JP2005321246A - Poly-capillary lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problems wherein an X-ray having an angle not below the critical angle on a reflecting surface in the middle of passage is generated in a conventional poly-capillary lens, to thereby lower a passage efficiency, and outgoing light passing through an optical path different from an essential lens action acts as an interfering line. <P>SOLUTION: The bending shape of each capillary 2 is formed so that the radius of curvature at the incident end face is minimum, and that the radius of curvature is equal or becomes larger gradually toward the outgoing end face. Hereby, an X-ray entering the capillary 2 through the incident end face and totally-reflected once by the internal surface is guaranteed to have the incident angle below the critical angle to the internal surface until reaching the outgoing end face, to thereby repeat surely total reflection. Though a part of the X-ray hitting onto the internal surface at an incident angle exceeding the critical angle is not totally reflected but transmitted near the incident end face, since the outgoing end face is far, the part is absorbed in the middle of transmission through the inner wall or absorbed by hitting onto a housing 4 and does not reach the outgoing end face. Hereby, the passage efficiency of the X-ray is heightened, and the convergence efficiency is also heightened. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention, for example, in an analyzer such as an electron probe microanalyzer, a scanning electron microscope, a transmission electron microscope, or a fluorescent X-ray analyzer, focuses radiation of very short wavelengths such as X-rays and neutrons or in parallel. The present invention relates to a polycapillary lens that is used to make a lens.

  2. Description of the Related Art Conventionally, there are various analyzers that use X-rays mainly for performing surface analysis of a sample. For example, in an electron beam probe microanalyzer (EPMA), a specific X-ray emitted to the outside when an electron beam having a high energy is irradiated as an excitation beam to the sample and the inner electrons of the components contained in the sample are thereby excited. By analyzing the above, the element is identified and quantified, and the distribution of the element is examined. On the other hand, a fluorescent X-ray analyzer irradiates a sample with primary X-rays as excitation rays, and thereby analyzes intrinsic X-rays (fluorescent X-rays) emitted from the sample in the same manner as EPMA.

  In such an X-ray analyzer, in recent years, an X-ray lens called a polycapillary lens has been used to collect and collimate X-rays. 7 and 8 are schematic configuration diagrams of a conventionally known polycapillary lens described in, for example, Patent Documents 1 and 2, and FIG. 6 is an X-ray passing through one capillary 2 constituting the polycapillary lens. It is a figure which shows the state to do typically. The polycapillary lens 1 has a basic structure in which a large number of thin tubes (capillaries) made of borosilicate glass are bundled, and is held by a housing case 4 made of metal or the like provided to cover the outside. As shown in FIG. 6, the X-rays incident on the inside of one capillary 2 strike the inner peripheral surface of the glass inner wall 3 and proceed while being totally reflected. With such a principle, X-rays can be guided efficiently.

  The polycapillary lens 1 shown in FIG. 7 takes in X-rays emitted from an X-ray emission source C1, which can be regarded as almost a point, at a large solid angle at the incident end face, and sets one point of X-rays emitted from the opposite emission end face. Focusing on C2. On the other hand, the polycapillary lens 1 shown in FIG. 8 similarly takes X-rays emitted from one point on the incident end face with a large solid angle, and then emits parallel light from the exit end face, or vice versa. To do.

As shown in FIG. 6 (a), in order for X-rays to be totally reflected inside the capillary 2, X-rays are formed at an angle smaller than a critical angle (total reflection critical angle) θc that satisfies the following equation (1). Needs to enter the glass inner wall 3.
θc≈1.64 × 10 ⁻³ λ√ρ (1)
Here, ρ is the density of the capillary material, and λ is the wavelength of the incident X-ray.

  In the polycapillary lens 1 shown in FIGS. 7 and 8, the X-rays incident at the critical angle θc or less at the incident end face and totally reflected inside each capillary 2 then proceed to the exit end face while being repeatedly totally reflected, but in the middle If there is a bent portion where the radius of curvature of the capillary 2 is smaller than before, the incident angle of a part of the X-rays hitting the glass inner wall 3 at that portion may be larger than the critical angle θc. In that case, the X-rays that have not been totally reflected are absorbed or transmitted by the glass inner wall 3, and in any case, the ratio of the X-rays that reach the exit end face, that is, the effective X-ray transmission rate decreases. . In addition, when the X-ray transmitted through the glass inner wall 3 is not completely absorbed and reaches the exit end face, the optical path of the X-ray is different from the original focusing optical path of the lens. Instead of focusing on the desired focusing point C2 in FIG.

  As can be seen from the above equation (1), the critical angle θc is substantially proportional to the X-ray wavelength, so that the shorter the wavelength, that is, the higher the energy, the smaller the critical angle θc. The effect of absorption and permeation increases. Therefore, when the energy intensity distribution on the plane P including the converging point C2 outside the emission end face is measured in the configuration shown in FIG. 7, the focusing efficiency near the converging point C2 is low with low energy X-rays as shown in FIG. On the other hand, high energy X-rays have very poor focusing efficiency near the focusing point C2, and energy is dispersed over a wide range.

Japanese Examined Patent Publication No. 7-11600 Japanese Patent Publication No. 7-40080

  The present invention has been made to solve such a problem, and the object of the present invention is to achieve a high passing efficiency even for radiation such as X-rays having a particularly high energy, and the degree of energy concentration. It is to provide a polycapillary lens that can effectively use radiation by increasing the height.

The first invention made to solve the above-mentioned problem is composed of a plurality of bundled capillaries, and radiation of a very short wavelength such as X-rays and neutrons emitted from one point located outside the incident end face. In a polycapillary lens that guides to the exit end face while passing through each capillary and focuses it to one point located outside the exit end face or emits it as a parallel line,
Each capillary is characterized in that the radii of curvature at any two locations along the longitudinal direction are equal or larger at the exit end face side than at the entrance end face side.

  For example, when radiation emitted from a radiation source that can be regarded as one point or one point enters each capillary through the incident end face of the polycapillary lens according to the first invention, the radiation hits the inner wall surface of the capillary with an incident angle less than the critical angle. Is totally reflected and sent to the rear. In the polycapillary lens according to the first aspect of the invention, the radius of curvature of each capillary is the smallest at the incident end face, and becomes larger or at least equal from there toward the exit end face (that is, the radius of curvature is closer to the exit end face than the entrance end face). It is formed so as not to become smaller. Therefore, once the radiation totally reflected by the inner wall surface of the capillary is incident on the inner wall surface, the incident angle does not become larger than the previous incident angle, and is surely below the critical angle until reaching the exit end surface. The angle of incidence is guaranteed. Thereby, total reflection is repeated until it exits from the exit end face, and it is not absorbed or transmitted through the inner wall surface of the capillary.

  In addition, there is radiation that does not satisfy the total reflection condition when radiation that is emitted from a radiation source or arrives as an almost parallel light beam is incident on the incident end face of the polycapillary lens, and such radiation is absorbed by the inner wall surface of the capillary. Or permeate. However, since this is the part farthest from the exit end face, there are several layers of capillary walls before the transmitted radiation reaches the exit end face, and each layer receives absorption. Further, since the optical path of such transmitted radiation is completely different from the original direction of the optical path exiting from the exit end face, even if there is little absorption by the capillary wall surface, the housing that covers the outer periphery of the lens before reaching the exit end face There is a high possibility of hitting the case. Therefore, such undesired radiation hardly reaches the emission end face. Therefore, the spread of radiation outside the emission end face can also be suppressed.

  By the way, when the incident radiation which is parallel light is focused on one point through the polycapillary lens, the incident end portions of the capillaries are usually aligned and bundled in parallel. In this case, the radius of curvature of each capillary at the incident end is It is infinite. Therefore, in this case, the configuration of the polycapillary lens according to the first invention cannot be adopted. Therefore, in such a case, the following configuration of the second invention may be used to solve the above-described problem.

That is, the second invention is composed of a plurality of bundled capillaries, and emits radiation with a very short wavelength such as X-rays and neutrons emitted from one point located outside the incident end face or incident as parallel lines. In a polycapillary lens that guides to the exit end face while passing through each capillary and focuses it to one point located outside the exit end face or emits it as a parallel line,
Each capillary has a bent portion having a minimum radius of curvature in the entire range in the longitudinal direction, at a position close to the incident end surface, and extends along the longitudinal direction in the range between the bent portion and the exit end surface. It is characterized in that the radii of curvature at any two locations are the same or formed so as to be larger at the location on the exit end face side than at the location on the bent portion side.

  In the first invention, the radius of curvature of each capillary is minimum in the vicinity of the incident end face. In the polycapillary lens according to the second invention, for example, as described above, all the capillaries are bundled in parallel in the vicinity of the incident end face. For this reason, the radius of curvature cannot be reduced very close to the incident end face due to restrictions such as the need for a straight line. Even in such a case, a bent portion having a minimum radius of curvature is provided as close to the incident end face as possible, and the condition of the radius of curvature similar to that of the polycapillary lens according to the first invention is satisfied between the bent portion and the exit end face. Like that. Therefore, it is guaranteed that the radiation that has passed through the bent portion has an incident angle that is less than or equal to the critical angle until reaching the exit end face. Thereby, total reflection is repeated until it exits from the exit end face, and it is not absorbed or transmitted through the inner wall surface of the capillary.

  On the other hand, the incident angle below the critical angle may not be reached between the incident end surface and the bent portion, and the radiation that has not been totally reflected may pass through the capillary wall surface. However, even in that case, since transmission occurs at a position relatively close to the incident end face, there are many opportunities to receive the absorbed radiation before reaching the exit end face as described above, and it is possible to hit the housing case. High nature. Accordingly, it is possible to reduce the arrival of such undesired radiation to the emission end face, and it is effective for suppressing the spread of the radiation outside the emission end face. In view of these actions and effects, in the polycapillary lens according to the second invention, the position of the bent portion hits the inner wall surface at an angle larger than the critical angle between the incident end surface and the bent portion. It is preferable to set the position where it is guaranteed that the light that has been transmitted without being reflected by the light hits the inner wall of the housing case that covers the outer periphery of the lens.

  According to the polycapillary lens according to the first and second inventions, even high-energy radiation such as CdKα and SnKα is guided to the emission end face with high passing efficiency and is focused on one point outside the emission end face. Or can be emitted as parallel rays. Therefore, high energy X-rays can be analyzed with high sensitivity by using this polycapillary lens in an X-ray analyzer or the like. In addition, since the radiation coming out from the exit end face can be reduced by an optical path different from the focusing action of the original lens, the degree of energy concentration increases especially when condensing at one point, and a high lens effect can be obtained. it can.

  Hereinafter, a polycapillary lens according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 2 is an overall configuration diagram of a polycapillary lens according to an embodiment of the first invention, and FIG. 1 is a diagram showing one capillary 2 among them. The polycapillary lens of this embodiment takes in X-rays emitted from the point C1 located outside the incident end face with a large solid angle, and focuses the X-rays from the exit end face to a point C2 located outside thereof. is there. One capillary 2 is made of, for example, a cylindrical tube-shaped glass having an inner diameter of, for example, about several μm, as in the prior art, but its overall shape is different from this conventional polycapillary lens.

That is, as shown in FIG. 1, the capillary 2 at a position close to the outer peripheral side, ie, the housing case 4 covering the periphery, has a curved shape as a whole, but has a curvature radius Rin at the entrance end face and a curvature radius Rout at the exit end face. The relationship of the radius of curvature Rn at an arbitrary position between the incident end face and the exit end face is as follows.
Rin ≦ Rn ≦ Rout
Further, the relationship between the radii of curvature Rn1 and Rn2 at two arbitrary positions (where Rn1 is closer to the incident end face than Rn2) is as follows:
Rn1 ≦ Rn2
It is. That is, when viewed with a single capillary 2, the radius of curvature is minimal at the entrance end face, and the radius of curvature always increases monotonously (at least does not decrease) toward the exit end face.

  Since the capillary 2 has the shape as described above, the incident angle when the X-ray which is introduced into the capillary 2 through the incident end face and is totally reflected once by the inner wall surface of the glass next hits the inner wall surface of the capillary 2 is immediately before that. Is equal to or smaller than the incident angle at the time of reflection. The same is true regardless of how many times the total reflection is repeated, and the total reflection condition that all incident angles are equal to or smaller than the critical angle θc before the X-ray reaches the emission end face is satisfied. Therefore, ideally, X-rays that have been totally reflected once are not absorbed or transmitted by the glass wall surface in the course of passing through the capillary 2. Further, all the capillaries 2 constituting the lens 1 satisfy the same conditions as described above. As a result, the X-ray passage efficiency is very high and energy is almost conserved.

  On the other hand, since X-rays of various directions are incident on the incident end face of one capillary 2, in practice, only a part of the X-rays hitting the glass inner wall with an incident angle equal to or smaller than the critical angle θc, Other X-rays hit the glass inner wall at an incident angle exceeding the critical angle θc and enter the glass inner wall. This X-ray passes through the glass inner wall while being absorbed. However, as described above, such transmission occurs at a position very close to the incident end face because most of the transmission hits the inner wall of the glass only after entering from the incident end face. In other words, the position is very far from the emission end face, and it is necessary that the X-rays that have passed through the glass inner wall pass through the glass inner walls of many capillaries 2 before reaching the emission end face. X-rays are absorbed and reduced in intensity each time they pass through the glass inner wall. Even if X-rays reach the exit end face, the intensity of the X-rays is negligible by passing through many glass inner walls. It has dropped to.

  As can be seen from FIG. 2, most of the X-rays that take an optical path (trajectory) that passes through the glass inner wall of the capillary 2 in the vicinity of the incident end face come into contact with the housing case 4 that surrounds the periphery. Since the housing case 4 made of metal has a much larger absorption effect than the inner wall of the glass, it can be said that the probability that X-rays transmitted near the incident end face can reach the output end face is extremely low even from the viewpoint of such an optical path. Accordingly, substantially only the X-rays that have passed through the inside of each capillary 2 that is the original optical path of the polycapillary lens 1 are emitted from the emission end face and focused on the point C2.

  FIG. 3 is a diagram showing an energy intensity distribution on the surface P including the focal point C2 by the polycapillary lens of the present embodiment. The horizontal and vertical axes in FIG. 3 are the same as those in FIG. 9. As is apparent from comparison between the two, in this embodiment, the energy is very focused near the focusing point C2 by the original lens effect. It turns out that it is favorable. In particular, it can be seen that high-energy X-rays, in which energy was dispersed in a wide range in the past, can be well focused. Further, as the X-ray passing efficiency increases, the peak value of energy itself increases, and it can be seen that the lens effect is great also in this respect.

  In the above embodiment, focusing is performed from point to point. However, as shown in FIG. 4, a polycrystal that takes in X-rays emitted from the point C1 located outside the incident end face and emits parallel rays from the exit end face. The capillary lens 1 can also be configured based on the same principle as in the above embodiment.

  On the other hand, a polycapillary lens in which X-rays, which are parallel rays, are incident on the incident end face and is focused on a focusing point C2 located outside the exit end face requires deformation. FIG. 5 is an overall configuration diagram of a polycapillary lens 1 according to an embodiment of the second invention to which such a modification is added.

In this configuration, the capillaries 2 are arranged almost completely in parallel on the incident end face of the polycapillary lens in order to efficiently capture X-rays incident substantially in parallel. Therefore, since the radius of curvature of the capillary at the incident end face is infinite, the condition for setting the radius of curvature in the above embodiment cannot be satisfied. That is, there is always a position where Rin> Rn. Therefore, in this embodiment, the bent portion 5 having the smallest radius of curvature in the entire range along the longitudinal direction of the capillary 2 is provided as close to the incident end face as possible, and the bent portion 5 and the exit end face are arranged as much as possible. The setting condition of the radius of curvature in the above-described embodiment can be satisfied only in between. That is, the radius of curvature at the bent portion 5 is Rmin, and the radius of curvature at any two positions between the bent portion 5 and the emission end face is Rn1, Rn2 (where Rn1 is a bent portion rather than Rn2). (Close to 5)
Rmin ≦ Rout
Rn1 ≦ Rn2
To be satisfied.

  Therefore, in each capillary 2, between the bent part 5 and the exit end face, it is the same as the above embodiment, and the X-ray is guaranteed to be totally reflected. On the other hand, between the incident end face and the bent portion 5, there is a possibility that the incident angle of some X-rays does not go below the critical angle θc and passes through the glass inner wall of the capillary 2. However, by providing the bent portion 5 not at a position close to the exit end face but at a position close to the entrance end face, the X-rays transmitted as described above can reach the exit end face as described above until the glass inner walls of many capillaries. The energy is greatly attenuated by absorption. Further, the possibility of hitting the inner wall surface of the housing case 4 is increased. As a result, almost no X-rays are emitted from the exit end face through an undesired optical path other than the optical path of the original lens action, and a high energy focusing effect can be obtained in substantially the same manner as in the above embodiment.

  Each of the above embodiments is merely an example of the present invention, and it is obvious that any modification, correction, or addition as appropriate within the scope of the present invention is included in the claims of the present application.

1 is a schematic external view showing one capillary in a polycapillary lens according to one embodiment of the first invention. FIG. The whole block diagram of the polycapillary lens by one Example of 1st invention. The figure which shows the energy intensity distribution characteristic of the polycapillary lens of FIG. The whole block diagram of the polycapillary lens by other Example of 1st invention. The whole block diagram of the polycapillary lens by one Example of 2nd invention. The figure which shows typically the state through which X-ray | X_line passes within one capillary in a polycapillary lens. The whole figure of the example of composition of the conventional polycapillary lens. The whole figure of the example of composition of the conventional polycapillary lens. The figure which shows the energy intensity distribution characteristic of the polycapillary lens of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Polycapillary lens 2 ... Capillary 3 ... Glass inner wall 4 ... Housing 5 ... Bending part C1 ... X-ray emission source C2 ... Focusing point

Claims (2)

It is composed of a plurality of bundled capillaries, and guides very short wavelength radiation such as X-rays and neutrons emitted from one point located outside the entrance end face to the exit end face while passing through each capillary. In a polycapillary lens that converges to one point located outside the emission end face or emits as a parallel line,
Each capillary is formed such that the radii of curvature at any two locations along the longitudinal direction are equal or larger at the exit end face side than at the entrance end face side lens. It is composed of a plurality of bundled capillaries, and X-rays and neutron rays such as X-rays and neutrons that are emitted from one point located outside the incident end face or incident as parallel lines are passed through each capillary. In the polycapillary lens that guides to the exit end face and converges it to one point located outside the exit end face or emits it as a parallel line,
Each capillary has a bent portion having a minimum radius of curvature in the entire range in the longitudinal direction, at a position close to the incident end surface, and extends along the longitudinal direction in the range between the bent portion and the exit end surface. A polycapillary lens, characterized in that the curvature radii at any two locations are equal or larger at a location closer to the emission end face than a location closer to the bent portion.

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