JP3741398B2 - X-ray measuring method and X-ray measuring apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an X-ray measurement method and an X-ray measurement apparatus for analyzing a sample using X-rays.
[0002]
[Prior art]
It has been widely known that there are a concentrated method and a parallel beam method as types of X-ray measurement methods. The concentration method is a general X-ray measurement method, in which a divergent X-ray beam is incident on a sample, and the X-ray diffracted by the sample, that is, the diffracted X-ray is concentrated at one point on the focal circle. Diffracted X-rays are detected by an X-ray detector. This concentrated method generally has the characteristics that the resolution is better than the parallel beam method and the intensity of the diffracted X-ray is strong.
[0003]
On the other hand, in the parallel beam method, a parallel X-ray beam is incident on a sample, and diffracted X-rays diffracted by the sample are detected by an X-ray detector without being concentrated at a specific point. This parallel beam method has a characteristic that, for example, diffraction X-rays from a thin film formed on a substrate such as Si can be effectively extracted.
[0004]
By the way, a crystal monochromator is often used for an X-ray optical system that performs X-ray measurement. The crystal monochromator is disposed at the front position of the sample as viewed from the X-ray traveling direction or at the rear position of the sample. In any case, the crystal monochromator is diffracted by the sample and is detected by the X-ray detector. The main purpose is to monochromatize the diffracted X-rays taken in to remove the background in the measurement results.
[0005]
When this crystal monochromator is used in the concentrated optical system, a curved crystal monochromator whose X-ray diffraction surface is in a curved state is widely used. When used in a parallel beam method optical system, a flat crystal monochromator having an X-ray diffraction surface in a planar state is widely used.
[0006]
[Problems to be solved by the invention]
In the field of conventional X-ray measurement, a concentrated optical system and a parallel beam optical system are each provided as dedicated machines, and a measurer selectively uses them as necessary. However, in such a measurement method, two types of apparatuses, a concentrated method optical system and a parallel beam method optical system, must be prepared in advance, and there is a problem that the equipment cost increases.
[0007]
The inventor considered whether both the concentrated method and the parallel beam method could be measured by the arrangement of one type of crystal monochromator, and conducted various experiments to realize it. What has been found through these experiments is that it is difficult to perform both measurements with a single crystal monochromator arrangement.
[0008]
Therefore, the present inventor experimented to perform both the concentrated method and the parallel beam method with a single crystal monochromator by adding various improvements to the monochromator. This experiment revealed the following.
(1) When a flat crystal monochromator that is normally used in the parallel beam method is used between the concentrated method and the parallel beam method, when the flat crystal monochromator is used as one element of the concentrated method optical system, a curved crystal is obtained. It has been found that the X-ray intensity is significantly attenuated compared to a normal case using a monochromator, specifically about 0.58. Under such an attenuation state of the X-ray intensity, it is impossible to perform the concentration method measurement with sufficient reliability.
[0009]
(2) When the curved crystal monochromator used in the normal concentration method is used between the concentration method and the parallel beam method while keeping the same usage pattern, when the curved crystal monochromator is used in the parallel beam method, The desired X-ray parallel beam could not be obtained on the output side, and therefore the parallel beam method could not be measured.
[0010]
(3) When a curved crystal monochromator used in the normal concentration method is used between both methods while the curved diffraction surface is rotated by 90 ° between the concentration method and the parallel beam method, the curved crystal monochromator is used. Is used in the parallel beam method, the X-ray intensity is attenuated slightly, specifically about 0.72, as compared with the normal case of using a flat crystal monochromator. However, with this level of attenuation, the parallel beam method could be measured to the extent that there was no practical problem.
[0011]
The present invention has been made on the basis of the above-described knowledge. By using a curved crystal monochromator while contriving a use form between the concentrated method and the parallel beam method, one type of crystal is obtained. It is an object to enable X-ray measurement based on both methods using a monochromator.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, an X-ray measurement method according to the present invention is an X-ray measurement method for analyzing a sample using X-rays, wherein a curved crystal monochromator is disposed on the X-ray optical path and concentrated. Measurement is performed with the curved crystal monochromator placed at different angular positions in the in-plane rotation direction between when used as a method optical system and when used as a parallel beam method optical system.
[0013]
According to this X-ray measurement method, X-ray measurement based on the concentration method can be performed as usual using a curved crystal monochromator. Furthermore, by changing the in-plane angular position of the curved diffractive surface of the curved crystal monochromator, X-rays with sufficient intensity can be extracted even when this curved crystal monochromator is applied to the parallel beam method. As a result, the curved crystal monochromator can be used with sufficient reliability even in the parallel beam method. As a result, only by changing the in-plane angular position of the curved crystal monochromator, it is possible to perform X-ray measurement with one type of crystal monochromator based on both the concentration method and the parallel beam method.
[0014]
The following configuration can be considered as a more specific embodiment of the X-ray measurement method. That is, (1) the arrangement in which the bending center axis of the curved crystal monochromator is oriented in a direction substantially perpendicular to the X-ray traveling path is a lateral arrangement, and (2) the bending center axis of the bending crystal monochromator is When an arrangement configuration that faces substantially the same direction as the X-ray traveling path is a vertical arrangement, (3) when used as a concentrated optical system, the curved crystal monochromator is set in a horizontal arrangement, and (4) parallel When used as a beam method optical system, the curved crystal monochromator is set in the vertical arrangement. Note that “substantially” means including a case where the position slightly shifts due to a manufacturing error or the like.
[0015]
According to this configuration, when performing X-ray measurement based on the concentration method, high-precision measurement can be performed as usual. In the X-ray measurement based on the parallel beam method, the X-ray with the highest possible intensity can be taken out using the curved crystal monochromator, and thus the measurement can be performed with sufficient accuracy.
[0016]
In the X-ray measurement method having the above-described configuration, desirably, the length L ₁ of the curved diffractive surface of the curved crystal monochromator is longer or equal to the length L _{2 in the} direction perpendicular to the curved central axis direction. Set. In this way, even when the curved crystal monochromator is used as one element of the parallel beam method optical system, it is possible to extract strong X-rays with the curved crystal monochromator. According to the inventor's experiment, when L ₁ = 20 mm and L ₂ = 25 mm, the attenuation ratio of the X-ray intensity was about 0.72 compared to when using a flat crystal monochromator. Further, when L ₁ = L ₂ = 25 mm, there was almost no attenuation.
[0017]
Next, an X-ray measuring apparatus according to the present invention is an X-ray measuring apparatus for analyzing a sample using X-rays, and a concentrated method optical system and a parallel beam selectively disposed on an X-ray optical path. An optical system, a curved crystal monochromator disposed on the X-ray optical path, and a monochromator in-plane angle varying means capable of changing an angular position in the in-plane rotation direction of the curved crystal monochromator and fixing the angular position to the position. The monochromator in-plane angle varying means has a lateral arrangement in which the curved center axis of the curved crystal monochromator is oriented substantially perpendicular to the X-ray traveling path, and a curved crystal between the curved central axis of the monochromator is the longitudinal arrangement is an arrangement form such as to face substantially the same direction and the X-ray traveling path, changing the angular position of plane rotation direction of the curved crystal monochromator And it features. According to this apparatus, by adjusting the in-plane angular position of the curved crystal monochromator appropriately by the monochromator in-plane angle varying means, both the concentrated method and the parallel beam method can be performed using one type of X-ray optical system. Measurements can be made.
[0018]
The monochromator in-plane angle varying means may be configured to rotate the monochromator in-plane to change its angular position and then clamp to that position, or to use a fastener such as a screw. When the monochromator is detachably fixed to the mounting plate by using the monochromator, the in-plane angle of the monochromator may be fixed differently. Among these cases, if the configuration of clamping after rotating in-plane is adopted, the angle changes compared to changing the in-plane angular position by attaching and detaching the curved crystal monochromator to the mounting plate. Work to make it easier.
[0019]
Also in this X-ray measuring apparatus, desirably, the length L ₁ of the curved surface of the curved crystal monochromator in the direction of the central axis of the curve is set longer than the length L _{2 in the} direction perpendicular to the direction of the central axis of the curve.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 3 shows an embodiment of the X-ray measuring apparatus of the present invention, and particularly shows a state in which the X-ray measuring apparatus is set to the optical arrangement of the concentrated optical system. This X-ray measuring apparatus includes an X-ray focal point 1 that emits X-rays, a divergence limiting slit 3 that limits the divergence of X-rays radiated from the X-ray focal point 1 and guides it to a sample 2, and the X-rays of the sample 2 And a goniometer 4 for measuring an angle with respect to. The X-ray focal point 1 and the divergence limiting slit 3 are fixedly arranged.
[0021]
The goniometer 4 is capable of rotating around the sample axis X1 and supporting the sample 2; a 2θ rotating table 8 capable of rotating around the sample axis X1 and having a 2θ arm 7; and a 2θ arm 7 And a monochromator arm 9 that is rotatable about the monochromator axis X2.
[0022]
The θ-rotation table 6 is driven by a θ-rotation drive system 11 and rotates around the sample axis X1, that is, so-called θ rotation. The 2θ turntable 8 is driven by a 2θ rotation drive system 12 and rotates around the sample axis X1 at an angular velocity twice that of θ rotation, so-called 2θ rotation. The θ rotation drive system 11 and the 2θ rotation drive system 12 can be configured by a rotation drive system having an arbitrary structure. For example, a worm wheel in which the rotation drive force of a pulse motor is fixed to the pulse motor and a worm wheel fixed to each turntable. It is possible to adopt a configuration in which the information is transmitted via
[0023]
A scattered radiation regulating slit 13 and a light receiving slit 14 are attached on the 2θ arm 7. A curved crystal monochromator 18 is disposed at the center of rotation of the monochromator arm 9, and an X-ray counter 22 is fixedly disposed at the tip of the arm 9. A light receiving slit 23 is disposed in front of the X-ray counter 22.
[0024]
The structure for supporting the curved crystal monochromator 18 is configured, for example, as shown in FIG. That is, the monochromator support 16 is fixed on the monochromator arm 9, and the rotary head 17 is supported by the rotation support device 19 attached to the monochromator support 16 so as to be rotatable about the monochromator axis X2. . The curved crystal monochromator 18 is supported by the rotation support device 21 attached to the rotary head 17 so as to be rotatable about the in-plane rotation axis X3. Reference numeral 29 denotes an attachment plate for attaching the curved crystal monochromator 18, and the monochromator 18 is fixed to the attachment plate 29 by a fastener such as a screw.
[0025]
The rotary support device 19 supports the rotary head 17 in a rotatable manner, and clamps or holds the rotary head 17 so as not to easily rotate at an arbitrary angular position. Similarly, the rotation support device 21 rotatably supports the curved crystal monochromator 18 and holds the monochromator 18 so as not to easily rotate at an arbitrary angular position. The structure for holding the monochromator and the like so as not to rotate can be any structure. For example, a structure that clamps using a fastener such as a set screw or a mechanical frictional force is used. For example, a structure to be clamped can be considered. The rotary head 17 and the monochromator 18 can be automatically rotated using a pulse motor or the like. In this case, the rotation angle position of the rotary head 17 or the like is set by locking the rotation of the pulse motor. Can be held.
[0026]
The operation of the X-ray measuring apparatus having the above configuration will be described below.
(Intensive method measurement)
First, when performing measurement based on the concentration method, in FIG. 2, the curved crystal monochromator 18 is rotated manually or automatically using a motor or the like about the in-plane rotation axis X3 in FIG. As shown by a), the curved central axis X4 of the curved diffractive surface 18a of the curved crystal monochromator 18 is oriented in a direction substantially perpendicular to the traveling path of the X-ray R, that is, the lateral direction of the figure, that is, laterally. Position to orientation.
[0027]
In FIG. 3, the monochromator arm 9 is set to a predetermined angle with respect to the 2θ arm 7, and the angle with respect to the incident X-ray of the curved crystal monochromator 18 is set to a predetermined angle. In regulating the X-ray incident angle for a bending crystal monochromator 18, it rotates the rotary head 17 about the monochromator axis X2 in FIG. 2, carried out by the so-called theta _M rotates.
[0028]
Thereafter, in FIG. 3, the sample 2 to be measured is mounted on the θ rotation table 6, and X-rays are emitted from the X-ray focal point 1, and the θ rotation table 6 is rotated θ, and the 2θ rotation table 8 is simultaneously rotated 2θ. . X-rays emanating from the X-ray focal point 1 are diffracted by the sample 2 when a predetermined diffraction condition is satisfied with the crystal lattice plane of the sample 2. The diffracted X-rays are concentrated on a point on the focal circle C ₁ where the light receiving slit 14 is disposed, and then enter the curved diffraction surface 18 a of the monochromator 18.
[0029]
The diffracted X-rays incident on the monochromator 18 are monochromated by the monochromator 18 and then concentrated on the light receiving slit 23 on the focal circle C ₂ , and then taken into the X-ray counter 22 to measure its intensity. The This measurement is performed for each of different 2θ rotation angle positions, that is, different diffraction angle (2θ) positions. As a result, on the graph, the diffraction angle (2θ) position is taken on the horizontal axis and the X-ray intensity value is taken on the vertical axis. An X-ray intensity distribution curve is obtained.
[0030]
(Parallel beam measurement)
Next, when performing measurement based on the parallel beam method, for example, X-ray measurement on a thin film sample, a vertical divergence limiting solar slit 26 is disposed between the X-ray focal point 1 and the thin film sample 24 as shown in FIG. Further, a lateral divergence limiting solar slit 27 is disposed between the sample 24 and the curved crystal monochromator 18. Further, in FIG. 2, the curved crystal monochromator 18 is rotated manually or automatically using a motor or the like about the in-plane rotation axis X3, as shown in FIG. The bending center axis line X4 of the curved diffractive surface 18a of the meter 18 is set so as to face the traveling path of the X-ray R, that is, substantially in the same direction as the horizontal direction in the figure, that is, in the vertical direction.
[0031]
In FIG. 4, the monochromator arm 9 is set to a predetermined angle with respect to the 2θ arm 7, and the angle of the curved crystal monochromator 18 with respect to the incident X-ray is set to a predetermined angle. Thereafter, in FIG. 4, the thin film sample 24 to be measured is mounted on the θ turntable 6, and X-rays are emitted from the X-ray focal point 1 and a parallel X-ray beam formed by the solar slit 26 is incident on the sample 24. At this time, the incident angle α of the X-ray with respect to the sample 24 is set to a low angle of about 0.5 °. This is to allow X-rays to pass through the thin film over a long distance.
[0032]
The parallel X-ray beam incident on the thin film sample 24 at a low angle passes obliquely through the thin film layer portion of the thin film sample 24, and diffracted X-rays are generated from the thin film layer portion when the diffraction conditions are satisfied. The diffracted X-ray is incident on the curved diffractive surface 18a of the curved crystal monochromator 18 in a state in which the lateral divergence is restricted by the solar slit 27, and is monochromatized. The monochromatic diffracted X-ray is taken into the X-ray counter 28 and its X-ray intensity is measured.
[0033]
In the present embodiment, since the X-ray monochromatization is performed using the curved crystal monochromator 18 even when the parallel beam method is measured, the intensity of the X-ray obtained on the output side of the monochromator 18 is the same as that of the flat crystal monochromator. It attenuates to some extent compared with the case of using it. However, in this embodiment, when performing measurement based on the parallel beam method, the arrangement state of the curved crystal monochromator 18 with respect to the X-ray is changed from the horizontal arrangement (FIG. 1A) to the vertical arrangement (FIG. 1B). Therefore, the degree of attenuation of X-rays can be suppressed to a very low level, and as a result, a highly accurate measurement result can be obtained to the extent that there is no practical problem.
[0034]
In FIG. 1B, the length L ₁ in the direction along the curved center axis X4 of the curved diffractive surface 18a of the curved crystal monochromator 18 is previously determined from the length L _{2 in the} direction perpendicular to the curved center axis X4. Also, it is desirable to set the length to be longer or equal (L ₁ ≧ L ₂ ). In this way, it has been found that when the curved crystal monochromator 18 is used for the measurement by the parallel beam method, a diffracted beam having a higher intensity can be obtained as compared with the case where L ₁ <L ₂ is set.
[0035]
As described above, according to the X-ray measuring apparatus of the present embodiment, the angle position of the curved crystal monochromator 18 is changed by 90 ° in the in-plane rotation direction, and the other optical elements are only slightly changed. The measurement method can be freely changed between the concentrated method and the parallel beam method.
[0036]
(Experimental example 1)
In order to confirm the reliability of the measurement, in the parallel beam method optical system of FIG. 4, a Si crystal is mounted at the sample 24, and a monochromator (1) flat crystal monochromator, (2) longitudinal arrangement The curved monochromators of FIG. 1 (b) and the curved crystal monochromator (3) laterally arranged (FIG. 1 (a)) are alternately installed, and the intensity of diffracted X-rays is set for each. It was measured. As a result, a measurement result as shown in FIG. 5 was obtained. In FIG. 5, the horizontal axis represents the diffraction angle 2θ, and the vertical axis represents the measured X-ray intensity (cps). The dimensions of the curved crystal monochromator used were L ₁ = 20 mm and L ₂ = 25 mm.
[0037]
5, was calculated for the peak intensity D ₂ of the curved crystal monochromator vertical placement and the peak intensity D ₁ of the flat crystal monochromator, the intensity ratio _{(D 2 / D 1),} D 2 / D 1 = 0.72 was obtained. In other words, if a curved crystal monochromator arranged in the vertical direction is used instead of a flat crystal monochromator that has been conventionally used in the measurement of the parallel beam method, an attenuation of X-rays of about 0.72 was observed. With this level of attenuation, the parallel beam method could be measured with high reliability that would not interfere with practical use.
On the other hand, with respect to the curved crystal monochromator arranged in the lateral direction, the degree of attenuation of the peak intensity D ₃ is very large. In this case, a highly reliable measurement result cannot be obtained at all in the parallel beam method. It was.
[0038]
(Experimental example 2)
The experiment was performed by changing the size of the curved crystal monochromator to L ₁ = L ₂ = 25 mm with respect to Experimental Example 1. As a result, D ₂ / D ₁ ≧ 1 was obtained. This seems to be because more diffracted X-rays could be captured by increasing the width of L ₁ .
[0039]
(Other embodiments)
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, in the embodiment described above, thin film measurement as shown in FIG. 4 is considered as an example of measurement based on the parallel beam method. However, the parallel beam method can be applied for various purposes other than thin film measurement. In the above embodiment, a goniometer having a structure in which the monochromator is disposed on the rear side of the sample as viewed from the X-ray traveling path is exemplified. However, the monochromator may be disposed on the front side of the sample.
[0040]
Further, in the above embodiment, the rotation support device 21 as shown in FIG. 2 is considered as the monochromator in-plane angle varying means for changing the angular position of the curved crystal monochromator in the in-plane rotation direction. The rotation support device 21 was mainly intended for manually rotating the curved crystal monochromator 18. However, the angle can be measured by automatically rotating the monochromator 18 with a pulse motor or the like.
[0041]
Further, as a method for changing the angular position in the in-plane rotation direction of the curved crystal monochromator, other than the method of clamping the monochromator 18 after in-plane rotation as in the embodiment shown in FIG. In addition, a method may be considered in which the mounting plate 29 is provided so as not to rotate, and the curved crystal monochromator 18 is attached and detached while being rotated by 90 ° with respect to the mounting plate 29.
[0042]
【The invention's effect】
According to the X-ray measurement method of the first aspect, X-ray measurement based on the concentration method can be performed as usual using a curved crystal monochromator. Furthermore, by changing the in-plane angular position of the curved diffractive surface of the curved crystal monochromator, X-rays with sufficient intensity can be extracted even when this curved crystal monochromator is applied to the parallel beam method. As a result, the curved crystal monochromator can be used with sufficient reliability even in the parallel beam method. As a result, only by changing the in-plane angular position of the curved crystal monochromator, it becomes possible to perform X-ray measurement based on both the concentrated method and the parallel beam method with one type of X-ray optical system. .
[0043]
According to the X-ray measurement method of claim 2, monochromatic X-rays can be extracted with the strongest intensity to the output side of the monochromator in both the concentrated method and the parallel beam method. Highly reliable measurement results can be obtained not only in the concentrated method but also in the parallel beam method.
[0044]
According to the X-ray measuring method according to claim 3 and the X-ray measuring apparatus according to claim 6, when a curved crystal monochromator is used for the parallel beam method, an X-ray having a higher intensity is applied to the output side of the monochromator. Obtainable.
[0045]
According to the X-ray measuring apparatus of claim 4, only by changing the in-plane angular position of the curved crystal monochromator, the X-ray measurement is performed by one type of crystal monochromator based on both the concentrated method and the parallel beam method. It can be performed.
[0046]
According to the X-ray measuring apparatus of the fifth aspect, the operation for changing the angle is simplified as compared with the case where the in-plane angular position is changed by attaching and detaching the curved crystal monochromator to the mounting plate.
[0047]
[Brief description of the drawings]
FIG. 1 is a diagram for explaining a method of using a curved crystal monochromator in an X-ray measurement method according to the present invention.
FIG. 2 is a diagram showing a main part of an embodiment of an X-ray measuring apparatus according to the present invention.
FIG. 3 is a plan view showing a case where a concentrated optical system is configured using the X-ray measuring apparatus according to the present invention.
4 is a plan view showing a case where a parallel beam method optical system is configured using the same X-ray measurement apparatus as FIG. 3. FIG.
FIG. 5 is an X-ray diffraction pattern showing the results of an experiment conducted for comparing the method of the present invention with a conventional method.
[Explanation of symbols]
1 X-ray focal point 2 Sample 3 Divergence limiting slit 4 Goniometer 6 θ rotation table 7 2θ arm 8 2θ rotation table 9 Monochromator arm 11 θ rotation drive system 12 2θ rotation drive system 13 Scattered ray regulating slit 14 Light receiving slit 16 Monochromator support table 17 Rotating head 18 Curved crystal monochromator 19, 21 Rotating support device 22, 28 X-ray counter 23 Light receiving slit 24 Thin film sample 26 Vertical divergence limiting solar slit 27 Horizontal divergence limiting solar slit 29 Mounting plates C ₁ , C ₂ Focal point R X-ray X1 Sample axis X2 Monochromator axis X3 In-plane rotation axis X4 Curve center axis

Claims (6)

In an X-ray measurement method for analyzing a sample using X-rays,
A curved crystal monochromator is placed on the X-ray optical path,
X-ray measurement characterized in that measurement is performed with the curved crystal monochromator placed at different angular positions in the in-plane rotation direction between when used as a concentrated method optical system and when used as a parallel beam method optical system Method. The X-ray measurement method according to claim 1,
An arrangement configuration in which the curved center axis of the curved crystal monochromator is substantially perpendicular to the X-ray traveling path is a lateral arrangement,
When an arrangement configuration in which the curved center axis of the curved crystal monochromator faces substantially the same direction as the X-ray traveling path is a vertical arrangement,
When used as a concentrated method optical system, the curved crystal monochromator is set in the lateral direction,
An X-ray measuring method characterized in that when used as a parallel beam method optical system, the curved crystal monochromator is set in a vertical arrangement. In the X-ray measuring method according to claim 1 or 2,
An X-ray measuring method, wherein a length L1 of a curved diffraction surface of a curved crystal monochromator is longer than or equal to a length L2 in a direction perpendicular to the curved central axis direction. In an X-ray measuring apparatus for analyzing a sample using X-rays,
A focusing method optical system and a parallel beam optical system, one of which is selectively disposed on the X-ray optical path;
A curved crystal monochromator disposed on the X-ray optical path;
A monochromator in-plane angle varying means capable of changing the angle position in the in-plane rotation direction of the curved crystal monochromator and fixing the angle position to the position ;
The monochromator in-plane angle varying means is
The lateral arrangement is such that the curved central axis of the curved crystal monochromator is oriented substantially perpendicular to the X-ray travel path, and the curved central axis of the curved crystal monochromator is substantially the same as the X-ray travel path. An X-ray measurement apparatus characterized in that the angular position in the in-plane rotation direction of the curved crystal monochromator is changed between the vertical crystal arrangements which are arranged in the same direction . 5. The X-ray measurement apparatus according to claim 4, wherein the monochromator in-plane angle varying means changes the in-plane angular position by rotating the curved crystal monochromator in-plane and locks the rotation to change the in- plane angular position. An X-ray measuring apparatus characterized by holding .   6. The X-ray measuring apparatus according to claim 4, wherein the length L1 of the curved diffractive surface of the curved crystal monochromator is longer than or equal to the length L2 of the curved center axis direction perpendicular to the curved center axis direction. An X-ray measuring apparatus characterized by that.

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