RU2529054C1 - Semiconductor detector for detecting neutron-accompanying charged particles in neutron generator with static vacuum - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: semiconductor detector for detecting neutron-accompanying charged particles in a neutron generator with a static vacuum comprises a semiconductor detecting element placed in a dielectric housing, closed on both the side of the charged particle stream and the opposite side by metal layers electrically connected to current terminals, wherein the dielectric housing is made of vacuum-tight material with gas desorption capacity of no more than 5·10^-8 mbar·cm^-2·s^-1, the detecting element is in form of a heterostructure which includes a substrate made of silicon carbide of the type n⁺6H-SiC, on which an expitaxial layer of silicon carbide of the type n-6H-SiC is grown, provided on the side opposite the substrate with a rectifying layer in the form of a Schottky barrier.

EFFECT: high radiation resistance of the semiconductor detector and efficiency of detecting neutron-accompanying charged particles.

2 dwg

Description

The invention relates to the field of nuclear physics and can be used to register charged particles associated with neutrons in a small diameter neutron generator with a static (non-pumpable) vacuum.

The device is intended for use in devices for non-destructive analysis of substances by the method of labeled neutrons. Here, a neutron generator with neutrons of 14 MeV is used as a neutron source. In this case, the D - T reaction ( ₁ H ² + ₁ H ³ → ₂ He ⁴ + ₀ n ¹ ) is used to generate neutrons, as a result of which an alpha particle with an energy of 3.5 MeV and a neutron with an energy of 14 MeV are formed. The emission of a neutron and an alpha particle occurs in opposite directions. Thus, if an alpha particle detector is placed next to a neutron source, its registration of an alpha particle will indicate that a fast neutron has flown in the opposite direction. Such devices are used in instruments for non-destructive analysis of substances, in particular in instruments for logging oil and gas wells.

During operation, the target of the neutron generator emits light radiation, electron radiation, deuterium and tritium ions generated during the scattering of the incident beam in the target, gamma radiation and neutron radiation with an energy of 14 MeV against the background of these emissions, it is necessary to register alpha-concomitant neutrons with high efficiency particles.

The process of obtaining a static vacuum before sealing the vacuum volume also requires high-temperature gas removal associated with the heating of the entire structure while continuously evacuating the vacuum volume together with the associated particles detector.

A semiconductor detector is known for detecting charged particles associated with neutrons in a neutron generator with a static vacuum, including a semiconductor recording element located in a dielectric housing, closed both from the side of the charged particle stream and from the opposite side by metal layers electrically connected to the collectors; the collector from the side of the flow of charged particles is made in the form of a rigid clamping metal plate with an opening opposite the sensitive zone of the semiconductor recording element attached to the dielectric housing, and the collector from the opposite side is made in the form of a rigid metal plate, pressed by the spring element to the semiconductor recording element, while the dielectric the body is made of a vacuum-tight material with a gas desorption capacity of not more than 5 · 10 ^-8 mbar · cm ^-2 · s ^-1 , RU 2247411 C1.

This technical solution is made as a prototype of the present invention.

. Это не позволяет разместить детектор на близком (менее 60 мм) расстоянии от мишени нейтронного генератора, так как в этом случае ресурс работы детектора резко сокращается под воздействием нейтронного потока генератора и становится меньше стандартного ресурса нейтронного генератора, составляющего 1000 часов при интенсивности нейтронного потока $${10}^8\frac{нейтр}{сек\times 4\pi }$$

. Однако в условиях ограниченного пространства, в частности внутри обсадной трубы нефтегазовой скважины, расстояние детектора от мишени генератора, как правило, не должно превышать 15-20 мм. Вследствие этого детектор должен обладать высокой радиационной стойкостью - не менее $${10}^{13}\frac{нейтр}{с{м}^2}$$

.The disadvantage of the prototype is the relatively low radiation resistance, component $${10}^{12}\frac{ne\mathrm{th}tR}{\mathrm{from}{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="00000005.png"\; state="\{\{state\}\}">m</figure-callout>}}^2}$$

. This does not allow the detector to be placed at a close (less than 60 mm) distance from the target of the neutron generator, since in this case the detector’s operating life is sharply reduced by the neutron flux of the generator and becomes less than the standard neutron generator resource of 1000 hours at the neutron flux intensity $${10}^8\frac{ne\mathrm{th}tR}{\mathrm{from}e\mathrm{to}\times \mathrm{four}\pi }$$

. However, in conditions of limited space, in particular inside the casing of an oil and gas well, the detector distance from the generator target, as a rule, should not exceed 15-20 mm. As a result, the detector must have high radiation resistance - not less than $${10}^{13}\frac{ne\mathrm{th}tR}{\mathrm{from}{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="00000005.png"\; state="\{\{state\}\}">m</figure-callout>}}^2}$$

.

In addition, the disadvantage of the prototype is the deterioration in the quality of its work (the efficiency of registration of neutrons associated with charged particles) due to an increase in the relative noise level (FWHM) with increasing temperature of the detector when it is heated (up to 200 ° C) in a limited space of an oil and gas well.

The objective of the present invention is to increase the radiation resistance of a semiconductor detector and the efficiency of registration of charged particles associated with neutrons.

According to the invention, in a semiconductor detector for detecting charged particles associated with neutrons in a neutron generator with a static vacuum, including a semiconductor recording element placed in a dielectric housing, closed both from the side of the charged particle stream and from the opposite side by metal layers electrically connected to current collectors, with this dielectric casing is made of a vacuum-tight material with a gas desorption capacity of not more than 5 · 10 ^-8 mbar · cm ^-2 · s ^-1 , register The alignment element is made in the form of a heterostructure, including an n ⁺ 6Н-SiC type silicon carbide substrate on which an n-6H-SiC type silicon carbide epitaxial layer is grown, equipped with a straightening layer in the form of a Schottky barrier on the opposite side substrate.

The applicant has not identified any technical solutions identical to the claimed one, which allows us to conclude that the invention meets the condition of patentability “Novelty”.

Thanks to the implementation of the distinguishing features of the present invention, a technical result is achieved, consisting in a significant, more than 10 times, increase in radiation resistance of the detector. This circumstance determines an almost very important new property of the object - the possibility of placing it in a limited space. In addition, in contrast to the known technical solution, the relative noise level not only does not increase with increasing detector temperature, but, on the contrary, decreases, which was a rather unexpected result of the implementation of the distinguishing features of the invention.

The applicant has not identified sources of information that would contain information about the influence of the distinguishing features of the invention on the achieved technical result. These new properties of the object determine, according to the applicant, the compliance of the invention with the condition of patentability "Inventive step".

The invention is illustrated by drawings, where Fig.1 schematically shows a detector in longitudinal section, Fig.2 is a graph of the relative noise level (FWHM) on the temperature of the detector.

A semiconductor detector for detecting charged particles associated with neutrons in a neutron generator with a static vacuum includes a semiconductor recording element located in a dielectric housing, which consists of two parts 1 and 2. In a specific example, parts 1, 2 of the case are made of vacuum-tight ceramic XC-22 (Sweden). The material of the dielectric body should have a gas desorption capacity of not more than 5 · 10 ^-8 mbar · cm ^-2 · s ^-1 . Otherwise, a static (non-pumped) vacuum is violated in the neutron generator due to excessive gas evolution of the case material, which leads to premature loss of operability of the neutron generator.

The semiconductor recording element is made in the form of a heterostructure including a n ⁺ 6H-SiC type silicon carbide substrate 3 on which an n-6H-SiC type silicon carbide epitaxial layer 4 is grown, which is provided with a rectifying layer 5 in the form of a Schottky barrier on the opposite side substrate. The recording element is closed on the side of the flow of charged particles by a layer 6, and on the opposite side by a layer 7 of metal (aluminum). Layers 6 and 7 act as electrical contacts and are connected to down conductors (not shown in the drawing).

The device operates as follows. A neutron generator with an integrated semiconductor detector is placed in a borehole logging tool, in this example, an MSI C / O type, which is immersed in a well casing. The target of a neutron generator emits neutrons and their accompanying α-particles flying in the opposite direction to the neutrons, α-particles fall on the recording element (heterostructure) and create an electric current between the contact layers 6 and 7. These electrical signals are amplified and recorded by nanosecond recording devices. The recorded flux of α particles corresponds to a directed probing neutron beam passing through the casing and entering the rock under study. Due to the directivity of the probe neutron beam, the reliability of rock logging increases. Moreover, it is very important that with increasing temperature of the semiconductor detector, the relative noise level decreases. Comparative tests of the detector were carried out by LLC Scientific and Technical Center for Applied Physics, St. Petersburg. The test results are reflected in the graph shown in figure 2.

For the manufacture of the device used conventional structural materials and factory equipment. This circumstance, according to the applicant, allows us to conclude that this invention meets the patentability condition “Industrial Applicability”.

Claims (1)

A semiconductor detector for detecting charged particles associated with neutrons in a neutron generator with a static vacuum, including a semiconductor recording element placed in a dielectric housing, closed both from the side of the charged particle stream and from the opposite side by metal layers electrically connected to the collectors, while the dielectric case made of a vacuum-tight material with a gas desorption capacity of not more than 5 · 10 ^-8 mbar · cm ^-2 · s ^-1 , characterized in that The forming element is made in the form of a heterostructure, including an n ⁺ 6H-SiC type silicon carbide substrate on which an n-6H-SiC type silicon carbide epitaxial layer is grown, equipped with a rectifying layer in the form of a Schottky barrier on the opposite side substrate.

Images