger than the divergence angle θ1 in the case of using the flat crystals 1a and 1b (FIG. 1). That is, θ1 <θ2 can be satisfied. This means that the characteristic X-ray intensity that can be extracted by the X-ray monochromator can be increased by bending the crystal.

[0014]

FIG. 2 shows an embodiment of an X-ray monochromator according to the present invention and an embodiment of an X-ray diffractometer using the X-ray monochromator. This X-ray diffractometer includes an X-ray tube 10 including an X-ray source F, and an X-ray monochromator 1 that monochromates continuous X-rays emitted from the X-ray source F.
And a goniometer unit 12 for measuring the angle of the sample 3.

The X-ray tube 10 has a filament 13 that emits thermoelectrons by generating heat when energized, and a target 14 arranged opposite to the filament 13. When the thermoelectrons emitted from the filament 13 collide with the target 14 at high speed, X
Rays, especially continuous x-rays, are generated. That is, the region where the thermoelectrons collide with the target 14, that is, the X-ray focal point constitutes the X-ray source F. The X-ray focus in the embodiment is a line focus X-ray focus that is long in the direction perpendicular to the plane of the drawing.

As shown in FIG. 1, the X-ray monochromator 1 is a flat plate-shaped first crystal 1a which is arranged in parallel with each other.
And the second crystal 1b. These crystals are formed by crystals having a wide mosaic angle width, for example, Pyrrolite graphite. For continuous X-rays diverging from the X-ray source F in all directions, those Rr within the range of divergence angle θ1 are incident on the first crystal 1a,
X-rays having a wavelength component satisfying the diffraction condition are diffracted and are incident on the second crystal 1b. In the second crystal 1b, only the X-rays satisfying the diffraction condition are diffracted again, and the X-rays having the specific wavelength, that is, the characteristic X-rays Rt are extracted to the downstream side (the right side in the figure).

The optical axis Lr of the continuous X-ray Rr incident on the X-ray monochromator 1 and the optical axis Lt of the extracted characteristic X-ray Rt.
Are parallel to each other. That is, the characteristic X-ray Rt that is the output X-ray is extracted as an X-ray beam that is shifted in parallel with the continuous X-ray Rr that is the incident X-ray by the dimension Z in the vertical direction of the figure. Further, when viewed from the optical system using the extracted characteristic X-ray Rt, in other words, from the optical system arranged on the downstream side of the second crystal 1b, the optical pseudo X-ray source F'is the actual X-ray. It is located at a position shifted from the source F by Z in the vertical direction and Y in the horizontal direction. Further, if the X-ray monochromator is constituted only by the first crystal 1a without using the second crystal 1b as in the conventional case, the X-ray diffracted by the first crystal 1a is focused on the pseudo focusing point A '. To do.

Returning to FIG. 2, the goniometer unit 12 in the embodiment is an X-ray focusing optical system for measuring a powder sample,
It is configured as an optical system that realizes the so-called Black-Brentano method. Specifically, the goniometer unit 12 includes the divergence slit 2 fixedly arranged on the traveling path of the characteristic X-rays extracted by the X-ray monochromator 1.
And a θ rotation table 6 that supports the powder sample 3 and that can rotate and move around the sample axis ω, a 2θ rotation table 7 that can rotate independently of the θ rotation table 6 and independently, and a 2θ rotation table 7
From the detector arm 8, a light receiving slit 4 arranged on the detector arm 8, and a light receiving slit 4
It further has an X-ray counter 5 as an X-ray detecting means arranged on the detector arm 8 on the further downstream side.
The θ rotation table 6 has a θ rotation motor 1 as a rotation drive source.
6, and a 2θ rotation base 7 is connected to a 2θ rotation motor 17 as a rotation drive source. These motors operate according to commands from the gonio drive circuit 23.

The X-ray counter 5 is composed of, for example, a scintillation counter, and has individual diffraction angles (2θ).
When a diffracted X-ray is generated at, a signal having a magnitude corresponding to the intensity of the diffracted X-ray is output, and the output signal is X
It is sent to the line intensity calculation circuit 21. X-ray intensity calculation circuit 21
Calculates the intensity of the diffracted X-rays captured by the X-ray counter 5 based on the output signal of the X-ray counter 5, and sends the calculation result to the main controller 22.

The main control unit 22 has, for example, a CPU (central processing unit) of a computer and a memory. The main controller 22 sends a command to the gonio drive circuit 23 according to a program stored in a predetermined storage location in the memory. The gonio drive circuit 23 drives the θ rotation motor 16 and the 2θ rotation motor 17 based on a command from the main control unit 22. Specifically, the θ rotation table 6 is continuously or intermittently rotated around the sample axis ω at a predetermined angular velocity, that is, the θ rotation is performed. At the same time, the 2θ rotation table 7 is synchronously moved in the same direction, that is, 2θ rotation about the sample axis ω at an angular velocity twice that of θ rotation. The CRT display 24 and the printer 25 connected to the output port of the main control unit 22 are controlled by the X-ray diffraction angle (2θ) measured by the gonio drive circuit 23 and the X-ray intensity calculation circuit 21 at each diffraction angle. A graph showing the relationship with the calculated diffracted X-ray intensity is displayed as an image or printed on paper.

The X according to this embodiment constructed as described above
In the line diffractometer, first, the optical axes are adjusted so that the optical axes of the various X-ray elements from the X-ray source F to the X-ray counter 5 are the same. When the optical axis adjustment is completed, a sample, for example, the powder sample 3 is mounted on the θ rotary table 6, and then X-rays are emitted from the X-ray source F. When the measurement start timing comes, the θ rotation table 6 and thus the sample 3 start θ rotation, and at the same time, the 2θ rotation table 7 and therefore the X-ray counter 5 and the light-receiving slit 4 start 2θ rotation in synchronization therewith. X-ray counter 5
Receives the diffracted X-rays when the diffracted X-rays are generated from the sample 3 at each of the diffraction angles 2θ, and sends a signal corresponding to the intensity to the X-ray intensity calculation circuit 21. The X-ray intensity calculation circuit 21 calculates the X-ray intensity based on the output signal of the X-ray counter 5, and the calculation result is displayed as a diffraction line pattern on the CRT display 24 together with the corresponding diffraction angle (2θ), or The printer 25 makes a hard copy as a diffraction line pattern. In this diffraction line pattern, various observations such as determining the constituent substances of the sample 3 are performed by observing what peak waveform appears at which diffraction angle (2θ) position.

In this embodiment, the first crystal 1a and the second crystal 1a are made of pyrolithic graphite having a wide mosaic angle width.
Since the crystal 1b is formed and the two crystals are arranged parallel to each other, the target characteristic X-ray Rt is parallel to the incident continuous X-ray Rr in the same direction from the second crystal 1b. To the divergent state. The X-ray divergence angle in this case is an angle corresponding to the mosaic angle width of each crystal 1a and 1b, and such a divergent X-ray is a monochromatic parallel beam obtained by, for example, a channel-cut monochromator made of a single crystal. Its X compared to X-ray beam
Line strength is very high. Therefore, a clear X-ray diffraction image which is not influenced by the background can be obtained for the powder sample 3.

Since the second crystal 1b outputs not a focused beam but a divergent beam, the goniometer unit 12 has a pseudo X-ray source F'located near the actual X-ray source F as the center. Configured as a centralized optical system. If the X-ray monochromator is composed of only one crystal 1a as in the conventional case, the focusing point A is located on the downstream side of the crystal 1a.
The goniometer unit 12 can be installed only on the further downstream side of the focusing point A because only a focused beam that focuses on the beam is obtained. That is, comparing the optical system of this embodiment with the conventional optical system, X is the distance L from the focus point A to the pseudo X-ray source F ′ when the conventional single crystal X-ray monochromator is used. The size of the entire line diffraction device can be reduced.

Further, in the case of adjusting the optical axis of the X-ray diffractometer, in the conventional apparatus using a single crystal X-ray monochromator, the X-ray monochromator 5 in FIG. 4 is used.
It was necessary to rotate the X-ray source F in the direction of the arrow E-E 'at a relatively large angle about the central axis ψ of 1 to adjust the angle. On the other hand, in the present embodiment shown in FIG.
Since the continuous X-rays Rr incident on the line monochromator 1 and the characteristic X-rays Rt emitted therefrom are parallel to each other, when the optical axis is adjusted, the X-ray source F is linearly moved by a slight distance in the DD ′ direction. Good. Therefore, the work for adjusting the optical axis is very simple.

FIG. 3 shows another embodiment of the X-ray monochromator according to the present invention. In the X-ray monochromator 11 shown here, the first crystal 11a and the second crystal 11b are not flat plates but are formed in a curved shape. More specifically, the X-ray incident surface of the first crystal 11a is formed as a cylindrical concave surface, and the X-ray incident surface of the second crystal 11b is formed as a cylindrical convex surface.

If such a curved shape is adopted, incident X-rays diffracted by the curved surface of the first crystal 11a, that is, continuous X-rays.
The divergence angle θ2 of the line Rr can be set larger than the divergence angle θ1 (FIG. 1) in the case of the flat plate crystal. If the divergence angle can be made large in this way, the X-ray intensity of the characteristic X-rays extracted will be correspondingly stronger. If X-ray diffraction measurement is performed using this high-intensity X-ray, a diffraction image can be obtained more clearly. In particular, if the X-ray incidence surfaces of the first crystal 11a and the second crystal 11b are curved, the divergence angle of the X-ray beam can be made larger than the mosaic angle width of each crystal.

The present invention has been described above with reference to the preferred embodiments, but the present invention is not limited to these embodiments and can be variously modified within the technical scope described in the claims. For example, the X-ray source F is not limited to line focus, but may be point focus. Further, the X-ray optical system installed at the subsequent stage position of the X-ray monochromator is not limited to the above-mentioned focusing optical system of the θ-2θ rotational movement system which measures the powder sample, and the X-ray optical system of any other structure. Can be a system. However, if the X-ray monochromator of the present invention is used, a strong monochromatic divergent beam, which cannot be obtained by the conventional single crystal monochromator or single crystal channel cut monochromator, can be obtained. It is desirable to install an X-ray optical system that can be utilized.

[0028]

According to the X-ray monochromator of the first aspect and the X-ray diffractometer of the fifth aspect, not only the characteristic X-rays can be formed by monochromatic continuous X-rays, but also the characteristic X-rays are focused beams. Instead, it can be extracted as a divergent beam with high intensity. When only the focused beam can be taken out from the X-ray monochromator, the X-ray optical system installed in the subsequent stage of the X-ray monochromator can be installed only at the position further behind the focusing point of the focused beam, and therefore the X-ray diffractometer. The overall shape of the becomes very large. On the other hand, according to the X-ray monochromator of the present invention capable of extracting the divergent beam, the X-ray optical system can be configured with the pseudo X-ray source close to the actual X-ray source as the center. That is, the X-ray passing path from the X-ray source to the sample can be shortened, and thus the overall shape of the X-ray diffraction device can be made extremely small.

According to the X-ray monochromator of the fourth aspect and the X-ray diffraction apparatus of the eighth aspect, the divergence angle of the X-ray beam can be made wider than the mosaic angle width of the crystal, so that the characteristic X with high intensity can be obtained. You can take out the wire.

[0030]

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of an X-ray monochromator according to the present invention.

FIG. 2 is a plan view showing an embodiment of an X-ray diffractometer according to the present invention.

FIG. 3 is a sectional view showing another embodiment of the X-ray monochromator according to the present invention.

FIG. 4 is a plan view showing an X-ray diffractometer using a conventional X-ray monochromator.

FIG. 5 is a diagram schematically showing an example of an X-ray measurement system for measuring a mosaic angle width of a crystal.

FIG. 6 is a graph showing a mosaic angle width regarding a crystal.

[Explanation of symbols]

 1 X-ray monochromator 1a 1st crystal 1b 2nd crystal 2 Light emission slit 3 Sample 4 Light receiving slit 5 X-ray counter 6 θ rotary table 7 2 θ rotary table 8 Detector arm 10 X-ray tube 11 X-ray monochromator 11a First crystal 11b Second crystal 12 Goniometer unit 13 Filament 14 Target 16,17 Motor F X-ray source A, B X-ray convergence point Rr Continuous X-ray Rt Characteristic X-ray

Claims (8)

[Claims] 1. An X-ray monochromator for extracting characteristic X-rays from continuous X-rays, the first crystal having a wide mosaic angle width arranged at a position where the continuous X-rays are incident and diffracting the X-rays in a divergent state. And a second crystal having a wide mosaic angle width, which is arranged substantially parallel to the first crystal and which receives the X-ray diffracted by the first crystal and diffracts the X-ray in a divergent state. X-ray monochromator characterized by. 2. The X-ray monochromator according to claim 1, wherein the mosaic angle width is in the range of 0.3 ° to 1 °. 3. The X-ray monochromator according to claim 1, wherein the first crystal and the second crystal are formed of pyrolithic graphite. 4. The X-ray monochromator according to any one of claims 1 to 3, wherein the X-ray incidence surface of the first crystal is formed as a cylindrical concave surface, and the X-ray of the second crystal is formed. An X-ray monochromator characterized in that the ray incident surface is formed as a cylindrical convex surface. 5. An X-ray source for generating continuous X-rays, and an X-ray monochromator for extracting characteristic X-rays from the continuous X-rays.
An X-ray diffractometer having an X-ray optical system configured to irradiate a sample with X-rays extracted by an X-ray monochromator, diffract the X-rays, and detect the diffracted X-rays by an X-ray detector. The meter is arranged at a position where continuous X-rays are incident, and has a wide mosaic angle first crystal that diffracts X-rays in a divergent state, and a meter that is arranged substantially parallel to the first crystal. An X-ray diffractometer, comprising: a second crystal having a wide mosaic angle width, which is incident on the X-ray diffracted by one crystal and diffracts the X-ray in a divergent state. 6. The X-ray diffraction apparatus according to claim 5, wherein
The mosaic angle width of the first crystal and the second crystal is 0.3 ° to 1
An X-ray diffractometer characterized by being in the range of °. 7. The X-ray diffractometer according to claim 5 or 6, wherein the first crystal and the second crystal are formed of pyrolithic graphite. 8. The X-ray diffractometer according to any one of claims 5 to 7, wherein the X-ray incidence surface of the first crystal is formed as a cylindrical concave surface, and the X-ray of the second crystal is formed. The X-ray diffractometer, wherein the ray incident surface is formed as a cylindrical convex surface.