RU2386148C1 - Prismatic detector - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: prismatic detector has a series of detector elements whose outer surface is coated with layers of protective material, and photodetector devices. Each detector element, which is made in form of a triangular prism with a light-reflecting element lying on the slanted surface of the prism, has a scintillator layer. The photodetector devices are placed on a common base. The photosensitive surface of the detector element and the surface of the scintillator layer lie in mutually perpendicular planes.

EFFECT: increased efficiency, lower threshold of detecting a radiation source, broader spectrometric capabilities.

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Description

The invention relates to the registration of x-ray and gamma radiation, to the determination of their energy spectrum, to medical x-ray tomography, to non-destructive testing of materials and products by radiographic and tomographic methods, to the detection of sources of ionizing radiation, to the control of baggage contents at checkpoints.

Known detector of penetrating radiation, containing a fiber module assembled from scintillating optical fibers, an optical system for detecting radiation emerging from the ends of these fibers.

The fiber module is made in the form of a combined luminescent screen-converter, the scintillating fibers of which are composed of series-connected segments of various types of scintillating materials.

The optical system contains a deflecting mirror and at least two optical channels, made in the form of an input projection lens with a filter, sequentially arranged along the channel axis, an image amplifier, a scaling lens, from which the light flux enters the CCD matrix. Patent of the Russian Federation No. 2290666, IPC G01T 1/20, G01N 23/02, 2006

Known scintillation prismatic detector with scintillators of various types with different emission spectra and photodetectors.

The scintillator is made composite and contains at least two composite elements of various types with different emission spectra that are installed in series, the same number of photodetectors with spectral sensitivities or light filters matched to the corresponding type of the composite element of the scintillator are installed on one of the ends of the composite scintillator.

A plastic scintillator was used to detect fast neutrons, a scintillator was made of ⁶ LiF crystal for detecting thermal neutrons, and a scintillator made of NaI (T1) crystal to register x-ray and gamma quanta. Utility Model Patent of the Russian Federation No. 76141, IPC G01T 1/20, 2008

Known scintillation prismatic detector containing two different scintillators, glowing in two ranges of wavelengths, arranged sequentially one after another.

The first serves to register soft x-ray radiation, the second - to register the hard component.

The first element of the scintillator includes gadolinium and has a thickness of 0.03 mm to 0.06 mm; the second element of the scintillator includes a separate crystalline cadmium tungstate, with a thickness of 2 mm to 3 mm.

One of the optical sensors includes a silicon photodiode. The total thickness of the scintillator elements is from 1.0 mm to 10.0 mm.

The total thickness of the scintillating crystals is sufficient to absorb 99% of all radiation. US patent No. 7388208, IPC G01T 1/00, 2008. Prototype.

The main disadvantage of all devices is the incomplete separation of signals arising in a given photodetector for several reasons:

- due to the partial overlap of the optical radiation spectra of the existing transparent scintillators and not the ideal filters that are facing the photodetectors, each of which partially passes light from another scintillator,

- due to the amplitude distribution of energy release in each of the scintillators, due to both the spectrum of the detected radiation and the size of the scintillator,

- due to the attenuation of light in scintillators and filters.

Reducing the effect of this drawback using amplitude discrimination of the recorded signal or by other means leads to a decrease in the efficiency of the detector.

The disadvantages of the devices are also the low sensitivity of detection of sources of ionizing radiation due to the presence of intrinsic noise of photodetector devices, the impossibility of taking into account the contribution of the radiation scattered in the detector, the need to use only transparent scintillators that differ to the necessary extent in the spectrum of optical radiation.

The invention eliminates the disadvantages of analog and prototype.

The technical result of the invention is to increase the efficiency, lower the threshold for detecting a radiation source, expand spectrometric capabilities through the use of a set of scintillation detector elements and subsequent mathematical processing of the number of signals received from them, expand the spectrum of scintillation materials used, including dispersed and powder ones.

The technical result of the invention is achieved in that in a prismatic detector containing successive detector elements, the outer surfaces of which are coated with layers of protective material, and photodetectors, each detector element made in the form of a triangular prism with an element that reflects light located on the inclined surface of the prism contains the scintillator layer, and the photodetectors are located on a common base, and the photosensitive surface of the detector element and the surface of the scinton layer llyatora located in mutually perpendicular planes.

The required number of detector elements of the same type in a prismatic detector is determined by the purpose of the detector and depends on the energy spectrum of the detected radiation, as well as the scintillator material.

The invention is illustrated in the drawings.

Figure 1 shows the detector prismatic element, where: 1 is a layer of a dispersed or powder scintillator, 2 is a triangular prism, 3 is a photodetector, 4 is an element that reflects light applied to the prism face, 5 is a scintillation flash, 6 is an adhesive layer with optical contact function.

Figure 2 presents a top view of the detector, where: 1 - layers of a dispersed or powder scintillator, 2 - triangular prisms, 3 - photodetectors, 4 - an element that reflects light deposited on the prism face, X - radiation direction, 7 - base for mounting photodetectors.

Triangular prisms 2 and the light reflecting element 4 are made of the least attenuating detected radiation material.

For example, for the manufacture of prisms 2, a transparent polymeric material, in particular polymethyl methacrylate, was used, and the light reflecting element 4 was made on the basis of dielectric layers.

The whole structure is placed in a lightproof housing.

Figure 3 presents a two-channel signal processing scheme, where: 1 - a layer of dispersed or powder scintillator; 2 - prismatic assemblies; 3, 3 ¹ - photodetectors, 8 and 8 ¹ - analog amplifiers; 9 and 9 ¹ - discriminators with adjustable thresholds of discrimination; 10 is a coincidence diagram.

The device operates as follows.

Radiation in the form of an x-ray or gamma ray is sent to the end face of the scintillation detector (Fig. 1).

When a scintillation flash is excited by a quantum in one of the scintillator layers of a dispersed or powder scintillator 1, the light from the scintillation flash 5 exits mainly through the surface of the scintillator layer 1 into reflective prisms 2.

In reflective prisms 2, light is directed by the light reflecting element (element 4) through the adhesive layer (optical contact) 6 to the photodetector devices 3 and 3 ¹ , in which an electric signal is generated under its action.

The signals from photodetectors 3 and 3 ¹ (silicon photomultipliers) are fed to analog amplifiers 8 and 8 ¹ , after which the analog signal is fed to discriminators 9 and 9 ¹ with adjustable discrimination thresholds (Fig. 3).

Logical signals from discriminators 9 and 9 ¹ go to coincidence circuit 10. If signals appear on both inputs of coincidence circuit 8, coincidence circuit 10 generates a request signal, which is stored in the output register of the circuit.

An external controller (not shown) polls the output registers of the coincidence circuit 10 and, if there is a signal (request) in them, reads the signals for transmission to a computer and further analysis. All logic circuits are made in the ESL standard. The AD 96687BP microcircuits were used as discriminators 9 and 9 ¹ , and the HEL microcircuit (MC10LD1) was used as the coincidence circuit 10.

The number of request signals from each layer at the end of registration is analyzed and the radiation spectrum is restored using a computer program.

To restore the radiation spectrum of the source, a system of integral equations is solved:

where Q _i is the number of requests from the i-th layer (plate) of the multilayer detector;

n is the number of layers; S _i (E) is the sensitivity of the ith layer to the flux of quanta with energy E;

φ (E) is the desired energy dependence of the quantum flux incident on the detector.

The system of equations is solved using an iterative method of minimizing directional divergence. Tarasco M.Z. The method of minimum directed divergence in distribution search problems. Preprint FEI No. 1446. Obninsk, 1983.

Claims (1)

A prism detector containing consecutive detector elements, the outer surfaces of which are covered with layers of protective material, and photodetector devices, characterized in that each detector element, made in the form of a triangular prism with an element that reflects light located on the inclined surface of the prisms, contains a scintillator layer, and photodetectors are located on a common base, and the photosensitive surface of the detector element and the surface of the scintillator layer are located in a mutually perp dikulyarnyh planes.

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