JPS585376B2 - lang camera - Google Patents

Description

Detailed Description of the Invention In a Lang camera, parallel X-rays with a nearly constant wavelength are projected onto a part of a flat single crystal sample, and the diffracted X-rays are incident on a photosensitive plate, which allows the specimen to be separated from the sample. A diffraction X-ray photograph of the entire surface of the sample is taken by moving the photosensitive plate at the same time.

However, the parallel X-rays have a certain opening angle, and the projected X-rays also generally include characteristic X-rays α1 and α2 having slightly different wavelengths.

Therefore, chromatic aberration occurs and the sharpness of the photographed diffraction X-ray image deteriorates.

The present invention attempts to correct the above-mentioned chromatic aberration using an extremely simple mechanism.

FIG. 1 is a plan view of a Lang camera according to an embodiment of the present invention, in which a flat single crystal sample 1 and an X-ray photosensitive plate 2 are arranged perpendicular to the plane of the paper.

The sample 1 and the X-ray photosensitive plate 2 are installed on a sample stand 3 and a base 4, respectively.
The base 4 of the photosensitive plate is slidably attached to guide tracks 5 and 6 constructed at an appropriate angle in a horizontal plane.

In addition, one end of a screw punch 7 arranged parallel to the track 5 is fixed to the sample stage 3, the screw punch 7 is screwed into a female threaded tube 8, and a gear 9 fixed to the female threaded tube 8 is connected to a reducer. Gear 1 of electric motor 10
It is meshed with 1.

Therefore, when the electric motor 10 is started, the sample stage 3 moves at a low speed as indicated by the arrow p.

Further, the sample stage 3 is provided with an arm 13 having a linear chromatic aberration correction guide surface 12, one end of which is tightened with a screw 14, and an index 15 is provided on the arm 13.
6 is provided.

Therefore, by loosening the screw 14 and rotating the arm 13, the guide surface 12 can be fixed at an arbitrary angle with respect to the surface of the sample 1 using the scale 16 and the index 15.

Further, an arm 18 is fixed to the base 4 of the X-ray photosensitive plate with a screw 17, a roller 19 is attached to the tip of the arm, the base 4 is pulled to the fixed part by a spring 20, and the roller 19 is moved to the guide surface. 12.

Note that since the screw 17 is fitted into the groove 21 of the arm 18, the effective length of the fence 8 can be adjusted by loosening this screw.
The position of the X-ray photosensitive plate 2 can be adjusted so that it faces the sample 1.

In the above-mentioned apparatus, a plate-shaped X-ray X perpendicular to the plane of the paper is projected onto the sample 1, and the X-ray X' diffracted by the sample 1 is made incident on the photosensitive plate 2. At the same time, the sample stage 3 is moved in the direction of the arrow p. move it.

Accordingly, the base 4 of the X-ray photosensitive plate is pushed by the arm 13 and moves in the direction of arrow q, and the roller 19 slides on the guide surface 12 at this time.

Figure 2 shows the X-ray optical system in this case.
Assume that the α1 ray is incident on a point A on the sample, diffracted by the sample, and incident on a point C on the photosensitive plate 2.

Further, when the sample 1 and the photosensitive plate 2 move in the directions of the arrows p and q and the point on the sample reaches the position of point B, diffraction occurs in the α2 ray, and the diffracted X-rays are reflected on the photosensitive plate. In this case, chromatic aberration can be corrected by moving point C on the photosensitive plate to the dot position.

Now, the distance from the point focus to the X-ray incident position on the sample 1 is l, the distance from the X-ray incident position on the sample to the incident position of the diffracted X-rays on the photosensitive plate 2 is m, and the diffracted X-rays are It is assumed that the incident angle is approximately perpendicular to 2.

In this case, when a perpendicular line AE is drawn from point A to the X-ray incident on point B, the distance AE is lΔθ.

Also, the diffraction angle θ1 of the α1 ray and the α2 ray. Since θ2 is approximately equal, if this is θ and the angle between the crystal lattice plane and the sample surface in sample 1 is α, then the incident angle of the X-ray incident on point B is approximately given by (α+θ).

Therefore, the distance AB between points A and B is It is expressed as

Further, if the point where a straight line passing through point B and parallel to the diffracted X-ray AC intersects with the photosensitive plate 2 is F, then the straight line crosses the photosensitive plate 2 at point F.
orthogonal to

Furthermore, if the point where a straight line passing through point C and parallel to straight line AB intersects straight line BP is G, then the distance σ is clearly equal to the distance layer, and the angle between straight lines GC and GF is given by (α-β). It will be done.

Therefore, the distance C〒 is CF=ABsin(α-β)...
...(2).

Also, since the angle between the straight line BF and the diffracted X-ray BD is approximately △θ, the distance FD is FD - mΔθ (3
).

Therefore, from equations (1), (2), and (3) above, the ratio of distances CD and AB is a constant value given by.

Also, Figure 3 shows the mechanism in Figure 1, and shows sample 1.
A guide surface 12 is provided to protrude from the guide surface 12 at an arbitrary angle ψ.

When the sample 1 moves in the direction of arrow p, the X-ray photosensitive plate 2 is pushed by the guide surface 12 and moves in the direction of arrow q.

Therefore, if the point where a straight line passing through an arbitrary point on the sample 1 and parallel to the guide surface 12 intersects with the photosensitive plate 2 is d, then when the sample moves from point a to b, the photosensitive plate touches the guide surface 12 at the point. Move from C to point d.

Now, if we draw a straight line passing through point C and parallel to sample 1, and let the point where the straight line intersects with straight line bd be hl, and the foot of the perpendicular line drawn from point d to straight line ch be 1, then the diffracted X-ray X' will be Since the light is incident on the photosensitive plate 2 at a right angle, the angle idc is equal to the angle between the diffracted X-ray X' and the sample 1.

And since the angle between the diffracted X-ray X' and the sample 1 is (α-β), and the straight lines ab and ch are equal, a right triangle cid
and hid between the distance ab and d between ab=cdsin(α-β)+cdcos(α-β)c
The relationship otψ holds true.

In other words.

Therefore, if the angle ψ of the guide surface 12 is set so as to satisfy equations (4) and (5), when point A on the sample 1 in Fig. 2 moves to point B, point C on the photosensitive plate becomes a point. Move up to.

That is, the diffraction line of the α1 ray and the diffraction line of the α2 ray are incident on the same point on the photosensitive plate, so that chromatic aberration can be corrected.

In the above-mentioned embodiment, the guide surface 12 was provided on the sample stage, but
It is also possible to provide a guide surface on the base 4 of the line-sensitive plate and to slide the sample stage onto the guide surface.

As mentioned above, the present invention has an extremely simple mechanism in which the sample and the X-ray photosensitive plate are moved parallel to their respective surfaces, and the other is brought into sliding contact with a guide surface provided at an appropriate angle on one side. This allows chromatic aberration to be corrected and sharp images to be taken.

In addition, since no gears or the like are required, the mechanism is simple, and an extremely long arm, etc., which is equivalent to the distance from the X-ray source to the sample, is not required, so the apparatus can be constructed in a compact size.

Furthermore, there are excellent effects such as the ability to easily make corrections for various samples by adjusting the angle α of the guide surface.

[Brief explanation of drawings]

FIG. 1 is a plan view of an embodiment of the present invention, FIG. 2 is a diagram showing the X-ray optical system in the apparatus shown in FIG. 1, and FIG. 3 is a schematic diagram showing the operating mechanism of the apparatus shown in FIG. In the figure, 1...sample, 2...
X-ray photosensitive plate, 3...sample stand, 4...X
Base of line-sensitive plate, 5, 6... Guide track, 12.
...Information surface.

Claims (1)

[Claims] 1 Hold the sample stage and the base of the X-ray photosensitive plate so that they can move along a trajectory parallel to the plane containing the sample and the X-ray photosensitive plate, respectively, and hold the base of the sample table or the base of the X-ray photosensitive plate on one side. A Lang camera characterized in that a linear chromatic aberration correction guide surface is formed and the other guide surface slides into contact with the guide surface.