RU2790574C1 - X-ray filter - Google Patents

Abstract

FIELD: X-ray technology.

SUBSTANCE: invention relates to the technique of X-ray methods of introscopy of objects, in particular to X-ray filters, and is intended for filtering radiation when determining the properties of multiphase flows, and is aimed at expanding the spectral measurement range and improving the accuracy of measuring X-ray radiation. An X-ray filter is a filter material made of two pairs of metals having different absorption coefficients, while each pair of metals has the same absorption coefficients above the edge of the absorption band of the heavier of them.

EFFECT: increase in the accuracy of determining the composition of the object under study due to the possibility, as a result of filtering, to obtain an image of the object under study simultaneously in two narrow-band radiation spectra, and since the two received radiation spectra do not intersect in energy, they do not interfere with each other.

1 cl, 11 dwg

Description

The invention relates to the technique of x-ray methods of introscopy of objects, in particular, to x-ray filters and is intended for filtering radiation during procedures for determining the properties of multiphase flows flowing in a pipe, flaw detection or other studies that use ionizing radiation to obtain various images of the object under study. The invention can be used with radiation from x-ray tubes or gamma radiation from isotope sources.

Known x-ray filter containing two foils made from different chemical elements, and the thickness of the foil of a lighter element is such that its absorption coincides with the absorption of the second type of foil beyond the K-absorption edge [Ed. certificate SU No. 934329, class. 23/20, publ. 07.06.82].

The disadvantage of this type of filter is that the possibilities of its application are limited only to obtaining a single selected X-ray line several keV wide, located below the K-absorption edge of a heavier filter element. Also, its use is limited to use in conjunction with two separate detectors.

Known x-ray filter that covers half of the pixels of the detector in a checkerboard pattern or in the form of parallel slats [Patent RU No. 2694331, cl. A61B 6/03, G21K 1/00, G01T 1/16, publ. July 11, 2019].

This filter is fixed at the end of the flat-panel X-ray detector, it absorbs the low-energy component of the X-ray spectrum and covers half of the detector pixels in a checkerboard pattern or by means of parallel lamellae, half of the detector pixels register radiation that did not interact with the filter and forms the first group of pixels. The other half of the detector pixels registers the radiation that has passed through the filter and forms the second group of pixels. This provides the condition for detecting radiation, when the combination of four adjacent pixels consists of two pixels of the first group, which register radiation that does not interact with the filter and represents the full spectrum of X-ray radiation, and two pixels of the second group, which register radiation that has passed through the filter and represents a high-energy component of the X-ray spectrum, when processing data in each of the groups of pixels, the signals are added, the signal of the second group of pixels is subtracted from the first one, and information is obtained about the low-energy component of the X-ray spectrum obtained for four pixels of the first and second groups, which is related to the average coordinate of these pixels at receiving a tomogram.

The disadvantage of this filter is that the possibilities of its application are limited only by the removal of the low-energy component of the emission spectrum. In addition, its use is limited to use with a flat panel detector for cone beam tomography.

Closest to the claimed object is an X-ray filter, which is made of two types of filter materials having different absorption coefficients and arranged in a checkerboard pattern so that each filter cell is above its own pixel of the matrix detector [Patent RU No. 2659763, cl. G01F 1/708, G01N 23/12, publ. 07/03/2018].

The disadvantage of this filter is that both filter materials absorb only the low-energy part of the spectrum of radiation that has passed through its materials. Even taking into account the fact that the absorption coefficient of a material with a high atomic number has a “dip” in the low-energy region, the radiation transmitted through this material is not narrow-band and has a significant intensity in the high-energy region, which, when solving the system of Bouguer-Lambert-Beer equations in the analysis of the composition of the object under study will adversely affect the accuracy.

The invention is aimed at expanding the range of spectral measurements and improving the accuracy of X-ray measurement by obtaining two different narrow-band radiation spectra.

This is achieved by the fact that in the X-ray filter, including filter materials made of metals, according to the invention, the filter materials are made of two pairs of metals having different absorption coefficients, while each pair of metals has the same absorption coefficients above the edge of the absorption band of the heavier of them.

Pairs of filter media can be arranged in any sequence depending on the requirements for its application.

For example, pairs of materials may be arranged in stripes, or staggered, or pixel-by-block aggregation may be used.

This makes it possible, as a result of filtering, to obtain an image of the object under study simultaneously in two narrow-band emission spectra. Since the two obtained radiation spectra do not intersect in energy, they do not mutually influence each other, thereby increasing the accuracy of determining the composition of the object under study.

In FIG. 1 schematically shows the proposed X-ray filter with two pairs of filter materials in blocks of four pixels,

in fig. 2 is a section along A-A in Fig. 1,

in fig. 3 is a section along B-B in FIG. 1,

in fig. 4 - filter with two pairs of filter materials arranged in strips,

in fig. 5 is a section along A-A in FIG. 5,

in fig. 6 - filter with a staggered arrangement of two pairs of filter materials,

in fig. 7 is a section along A-A in FIG. 6,

in fig. 8 is a section along B-B in FIG. 6,

where 1 and 2 are materials that form the first passband, for example, tin and copper, 3 and 4 are materials that form the second passband, for example, tungsten and gold, 5 is a pixel of a multi-pixel detection device or a single detector;

in fig. 9 shows a device for analyzing the flow of a multi-phase fluid, which uses the proposed x-ray filter,

where 6 is a source of ionizing radiation - an x-ray tube or a radioisotope source, 7 is an object of study, for example, a pipe with a multiphase liquid flow, 8 is an x-ray filter (filter sections corresponding to two different narrow-band spectra are shown in black and white), installed in front of the detecting device , 9 - detection devices or pixels of one multi-pixel detection device, for example, a matrix detector;

in fig. 10 shows the absorption coefficients of filter materials, in particular tin, copper, tungsten and gold,

in fig. 11 shows the intensities of the obtained bandwidths for the first and second pair of filter materials.

The device works as follows:

The X-ray radiation of the source 6 passes through the object of study 7 and enters the X-ray filter 8. After the radiation passes through two pairs of filter materials 1-4 of the X-ray filter 8, an image is formed on the matrix X-ray detector 9 in the form of two well-separated narrow-band radiation lines.

Then the images are taken from the detecting device 9, processed by the analysis tool, and then, using mathematical algorithms, the composition of the multiphase fluid flow is determined by solving the well-known system of Bouguer-Lambert-Beer equations.

For example, two pairs of materials with different absorption coefficients are chosen: one pair of materials consists of tin and copper to highlight the band in the low-energy part of the spectrum, the other of tungsten and gold to highlight the high-energy transmission band. Each pair of metals has the same absorption coefficients above the edge of the absorption band of the heavier one, in particular, for a pair of materials consisting of tin and copper, the absorption coefficients are 15-30 keV, and for a pair of materials consisting of tungsten and gold, from 67 to 72 keV (see Fig. 10). When radiation passes through these two pairs of filtering materials, one pair of filtering materials forms an image in the form of the first transmission band - in the range from 15 to 30 keV, and the other pair of filtering materials - in the form of a second transmission band in the range from 67 to 72 keV (see Fig. Fig. 11).

The filter can be made from two other pairs of filter materials having different absorption coefficients of radiation, and matching absorption coefficients above the edge of the absorption band of the heavier of them for each pair of metals. In this case, an element with a lower atomic number, used as the first filter material, absorbs all radiation in the selected energy range and below it. The element with a higher atomic number used as the second filter material has a K-edge of the absorption band in the selected area, below which its absorption coefficient decreases sharply and the material partially transmits radiation. If we choose the thickness of two materials so that their absorption coefficients above the K-edge of the absorption band coincide, then subtracting from the spectrum obtained after the passage of the filter material with a higher atomic number the spectrum after the material with a lower atomic number, we get the emission spectrum of the required energy band.

The proposed X-ray filter will ensure the selection of two X-ray lines and will allow using only radiation of the corresponding energy range (high-energy or low-energy) when solving each of the equations of the Bouguer-Lambert-Beer system of equations. Accordingly, the influence of low-energy radiation on the solution of the equation for high-energy radiation is minimized.

Thus, the use of the proposed X-ray filter provides, as a result of filtering, the simultaneous obtaining of a high-quality image of the object under study in two different radiation spectra: both the low-energy part of the spectrum and the high-energy part of the spectrum, which indicates the expansion of the region of spectral measurements and leads to an increase in the accuracy of measuring the parameters of the multiphase flow. liquids.

Claims (1)

X-ray filter, including filter materials made of metals, characterized in that the filter materials are made of two pairs of metals having different absorption coefficients, while each pair of metals has the same absorption coefficients above the edge of the absorption band of the heavier of them.

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