JPH0926500A - Capillary for X-ray focusing - Google Patents

Abstract

(57) An object of the present invention is to provide a capillary for X-ray focusing, which is easy to manufacture, and which is capable of obtaining a fine beam with high illuminance. An X-ray condensing capillary according to the present invention facilitates production by making the shape of an inner wall (6) of a tube into a simple truncated cone shape. Further, the X-ray condensing capillary according to the present invention has an X-ray (1, 2,
All the collisions between 3) and the inner wall of the capillary are totally reflected,
Prevents leakage of X-rays due to transmission from the wall surface
By designing the shape of the inner wall of the tube so that all of the lines can reach the exit hole (7) of the capillary, it is possible to obtain a beam of fine and high illuminance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an X-ray diffractometer, fluorescent X
In an analyzer using an X-ray beam as a probe, such as an X-ray analyzer or a photoelectron spectroscopy analyzer, an X-ray condenser for condensing the X-ray beam and irradiating it to a minute portion on an analysis sample. For capillaries.

[0002]

2. Description of the Related Art Conventionally, as an X-ray condensing capillary for performing X-ray diffraction of a microcrystal or a microregion, for example, as disclosed in Japanese Patent Laid-Open No. 1-141343,
For the purpose of miniaturizing the beam and increasing the illuminance by condensing the X-ray flux, the curved surface of the inner wall of the capillary is devised so that the emitted light is condensed at a fixed focus.

[0003]

However, in the above-mentioned prior art, since the inner wall of the capillary is provided with a predetermined curved surface, a sophisticated processing technique is required, and it is easy to obtain a desired X-ray focusing capillary. Not. Therefore, an object of the present invention is to provide a capillary for X-ray focusing, which has a simple shape, is easy to manufacture, and is capable of obtaining a fine beam with high illuminance.

[0004]

The capillary for X-ray focusing according to the present invention facilitates the manufacture by making the shape of the inner wall of the tube simple frustoconical. Furthermore, the X-ray condensing capillary according to the present invention is configured to totally reflect all collisions with the inner wall of the capillary until X-rays incident parallel to the central axis of the tube are emitted from the emission hole. X-rays are prevented from leaking due to transmission from the wall surface, so that a beam of fine and high illuminance can be obtained.

Specifically, in an X-ray capillary for condensing an X-ray beam by utilizing the total reflection on the inner wall of the tube, the shape of the inner wall is frustoconical and the X-ray beam enters. When the diameter of the entrance hole is B, the diameter of the exit hole through which the focused X-ray beam exits is D, and the critical angle of total reflection determined by the wavelength of the incoming X-ray and the material of the inner wall of the tube is θ. , The length L of the X-ray focusing capillary is given by the following equation. 2.0 × (B−D) × (B−2D) / (2Dθ) ≧ L ≧ 0.9 × (B−D) × (B−2D) / (2Dθ) (1)

[0006]

According to the present invention, when X-rays are incident at an angle equal to or less than a certain critical angle from a medium having a high refractive index to a medium having a low refractive index, all of the X-rays are reflected to cause refraction or transmission. It utilizes the phenomenon of total internal reflection where X-ray leakage does not occur. That is, when the X-rays incident parallel to the central axis of the X-ray condensing capillary collide with the inner wall of the truncated cone-shaped capillary, they are totally reflected to prevent leakage from the inner wall, and all of the incident X-rays are prevented. So as to reach the emission hole so that a minute beam with high illuminance can be obtained. The relationship between the X-ray and the refractive index of the medium is such that a medium made of an element having a small atomic number, such as air, has a large refractive index, and a medium made of an element having a large atomic number, such as glass or metal, has a small refractive index. Become. Therefore, the X-ray condensing capillary according to the present invention is made of a hollow glass thin tube or the like.

FIG. 1 shows a relationship between an X-ray converging capillary having a truncated cone-shaped inner wall according to the present invention and an X-ray incident parallel thereto. Based on this figure, conditions for all the X-rays incident in parallel to the X-ray condensing capillary to be totally reflected by the inner wall of the truncated cone and to be emitted from the emission hole will be described.

First, let the diameter of the exit hole 7 be D, the diameter of the entrance hole 8 be B, and the inclination angle of the inner wall 6 of the truncated cone with respect to the central axis 10 of the capillary be α. The inclination angle α of this inner wall
Since the total reflection angle θ is generally as small as about 0.01 radian, the value is smaller than this.

Of the X-rays incident on the incident hole 8 in parallel, the cylindrical X-ray flux 11 including the central axis 10 having the same diameter as the diameter D of the emission hole 7 is emitted without reflection on the inner wall. The light is directly emitted from the hole 7.

X-rays 1 and X around the cylindrical X-ray flux 11
The cylindrical X-ray flux 12 sandwiched by the lines 2 is totally reflected once from the inner wall and emitted from the emission hole 7. For example, a cylindrical X
The X-ray 1 which travels in the innermost part of the ray bundle 12 is totally reflected by the inner portion of the tip of the emission hole 7 at an angle α with the inner wall thereof and emitted in the direction of an angle 2α with the central axis. The X-ray 2 traveling on the outermost side is totally reflected at the angle α formed by the inner wall 4 with the inner wall, and is emitted in the direction of the angle 2α formed by the central axis by grazing the inner portion of the tip of the emission hole 7. The cylindrical X-ray flux 12 has an angle 2α between the exit hole 7 having a diameter D and the central axis.
Since the light is emitted in the direction of, the width is Dcos2α over the entire path from the incidence to the emission, and it collides with the portion of the inner wall 4 of the capillary whose total length in the vertical direction is Dcos2α / tanα (≈D / α) by total reflection. .

The cylindrical X-ray flux 23, which is located outside the X-ray flux 12 and is sandwiched between the X-rays 2 and the X-rays 3, is totally reflected on the inner wall only twice and is emitted from the emission hole 7. This X-ray flux 23 is emitted from the emission hole 7 having the diameter D in the direction of the angle 4α formed by the central axis after total reflection twice on the inner wall, and thus the width is Dcos4α over the entire path from the incidence to the emission. Further, the first total reflection occurs with the portion of the inner wall 5, and the length in the vertical direction in which the first total reflection occurs is Dcos4α / tanα (≈D /
over α).

If the diameter B of the entrance hole 8 is larger than that of FIG. 1, there may be a cylindrical X-ray flux which is totally reflected three times or more and is emitted outside the X-ray flux 23. It can be easily inferred from the above consideration regarding 12, 23.

Generally, X incident on the capillary in parallel.
Each time the wire bundle collides with the inner wall, the angle it makes with the inner wall is 2α.
It increases in steps. The X-ray of the outermost layer that has the most number of collisions with the inner wall before the X-ray flux incident parallel to the capillary is emitted.
If the number of total reflections of a ray bundle is N, then this X
The angle formed by the X-ray and the inner wall at the time of the last collision with the inner wall before the ray bundle is emitted is represented by (2N-1) α. Therefore, in order to cause all the X-rays incident on the capillary to be emitted from the emission hole 7 by total reflection, this angle may be made smaller than the critical angle θ of total reflection determined by the material of the capillary as in the following formula. (2N-1) α ≤ θ (2)

Next, there is the following relationship between the diameter B of the entrance hole and N, α, and D. First, the diameter of the entrance hole B must be equal to the diameter of the entire incident X-ray flux. Assuming that the total diameter of the incident X-ray flux is totally reflected on the inner wall N times before the X-ray flux of the outermost layer is emitted, the diameter D of the cylindrical X-ray flux 11 and the thickness of the cylindrical X-ray flux 12 on the outer side thereof. 2 x Dc
os2α, the thickness of the X-ray flux 23 2 × Dcos4α, etc. Therefore, the following equation is established. B = D + 2 × Dcos2α + 2 × Dcos4α ... ≈ (2N + 1) D (3) FIG. 2 shows an example in which the number N of total reflections is 2.

Next, the length L of the capillary and B, D, α
Has the following relationship. L = (B−D) / 2 tanα ≈ (B−D) / 2α ≈N × D / α (4) Incidentally, the length L of the capillary is the cylindrical X-ray flux 1
Since 2, 23, etc. are the sums of the lengths in the central axis direction of the regions that first collide with the inner wall, they can be described by the following equations and give the same result. L = Dcos2α / tanα (≈D / α) + Dcos4α / tanα (≈D / α) + ... ≈D / α + D / α + ... …… = N × D / α (4a)

Since N and α are determined from the equations (2) and (3), when these are substituted into the equation (4), the following equation is obtained. L ≧ (B−D) × (B−2D) / (2Dθ) (5)

Equation (5) is defined by the diameter B of the entrance hole 8 and the exit hole 7
When the critical angle θ of total reflection determined by the diameter D, the wavelength of the incident X-ray, and the material of the capillary is given, all X-ray fluxes incident in parallel are totally reflected and emitted from the emission hole 7. The condition of the length L of the condensing capillary is shown.

[0018]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description.

The first embodiment will be described. FIG.
It is a longitudinal cross-sectional view in the direction of the central axis 10 of the X-ray focusing capillary. In FIG. 1, reference numeral 6 denotes an inner wall of a capillary made of lead glass, which has a simple truncated cone shape. The critical angle θ of total reflection of this lead glass is 10 milliradians. The diameter B of the entrance hole 8 is 90 μm, the diameter D of the exit hole 7 is 1 μm, and the length L of the capillary is 39 cm. Incidentally, in the case of this X-ray condensing capillary, the X-ray flux incident in parallel from the incident hole 8 is emitted after being totally reflected up to 44 times on the inner wall.

First, a lead glass thin tube having an inner diameter of 90 μm and a wall thickness of 0.5 mm is prepared, and a part of the glass tube is heated, and a certain weight is applied to the thin tube, which is stretched at a certain speed. The desired temperature can be selected from the trial-produced capillaries by adjusting the heating temperature, tensile load, and speed and repeating the above operations until the desired capillaries are formed. If an appropriate heating temperature, tensile load, and speed are determined by initial trial and error, the desired capillary can be easily obtained thereafter. X-rays are made to enter the entrance hole 8 of this capillary in parallel and the exit hole 7
The illuminance of the focused X-ray flux and the diameter of the beam were measured by directly applying a photographic film to and exposing and developing the image. As a result, it was possible to obtain an X-ray beam having a theoretically expected illuminance that was about 8000 times that of the incident X-ray in the vicinity of the exit hole 7. Moreover, the size of the focused X-ray flux was about 1 μm in diameter, and an extremely fine X-ray flux could be obtained.

In the above embodiment, the length L of the capillary is
The case is equal to the right side of Expression (5), but the present invention is not limited to this. When the length of the capillary is shorter than the range of L determined from the equation (5), the angle formed by the X-ray and the inner wall exceeds the critical angle θ of total reflection with the number of collisions smaller than N, and the incident angle A part of the generated X-rays is refracted and leaks out from the inner wall of the capillary by transmission. Therefore, all of the incident X-ray flux cannot reach the exit hole 7 of the capillary, the illuminance of the emitted X-ray flux becomes low, and analysis takes time. From the experience, it is not preferable that the length L of the capillary is less than 90% of the value determined from the right side of the formula (5). When the length of the capillary is larger than the value determined by the right side of the equation (5), all the incident X-ray flux can reach the exit hole 7 of the capillary, but if it is too large, it becomes difficult to manufacture the capillary with high accuracy. Become. The length L of the capillary is 200% of the value determined from the right side of Expression (5).
The following is preferred.

[0022]

As described above, according to the present invention, it is possible to obtain a capillary for X-ray focusing which is extremely easy to manufacture. Further, since the X-ray flux with sufficient illuminance can be obtained, the analysis time is shortened and the analysis becomes efficient. Further, since an extremely thin X-ray beam can be obtained, it is possible to analyze fine crystals with high resolution.

[0023]

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view in the direction of the central axis of an X-ray condensing capillary according to the present invention, showing the relationship between the shape of the capillary and the number of total reflections of incident X-rays.

FIG. 2 is a cross-sectional view of the X-ray condensing capillary according to the present invention, showing the relationship between the number of total reflections of incident X-rays and the diameters of the entrance hole and the exit hole of the capillary.

[Explanation of symbols]

 1, 2 and 3: incident X-rays 4: region where X-ray flux 12 totally reflects from inner wall 5: region where X-ray flux 23 totally reflects from inner wall first 6: inner wall of X-ray focusing capillary 7: X-ray collection Emission hole of light capillary 8: Incident hole of X-ray condensing capillary 11, 12, 23: X-ray flux

Claims (1)

[Claims] 1. An X-ray beam utilizing total internal reflection on the inner wall of the tube.
In the X-ray capillary that focuses the beam, the diameter of the entrance hole through which the X-ray beam enters is B, the diameter of the exit hole through which the focused X-ray beam exits is D, and the diameter of the incoming X-ray When the critical angle of total reflection determined by the wavelength and the material of the inner wall of the tube is θ, the length L of the X-ray capillary is (BD) × (B-2D).
Capillary for X-ray focusing, which is in the range of 90% to 200% of the value given by / (2Dθ)