RU2254566C2 - Small-angle introscopy method - Google Patents

Abstract

FIELD: radiation methods of testing.

SUBSTANCE: tested object is subject to illumination of narrow low-divergent beam of penetrating radiation and radiation passed through object is registered by means of coordinate-sensitive detectors. Structure of matters composing the object is identified from small-angle coherent dissipation of radiation passed through object. Distribution of radiation intensity across the beam is registered when object is present and absent correspondingly. Attenuation factor of penetrating radiation is determined for center of the beam by means of comparing intensities of incident beam and passed beam. Intensity distribution curve is normalized for incident radiation at the area of central peak of diffraction for angle of dissipation by attenuation factor and is subtracted from curve of distribution of radiation passed through the object.

EFFECT: higher quality of building of internal structure of object.

1 tbl, 1 dwg

Description

The invention relates to determining the structure and changing its state for inhomogeneous, weakly scattering, opaque to visible light objects with the help of transmitted and scattered at small angles of x-ray radiation.

The prior art is as follows.

A known method of recording radiation coherently scattered by an object (US 4751772, G 01 N 23/201, 1988), based on recording the spectrum of coherent scattered radiation at angles lying in the range from 1 to 12 ° with respect to the direction of the incident beam. The paper indicates that most of the elastically scattered radiation is concentrated in these angles if the energy of the x-ray radiation is not very large. The basis of this invention is the fact that the energy spectra of the elastically scattered radiation and the radiation of the primary beam are identical, and the elastically scattered radiation has a characteristic angular dependence, determined both by the irradiated substance itself and by the energy of the incident radiation. Since the distribution of the intensity of coherently scattered radiation at small angles depends on the molecular structure of the substance, various substances having the same absorption capacity (which cannot be distinguished by ordinary transillumination) can be distinguished from each other by the angular intensity distribution of coherently scattered characteristic for each substance radiation. In the said patent, it is proposed to use a narrow collimated beam of monochromatic or polychromatic radiation to illuminate the object. The intensity of coherently scattered radiation is measured using a detecting system with a resolution in both energy and coordinate (scattering angle).

The described method has a relatively low luminosity, since the coherent scattering cross section in this angular range is small and requires high doses of the object when it is studied.

The closest set of essential features is the method of small-angle introscopy (Russian patent No. 2137114, G 01 N 23/201, G 01 T 1/16, 1997). A method for determining the composition and structure of an inhomogeneous object includes irradiating a controlled object with a narrow, low-dispersing beam of penetrating radiation, registering radiation transmitted through the object, identifying substances entering the controlled object by small-angle coherent scattering of radiation transmitted through the object, and radiation absorbed in the object. In this case, the distribution of the radiation intensity is recorded over the beam cross section in the absence and presence of an object. The resulting intensity distributions are normalized to the total intensity of the incident and transmitted radiation, respectively. By changing the normalized spatial distribution of intensities and comparing it with the reference values previously obtained under the same conditions, the substances entering the object are identified.

It should be noted that the method described in the prototype for low-scattering objects does not allow to determine their internal structure and its subsequent changes. This primarily relates to colloidal systems that are opaque to visible light and objects dispersed in them, for example, oil media containing various additives.

The invention consists in the following.

The invention is aimed at solving the problem of obtaining an image of the internal structure of an object and determining its change during the course of certain processes.

The solution of the problem is mediated by a new technical result of recording small-angle scattering of penetrating radiation limited by the region of the central diffraction peak. The technical result of the proposed method is achieved through the following procedures. The controlled object is irradiated with a narrow, slightly diverging beam of penetrating radiation, the radiation transmitted through the object is recorded using a position-sensitive detector. The distribution of radiation intensity is recorded over the beam cross section in the absence and presence of an object. The received information is processed according to the following relationship:

where I _2θ is the intensity of the scattered x-ray radiation;

I _0,2θ , I _CR , _2θ , respectively, the intensity of x-ray radiation incident on the object and passed through it in the region of the central peak of diffraction;

To _{attenuated., O} is the attenuation coefficient of the x-ray beam;

2θ is the scattering angle between the center of the beam of penetrating radiation and the guides emanating from the center of the object and located within the beam section.

The attenuation coefficient (K _{atten., O} ) in equation (1) is determined:

where I _{0,2θ = 0,} I _{ol , 2θ = 0} , respectively, the intensity of the x-ray radiation incident on the object and passed through it for an angle of 2θ = 0.00 °.

Dependence (1) allows the scattering curves to be reduced relative to the angle 2θ = 0.00 °. In all cases, for each test substance, the intensity of the scattered x-ray radiation for an angle of 2θ = 0.00 ° is zero. This allows you to compare the scattering curves with each other.

The essential features common with the prototype are the following: irradiation of the controlled object with a narrow low-dispersing beam of penetrating radiation, registration of radiation transmitted through the object using a position-sensitive detector, and identification of the structure of the controlled object by small-angle coherent scattering of radiation transmitted through the object and radiation absorbed in the object, registration of distribution radiation intensity over the beam cross section in the absence and presence of an object.

The main distinguishing features of the claimed invention are:

- determination of the attenuation coefficient of penetrating radiation for the center of the beam through the ratio of the intensities of the incident incident on the object and radiation transmitted through it according to the equation

where I _{0,2θ = 0} , I _{ol , 2θ = 0} , respectively, the intensity of the x-ray radiation incident on the object and passed through it for an angle of 2θ = 0.00 °.

- normalization of the intensity distribution curve of the radiation incident on the object over the beam cross section (scattering angle) by the attenuation coefficient and its subtraction from the intensity distribution curve of the radiation transmitted through the object according to the equation

where I _2θ is the intensity of the scattered x-ray radiation;

I _0,2θ , I _CR , _2θ , respectively, the intensity of x-ray radiation incident on the object and passed through it in the region of the central peak of diffraction;

To _{attenuated., O} is the attenuation coefficient of the x-ray beam;

2θ is the scattering angle between the center of the beam of penetrating radiation and the guides emanating from the center of the object and located within the beam section.

After carrying out these procedures, a distribution curve of the x-ray scattered by the object is obtained, which characterizes its structure.

Information indicating the feasibility of the invention can be confirmed by the following examples.

Example 1

- излучения. В держатель образца, расположенный перпендикулярно падающему излучению, помещают пустую жидкостную кювету и с помощью позиционно-чувствительного детектора определяют интенсивность прошедшего излучения в области центрального пика дифракции для данного набора щелей (2θ=0-0,25°). Проводят 3-5 параллельных измерений для получения статистических сведений. После этого в кювету заливают образец масла-компаунда и проводят съемку в аналогичных условиях (3-5 параллельных измерений). Полученные экспериментальные данные обрабатывают по зависимостям (1) и (2). Результаты обработки представлены на чертеже (зависимость 1).Using two narrow slots (for example, 0.1 mm wide), a low-diverging x-ray beam is installed

- radiation. An empty liquid cuvette is placed in the sample holder located perpendicular to the incident radiation and the intensity of transmitted radiation in the region of the central diffraction peak for a given set of slits is determined using a position-sensitive detector (2θ = 0-0.25 °). 3-5 parallel measurements are carried out to obtain statistical information. After that, a sample of the compound oil is poured into the cuvette and shooting is carried out under similar conditions (3-5 parallel measurements). The obtained experimental data are processed according to dependencies (1) and (2). The processing results are presented in the drawing (dependence 1).

Example 2

An empty liquid cuvette is placed in the sample holder and, under the conditions of Example 1, the intensity of transmitted radiation is determined. Then, a sample of CPV additive opaque to visible light is poured into the cuvette. The conditions for shooting an additive sample and subsequent processing of experimental information are carried out in accordance with example 1. The calculation results are presented in the drawing (dependence 2).

Example 3

An empty liquid cuvette is placed in the sample holder and, under the conditions of Example 1, the intensity of transmitted radiation is determined. After that, a sample of KND additive was placed in a cuvette, previously diluted with 50 wt.% With compound oil (see Example 1) and kept for some time until measurements. The conditions for shooting a sample of a diluted additive and subsequent processing of experimental data is carried out in accordance with example 1. The processing results are shown in the drawing (dependence 3).

As follows from the drawing, the scattering curves are of a different nature, which is due to the different state of the structure of the studied samples (primarily from the point of view of their dispersion).

The normalization of the distribution curves of the intensity incident on the object (empty cuvette) and transmitted through the object of radiation (test sample) for examples 1, 2 and 3 according to the prototype. The normalization results are shown in the table.

Scattering angle 2θ, ° 0.00 0.05 0.10 0.15 0.20 0.25 Normalized
value, I _i / ΣI _i The object is absent (empty cell, examples 1, 2, 3) 0.33 0.30 0.24 0.11 0.02 0.00 Example 1 (oil compound) 0.33 0.30 0.24 0.11 0.02 0.00 Example 2 (commercial additive KND) 0.34 0.30 0.22 0.11 0,03 0.01 Example 3 (Additive KND, diluted in 50 wt.% Oil compound) 0.33 0.30 0.24 0.11 0,03 0.01

Designations in the table:

I _i - the intensity of the incident on the object (empty cell, examples 1, 2, 3) and radiation transmitted through it (test samples, examples 1, 2, 3), corresponding to a given scattering angle;

ΣI _i is the total intensity of either incident on the object (empty cell, examples 1, 2, 3), or radiation transmitted through it (test samples, examples 1, 2, 3), respectively.

As follows from the table, the normalized values of the intensity of radiation incident on the object (the object is absent, an empty cell) and different scattering angles practically coincide with the similar normalized values of the intensity of radiation transmitted through various objects (examples 1, 2, 3). This allows us to argue about the impossibility of identifying the internal structure of the studied objects according to the method of small-angle introscopy given in the prototype.

Thus, the proposed method of small-angle introscopy allows you to determine the internal structure of low-scattering objects, such as oil samples with additives, and its change during the course of the processes.

Claims (1)

A small-angle introscopy method, which consists in irradiating a controlled object with a narrow low-dispersing beam of penetrating radiation, detecting radiation transmitted through the object using a position-sensitive detector and identifying the structure of substances entering the controlled object by small-angle coherent scattering of radiation transmitted through the object and recording the distribution of radiation intensity over the beam cross section in the absence of the object and its presence, characterized in that they determine the attenuation coefficient for the center of the penetrating radiation beam through the ratio of the intensities of the radiation incident on the object and transmitted through the object, the intensity distribution curve of the radiation incident on the object in the region of the central diffraction peak in terms of the scattering angle by the attenuation coefficient is subtracted from the distribution curve of radiation transmitted through the object.