JP4492507B2 - X-ray focusing device - Google Patents

Description

  The present invention relates to an X-ray analyzer, an XRD, and an X-ray that perform analysis using X-rays, such as an electron probe microanalyzer (EPMA), a scanning electron microscope (SEM), a transmission electron microscope, and a fluorescent X-ray analyzer. The present invention relates to an X-ray focusing apparatus used for focusing X-rays in a CT, an X-ray apparatus or the like.

  The electron beam probe microanalyzer (EPMA) irradiates a sample with an electron beam with a small diameter having high energy as an excitation ray, and thereby the intrinsic electron emitted to the outside when the inner electrons of the components contained in the sample are excited. By analyzing X-rays (characteristic X-rays), elements are identified and quantified, and the distribution of elements is examined. In addition, the scanning electron microscope (SEM) generally detects secondary electrons and reflected electrons generated from the irradiation position of the electron beam, but recently, an X-ray analysis is performed by adding an energy dispersive X-ray detector. A device that enables this is also being developed.

  In order to collect and collimate X-rays in this type of X-ray analyzer, a kind of X-ray focusing device called a multi-capillary (sometimes called polycapillary) X-ray lens has been known. (See Patent Documents 1 and 2, etc.). FIG. 6 is a diagram showing an example of a multi-capillary X-ray lens, and FIG. 7 is a principle diagram of X-ray transmission in the multi-capillary X-ray lens.

  A multi-capillary X-ray lens has a basic structure in which a large number of capillaries (about several hundred to one million) made of borosilicate glass having a small diameter of, for example, an inner diameter of about 2 to about 10 μm are bundled. As shown in FIG. 7, by using the principle that X-rays incident on the inside of one capillary 22 travel while totally reflecting the inner peripheral surface of the glass wall at an angle less than the critical angle, X-rays are guided efficiently. Even if the capillary 22 is linear as shown in FIG. 7A or the capillary 22 is curved as shown in FIG. 7B, X-rays can be guided in the same manner.

  There are various forms of multicapillary X-ray lenses. For example, the multicapillary X-ray lens 20 shown in FIG. 6A has a large solid angle at the incident side end face for X-rays emitted from an X-ray source that can be regarded as almost a point. Thus, it is a point / point type that focuses and collects X-rays emitted from the opposite emission side end face at one point. Similarly, the multicapillary X-ray lens 21 shown in FIG. 6B takes out X-rays emitted from substantially one point on the incident side end face with a large solid angle, and then emits a parallel beam from the emission side end face. Or it is a point / parallel type as the reverse path. By using such a multicapillary X-ray lens, it is possible to efficiently collect excitation X-rays generated by the X-ray source without using a powerful X-ray source such as synchrotron radiation (SR light). The sample can be irradiated with a reduced irradiation area.

  As described above, the multicapillary X-ray lens can collect and guide X-rays with high efficiency, but sufficient performance is not necessarily obtained in terms of reducing the area to which the collected X-rays are irradiated. The main reason for this is that the principle defocusing occurs in the multicapillary X-ray lens. That is, as shown in FIG. 8, X-rays travel while totally reflecting the inner wall surface of one capillary 22, but the maximum reflection angle is a critical angle. Therefore, when X-rays are emitted from the capillary 22, the X-rays may spread with an opening angle of the critical angle θ with respect to the optical axis (center axis of the capillary 22) S. As a result, as shown in FIG. 9, the irradiation region of the X-rays emitted from the end surface on the point focal point side of the multicapillary X-ray lens 21 is not an ideal point, but a region 23 having a certain size. End up.

  Even when only the optical axis of each capillary is considered as having no light spread after exiting the capillaries as described above, all of the enormous number of capillaries are limited due to the manufacturing limitations of the multicapillary X-ray lens. Since it is actually impossible to make the optical axis of the lens completely converge to one point, there is a defocusing due to such factors. Due to both theoretically unavoidable factors and factors due to manufacturing limitations, the minimum focal size of a conventional multicapillary X-ray lens is limited to about 20 to 30 μm at most. Was difficult.

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

  The present invention has been made to solve the above-mentioned problems, and its object is not only to collect X-rays efficiently, but also to reduce the focal spot size without greatly reducing the X-ray intensity. It is to provide an X-ray focusing apparatus capable of

  As described above, the multicapillary X-ray lens is a very effective element for efficiently collecting X-rays and narrowing down to a certain diameter. Accordingly, the present inventor has come up with a combination of a Fresnel zone plate (FZP) and a multicapillary X-ray lens, which are particularly excellent in X-ray aperture characteristics, utilizing such characteristics of the multicapillary X-ray lens.

Ie, X-ray focusing device according to the present invention comprises a plurality of capillary X-ray guiding bundled in the same direction as both end faces are formed, at least one end, the optical axis direction from the end face Of the narrow tube assembly which is a focusing end for irradiating X-rays intensively to a minute region which is a point focal point on the optical axis, and the end surface of the focusing end of the thin tube assembly and the focusing end It is characterized by comprising a condensing lens by one Fresnel zone plate arranged so that the optical axis of the focusing end coincides with the optical axis at the focal point .

  As is well known, the Fresnel zone plate is a lens that uses Newton's ring diffraction and interference. By increasing the processing accuracy, the aperture diameter can be made very small, but it is difficult to make the size itself large and light. The solid angle for taking in (X-rays) is small. However, as described above, in the multicapillary X-ray lens, even if it is difficult to reduce the X-ray to a very small diameter, it is easy to reduce the X-ray below the size of the Fresnel zone plate (for example, about 1 mm or less). The disadvantages of the Fresnel zone plate as described above do not matter. That is, the combination of the multi-capillary X-ray lens and the Fresnel zone plate is an excellent combination that makes use of the advantages of both and conversely compensates the defects.

  Therefore, according to the X-ray focusing apparatus according to the present invention, for example, X-ray intensity emitted by an X-ray source can be efficiently collected to increase the X-ray intensity and irradiate it to a very small area intensively. it can. Thereby, for example, even if the same X-ray source is used, the X-ray intensity per unit area in the X-ray irradiation region can be considerably increased as compared with the conventional case, and the interaction between the substance existing in the minute region and X-rays can be achieved. Information by (transmission, reflection, absorption, etc.) can be detected with high sensitivity and accuracy. Alternatively, the X-ray intensity of the X-ray source can be reduced by that amount, and a small and inexpensive X-ray source can be used.

  Hereinafter, an embodiment of an X-ray focusing apparatus according to the present invention will be described with reference to FIGS.

  FIG. 1 is a configuration diagram of a main part of the X-ray focusing apparatus of the present embodiment, FIG. 2 is an optical path configuration diagram showing a light condensing operation by a multilayer Fresnel zone plate as an example of a Fresnel zone plate, and FIG. FIG. 4 is a schematic configuration diagram of an X-ray inspection apparatus which is an application example of the X-ray focusing apparatus of this embodiment, and FIG. 5 explains the effect of the X-ray focusing apparatus of this embodiment. FIG.

  As shown in FIG. 4, in the X-ray inspection apparatus using the X-ray focusing apparatus 1 of this embodiment, the X-ray focusing apparatus 1 is interposed between the X-ray source 12 and the inspection object 11 moving on the production line 10. The primary X-rays emitted from the X-ray source 12 are efficiently irradiated to the inspection object 11 with a very small diameter by the X-ray focusing apparatus 1. In response, secondary X-rays emitted from the inspection object 11 are detected by the X-ray detector 13, and information (for example, an image) of the X-ray irradiation site on the inspection object 11 is obtained according to the detection signal. It is done. Of course, a multicapillary X-ray lens or the like may be provided on the detection side.

  As shown in FIG. 1, the X-ray focusing apparatus 1 according to this embodiment has a focusing end 2a having a point focal point that can be regarded as one point when one end portion does not consider the spread of light after exiting from each capillary. And an X-ray lens formed of a multilayer Fresnel zone plate outside the focusing end 2a of a point / parallel type multicapillary X-ray lens (capillary tube assembly in the present invention) 2 whose other end is a parallel end 2b. (Hereinafter referred to as an FZP lens) 3 is provided. Both so that the optical axis of the converging end 2a of the multicapillary X-ray lens 2 (which can be considered as the optical axis of a capillary located at the center of a bundle of many capillaries) matches the optical axis of the FZP lens 3. Is arranged. For example, the FZP lens 3 has an outer diameter of 1 mm, and the multicapillary X-ray lens 2 has a configuration in which the condensing diameter of the converging end 2a is less than 1 mm. In the multicapillary X-ray lens 2, it is very easy to reduce the light collection diameter to such a size.

  As is well known, the FZP lens 3 is a type of transmissive diffraction grating in which a substance that allows X-rays to pass through and a substance that blocks the X-ray are alternately arranged concentrically around the center optical axis. As shown in FIG. 3, the X-rays that are incident in parallel (see (a)), focused (see (b)), or spread (see (c)) are each focused on a certain point F. Have. The size and focal length of the focal point can be arbitrarily determined depending on the type of substance constituting the FZP lens 3 and the interval of the annular zone pattern, but since it also depends on the wavelength of the X-ray passing therethrough, It may be determined appropriately in consideration of the wavelength band of the line.

  In the configuration of the X-ray focusing apparatus 1 of the present embodiment, for example, as shown in FIG. 4, X-rays emitted from the X-ray source 12 are efficiently taken into each capillary from, for example, the parallel end 2b of the multicapillary X-ray lens 2. , The inside of each capillary is guided to the focusing end 2a while being totally reflected. The X-rays emitted from the capillaries at the focusing end 2a are focused as a whole and hit the small-diameter FZP lens 3. At this time, in detail, theoretically, the X-rays emitted from the capillaries are solid angles obtained by rotating a line indicating the angle formed by the critical angle θ about the optical axis S as shown in FIG. May extend to However, since the X-rays to be expanded in this way are focused when passing through the FZP lens 3 as shown in FIG. 3, the X-ray emitted from each capillary is a very small area that can be regarded as almost one point. 4 will be passed. Of course, as described above, there are not only theoretical defocusing but also defocusing factors due to manufacturing limitations of the multicapillary X-ray lens, but the influence is also reduced.

  The above operations and effects can be easily understood with reference to FIG. FIG. 5 is a graph in which the abscissa indicates the width of the irradiated X-ray and the ordinate indicates the X-ray photon number (that is, the X-ray intensity), and the area of the region surrounded by the curve as shown in FIG. Represents the total X-ray photon number. That is, the Fresnel zone plate is not disposed outside the converging end 2a of the multicapillary X-ray lens 2, that is, in the conventional configuration, as shown in FIG. However, the spread of the irradiated X-ray is relatively large (at least about 20 to 30 μm), but the X-ray emitted from the converging end 2a is hardly lost, so that a large amount of X-ray can be irradiated. On the other hand, with the Fresnel zone plate alone, as shown by B in the figure, the spread of irradiated X-rays can be made extremely small, but the total X-ray photon number of irradiation is small because of less light intake.

  On the other hand, in the configuration in which the multi-capillary X-ray lens and the Fresnel zone plate are combined as in the present invention, the collected X-rays can be efficiently focused with a small size, and as shown in C in the figure. Become. That is, the irradiation X-rays can be reduced as compared with the conventional case, and the total number of irradiation X-ray photons is increased, so that both high spatial resolution and high sensitivity can be achieved.

  That is, according to the X-ray focusing apparatus of the present embodiment, X-rays are efficiently collected by the multi-capillary X-ray lens 2, and the condensed diameter thereof is reduced to some extent and introduced into the small-diameter FZP lens 3 without waste. X-rays can be further narrowed down by the FZP lens 3 to irradiate, for example, a very small region 4 on the inspection object 11. When X-rays pass through the FZP lens 3, a part of the X-rays are absorbed or scattered and attenuated. However, the degree of attenuation is small compared to the degree of the X-ray aperture and can be substantially ignored. It is. As described above, according to the X-ray focusing apparatus according to the present embodiment, even if the intensity of the X-ray generated by the X-ray source is not so high, it is possible to irradiate a very small region with a high intensity X-ray. .

  It should be noted that the above embodiment is 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 scope of the claims of the present application.

The block diagram of the principal part of the X-ray focusing apparatus which is one Example of this invention. The optical path block diagram which shows the condensing operation | movement by a multilayer film Fresnel zone plate single-piece | unit. FIG. 2 is an optical path configuration diagram in the vicinity of a focusing end in FIG. 1. The schematic block diagram of the X-ray inspection apparatus which is an application example of the X-ray focusing apparatus of a present Example. The figure for demonstrating the effect of the X-ray focusing apparatus of a present Example. The figure which shows the example of a form of the conventionally known multicapillary X-ray lens. The principle figure of transmission of X-rays in a multicapillary X-ray lens. The figure for demonstrating the problem of the conventional multicapillary X-ray lens. The figure for demonstrating the problem of the conventional multicapillary X-ray lens.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... X-ray focusing apparatus 2 ... Multicapillary X-ray lens 2a ... Converging end 2b ... Parallel end 3 ... Multilayer Fresnel zone plate (FZP) X-ray lens

Claims (1)

Consists of a number of tubules X-ray guidance in bundled in the same direction as both end faces are formed, at least one end, at the focal point on the optical axis in the outside of the optical axis direction from the end face A tubule assembly serving as a focusing end for irradiating X-rays intensively to a minute region;
A condensing lens composed of one Fresnel zone plate arranged so that the optical axis of the converging end coincides with the optical axis between the end face of the converging end of the capillary tube assembly and the point focus formed by the converging end; ,
An X-ray focusing apparatus comprising:

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