RU2377598C2 - Scintillation detector - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: invention relates to detecting ionising radiations. The technical outcome is achieved due to that, the scintillation detector has an electronic board with amplifiers-discriminators, a crystal scintillator for detecting gamma-ray quanta, made in form of two plates. In at least one of the scintillator plates there is a light-reemitting fibre in form of a loop, the ends of which reach one of the edges of the plate. At least one end of the said fibre is connected to a photodiode. The packet of three plates is surrounded by shells made from light-reflecting and light-protective material. Photodiodes are connected to a coincidence circuit. The detector is made in form of a multilayer block in which each packet of plates is separated from another packet by a light-reflecting partition.

EFFECT: simpler design, more efficient detection of radiation, wider range of detection.

3 cl, 3 dwg

Description

The invention relates to the field of registration of ionizing radiation.

A known detector for detecting ionizing radiation, neutrons and gamma rays, comprising a sensor and an electronic information processing unit including a temporal selection of scintillation pulses, characterized in that for detecting fast and slow neutrons against a background of simultaneously detected accompanying gamma radiation, the sensor is made in the form of three parallel-series connected scintillators: an external neutron scintillator made of a hydrogen-containing substance sensitive to fast neutrons based on plastic (CH) _n or stilbene; a Nal-Tl scintillator sensitive to gamma radiation located in a well of an external scintillator; an internal glass scintillator sensitive to thermal neutrons, and a photomultiplier placed in a single housing, and the electronic signal processing unit additionally includes a spectrometric analyzer of scintillation pulses coming from a Nal-Tl scintillation crystal. The thickness of the external scintillator from the hydrogen-containing material is selected sufficient to slow the fast neutrons passing through the scintillator to thermal energies (Patent of the Russian Federation No. 2143711, IPC: G01T 1/20, 12/27/1999).

However, the known detector has a number of drawbacks: the efficiency of the photo-collection of signals from fast neutrons arising in plastic (SN) _n is not high due to the fact that, firstly, the signals arrive at the photodetector (PMT) only along the peripheral ring, providing for scintillation photography at a level of up to 30-40% due to the fact that the Nal-Tl crystal is in an opaque body and shields part of the light flux arising in the plastic, and secondly, due to the fact that the radiation of a fast plastic scintillator does not directly hit the PMT , and enters it through the glass and is partially absorbed in this glass, which has a transmission boundary of 350-380 nm, as a result, up to 32-43% of useful information can be lost; reduced resistance to shock loads, since the detector contains a Nal-Tl scintillation crystal, which is highly hygroscopic, which increases the requirements for sealing. Thus, the known detector cannot provide efficient detection of fast and thermal neutrons.

Known scintillation detector of fast and thermal neutrons, containing a sensor including a scintillator based on an organic hydrogen-containing plastic that is sensitive to fast neutrons, and a glass scintillator based on ⁶ Li-silicate glass sensitive to thermal neutrons, and a photoelectronic multiplier, as well as an electronic signal processing unit characterized in that the scintillators are made in the form of plates with parallel contacting faces, the organic scintillator is made in the form of a wedge, and glass the one 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, and the photoelectron multiplier is installed at the end of the plastic scintillator (Patent of the Russian Federation No. 2259573, MPK: G01T 1/20, G01T 3/06, 2005 Prototype).

Both analog and prototype are bulky, difficult to manufacture, and have low registration efficiency.

The invention eliminates these disadvantages.

The technical result of the invention is to simplify the design, increase the efficiency of registration of the fact of radiation, expanding the range of registration.

The technical result is achieved in that the scintillation detector, comprising a sensor, including scintillators made in the form of plates with parallel contacting faces, a scintillator sensitive to fast neutrons, a scintillator sensitive to thermal neutrons, and an electronic signal processing unit, contains an electronic board with amplifiers discriminators, a crystalline scintillator for detecting gamma rays, made in the form of a plate, in at least one of the plates of scintillators located with etopereizluchayuschee fiber in a loop, the ends of which are derived at one of the faces of the plate, at least one end svetopereizluchayuschego fiber coupled to a photodiode, surrounded by a package of three plates and shells of reflective light-shielding material. Photodiodes are connected to a matching circuit. The detector is made in the form of a multilayer block in which each platinum packet is separated from the other packet by a reflective partition.

The invention is illustrated in figure 1, figure 2 and figure 3.

Figure 1 schematically shows a section of a scintillation detector, where: 1 - a plastic scintillator used to detect fast neutrons, 2 - a crystalline scintillator used to detect gamma rays, 3 - a light-emitting fiber, 4 - a scintillator for detecting thermal neutrons, 5 - reflective material, 6 - reflective material.

Figure 2 schematically shows a top view of the package of plates of the scintillator, where: 1 - a plastic scintillator, used to register fast neutrons, 3 - light-emitting fiber, 7 - photodiodes.

Figure 3 schematically shows a multilayer block of packet plates, where: 1 - a plastic scintillator used to detect fast neutrons, 2 - a crystalline scintillator used to detect gamma rays, 3 - a light-emitting fiber, 4 - a scintillator for registration of thermal neutrons, 5 - reflective material, 6 - reflective material, 8 - light separating partition.

A scintillation detector is designed for the simultaneous registration of several types of ionizing radiation and contains scintillation plates 1, 2, 4, designed to register a particular type of radiation.

For registration of fast neutrons 1 - for example, polystyrene or polyvinyltoluene plates. For registration of thermal neutrons 4 - plates of lithium glass or light composition ⁶ LiFZnS: Ag. To register gamma rays 2, for example, bismuth germanate plates, etc.

One or more plates 1, 2, 4 contain a light-emitting fiber 3 with one or two photodiodes 7 at the ends of the light-emitting fibers 3, an electronic board with discriminating amplifiers and, when two photodiodes are used, a matching circuit (not shown). The discriminators and the coincidence circuit suppress the intrinsic electronic noise of photodiode 7 and some background radiation.

The sizes of the plates 1, 2 and 4 are determined by the energy of the detected radiation. The length is from a few centimeters to several tens of centimeters. The thickness of the plates is a few centimeters.

The material of the scintillation plates 1, 2, and 4 is transparent to light radiation formed in them by the action of particles, and has a high detection efficiency with a small thickness.

So, in the case of a light composition of ⁶ LiFZnS: Ag, sufficient efficiency is ensured at a thickness of several hundred micrometers. The diameter of the light emitting fibers 3 is from one to several millimeters. To improve light gathering, the plates 1, 2 and 4 are coated with reflective material 5, for example, based on titanium oxide or reflective films. To prevent external light from entering the photodiodes 7, the plates 1, 2, and 4 are coated externally with a light-shielding material 6, for example black paper.

The presence of an air gap between the reflective material 5 and the plate 1, 2, or 4 improves the light collection. Photons of a scintillation flash arising in scintillation plate 1, 2, and 4 propagate in its volume, are reflected from the surface of plates 1, 2, and 4 and reflective material 5 and partially get into light-emitting fiber 3, where they are reradiated with a probability of about 80%. The photons arising in the light-emitting fiber 3 propagate to its ends and fall on the photodiodes 7. Photons entering the photodiode 7 cause an electrical signal.

The use of silicon photomultiplier tubes for reading the scintillation signal of silicon photovoltaic photomultipliers (CFEUs) eliminates high supply voltages and provides higher detection efficiency due to the higher quantum efficiency of photovoltaic photovoltaics compared to photocathodes.

The signal passed through the discriminator amplifier enters the amplitude-to-digital converter and then through the interface board to a personal computer. Amplitude analysis makes it possible to identify the type of radiation detected.

To increase the efficiency of radiation registration packages are combined in a block.

Claims (3)

1. A scintillation detector comprising a sensor including scintillators made in the form of plates with parallel contacting faces, a fast neutron sensitive scintillator, a thermal neutron sensitive scintillator, and an electronic signal processing unit, characterized in that the detector contains an electronic board with amplifiers -discriminators, a crystal scintillator for detecting gamma quanta, made in the form of a plate, a light-emitting fiber is located in one of the plates of scintillators in the form of a loop, the ends of which are brought out to one of the faces of the plate, at least one end of the light-emitting fiber is connected to the photodiode, the package of three plates is surrounded by shells of reflective and light-protective material. 2. The scintillation detector according to claim 1, characterized in that the photodiodes are connected to a matching circuit. 3. The scintillation detector according to claim 1 or 2, characterized in that the detector is made in the form of a multilayer block, in which each package of plates is separated from the other package by a reflective partition.

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