CN110687578A

CN110687578A - Thallium-doped cesium iodide scintillation crystal radiation detector with high light extraction rate

Info

Publication number: CN110687578A
Application number: CN201911196599.XA
Authority: CN
Inventors: 刘娟
Original assignee: Individual
Current assignee: Sichuan Engineering Equipment Design And Research Institute Co ltd
Priority date: 2019-11-29
Filing date: 2019-11-29
Publication date: 2020-01-14
Anticipated expiration: 2039-11-29
Also published as: CN110687578B

Abstract

The invention relates to a scintillation crystal radiation detector with high light-emitting rate, which carries out the conception of pertinently designing a film layer aiming at the main emergent wave band of a scintillation crystal, overcomes the difficulty that the research data volume of a film is overlarge and is difficult to analyze, obtains a proper reflective film layer material, has good adhesive force with the crystal, has fewer film layers and is easy to realize, and correspondingly improves the measurement efficiency and the measurement precision.

Description

Thallium-doped cesium iodide scintillation crystal radiation detector with high light extraction rate

Technical Field

The present invention relates to the measurement of nuclear or X-ray radiation, and in particular to the measurement of X-ray radiation, gamma-ray radiation, corpuscular radiation or cosmic radiation, and in particular to scintillation detectors in which the scintillator is a crystal in the measurement of the intensity of the radiation.

Background

Radiation measurement has played an important role in many fields, such as nuclear power plant and thermal power plant radiation measurement, continuous measurement of radiation dose at a measurement site; the radiation measurement is widely applied to radioactive places such as radioactivity monitoring, industrial nondestructive inspection, hospital treatment and diagnosis, isotope application, waste recovery and the like, the radiation measurement monitors radiation to prevent radiation from generating harm on one hand, and plays a role in monitoring and calculating diagnosis and treatment on the other hand.

Radiation detection is the most fundamental research field of radiation measurement, the basic principle of radiation detectors is that radiation detection is performed by using an ionization excitation effect or other physical or chemical changes caused by radiation in gas, liquid or solid, the known types of detectors include gas detectors, scintillation detectors and semiconductor detectors, the gas detectors are complex in structure and the semiconductor detectors are not ideal in detection efficiency, the scintillation detectors are the most commonly used detectors at present, the scintillation detectors are strictly classified into liquid scintillation detectors and solid scintillation detectors, the liquid scintillation detectors are much less portable than the solid scintillation detectors, and the liquid scintillation detectors are basically used for laboratory research, and the solid detectors for measuring radiation by using scintillation crystals are the most researched detector types in the field.

A typical structure of a conventional scintillation crystal radiation measuring apparatus is shown in fig. 1, in which a scintillation crystal is used as a detection crystal, a reflective layer is disposed on a surface facing an emission source and around the surface, and the remaining surface is an excited light emitting surface, and the excited light emitting surface is connected to a photosensor (typically, a photomultiplier tube, for example) through an optical coupling structure, and the photosensor photomultiplier tube is respectively connected to a high voltage divider and a preamplifier; the input high voltage is loaded on the photomultiplier through the high voltage divider, and the output signal is processed by the preamplifier, the linear amplifier and the multi-channel analyzer in sequence to form the final output signal. Such detectors using scintillation crystals have also been well studied by those skilled in the art because of their ease of use and simplicity of construction to provide the most widely used detectors.

The known reflective layer material usually uses polytetrafluoroethylene or barium sulfate, the arrangement mode of the reflective layer is usually wrapping or filling, the mode is simple, but the protection and reflection effects on the scintillation crystal are not ideal, the requirement of developing a high-performance detector cannot be met, and the further improvement of the energy resolution and the time resolution becomes a difficult problem, on the basis, researchers further provide a film coating mode, the mode comprises a mode of plating an MgF2/CeO2 dielectric film/metal aluminum film on the surface of the crystal, the higher reflectivity at a specific wavelength is realized, a design of adopting two materials Ta2O5/SiO2 for high reflection and a concept of combining three materials HfO2/TiO2/SiO2 are also designed, a scheme design of coating more than 48 layers is even provided for achieving the effect of total reflection, however, the scheme is only theoretically feasible, the more the number of layers of the actual coating film is, the larger the error is, and the effect of promoting after a certain number of layers is achieved is also negligible.

The idea of coating still opens new ideas for those skilled in the art, however, the coating scheme needs to overcome various problems, firstly, the scintillation crystal can be easily coated, the coating needs to have sufficient firmness, and the problems that the film layer and even the crystal itself are not affected by the environment, such as oxidation and deliquescence need to be avoided, are not considered, and the performance of the detector can not be further obviously improved through the existing design regardless of the material selection or the design of the film layer.

At present, how to further improve the energy resolution and the time resolution of the detector is a technical bottleneck for developing a high-performance detector.

In order to break the bottleneck, a technical team of the applicant invests a large amount of funds through careful research, and by means of a high-flux test instrument, a high-flux linear experiment method is designed in a large amount of experiment data in a breakthrough manner, so that a plurality of groups of feasible coating schemes (a plurality of groups of patent layouts are planned on research results) are obtained for different scintillation crystals.

It should be noted that, after more than three years of research in this field, the technical team of the applicant has arrived at a plurality of technical achievements, and in order to avoid the prior art that may become the later application or the conflicting application, the technical achievements are purposely proposed to be applied on the same day and combined with different techniques to form a patent layout, the prior art mentioned in the corresponding background art is not necessarily the one that has been disclosed to the public, and some of the prior art that is not disclosed when the technical team of the applicant researches the corresponding technique, so neither the prior art mentioned in the background art nor the claimed prior art can be taken as the evidence that the related art has been known to the public, and can not be the evidence of common knowledge.

Disclosure of Invention

Aiming at the problems and bottlenecks existing in the prior art, the invention provides a corresponding total reflection coating scheme for a specific scintillation crystal, and provides a thallium-doped cesium iodide scintillation crystal radiation detector with high light-emitting rate based on the scheme, and the invention mainly aims to provide a structure capable of further improving the light-emitting rate when a high-performance radiation detector is developed so as to improve the detection efficiency and precision.

In order to achieve the purpose, the invention is realized by the following technical scheme:

a radiation detector with a special light-emitting surface scintillation crystal comprises a scintillation crystal, a light sensor, a pre-amplification circuit and a multi-channel analyzer, wherein a reflecting layer and an anti-reflection layer are arranged on the surface of the scintillation crystal, the reflecting layer is arranged on the surface except the scintillation light-emitting surface, the anti-reflection layer is arranged on the scintillation light-emitting surface, the scintillation crystal is a thallium-doped cesium iodide crystal, and the scintillation crystal and the light sensor are arranged in a packaging shell, and the radiation detector is characterized in that: the reflecting layer is a reflection increasing film layer, the reflectivity of the reflection increasing film layer to the scintillation light of the scintillation crystal is more than 99%, and the number of film layers is less than 10;

furthermore, the anti-reflection film layer is a multilayer film, and the film layers sequentially comprise yttrium oxide (Y2O3), magnesium fluoride (MgF 2), hafnium dioxide (HfO 2), silicon dioxide (SiO 2), titanium dioxide (TiO 2), aluminum (Al) and yttrium oxide (Y2O3) from the contact surface of the scintillation crystal, and the film thicknesses of the film layers are respectively 30nm, 150nm, 30nm, 30nm, 30nm, 40nm and 20 nm;

further, the multilayer film is obtained by means of physical deposition;

further, the physical deposition mode is electron beam evaporation.

Compared with the prior art, the invention has the advantages that:

it is common in the art to develop a broad spectrum of total reflection and antireflection films, in order to hopefully increase the energy resolution of the detector and to obtain versatile materials, this concept reduces the difficulty of development because it is expected that large band coverage, rather than extensive research into specific bands, can be achieved by additive combination based on known reflective films, but the improvement of the energy resolution ratio to the detection precision is limited, the invention provides the conception of pertinently designing the film layer aiming at the main emergent wave band of the scintillation crystal, and overcomes the difficulty that the film research data volume is overlarge and difficult to analyze, obtains a proper reflective film layer material, not only has good adhesive force with thallium-doped cesium iodide crystal, and the number of the layers of the film layers is less, the realization is easy, the overall design of the detector based on the structure can obviously improve the light-emitting rate of the scintillation crystal, and the time resolution and the measurement precision are correspondingly improved.

Drawings

FIG. 1 is a schematic diagram of a prior art radiation detector;

FIG. 2 is a schematic view of a radiation detector of the present invention;

FIG. 3 shows the band pass test results of the high reflective film of the present invention;

in the figure: r: radiation source S1: scintillation crystal light exit surface S2: scintillation crystal light reflection surface S3: light-receiving surface 1 of photomultiplier: scintillation crystal 2: the optical sensor 3: internal circuit 4: the detector packaging shell 5: external power supplies and circuits.

Detailed Description

The present invention is further explained with reference to the accompanying drawings, as shown in fig. 2, a radiation detector with a scintillation crystal with a special light emitting surface includes a scintillation crystal 1, a photosensor 2, a preamplifier circuit and a multichannel analyzer 3, wherein a light reflecting layer and an anti-reflection layer are disposed on the surface of the scintillation crystal, the light reflecting layer is disposed on a surface S2 except for the scintillation light emitting surface, the anti-reflection layer is disposed on the scintillation light emitting surface S1, the scintillation crystal is a thallium-doped cesium iodide crystal, and the scintillation crystal 1 and the photosensor 2 are disposed in a package case 4.

Thallium-doped cesium iodide is one of conventional scintillation crystals known in the prior art, low-energy visible photons generated in the scintillation crystal are distributed isotropically, and can be detected only when the photons exit from an exit surface S1, the invention departs from the traditional concept of overlapping a periodic film material with optical thickness for redesigning, and through a high-flux experiment, a film with an unexpected effect is found from mass data, so that the cesium iodide is easy to plate on the crystal surface, has good adhesion capability and environmental adaptability, and is not easily influenced by the environment, and the reflective layer is specifically designed as follows:

the reflection layer uses a reflection enhancement film layer which is a multilayer film, the film layers are sequentially yttrium oxide (Y2O3), magnesium fluoride (MgF 2), hafnium dioxide (HfO 2), silicon dioxide (SiO 2), titanium dioxide (TiO 2), aluminum (Al) and yttrium oxide (Y2O3) from the contact surface of the scintillation crystal, and the film thicknesses of the layers are respectively 30nm, 150nm, 30nm, 30nm, 30nm, 40nm and 20 nm.

Although the film combination of the invention has originality, each film is a common material, the film coating can be realized by using a conventional film coating method, the common film deposition methods include sol-gel method, physical vapor deposition, chemical vapor deposition, atomic layer deposition, electroplating, pulse laser deposition and the like, the emission film is prepared by using a physical vapor deposition method of electron beam thermal evaporation in the actual research and development process of the invention, however, the skilled person in the art knows that the film coating mode can be selected according to the actual conditions after the film combination scheme is known.

Before coating, all crystal samples are subjected to ultrasonic cleaning, alcohol soaking wiping, drying and other treatments before coating, and before coating, a plane grinding and polishing method is adopted to carry out precision processing on the scintillation crystal, in the processing, firstly, alumina hard abrasive materials with graded particle sizes are adopted to carry out step-by-step grinding to quickly remove the defects on the surface of the crystal, the light emitting surface of the crystal is ground into a designed shape according to the design, then cerium oxide polishing solution is adopted to carry out precision polishing on the crystal, the roughness of the surface of the processed crystal can reach the nanometer level and is preferably less than 1nm, then, corresponding film layer materials are added into thermal evaporation coating equipment (a commercially available conventional electron beam evaporation coating machine) to carry out coating, after coating, the surface quality of a reflecting film, the evaluation on the aspects of mechanical properties (hardness, film-base binding force and the like) and the like are carried out, and then the reflection performance test is carried out after, the test results are shown in fig. 3:

the reflectivity of the reflection increasing film layer to the main wave band of the scintillation light emitted by the thallium-doped cesium iodide crystal is more than 99%, the number of film layers is low and far lower than that of the film layers proposed in the prior art, the number of the film layers can be controlled to be below 10, repeated periodic film coating is not needed, and the realization is easy.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.

Claims

1. The utility model provides a thallium doped cesium iodide scintillation crystal radiation detector with high light-emitting rate, includes scintillation crystal, photosensor, preamplification circuit and multichannel analysis appearance, and the scintillation crystal surface is provided with reflector layer and anti-reflection coating, and the reflector layer sets up at the scintillation light-emitting surface except that scintillation light-emitting surface, and anti-reflection coating sets up at scintillation light-emitting surface, the scintillation crystal is thallium doped cesium iodide crystal, and scintillation crystal and photosensor setting are in the encapsulation casing, its characterized in that: the reflecting layer is a reflection increasing film layer, the reflectivity of the reflection increasing film layer to the scintillation light of the scintillation crystal is more than 99%, and the number of film layers is less than 10.

2. The radiation detector of claim 1, wherein: the reflection increasing film layer is a multilayer film, and the film layers are sequentially yttrium oxide (Y2O3), magnesium fluoride (MgF 2), hafnium oxide (HfO 2), silicon dioxide (SiO 2), titanium dioxide (TiO 2), aluminum (Al) and yttrium oxide (Y2O3) from the contact surface of the scintillation crystal.

3. The radiation detector of claim 2, wherein: the film thicknesses of yttrium oxide (Y2O3), magnesium fluoride (MgF 2), hafnium oxide (HfO 2), silicon dioxide (SiO 2), titanium dioxide (TiO 2), aluminum (Al) and yttrium oxide (Y2O3) are respectively 30nm, 150nm, 30nm, 30nm, 30nm, 40nm and 20 nm.

4. The radiation detector of claim 2, wherein: the multilayer film is obtained by means of physical deposition.

5. The radiation detector of claim 4, wherein: the physical deposition mode is electron beam evaporation.