RU215240U1 - SENSITIVE ELEMENT OF THE MECHANICAL CALIBRATION UNIT - Google Patents

Abstract

The utility model relates to the implementation of automatic energy calibration of materials analysis devices by means of tagged neutrons.

The technical result is the possibility of implementing automatic energy calibration of materials analysis devices by means of tagged neutrons.

The technical result is achieved by the fact that the sensitive element of the mechanical calibration unit, consisting of two parallelepipeds of graphite and silicon connected to each other at the end of a rectangular shape, providing intense, non-overlapping by other gamma peaks, calibration gamma peaks of silicon 1779 keV and graphite 4439 keV, is introduced inside the zone of tagged neutrons, between the mechanical protection of the gamma detector and the gamma detector itself. In this case, the sensitive element of the mechanical calibration unit is located on one side of the gamma detector as close as possible to the gamma detector, and the inspection object is located on the other side of the gamma detector in the direction of the tagged neutrons. 8 ill.

Description

The utility model is designed to implement automatic energy calibration of materials analysis devices using tagged neutrons.

A device for analyzing materials using tagged neutrons is known, in which automatic energy calibration is implemented for two-sided geometry (the inspection object is located between the neutron generator and the gamma detector) by introducing a scintillation oxygen-containing gamma detector into the zone of tagged neutrons, RF patent for utility model No. 137122, IPC G01N 23/222, 01/27/2014.

This oxygen-containing gamma detector, which performs the function of a calibration material, implements automatic calibration as follows: tagged neutrons emitted by a neutron generator corresponding to the calibration pixel of the alpha detector enter the oxygen-containing gamma detector located behind the object of inspection at a minimum distance S=3vt (v is the speed of tagged neutrons, t is the time resolution when measuring alpha-gamma coincidences) in order to avoid mixing responses from the object of inspection and from the gamma detector extended into the zone of tagged neutrons;

The 3.76 meV and 6.12 MeV oxygen gamma lines obtained using the data acquisition equipment are used to determine the parameters k and b of the calibration function:

where A is the value of the signal amplitude in the channels;

k and b are the parameters of the calibration function (1).

The disadvantage of the known detector is:

- reduction in the number of recorded signal from the object of inspection, due to the need to move the gamma detectors away from the object of inspection at a distance S=3vt (v is the speed of tagged neutrons, t is the time resolution when measuring alpha-gamma coincidences) in order to avoid mixing responses from the object of inspection and gamma - a detector extended into the zone of tagged neutrons;

- the impossibility of using gamma detectors that do not have oxygen in their composition.

The utility model eliminates these shortcomings. The technical result is:

- increase in the number of recorded signal from the object of inspection. This is achieved by reducing the required distance between the gamma detector and the object of inspection, since the minimum distance S is measured from the sensitive element of the mechanical calibration unit, and not from the gamma detector;

- the possibility of using any gamma detectors, regardless of their elemental composition.

The technical result is achieved by the fact that the sensitive element of the mechanical calibration unit consists of two parallelepipeds of graphite and silicon connected to each other by the ends of a rectangular shape.

The list of item designations shown in Fig. 1-4:

1 - rectangular parallelepiped of graphite;

2 - rectangular silicon parallelepiped;

3 - plate;

4 - sensitive element of the mechanical calibration unit;

5 - gamma detector;

6 - mechanical protection of the gamma detector 5 from the direct impact of neutrons from the neutron generator 7;

7 - neutron generator with built-in alpha detector 8;

8 - multipixel alpha detector;

9 - object of inspection;

10 - boundary of the zone of tagged neutrons;

11 - calibration area of the alpha detector 8 corresponding to graphite;

12 - calibration region of the alpha detector 8 corresponding to silicon.

In FIG. 1 shows a sensitive element of the mechanical calibration unit, consisting of two bonded parallelepipeds - graphite parallelepiped 1 and silicon parallelepiped 2 using plate 3.

In FIG. 2 shows a top view of the location of the sensitive element 4 of the mechanical calibration unit relative to the inspection object 9, the gamma detector 5 and the boundaries 10 of the zone of tagged neutrons determined by the multipixel alpha detector 8 built into the neutron generator 7.

In FIG. 3 shows a front view from the side of the neutron generator 7 of the sensitive element 4 of the mechanical calibration unit, and its location relative to the gamma detector 5 and the boundary 10 of the zone of tagged neutrons.

In FIG. 4 shows a top view of a multi-pixel alpha detector 8 showing two calibration regions 11 and 12 of the alpha detector 8, consisting of calibration alpha pixels, and corresponding to a graphite box 1 and a silicon box 2.

In FIG. Figures 5 and 6 show examples of gamma spectra from parallelepiped 2 silicon (Si) and parallelepiped 1 graphite (C) and the result of approximation of their gamma lines 1779 keV (Si) and 4439 keV (C) by the Gaussian function, taking into account the substrate in the form of an inclined straight line (values on the abscissa axis are given in arbitrary units (channels), along the ordinate axis the number of readings is given).

In FIG. Figure 7 shows an example of the initial uncalibrated amplitude gamma spectrum from the inspection object 9, which was a TNT simulator (the values on the abscissa axis are given in arbitrary units (channels), the number of readings is given on the ordinate axis).

In FIG. Figure 8 shows a view of the calibrated energy gamma spectrum from a TNT simulator, obtained after performing automatic calibration (values on the abscissa axis are given in MeV, along the ordinate axis the number of readings is given).

The sensing element 4 of the mechanical calibration unit (Fig. 1) contains a graphite parallelepiped 1 and a silicon parallelepiped 2, which are interconnected, for example, using a plate 3.

The sensitive element 4 of the mechanical calibration unit consists of two, connected to each other by ends using, for example, glue or a plate 3 with curved edges, while the edges do not fall outside the boundary 10 of the zone of tagged neutrons, parallelepipeds - graphite parallelepiped 1 and silicon parallelepiped 2 , each of which is attached with its back side, for example, glued to the plate 3, resulting in reactions of inelastic scattering of 14 MeV neutrons on their nuclei, intense, non-overlapping by other gamma peaks, gamma peaks of carbon 4439 keV and silicon 1779 keV, respectively.

The sensitive element 4 of the mechanical calibration unit is part of the mechanical calibration unit and is located with it as close as possible to the gamma detector 5, protruding beyond the boundary 10 of the zone of tagged neutrons (Fig. 2, 3), between the gamma detector 5 and its mechanical protection 6 from the direct impact of neutrons from a neutron generator 7 with a built-in multi-pixel alpha detector 8, the calibration areas 11 and 12 of which (Fig. 4) correspond to a graphite parallelepiped 1 and a silicon parallelepiped 2, respectively. In this case, the inspection object 9 is located on the other side of the gamma detector 5 inside the boundary 10 of the zone of tagged neutrons (Fig. 2).

The mechanical calibration unit (no position in the figure) consists of a sensitive element 4 and means for its positioning and fastening inside the device for neutron analysis of materials.

The device works as follows.

The sensitive element 4 of the mechanical calibration unit is placed and installed inside the device for neutron analysis of materials using the mechanical calibration unit, of which it is included.

The sensitive element 4 of the mechanical calibration block is installed as close as possible to the gamma detector 5 (Fig. 2), between the gamma detector 5 and the mechanical protection 6 of the gamma detector 5 from direct neutron radiation of the neutron generator 7 with a built-in multi-pixel alpha detector 8, calibration areas 11 and 12 of which (Fig. 4) correspond to parallelepipeds 1 and 2 of graphite and silicon, respectively. The sensitive element 4 of the mechanical calibration unit consists of two, glued together or pressed against each other by the ends, for example, using a plate 3 with curved edges that do not fall beyond the boundary 10 of the zone of tagged neutrons, parallelepipeds - graphite parallelepiped 1 and silicon parallelepiped 2 , each of which is attached with its back side, for example, glued to the plate 3, resulting in reactions of inelastic scattering of 14 MeV neutrons on their nuclei, intense, non-overlapping by other gamma peaks, gamma peaks of carbon 4439 keV and silicon 1779 keV, respectively. In this case, the inspection object 9 is located on the other side of the gamma detector 5 inside the boundary 10 of the zone of tagged neutrons (Fig. 2).

The placement of the sensitive element 4 of the mechanical calibration unit attached to the plate 3, inside the boundary 10 of the zone of tagged neutrons relative to the gamma detector 5, is selected based on the density of the parallelepipeds - the parallelepiped 1 of graphite and the parallelepiped 2 of silicon, the measurement time of the inspection object 9, the gamma spectrum and the level of background events registered by the gamma detector 5 as a result of the neutrons of the generator 7 entering the surrounding objects in addition to the inspection object 9.

The size and shape of the parallelepipeds 1 and 2 are determined by the size of the borders 10 of the zone of tagged neutrons in the area where the sensitive element 4 of the mechanical calibration unit is located, the gamma detector 5 and the spatial resolution of the device for neutron analysis of materials, determined by the neutron generator 7 with a built-in multipixel alpha detector 8, as well as the measurement time, the radiation intensity of the neutron generator 7, the density of the materials of the parallelepipeds 1 and 2.

For example, with the size of the boundaries 10 of the zone of tagged neutrons 10×10 cm and a spatial resolution of 1.5 cm of the device for neutron analysis of materials in the area where the sensitive element 4 of the mechanical calibration unit is located, the sensitive region of the gamma detector is 7.6×07.6 cm, the intensity of the neutron generator 7 component 5×10 ⁷ neutr./s, the density of the graphite parallelepiped 1 and the silicon parallelepiped 2 is not less than 1.8 g/cm, the measurement time is from 1 to 10 minutes, the parallelepipeds 1 and 2 will have a rectangular shape with dimensions in the range (B ×W×D), cm: (10-13)×(3-5)×(1×3). Thus, the rectangular shape of the parallelepipeds is determined directly by the size of the zone of tagged neutrons.

The tagged neutrons of the neutron generator 7, corresponding to the calibration regions 11 and 12 of the alpha detector 8, fall, respectively, into the fractions of the graphite parallelepiped 1 and the silicon parallelepiped 2, located inside the boundary 10 of the tagged neutron zone, causing inelastic neutron scattering with the formation of intense gamma lines of carbon 4439 keV (about ~ 187 mb [10]) and silicon 1779 keV (about ~ 403 mb [10]), which are registered by gamma detector 5. These lines of silicon and graphite are ideal for implementing the calibration procedure, not only because they have large cross sections interactions, but also because they are not overlapped by other gamma lines, which is important for the accuracy of determining the position of the peak center using its approximation. On FIG. Figures 5 and 6 show examples of gamma spectra from silicon and graphite, as well as the result of approximation of their gamma peaks of the total absorption of silicon 1779 keV (Si) and graphite 4439 keV (C) by the Gaussian function, taking into account the substrate in the form of an inclined straight line. Based on these approximations, the approximation parameters of the gamma peaks of silicon A _Si and graphite A _c are determined, which characterize the positions of peak centers expressed in channels. The obtained parameters A _Si and A _c are used to determine the parameters k and b of the calibration function (1) according to the classical formulas:

The found calibration function (1) allows you to perform automatic energy calibration of the gamma response from the object 9 inspection. On FIG. Figures 7 and 8 show examples of the original uncalibrated amplitude gamma spectrum from a TNT simulator (values on the abscissa are given in arbitrary units, the ordinate is the number of readings) and the result of its automatic calibration in the form of an energy spectrum (values on the abscissa are given in MeV). As you can see, on the example of the calibrated gamma spectrum of the TNT simulator, automatic calibration correctly determines the energy of the gamma peaks corresponding to the chemical elements oxygen - 6.13 MeV, carbon - 4.44 MeV and nitrogen - 2.31 MeV contained in the TNT simulator, which confirms the possibility of implementing automatic calibration using the sensing element 4 of the mechanical calibration unit.

Thus, the claimed technical result is achieved, namely:

- increase in the amount of the recorded signal from the object of inspection by reducing the required distance between the gamma detectors and the object of inspection;

- the possibility of using any gamma detectors, regardless of their elemental composition.

Literature:

1. Simakov S.P., Pavlik A. et. al. Status of Experimental and Evaluated Discrete Gamma-Ray Production at En=14.5 MeV. IAEA, 1998 - https://www-nds.ieaa.orR/publications/indc/indc-ccp-0413

Claims (1)

The sensitive element of the mechanical calibration block, consisting of two parallelepipeds of graphite and silicon connected to each other by the ends of a rectangular shape.

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