JPS61256243A - Monochromatic x-ray tomographic apparatus - Google Patents

Abstract

PURPOSE:To obtain the titled tomographic apparatus having high resolving power, constituted so that a monocrystal element is arranged behind an object to be examined and X-rays diffracted by a monocrystal are detected to be formed into an image in the same side as X-rays incident to the surface of the monocrystal. CONSTITUTION:The titled tomographic apparatus is constituted of a slit 5 for determining the shape of parallel X-rays 1 made monochromatic by a proper technique and that of X-rays incident to an object to be examined, a rotatable and scanning possible stage 6 supporting the object to be examined, a slit 8 removing scattered X-rays from the object to be examined, a monocrystal 3 for enlarging an X-ray image, a slit 13 for permitting the transmission only of X-rays diffracted by the monocrystal, a position-sensitive type detector 11 arranged immediately after said slit 13 and a measuring/data processing system 12. By this constitution, the X-ray image can be arbitrarily enlarged according to a predetermined formula and the position resolving power inherently possessed by the detector 11 can be enhanced. Further, because only an extremely narrow wavelength region is diffracted from the aspect of the essence of an X-ray diffraction phenomena by the monocrystal, X-rays having a wavelength different from that of incident X-rays generated from the object to be examined can be removed.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a high-resolution X-ray tomography device using a monochromatic and parallel X-ray source, and in particular, it is used to measure the density, defects, and element distribution of an arbitrary cross section of industrial materials. The present invention relates to an X-ray tomography apparatus suitable for obtaining high spatial resolution.

[Background of the invention]

Generally, X-ray tomography (X-CT: X-ray C
om -puterized 'l'omograph
y) is widely used in the medical field as a diagnostic device for living organisms (human bodies).

Since this method enables non-destructive observation of the inside of a specimen, its application to detecting internal defects in industrial materials has recently attracted attention. However, there are the following problems when applying the conventional tomography apparatus for human body to internal observation of industrial materials. Firstly, conventional equipment uses a white X-ray source and uses the average absorption value of X-rays of various energies for image formation, so even if the defect (vacancy) distribution is obtained, it is not accurate. Density distribution and elemental distribution cannot be obtained.

However, for industrial materials, it is important to obtain not only so-called defect distribution information but also density and element distribution information.

The second problem is that the spatial resolution of images is φ0.
The diameter is about 2 m to φ0.5 m, which is insufficient for internal observation of industrial materials.

To address the first of the above problems, a nine tomography method has been proposed that uses a powerful X-ray source, such as synchrotron radiation, and monochromates it with a crystal spectrometer or the like, and then uses an fc X-ray source (Reference; , drodzins , Nue fearI
instruments and methods 20
6 ('83) p 547.

p541). If this method is used, the first problem will be solved. However, there is a second problem that needs to be solved at the same time, that is, a method for improving resolution, which is related to the method of detecting the transmitted X-rays, but the above-mentioned document does not clarify anything regarding this point.

As an X-ray detection method that uses monochromatic X-rays as a light source and improves spatial resolution, monochromatic X-rays are detected using a slit, etc.
< It is easy to think of a method of detection using a Henkle shape, a thin-circle counter, a semiconductor detector, etc., but in this case, a new problem arises in that the time required for measurement becomes longer. It is also easy to consider a method of creating a monochromatic X-ray beam spread in a -dimensional sheet shape, inserting the subject into the beam, and installing a position-sensitive detector behind it, but in this case, the spatial resolution of the image is determined by the position resolution of the position-sensitive detector, and the current limit is about 0 to 0.2.

[Purpose of the invention]

An object of the present invention is to provide a monochromatic X-ray tomography apparatus that uses a monochromatic parallel X-ray source and a light source that are wide in the dimension and in the form of a solid sheet, and detects transmitted X-rays using a -dimensional array detector. and the position-sensitive detector so as to transmit the 7'f-X-rays through the subject and enlarge the X-ray image without damaging the intensity distribution (X-ray image) of the 7'f-X-rays to guide the position-sensitive X-rays to the detector. An object of the present invention is to provide a high-resolution monochromatic X-ray tomography apparatus.

[Summary of the invention]

That is, when X-rays of wavelength λG are incident on a single crystal, the Bragg condition 2d4sicθ et al.=λ. When the following is satisfied, diffraction occurs in the direction of the angle 2θB as shown in Figure 1, and when the direction of the diffracted X-rays is emitted on the same side of the crystal plane as the incident X-rays (Brgg (ase), It is a well-known fact that only X-rays with a certain small incident angle range and a small wavelength width are totally reflected.Here, do is the distance between the crystal lattice planes involved in the diffraction of the single crystal, θB is the angle between the incident X-ray and the crystal lattice plane.''Also, when the angle between the actual crystal surface and the crystal lattice plane that participates in diffraction is α, the horizontal angle of the diffracted X-ray is It is also known that the spread υS has the following relationship with the lateral spread So of the incident X-ray.

5-bSII (1
) The main point of the present invention is to utilize the above-mentioned X-ray diffraction phenomenon caused by the single crystal and apply it to a detection system of a tomography apparatus. That is, a 2-axis rotary goniometer (referred to as a θ-20 rotary goniometer) that can be adjusted in small angles is installed behind the subject, and a θ angle of 0.05° is formed on the θ rotary goniometer. A cut single crystal is installed, a position-sensitive detector is installed on a 20-turn goniometer, and only the secondary X-rays are detected by diffraction by the single crystal.

According to the present invention, if α is appropriately selected, the X-ray image can be enlarged arbitrarily according to equation (1), (■), and the positional resolution originally possessed by the position-sensitive detector is improved by a factor of b. I can do it. Furthermore, due to the nature of the X-ray diffraction phenomenon with a single crystal, only a very narrow wavelength region is diffracted, so X-rays that are different in wavelength from the incident X-rays generated from the object, such as fluorescent X-rays and inelastically scattered X-rays, are It can be removed and image quality can be expected to improve.

[Embodiments of the invention]

FIG. 1 shows an embodiment of the present invention. The device uses a parallel X-ray flux 1 that has been made monochromatic by an appropriate method, and the X-ray beam incident on the subject.
A slit 5 that determines the shape of the line, a rotation that supports the subject,
A stage 6 that can be scanned, a slit 8 that removes scattered X-rays from the subject, a single crystal 3 that magnifies the X-ray image, a slit 13 that transmits only the X-rays diffracted by the single crystal, and was installed immediately after the slit 13. It consists of a position sensitive detector and a measurement circuit system.

In this example, a monochromatic X-ray flux with a horizontal spread of 920 mm, a vertical spread of 5 mm, and a wavelength of 1 was obtained from a white X-ray source of synchrotron radiation using a channel/channel cut crystal spectrometer. The X-ray flux was limited to 6 x 0, 1 wg by the slit 2, and was irradiated to the subject. A Si single crystal is used as the crystal 3 for enlarging the X-ray image, and the crystal lattice plane 4 that causes diffraction is selected as (220).
The angle α between the lattice plane and the actual crystal surface was set to 10.2°.

In addition, for the position-sensitive detector 11, a photodiode array coated with a phosphor and having an element spacing of 25 μm and a height of 25 μm and 1024 elements was used. At this time, the X-ray flux with a horizontal spread of 96 degrees, which passes through the object and has an intensity distribution that depends on the absorption coefficient of X-rays at the wavelength of the object, is the (220
) is diffracted and expanded into an X-ray flux with a lateral spread of approximately 30 m, and the intensity distribution is detected by a detector. In other words, the nine X-ray flux that passes through the object is expanded by about 6 times by the crystal, and it is expected that the spatial resolution will be improved by about 6 times compared to the resolution inherent to the photodiode array detector. What is diffracted by the mirror crystal is only those in a very narrow wavelength region centered on one wavelength, making it possible to obtain a truly monochromatic X-ray image, and also improving the S.

The other embodiments have basically the same configuration as the first embodiment, but
Mechanism 14 for vibrating the enlarging crystal element parallel to the crystal surface
is added. The intensity of X-rays diffracted by a crystal is completely influenced by the surface condition of the crystal. That is, if a small scratch exists on the crystal surface, a structure due to the scratch will occur in the intensity distribution of the diffracted X-ray flux, and will be detected as being overlapped with the intensity distribution to be measured generated by the object, causing an error. In this example, the width of the vibration of the magnifying crystal was set to be five times or more the distance between the detector elements, and the period of vibration was set to be 115 times or less than the IX-ray image measurement time. According to this method, X-rays incident on one detection element are diffracted from an area five times or more larger than the detection element, which has the effect of averaging out differences in crystal surface conditions depending on location.

〔Effect of the invention〕

According to the present invention, tomographic images using monochromatic X-rays can be taken with high resolution, making it possible to non-destructively measure the accurate density distribution of arbitrary cross sections in industrial materials, and using wavelengths around the absorption edge of the elements. Processing between tomograms enables non-destructive acquisition of elemental distributions with high spatial resolution.

[Brief explanation of the drawing]

FIG. 1 is a principle diagram showing the diffraction of X-rays by a crystal, and FIG. 2 is a basic configuration diagram of a monochromatic X-ray tomography apparatus showing the direction in which X-rays travel according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Monochromated X-ray flux, 2... Diffracted X-ray flux, 3... Single crystal element, 4... Crystal lattice plane in single crystal, 6... Rotation for supporting the object , Run ■ Stage, 7...
・Subject, 9...Rotary stage for crystal element, 10...
- Detector rotation stage, 11...Position sensitive detector, 12...Measurement and data processing system, 14...Crystal element vibration table.

Claims (1)

[Claims] 1. A monochromatic X-ray tomography device having an X-ray spectrometer that extracts any wavelength from parallel white X-rays, a sample stage that can scan and rotate a subject, and a position detector for X-ray detection. A monochromatic X-ray characterized in that a single crystal element is installed behind the subject, and X-rays diffracted by the crystal are detected and imaged on the same side of the crystal surface as the incident X-rays. Tomography device. 2. A monochromatic X-ray tomography apparatus according to claim 1, characterized in that diffracted X-rays from the crystal are detected while the crystal element is vibrated parallel to the crystal surface.