JP2017211290A - X-ray irradiation equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray irradiation device with which it is possible to irradiate a sample with an X-ray narrowed down to a microscopic diameter.SOLUTION: The X-ray irradiation device comprises: an X-ray source 1 that is a surface light source; and a multi-capillary X-ray lens 20 in which a large number of capillaries 20 are bundled in a generally truncated cone shape, the central axis of each having a shape of straight line, with the inside diameter gradually reduced from an incident side end face 20a toward an emission side end face 20b. A portion of the X-ray released from the X-ray source 1 is transmitted without colliding the inner wall of each capillary 20 and emitted as a linear X-ray from the emission side end face 20b. The linear X-rays emitted from each capillary 20 and unattenuated inside the capillary 20 overlap at a substantially one point F on a sample 3, making it possible for an X-ray of high X intensity to be radiated onto a very narrow area.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an X-ray irradiation apparatus that irradiates a sample with X-rays in an X-ray analysis apparatus that analyzes and observes the sample using X-rays. More specifically, the present invention relates to a minute region or a minute sample on a sample. The present invention relates to an X-ray irradiation apparatus for irradiating X-rays.

Analyzing and observing a sample by irradiating the sample with X-rays, detecting X-rays, electrons, ions, or other various particles emitted from the sample, or detecting X-rays transmitted through the sample Conventionally, X-ray analysis techniques for performing the above are known. In general, X-rays have the following characteristics.
-Since the wavelength of X-rays is about the same as that of atoms and interatomic distances, it has much information on atoms and atomic arrangements.
-X-rays are almost non-destructive to matter upon collision, scattering, diffraction, etc.
-Although the number of X-ray photons decreases when X-rays pass through the material, the wavelength and energy do not change, and the original properties when X-rays are generated are not lost.
These X-ray features are very useful for analyzing samples, and X-ray analysis is one of the most important analysis methods, and is currently used for precise composition analysis of all solids, It is also used for trace element analysis.

  The most representative X-ray analysis method is X-ray fluorescence analysis, which is a typical analysis method including non-destructive, highly accurate qualitative and quantitative analysis including trace elements. Total reflection X-ray fluorescence analysis, which is one of the X-ray fluorescence analysis methods, is the best of all the analytical methods in the microanalysis of the surface of a solid material. X-ray photoelectron spectroscopy is a typical analysis method for structural analysis of material surfaces, element bond analysis, and electronic state analysis.

On the other hand, unlike charged particle beams, X-rays are not affected by an electric field or magnetic field, are not reflected under special conditions, and have no characteristic refractive materials. This feature is also a limitation of X-ray analysis as follows.
That is, in the X-ray analyzer, in order to increase the spatial resolution of analysis and observation, it is necessary to reduce the irradiation diameter or irradiation area of the X-ray irradiated to the sample and the target region on the sample as small as possible. In general, in order to increase the sensitivity and accuracy of analysis, it is necessary to irradiate a sample and a target region on the sample with X-rays with a certain high intensity. For example, with a charged particle beam such as an electron beam, the irradiation diameter can be reduced to a very small diameter by using a lens based on an electric field or a magnetic field. On the other hand, X-rays cannot be controlled using an electric field or a magnetic field as described above, so it is very difficult to narrow the X-ray irradiation diameter to a very low level. An X-ray irradiator that narrows down to a very small diameter and obtains a large gain has not been realized.

In a conventional X-ray analyzer such as a fluorescent X-ray analyzer, an X-ray irradiation apparatus using a multicapillary X-ray lens is widely used to irradiate a minute region on a sample with high efficiency. ing.
As disclosed in Patent Document 1 and the like, a multicapillary is formed by bundling a large number of capillaries (several hundreds to 1,000,000) made of glass or the like having a small diameter of about 2 to several tens μm. X-rays that enter the inside of one capillary and use the principle that X-rays travel while totally reflecting the inner wall surface of the glass at an angle less than the critical angle. It is an element that guides the line efficiently. Usually, in a multi-capillary X-ray lens, each capillary is formed so that the central axis of a large number of capillaries intersects at one point at a predetermined position outside the end face on one or both of the entrance-side end face and the exit-side end face. It is a point focus end face. Thereby, in a multicapillary X-ray lens, X-rays emitted from a minute X-ray source that can be regarded as almost a point are captured with a large solid angle, or conversely, bundled X-rays guided through each capillary. Can be emitted so as to be focused at approximately one point.

However, the X-ray irradiation diameter that can be realized in an X-ray irradiation apparatus that combines the above-described multicapillary X-ray lens and an X-ray source that is a point light source is about several tens of μm at most.
The reason is clear. That is, as described in Patent Document 2 and the like, in a general multi-capillary X-ray lens, X-rays travel while being totally reflected on the inner wall surface of one capillary. When the line is emitted, the X-ray spreads with an opening angle that maximizes the critical angle with respect to the central axis of the capillary. Therefore, the irradiation region of the X-rays emitted from the point focal end face of the multicapillary X-ray lens is not an ideal point and has a predetermined size. That is, a fundamental defocusing occurs. Ideally, the intensity does not decrease when the X-rays are totally reflected, but actually the intensity is attenuated little by little every time the X-rays are totally reflected in the capillary. Therefore, the intensity of X-rays finally emitted from the exit end face of the multi-capillary X-ray lens is considerably lower than the intensity of X-rays incident on the lens.

  Patent Document 2 discloses an X-ray irradiation apparatus for focusing X-rays emitted from a point focal end face of a multicapillary X-ray lens and converged to some extent with a Fresnel zone plate. Patent Document 3 discloses an X-ray irradiation apparatus in which a Fresnel zone plate is disposed outside a parallel end face in which very small diameter capillaries formed by narrowing the middle of a multicapillary X-ray lens into a bottleneck shape. Is disclosed. Thus, according to the combination of the multi-capillary X-ray lens and the Fresnel zone plate, in principle, the X-ray irradiation diameter can be considerably reduced compared to the multi-capillary X-ray lens alone. However, the former requires a special Fresnel zone plate in which the shielding region and the passage region are each formed in a conical circumferential shape in the thickness direction of the plate, and the latter requires a special-shaped multicapillary X-ray lens. Is required. All of these are difficult to manufacture, and even if they can be manufactured, the cost is considerably high. Further, in order to reduce the X-ray irradiation diameter, it is necessary to arrange the multicapillary X-ray lens and the Fresnel zone plate with high accuracy, which increases the cost of assembly.

  On the other hand, increasing the intensity of X-rays emitted from an X-ray source is effective for increasing the intensity of X-rays irradiated on a sample, but the X-ray intensity is high and can be obtained at a relatively low cost. The X-ray source is a surface light source having a light emitting surface size of about several mm □. This is because the smaller the size of the light source, the greater the influence of thermal damage on the target, making it difficult to inject a large current. Therefore, instead of the X-ray source that is a point light source, an X-ray source 50 that is a surface light source as shown in FIG. 7 is used, and the end face on the incident side is not a point focus end face but a parallel end face in which capillaries are bundled in parallel. By using the capillary X-ray lens 51 or the multicapillary X-ray lens 52 whose incident side end surface is a long focal end surface, X-rays emitted from the surface light source 50 can be collected efficiently. However, even in that case, since the intensity of the X-rays is unavoidably attenuated while passing through the capillaries of the multicapillary X-ray lens as described above, the intensity of the X-rays irradiated to the sample is considerably reduced. End up.

  When a surface light source is used, as shown in FIG. 8, an aperture member 61 having a very small diameter aperture hole is disposed at a position separated from the surface light source 60 by a predetermined distance. A configuration for irradiating a line is also possible. Assuming that the size of the surface light source 60 is 1 mm, the distance L1 between the surface light source 60 and the aperture member 61 is 200 mm, and the distance L2 between the aperture member 61 and the sample surface 62 is 20 mm, the simple calculation calculates the diameter of the aperture hole. Is close to zero, the size d1 of the X-ray irradiation region on the sample surface 62 is 100 μm. In addition, a blur of at least about several tens of μm occurs on the exit side of the minute aperture hole due to scattering and diffraction of incident X-rays. On the other hand, since the aperture member 61 needs to completely shield X-rays, it is necessary to use a heavy metal such as Mo or Cu and ensure a certain thickness, for example, about 1 mm. It is difficult to make a hole of several tens μm or less in such a member. Therefore, with such a configuration, it is substantially difficult to make the size of the X-ray irradiation region several tens μm or less.

Japanese Examined Patent Publication No. 7-11600 JP 2007-93316 A JP 2010-276423 A

Yoshida, Soejima, “Development and application of microscopic Mossbauer spectrometer”, Surface Science Society of Japan, Surface Science, Vol. 31, No. 5, 2010, pp. 255-260

  In recent years, there has been a strong demand for elemental analysis, compositional analysis, or surface analysis in a very small area (for example, several μm or less). The above-mentioned limitation in the X-ray irradiation apparatus, that is, there is no X-ray irradiation apparatus that can reduce the X-ray to a very small diameter and obtain a large gain at a low cost. .

  The present invention has been made to solve these problems. The object of the present invention is to irradiate a sample with high-intensity X-rays with a very small diameter at a relatively low cost. It is providing the X-ray irradiation apparatus which can be performed.

The present invention made to solve the above problems is an X-ray irradiation apparatus for irradiating an irradiation object with X-rays focused on a small diameter,
a) an X-ray source which is a surface light source;
b) A large number of X-ray guiding thin tubes whose central axes are straight and whose inner diameter gradually decreases from the incident side end surface to the output side end surface are bundled in a substantially truncated cone or substantially truncated pyramid shape. A multi-capillary arranged so that the incident side end face faces the X-ray source;
And irradiating an object to be irradiated arranged at a predetermined distance from the emission side end face of the multicapillary with X-rays.

  In the X-ray irradiation apparatus according to the present invention, preferably, in the multicapillary, straight lines passing between the incident side end face and the emission side end face of each X-ray guiding capillary tube are gathered at substantially one point outside the emission side end face. It is preferable that the configuration and the arrangement of a large number of X-ray guiding narrow tubes are determined.

  As described above, in the multicapillary X-ray lens in which the end surface is generally a point-focus end surface as described above, the wall surface of the narrow tube located not around the bundled central portion but around it is curved in the X-ray traveling direction. The incident X-ray is always reflected at least once (usually many times) by the inner wall surface of the thin tube. On the other hand, in the X-ray irradiation apparatus according to the present invention, the inner wall of each thin tube constituting the multicapillary is linear in the direction of the central axis from the incident side end surface to the output side end surface and does not have a curved portion. For this reason, at least a part of the X-rays incident on each thin tube completely parallel to the central axis of the thin tube and at least a part of the X-rays incident with an inclination of a predetermined angle or less with respect to the central axis are However, it does not hit the inner wall of the narrow tube, that is, does not reflect, and reaches the emission side end face and emits. As described above, the intensity of X-rays that are not reflected by the inner wall of the narrow tube, that is, directly pass through the narrow tube, is hardly attenuated. Therefore, although the area of X-rays that pass directly through the inside of a single thin tube and radiate the irradiated object is very small, the X-ray intensity is irradiated with X-rays that are repeatedly reflected. It is considerably higher than the part.

  The X-ray intensity increases in accordance with the number of overlaps in the portions where X-rays that pass directly through the narrow tubes and are emitted from the end face on the emission side are overlapped. For example, in the above preferred configuration, the X-rays that have passed through the narrow tubes constituting the multicapillary in a straight line, that is, directly, are collected at a substantially single point, that is, overlapped with a very narrow region. Compared with the X-ray irradiation apparatus using the multicapillary X-ray lens, sufficiently high intensity X-rays can be obtained.

  In addition to the X-rays that have passed directly through the narrow tubes, X-rays that have repeatedly reflected from the inner walls of the thin tubes are also emitted from the emission side end face of each thin tube, and the irradiation region of the X-rays is directly irradiated by the X-rays. Widely outside the region. Although the X-ray intensity in this region is considerably smaller than the region irradiated by direct X-rays, X-rays are not irradiated to a very narrow region, but rather a certain wide region is irradiated for more sensitive analysis and observation. In the case where it is desired to perform this, the irradiation region by this reflected X-ray can be sufficiently utilized.

  According to the X-ray irradiation apparatus according to the present invention, high-intensity X-rays can be intensively irradiated onto a very small region as compared with the conventional X-ray irradiation apparatus. Accordingly, for example, by using the X-ray irradiation apparatus according to the present invention for various X-ray analysis apparatuses, it becomes possible to perform analysis or observation with high spatial resolution and high sensitivity and accuracy that cannot be realized conventionally. . In addition, since the multicapillary used in the X-ray irradiation apparatus according to the present invention is basically a bundle of a large number of straight tubes, it is compared with a conventional point-focus type multicapillary X-ray lens. However, manufacturing is easy and mass production is also easy. Therefore, the X-ray irradiation apparatus according to the present invention can be realized at a low cost.

Further, for example, in a microscopic Mossbauer spectrometer described in Non-Patent Document 1, a very small region of about several tens of μm or less is irradiated with γ-rays with a very narrow energy width (about 10 ⁻⁹ eV). There is a demand for an X-ray irradiation apparatus capable of performing the above. In the X-ray irradiation apparatus using the above-described conventional multi-capillary X-ray lens, not only is it difficult to narrow the X-ray irradiation diameter to a very small size, but the energy width is reduced while the X-ray repeats total reflection. The S / N ratio of the Mossbauer spectrum becomes very bad. On the other hand, according to the X-ray irradiation apparatus according to the present invention, since there is no rounding of the energy width due to the total reflection of the X-rays in the capillaries (capillaries), X-rays (γ rays) with a very narrow energy width are sampled. It is also suitable for a microscopic Mossbauer spectrometer.

The schematic block diagram of the X-ray irradiation apparatus which is one Example of this invention. FIG. 2 is a schematic configuration diagram illustrating a multi-capillary structure and an X-ray path inside each capillary in FIG. 1. The figure which shows the irradiation area | region by the X-ray which passed through one capillary. The figure which shows X-ray intensity distribution in a X-ray irradiation area | region. The figure which shows the X-ray image obtained by the experimental apparatus based on the X-ray irradiation apparatus of a present Example. The figure which shows the measurement result (a) of the X-ray intensity distribution of the X-ray image by the said experimental apparatus, and the measurement result (b) of the X-ray intensity distribution of the X-ray image by a conventional apparatus. The schematic block diagram of the conventional X-ray irradiation apparatus which combined the surface light source and the multicapillary X-ray lens. The schematic block diagram of the conventional X-ray irradiation apparatus which combined the surface light source and the simple aperture_diaphragm | restriction.

  Hereinafter, an embodiment of an X-ray irradiation apparatus according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram of an X-ray irradiation apparatus according to the present embodiment, and FIG. 2 is a schematic configuration diagram illustrating a multi-capillary structure and an X-ray path inside each capillary in FIG.

  The X-ray irradiation apparatus of the present embodiment includes an X-ray source 1 having a light emitting surface that extends two-dimensionally in the X-axis-Y-axis direction among the three axes (X, Y, Z) shown in FIG. A multi-capillary X-ray lens 2 having an incident-side end face 2a that is substantially flat facing the flat light-emitting surface of the X-ray source 1, and a predetermined distance from the emission-side end face 2b of the multi-capillary X-ray lens 2 The focused X-ray is irradiated on the surface of the sample 3 placed at a distant position.

  The multicapillary X-ray lens 2 has a substantially truncated cone shape as a whole. The central axis of the substantially truncated cone-shaped body extends in the Z-axis direction, that is, the direction perpendicular to the light emitting surface of the X-ray source 1, and the sample 3 is placed on the extension. As shown in FIG. 2, the multicapillary X-ray lens 2 has a linear central axis, and the inner diameter gradually decreases from the incident side end surface 20a toward the output side end surface 20b, for example, a capillary made of borosilicate glass. (Thin tube) 20 is an aggregate. That is, each capillary 20 is basically a straight tube, but is a straight tube formed in a tapered shape corresponding to the distance from the central axis of the multicapillary X-ray lens 2. The number of capillaries 20 is much larger than that shown in FIG. 2, for example, about several hundred to one million.

  Further, since each capillary 20 is a straight tube, there is always a straight line extending from the incident side end face 20a to the emission side end face 20b at the central axis of each capillary 20 or other than that. In the multi-capillary X-ray lens 2, the shape and arrangement of each capillary 20 are determined so that the straight line of each capillary 20 passes through one point (focal point F) outside the emission side end face 20b. As shown in FIG. 2, the distance between the emission side end face 2 b of the multicapillary X-ray lens 2 and the sample 3 is usually determined so that the focal point F is positioned on the surface 3 a of the sample 3.

  From each point on the light emitting surface of the X-ray source 1, X-rays with substantially uniform intensity within a predetermined solid angle range centered on the Z axis direction as well as the Z axis direction (direction orthogonal to the light emitting surface). Is released. Therefore, as shown in FIG. 2, the X-rays emitted from the X-ray source 1 are incident on the capillaries 20 at any position of the multicapillary X-ray lens 2, and a part thereof is the inner wall of the capillaries 20. The light passes through the capillary 20 without hitting and exits from the exit-side end face 20b. In this way, the direct X-rays that have passed through the inner wall of each capillary 20 without being reflected once are hardly attenuated and overlap each other at the position of the focal point F while maintaining their respective intensities.

  FIG. 3 is a diagram showing an irradiation region by X-rays that have passed through one capillary 20. However, in this figure, the capillary 20 is shown as a simple straight pipe having a constant inner diameter. In the drawing, the X-rays indicated by the alternate long and short dash line are direct X-rays that do not hit the inner wall of the capillary 20, and the region Fa irradiated with the direct X-rays emitted from the capillary 20 is very narrow. On the other hand, as indicated by a dotted line in the figure, for example, X-rays incident on the central axis of the capillary 20 with an angle larger than the direct X-ray (but with an angle smaller than a predetermined angle) are capillary The light strikes the inner wall 20 at least once and travels while being totally reflected, and is directly emitted from the capillary 20 while being broadened more than X-rays. Therefore, the region Fb irradiated with this X-ray spreads around the region Fa.

  In the X-ray irradiation apparatus according to the present embodiment, the area Fa by the direct X-rays emitted from the capillaries 20 overlaps on the surface 3a of the sample 3 so that a minute area having a high X-ray intensity is formed. In addition, an area having a considerably lower X-ray intensity than the area Fa is formed around the area by overlapping the area Fb of X-rays emitted after being reflected at each capillary 20 at least once.

  FIG. 4 is a diagram showing the X-ray intensity distribution in the X-ray irradiation region by the X-ray irradiation apparatus of the present embodiment. In the figure, a curve indicated by a dotted line is an intensity distribution by an X-ray irradiation apparatus using a conventional multicapillary X-ray lens, and a curve indicated by a solid line is a direct X-ray (non-reflective X-ray) in the X-ray irradiation apparatus of the present embodiment. ), And the curve indicated by the alternate long and short dash line is the intensity distribution by total reflection X-rays in the X-ray irradiation apparatus of the present embodiment. In a conventional X-ray irradiation apparatus using a multi-capillary X-ray lens, all irradiated X-rays are totally reflected many times on the inner wall of the capillary, and the region Fa in FIG. It only exists. Basically, the X-ray intensity distribution in this region Fb has a Gaussian distribution shape. On the other hand, in the X-ray irradiation apparatus of the present embodiment, since the direct X-ray hits the narrow area Fa intensively, the peak width of the direct X-ray intensity distribution is larger than the peak width of the X-ray intensity distribution in the conventional apparatus. It is quite narrow and its peak height is significantly higher. That is, the X-ray irradiation apparatus of the present embodiment can irradiate high-intensity X-rays in a narrow range as compared with the conventional apparatus.

  Since the critical angle for total reflection depends on the wavelength of X-rays, the irradiation region of the total reflection X-rays on the surface 3a of the sample 3 placed a fixed distance away from the emission side end face of the multicapillary X-ray lens 2 is used. The size depends on the wavelength of the X-ray. The same applies to the size of the X-ray irradiation area in the conventional apparatus. On the other hand, since the size of the irradiation region by direct X-rays is independent of the total reflection critical angle, the minimum value of this size does not depend on the wavelength of X-rays, and is mainly the structure of the multicapillary X-ray lens 2, that is, It is determined by the inner diameter of each capillary 20 (the inner diameter of the incident side end face 20a and the outgoing side end face 20b), the length, and the like. Therefore, it is possible to miniaturize the high-intensity X-ray irradiation region by improving the accuracy in manufacturing the multicapillary X-ray lens.

The inventor manufactured an experimental apparatus based on the X-ray irradiation apparatus of the above-described embodiment and confirmed the X-ray convergence effect. In this experimental apparatus, a multicapillary X-ray lens having a total length of 17 mm, an outer diameter of the incident side end face of 3.5 mm, an outer diameter of the exit side end face of 2.3 mm, and a focal length of about 35 mm was used.
FIG. 5 is a view showing an X-ray image obtained by the experimental apparatus. FIG. 6A is a diagram showing a measurement result of the X-ray intensity distribution of the X-ray image shown in FIG. 5, and FIG. 6B is an X-ray image obtained by an apparatus using a conventional multicapillary X-ray lens. It is a figure which shows the measurement result of X-ray intensity distribution.

As shown in FIG. 5, in the X-ray image obtained by this experimental apparatus, an area having a remarkable difference in brightness may be spread around a very bright center, that is, a portion having a high X-ray intensity. I understand. As can be seen from a comparison between FIG. 6A and FIG. 6B, a remarkable peak-shaped X-ray intensity distribution appears narrow and high in this experimental apparatus. On the other hand, in the conventional apparatus, a Gaussian X-ray intensity distribution appears with a wide skirt and a low height. From this result, it can be confirmed that the X-ray is irradiated with high intensity in a narrower region in the experimental device than in the conventional device.
In the experimental apparatus, the size of the X-ray irradiation region where high X-ray intensity can be obtained is not sufficiently limited due to the limitations of the specifications of the used multi-capillary X-ray lens. It is clear that the high-intensity X-ray irradiation region can be miniaturized by improving the accuracy in manufacturing the lens.

The above-described embodiment is an example of the present invention, and it is a matter of course that the present invention is encompassed by the scope of the claims of the present application even if appropriate modifications, corrections or additions are made within the scope of the present invention.
For example, an X-ray source that is a surface light source may not be a surface light source in a strict sense, and may be a surface light source having, for example, a certain uneven surface, curved surface, or inclined surface. Further, X-rays emitted while spreading from a point light source (a small X-ray source that can be regarded as a point light source) are irradiated to a thin film such as Al or Mo, and the X-rays generated from the thin film are used as outgoing X-rays. A pseudo surface light source may be used.

DESCRIPTION OF SYMBOLS 1 ... X-ray source 2 ... Multicapillary X-ray lens 2a ... Incident side end surface 2b ... Output side end surface 20 ... Capillary 20a ... Incident side end surface 20b ... Output side end surface 3 ... Sample 3a ... Surface

Claims (2)

An X-ray irradiation apparatus for irradiating an object with X-rays focused on a minute diameter,
a) an X-ray source which is a surface light source;
b) A large number of X-ray guiding thin tubes whose central axes are straight and whose inner diameter gradually decreases from the incident side end surface to the output side end surface are bundled in a substantially truncated cone or substantially truncated pyramid shape. A multi-capillary arranged so that the incident side end face faces the X-ray source;
And an X-ray irradiation apparatus for irradiating an irradiation object disposed at a predetermined distance from the emission side end face of the multicapillary. The X-ray irradiation apparatus according to claim 1,
In the multicapillary, the shape and arrangement of a large number of capillaries are determined such that straight lines passing between the incident side end face and the exit side end face of each narrow tube are gathered at substantially one point outside the exit side end face. X-ray irradiation apparatus.