JPH0153416B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an analysis method for performing elemental analysis using radiation such as X-rays and γ-rays.

There are cases where it is necessary to know the distribution state of a specific element in an arbitrary cross section of a plate, rod, or block-like test specimen. For example, the distribution of Zn, K, etc. in carbon bricks at the bottom of a blast furnace that have deteriorated due to use provides a powerful clue to elucidating the deterioration mechanism. Furthermore, the distribution of Mn, S, etc. in continuous slabs is useful for analyzing the formation of central segregation zones.

By knowing the distribution of specific elements in several cross sections, it is possible to further obtain the three-dimensional distribution of elements in the test specimen, and it is possible to proceed with the above-mentioned analysis more effectively.

Conventionally, it has been difficult to obtain the three-dimensional distribution of elements as described above. For any cross section, the specimen can be sliced into thin slices for analysis. However, depending on the material of the test piece, it may be brittle and difficult to slice, or the cut surface may break or change in quality during slicing, making it impossible to preserve the internal state of the test piece as it is. Therefore, it is desirable to know the elemental distribution in any cross section of such test specimens in a non-destructive manner.

This invention was made to solve the above-mentioned problems in general radiation analysis methods, and provides a radiation analysis method that can obtain the distribution of specific elements in any cross section of a specimen in a non-destructive and non-contact manner. This is what I am trying to do.

This invention is applicable to X-ray transmission computer tomography (often used for medical purposes) and fluorescent X-ray
Applying line analysis technology. That is, in the first invention, first, a radiation source that emits a narrow radiation beam and an X
The test specimen is placed between the test specimen and the radiation detector so that the radiation beam passes through the required test cross section of the specimen.
As a radiation source, an X-ray generator or a gamma-ray source is suitable. In the case of an X-ray generator, the tube voltage is about 100 to several hundred KV. The radiation from the source is constricted using a diaphragm device, such as a lead plate with pinholes, to reduce the beam diameter to a few millimeters or less. As the X-ray detector, a proportional counter, a scintillation counter, a semiconductor radiation detector, etc. are used. In order to increase spatial resolution, semiconductor detectors with a diameter of several mm or less, e.g.
It is preferable to use CdWO ₄ (cadmium tungstate), BGO (beryllium germanium oxide), or the like. The distances between the radiation source and the test object and between the test object and the X-ray detector are approximately several to several tens of centimeters, respectively, depending on the size of the test object.

Next, the radiation source and the X-ray detector are linearly moved together to scan the test section with the radiation beam, and the fluorescence X-ray intensity at a position along the scanning direction is selectively measured for the specific wavelength. To detect. Then, the fluorescent X-ray intensity of the specific wavelength at each of the positions is stored in the computer together with the position. Through this scanning, the specimen is cut by a line connecting the radiation source and the X-ray detector at the position where elemental analysis is to be performed. Fluorescence X of a specific wavelength
To selectively detect lines, a multichannel analyzer or spectrometer is used.

When fluorescence X-ray detection of a specific wavelength in one scanning direction is completed as described above, the radiation source and
The radiation detector is rotated around the specimen to change the direction of scanning by the radiation beam. Then, the scanning,
The detection of the fluorescent X-ray intensity of a particular wavelength along the scanning direction and the storage of the detected fluorescent X-ray intensity in the computer are repeated at least three times. Then, the fluorescence X-ray intensity of the specific wavelength at each position is calculated and synthesized by the computer, and the distribution of elements corresponding to the fluorescence X-rays of the specific wavelength in the test cross section is determined.

In the second invention, a radiation source that emits radiation that spreads over the entire surface of the test cross section of the test object and a plurality of X-ray detectors that are arranged along an arc centered on the radiation source and facing the radiation source. In the center between
Place the specimen so that the radiation passes through the required test cross section. The radiation source, the X-ray detector, the distance between the radiation source and the specimen, the distance between the specimen and the X-ray detector, etc. are the same as in the first invention. The spread of the radiation beam is fan-shaped or conical. A fan shape is preferable from the point of view of spatial resolution and radiation protection. The number of X-ray detectors arranged ranges from several to several hundred.

Following the above operations, the fluorescence X-ray intensity is detected, stored in the computer, the X-ray detection direction is changed, these operations are repeated, and the fluorescence X-ray intensity of a specific wavelength at each position is calculated and synthesized by the computer. In the same way as the invention of
The distribution of the element corresponding to the line in the test section is determined.

In the third invention, a plurality of X-ray detectors are arranged along a circumference that includes a radiation source that emits radiation that spreads over the entire surface of the test cross section of the test object, and the test object is placed at the center of the circumference. Place it on. The radiation source, the X-ray detector, the distance between the radiation source and the specimen, the distance between the specimen and the X-ray detector, etc. are the same as in the first invention. The spread of the radiation beam is fan-shaped or conical. A fan shape is preferable from the point of view of spatial resolution and radiation protection. The number of X-ray detectors arranged is about several tens to several hundreds.

Following the above operations, the fluorescence X-ray intensity is detected, stored in the computer, the X-ray detection direction is changed, these operations are repeated, and the fluorescence X-ray intensity of a specific wavelength at each position is calculated and synthesized by the computer. In the same way as the invention of
The distribution of the element corresponding to the line in the test section is determined.

As described above, in the radiation analysis method of the present invention, the distribution of a specific element can be determined in any cross section of the specimen in a non-destructive and non-contact manner. Therefore,
Even with materials that are difficult to slice as described above, quantitative analysis can be performed on the required cross section. Moreover, if the distribution of elements is obtained for a plurality of cross sections, it is also possible to obtain a three-dimensional distribution of the elements.

In the present invention, either a wavelength dispersion method or an energy dispersion method may be used to detect fluorescent X-rays of a specific wavelength. Moreover, the number of elements to be detected may be one or two or more. Furthermore, the distribution of a specific element may be displayed graphically on an image reproducing device, or the distribution may be shown numerically and the numerical values printed out using a printer.

The present invention will be described in detail below, taking as an example a case where the distribution of Zn in a carbon brick is determined by an energy dispersion method using an X-ray source as a radiation source.

FIG. 1 is a schematic diagram showing a cross section 2 of a carbon brick 1 (refractory brick for the bottom of a blast furnace) being analyzed by the method of the present invention. As shown in the drawing, a narrow beam of X-rays 14 is emitted from the X-ray tube 12. An X-ray semiconductor detector 16 is arranged to face the X-ray tube 12 and detects the fluorescent X-ray beam 15.

To obtain the distribution of Zn on the cross section 2 of the brick 1, first, the beam 14 passes through the intended cross section 2, and the straight line 5 between the X-ray tube 12 and the detector 16 is
move as a unit along the During this movement, the detector 16 detects the fluorescent X-rays 15 emitted from the brick 1.

As shown in FIG.
6 is input. Multi-channel analyzer 2
2, a specific X-ray among the fluorescent X-rays detected by the detector 16 (in this example, specific X-rays of Zn)
The line Kα ₁ : 1.435 Å) is selected. Then, the intensity of the specific X-ray detected in this manner is stored in correspondence with the moving distance of the detector 16 from the scanning starting point 6 shown in FIG. That is, the buffer memory 26 stores the intensity distribution of the fluorescent X-rays 15 along the scanning direction.

The intensity stored in the buffer memory 26 is processed in a central processing unit (CPU) 27 so as to be back-projected onto the cross section 2 of the brick 1. For example, the detected intensity I as shown in Figure 3a is
It is uniformly distributed on the cross section 2 in a direction perpendicular to the scanning direction S in proportion to the intensity I. The distributed values represent the shading of the image when it is played back, and are displayed on a CRT, for example, in 16 levels of gray scale.

When the first scan of the cross section 2 is completed as described above, the pair of radiation irradiation device 11 and detector 16 is rotated around the brick 1 in the extended plane of the cross section 2, and the X-ray beam 15 is change direction 1
Perform the same scan as the second time. By repeating the above operations, back projection images as shown in Figure 3 a, b, c, etc. are obtained in sequence. These back-projected images are superimposed by arithmetic processing in the CPU 27 and stored in the main memory 28. Image B superimposed as shown in Figure 4
represents the concentration corresponding to the amount of Zn in part A shown in FIG. A clear distribution cannot be obtained unless the number of scans is at least three times or more. In this example, scanning was performed 12 times by sequentially changing the scanning direction by 15 degrees.

For example, an image is composed of 512 x 512 pixels,
Each pixel is displayed in 16 gray scales as described above. The main memory 28 stores pixels corresponding to respective addresses in a two-dimensional arrangement. Note that as shown in FIG. 4, image blur occurs around image B, but this can be removed by performing filtering processing on the detected intensity by calculation in the CPU 27. The size of one pixel is, for example, 1 mm×1 mm.

The image stored in the main memory 28 is read out by a reading device 29.
is read out by the digital-to-analog converter 3
1 is converted to an analog signal. The analog signal is input to the CRT 35 via the amplifier 32, and an image showing the distribution of Zn in the cross section 2 of the brick 1 is displayed.

Arithmetic processing in the computer 27 is executed according to a program read from the program store 30.

In the above embodiment, the multi-channel analyzer 2
2, the distribution of specific elements is determined by electrically spectroscopy of fluorescent X-rays. However, in the present invention, as described above, a wavelength dispersion method in which fluorescent X-rays are optically dispersed can also be applied.

As shown in FIG.
It is diffracted at . The spectroscopic crystal 18 and the detector 19 are arranged so as to detect the characteristic X-rays of the element to be analyzed. That is, the angle between the spectroscopic crystal 18 and the detector 19 is set so that only the X-rays satisfying the Bragg condition are effectively diffracted and reach the detector 19. As the detector 19, a proportional counter or a scintillation counter is used.

The signal from the detector 19 is input to a pulse height analyzer 24 via an amplifier 21, where noise signals such as high-order X-rays are removed. The signal from the pulse height analyzer 24 has the drawback of being inferior to the analog-to-digital converter 25', which is useful for thin and light elements. Gamma rays are also practical, but require strict radiation control. Furthermore, if the energy of the generated fluorescent X-rays is weak, it may be absorbed within the test body and measurement may take a long time, so care must be taken.

In addition, when displaying the distribution of multiple elements as an image,
It is convenient to display each element in a different color. Furthermore, in the case of image display, the element amounts are displayed with a width based on the gray scale. The exact value of the elemental content is displayed numerically. In order to ensure accurate and highly accurate analysis of the target element, it is desirable to calibrate using a standard sample whose analytical value is known, as is done in normal analytical techniques.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram illustrating radiation irradiation and detection in this invention, and FIG. 2 is a block diagram of an apparatus for carrying out the method of this invention using an energy dispersion method.
FIG. 3 is an explanatory diagram of the back projection method of images, and FIG. 4 is a diagram explaining the principle of image formation by the back projection method.
The data is input to the computer 25 via the . The subsequent signal processing is the same as in the case of the energy dispersion method.
FIG. 6 explains another method of scanning the cross section of the test specimen 1. In FIG. 1, one detector 16 corresponds to the X-ray tube 12, forming a pair. On the other hand, the sixth
In FIG. 1A, a plurality of detectors 37 are combined with the X-ray tube 12 to scan the specimen 1. This scanning method can reduce the number of scans. In FIG. 6B, a large number of detectors 38 are arranged in an arc shape facing the X-ray tube 12. The X-ray tube 12 and the detector 38 rotate around the specimen 1 as a pair. In FIG. 6C, a large number of detectors 39 are arranged around the entire circumference of the test object 1. In this case, the detector 39 is fixed;
Only the X-ray tube 12 is rotated around the specimen 1. All of these methods allow the test specimen 1 to be scanned at high speed. Note that the radiation mentioned in the present invention refers to X-rays, γ-rays, β-rays, and neutron beams. X
The transmission line is the most practical and convenient to use, but when the specimen is thick or made of an element with a high atomic number, transmission Figure 5 shows an apparatus for carrying out the method of this invention using the wavelength dispersion method. and FIG. 6 are diagrams explaining a method of scanning a cross section of a test specimen. 1... Test specimen, 12... X-ray, 16, 19, 3
7, 38, 39... X-ray detection section, 17... Slit, 18... Spectroscopic crystal, 22... Multi-channel analyzer, 24... Pulse height analyzer, 25... Computer, 35... Image display device.

Claims (1)

[Scope of Claims] 1. A method for elemental analysis of a specimen by irradiating the specimen with radiation and detecting the intensity of the fluorescent X-rays of a specific wavelength among the fluorescent X-rays emitted from the specimen, A test specimen is placed between a radiation source that emits a narrow radiation beam and an X-ray detector placed opposite the radiation source so that the radiation beam passes through a required test cross section of the specimen, moving the radiation source and the X-ray detector together linearly to scan the test section with a radiation beam;
The fluorescence X-ray intensity at positions along the scanning direction is selectively detected for the specific wavelength, the fluorescence X-ray intensity of the specific wavelength at each position is stored in a computer together with the position, and the radiation source and A radiation detector is rotated around the specimen to change the scanning direction of the radiation beam, and the scanning direction detects the fluorescent X-ray intensity of a specific wavelength along the scanning direction and transmits the detected fluorescent X-ray intensity to a computer. Memorization is repeated at least three times, and the fluorescent X-ray intensity of the specific wavelength at each position is calculated and synthesized by the computer, and the distribution of elements corresponding to the fluorescent X-rays of the specific wavelength in the test cross section is determined. Radiological analysis method. 2. In a method for elemental analysis of a test specimen by irradiating the specimen with radiation and detecting the intensity of the fluorescent X-rays emitted from the specimen at a specific wavelength, A radiation source that emits radiation that spreads over the entire surface and a plurality of X-ray detectors that are arranged along an arc centered on the radiation source to face the radiation source, the radiation spreads across the required test cross section. The specimen is placed so as to pass through the test cross section, and each X-ray detector selectively detects the fluorescent X-ray intensity at a position along the direction transverse to the test cross section, and The fluorescence X-ray intensity of the wavelength is stored in a computer along with its position, and the radiation source and a plurality of X-ray detectors are rotated as a unit around the test object to change the X-ray detection direction and cross the test section. Detecting the fluorescence X-ray intensity of a specific wavelength along the direction and storing the detected fluorescence X-ray intensity in a computer is repeated at least three times, and the fluorescence X-ray intensity of the specific wavelength at each position is calculated by the computer. A radiation analysis method characterized by synthesizing and determining the distribution of elements corresponding to fluorescent X-rays of a specific wavelength in the test cross section. 3. In a method for elemental analysis of a test specimen by irradiating the specimen with radiation and detecting the intensity of the fluorescent X-rays emitted from the specimen at a specific wavelength, A plurality of X-ray detectors are arranged along a circumference that includes a radiation source that emits radiation that spreads over the entire surface, a test specimen is placed at the center of the circumference, and a direction that crosses the test cross section is arranged. The fluorescent X-ray intensity at a position along the specific wavelength is selectively detected by each X-ray detector, and the fluorescent X-ray intensity of the specific wavelength at each position is detected.
The line intensity is stored in a computer along with its position, and the radiation source is moved along the circumference to change the fluorescent X-ray detection direction, and the fluorescent X-ray intensity of a particular wavelength along the transverse direction of the test surface is determined. Detection and storage of the detected fluorescence X-ray intensity in a computer are repeated at least three times, and the fluorescence X-ray intensity of the specific wavelength at each position is calculated and synthesized in the computer to correspond to the fluorescence X-ray of the specific wavelength. A radiation analysis method characterized by determining the distribution of elements in the test cross section.