RU2308056C1 - Scintillation detector - Google Patents

Abstract

FIELD: methods of registration of neutrinos and antineutrinos.

SUBSTANCE: method can be used for registration neutrinos and antineutrinos including solar, cosmic, reactor neutrinos and neutrinos produced by accelerators. Scintillation detector has at least one transducer made of plastic scintillator on base of organic hydrogen-containing material, which material is sensitive to neutrons and neutrinos; light-collecting fiber light guide; photoreceiver, and signal electronic processing unit. Plastic scintillator is made in form of cylinder covered with light-reflecting film. There is hollow channel in center cylinder. Light-collecting fiber light guide is placed inside channel. Any transducer has case in form of parallelepiped. Set of transducers, from one to thousands pieces, forms scintillation unit while registering neutron flows and neutrinos. Scintillation unit is connected with photoreceiver. Registration of small flows of neutrons and neutrinos is possible due to increase in level of light collection in plastic cylinder of volumetric-fiber scintillation detector.

EFFECT: ability of registration of small neutron and neutrino flows.

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Description

The invention relates to the field of nuclear physics, astrophysics and high energy physics, specifically to the field of technology for detecting neutrinos and antineutrinos (hereinafter neutrinos), including solar, space, reactor neutrinos, neutrinos obtained using accelerators; it is suitable for the creation of neutrino telescopes, neutron and neutrino detectors and ground-based and space-based detector complexes designed for remote, including trans-ground, detection of stationary and mobile nuclear reactor and accelerator installations, and can be used in production and customs control systems for neutron sources and fissile radioactive materials, as well as in radiation monitoring systems of the Earth's radiation background.

обладают огромной проникающей способностью вследствие их чрезвычайно низкого сечения взаимодействия с большинством ядер элементов. Например, сечение взаимодействия антинейтрино с ядрами водорода (наиболее часто использующимися при детектировании в составе большеобъемных жидких или пластиковых сцинтилляционных детекторов) по реакцииFast neutrons are effectively detected using scintillators containing hydrogen. Scintillations occur during neutron scattering on hydrogen nuclei. It is more difficult to register a neutrino than to register neutrons. Neutrino ν and antineutrino

possess enormous penetration due to their extremely low cross-section for interaction with most element nuclei. For example, the cross section for the interaction of antineutrinos with hydrogen nuclei (most often used in the detection of large volume liquid or plastic scintillation detectors) by the reaction

(Большой энциклопедический словарь. Физика. Ред. А.М.Прохоров. Большая Российская энциклопедия. М. 1998, 944 с.) Нейтрино и антинейтрино отличаются своим происхождением: нейтрино рождается в паре с позитроном, а антинейтрино - в паре с электроном. Продукты реакции (1) вызывают сцинтилляции в сцинтилляторе, содержащем ядра водорода. Таким образом, и для регистрации нейтрино используется сцинтилляционный метод с применением водородосодержащих сцинтилляторов.equally

(The Great Encyclopedic Dictionary. Physics. Ed. A.M. Prokhorov. The Great Russian Encyclopedia. M. 1998, 944 p.) Neutrinos and antineutrinos are distinguished by their origin: neutrinos are paired with a positron, and antineutrinos are paired with an electron. The products of reaction (1) cause scintillation in a scintillator containing hydrogen nuclei. Thus, the scintillation method using hydrogen scintillators is also used to record neutrinos.

Known scintillation neutron detector (RF Patent No. 2189057, IPC G01T 1/20, 3/06, bull. No. 25. 09/10/2002). The detector contains a plastic scintillator, (n, α, γ) a converter made of carbide or boron nitride, a NaI-Tl scintillation crystal, and a photodetector (PMT).

The main disadvantage is that the light collection efficiency of the scintillations arising in the plastic scintillator from fast neutrons is not high, since the plastic scintillator in the known detector does not come into contact with the photodetector along the entire plane, but only along the peripheral ring. The contact area of the plastic scintillator with the window of the photodetector is 30-40% of the window area, therefore, the photo-taking efficiency does not exceed 30-40% of the photo collection in the mode when the scintillator is in contact with the PMT with all its working end face. (n, α, γ) - the converter made of carbide or boron nitride is opaque and part of the scintillation from the plastic scintillator is lost in it. Thus, the well-known neutron detector (RF Patent No. 2189057) has an insufficiently high level of scintillation light collection and, as a result, is not sufficiently sensitive to fast neutrons and neutrinos.

Known scintillation detector of fast and thermal neutrons based on a plastic scintillator and ⁶ Li-silicate glass (RF Patent No. 2143711, G01T 1/20, 3/00, bull. No. 36. 29.12.1999). The known detector comprises a sensor and an electronic signal processing unit. The sensor consists of a photodetector placed in a single housing and three scintillators connected in parallel:

1) an external neutron scintillator made of a fast-neutron-sensitive organic hydrogen-containing substance based on plastic (CH) _n or stilbene (scintillator with a well);

2) a NaI-Tl scintillation crystal located in a well of an external scintillator in a standard container, sensitive to gamma radiation;

3) an internal scintillator sensitive to thermal neutrons based on cerium-activated ⁶ Li-silicate glass.

The electronic signal processing unit includes a scheme for temporal selection of scintillation pulses from neutron-sensitive scintillators and a gamma-sensitive scintillator, as well as a spectrometric analyzer for processing scintillation pulses from a NaI-Tl scintillation crystal.

However, for a well-known detector, the efficiency of light collection of fast-neutron scintillations arising in the internal plastic scintillator (SN) _n is not high due to the fact that, firstly, the signals arrive at the photodetector only along the peripheral ring, providing photo scintillation at a level of up to 30 -40% due to the fact that the NaI-Tl crystal is in an opaque body and shields part of the light flux arising in the plastic, as well as due to the fact that the radiation of a fast plastic scintillator is not directly enters the photodetector, and enters it through an internal glass scintillator and is partially absorbed in it. As a result, up to 32-43% of useful information can be lost. Thus, the known detector cannot provide efficient detection of fast neutrons and neutrinos due to the insufficiently high level of scintillation light collection.

Known scintillation detector of fast and thermal neutrons (RF Patent No. 2259573, IPC G01T 1/20, 3/00, bull. No. 36. 12/29/1999), containing a sensor that includes a scintillator based on organic hydrogen-containing plastic that is sensitive to fast neutrons, and glass scintillator based on ⁶ Li-silicate glass sensitive to thermal neutrons, and a photodetector, as well as an electronic signal processing unit, while the sensor scintillators are made in the form of plates with parallel contacting faces, moreover, organic scinti the radiator is made in the form of a wedge, and the glass one is in the form of a parallelepiped, forming a single sensory scintiblock equipped with a lead collimator and placed together with the latter in an additional plastic thermal neutron storage case.

However, when a photoelectron multiplier is installed at the end of a plastic scintillator, the scintillation light collection efficiency is low, which does not provide high sensitivity to fast neutrons and neutrinos.

Of all the known scintillation detectors, the closest to the claimed one is the volume-fiber scintillation neutron and neutrino detector, called by the authors the Sci-Bar detector (N. Maesaka / The K2K SciBar Detector // Proceeding of the KEK-RCNP International School and Miniworkshop for Scintillating for Scintillating Crystal and their Application in Particle and Nuclear Physics. 2004 KEK, Tsukuba, Japan, pp. 185-198; M. Hasegawa / Calibration System of the K2K SciBar Detector. // Proceeding of the KEK-RCNP International School and Miniworkshop for Scintillating for Scintillating Crystal and their Application in Particle and Nuclear Physics. 2004 KEK, Tsukuba, Japan, pp. 243-248). Known scintillation detector of neutrons and neutrinos contains 14400 scintillation blocks in the form of parallelepipeds of plastic scintillators and a photodetector. Each scintillation block has a longitudinal channel located along its central axis, in which a light-collecting fiber is placed, which simultaneously plays the role of a spectrum shifter. The sensor, a substance sensitive to neutrons and neutrinos, is a plastic scintillator (a hydrogen-containing substance based on polystyrene with the addition of PPO (1 wt.%) POPOP (0.03 wt.%)). As a photodetector, a PIN photodiode or a multi-channel electronic multiplier is used.

However, the well-known neutron and neutrino detector does not have a sufficiently high level of scintillation light collection (due to the fact that the plastic scintillator is made in the form of a parallelepiped) and, as a result, is not sufficiently high sensitive to fast neutrons and neutrinos.

The objective of the invention is the ability to detect weak fluxes of neutrons and neutrinos by increasing the level of light collection in a plastic scintillator of a fiber-optic scintillation detector.

This problem is solved due to the fact that in a scintillation detector containing at least one sensor, consisting of a plastic scintillator based on an organic hydrogen-containing material sensitive to neutrons and neutrinos, a light-collecting fiber, a photodetector and signal processing unit, a plastic scintillator made in the form of a cylinder coated with a retroreflective film, in the center of which there is a hollow channel with a light-collecting optical fiber placed in it.

The essence of the invention lies in the fact that the hydrogen-containing plastic scintillator has a cylindrical shape, due to which the reflective coating focuses the light flashes on the axis of the cylindrical scintillator along which the optical fiber passes, which provides increased light collection compared to a plastic scintillator having the shape of a parallelepiped in which the focusing action no reflective coating.

The proposed device provides registration of neutrons and neutrinos with increased efficiency.

A block diagram of the inventive device is shown in the drawing.

The device consists of three sensors 1, a photodetector 2 and an electronic signal processing unit 3. Each sensor 1 consists of a plastic hydrogen-containing scintillator 4 having a cylindrical shape, with a reflective coating 5. In the center of the plastic scintillator 4 there is a hollow channel 6 along its axis. Each the sensor 1 has a housing 7 in the form of a parallelepiped for the convenience of forming the entire scintillation detector from such parallelepipeds.

(нейтрино), вызывают в нем появление световых вспышек (сцинтилляций), которые благодаря светоотражающему покрытию 5 поступают на световод 8 и затем регистрируются с помощью фотоприемного устройства 2, в качестве которого обычно используют PIN-фотодиод или многоканальный фотоэлектронный умножитель. Сигналы с фотоприемного устройства 2 поступают в блок обработки сигналов 3.In the hollow channel 6 of the cylindrical scintillator there is a light-collecting fiber optical fiber 8 located, like the hollow channel, along the main axis of the scintillator. The optical fibers from each sensor are connected to a photodetector 2, and through it to a signal processing unit 3. A scintillation detector operates as follows. Registered neutrons or neutrinos falling into a plastic hydrogen scintillator 4 and scattering on hydrogen nuclei (neutrons) or entering into a nuclear reaction

(neutrinos), cause the appearance of light flashes (scintillations) in it, which, thanks to the reflective coating 5, enter the optical fiber 8 and then are recorded using a photodetector 2, which is usually used as a PIN photodiode or a multi-channel photoelectronic multiplier. The signals from the photodetector 2 enter the signal processing unit 3.

An additional advantage of the proposed scintillation detector is the possibility of detecting gamma radiation with it, which allows it to be used to detect radioactive sources of gamma radiation.

A system of cylindrical sensors placed in parallelepiped-shaped housings can contain from units to thousands of sensors, forming a scintillation detector of increased sensitivity. The latter is necessary for detecting neutrinos (several thousand sensors); for neutron detection, the detector may contain one or more sensors of the proposed design.

Claims (1)

A scintillation detector containing at least one sensor, consisting of a plastic scintillator based on an organic hydrogen-containing material sensitive to neutrons and neutrinos, a light-collecting fiber, a photodetector and an electronic signal processing unit, characterized in that the plastic scintillator is made in the form of a cylinder coated reflective film, in the center of which there is a hollow channel with a light-collecting fiber light guide placed in it, each sensor having a case in the form of a parallelepiped, a set of which from one to several thousand pieces, when registering neutron fluxes and a neutrino, forms a scintillation unit associated with a photodetector.