CN110687578B

CN110687578B - Thallium-doped cesium iodide scintillation crystal radiation detector with high light extraction rate

Info

Publication number: CN110687578B
Application number: CN201911196599.XA
Authority: CN
Inventors: 刘娟
Original assignee: Sichuan Engineering Equipment Design And Research Institute Co ltd
Current assignee: Sichuan Engineering Equipment Design And Research Institute Co ltd
Priority date: 2019-11-29
Filing date: 2019-11-29
Publication date: 2023-05-30
Anticipated expiration: 2039-11-29
Also published as: CN110687578A

Abstract

The invention relates to a scintillation crystal radiation detector with high light extraction rate, which aims at the conception of purposefully 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 too large and is difficult to analyze, obtains a proper reflective film layer material, has good adhesive force with a crystal, has fewer film layers, 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, corpuscle radiation or cosmic ray radiation, and in particular to scintillation detectors in which the scintillator is a crystal in the measurement of radiation intensity.

Background

Radiometry has played an important role in many fields, such as radiometry in nuclear power plants, for continuous measurement of the radiation dose at the measurement site; the radiation measurement and radiation therapy (CT, PET, ray knife and the like) used in medical treatment are used for diagnosis and treatment by measuring the radiation intensity, and the radiation measurement is widely applied to radioactive sites such as radioactive monitoring, industrial nondestructive inspection, treatment and diagnosis of hospitals, isotope application, waste recovery and the like, and the radiation measurement monitors radiation to prevent radiation hazard on one hand and plays a role in monitoring and calculating diagnosis and treatment on the other hand.

Radiation detection is the most basic research field of radiation measurement, the basic principle of the radiation detector is that the radiation detection is performed by utilizing ionization excitation effect or other physical or chemical changes caused by radiation in gas or liquid or solid, the well-known types of detectors include gas detectors, scintillation detectors and semiconductor detectors, the gas detectors have complex structures, the detection efficiency of the semiconductor detectors is not ideal, the scintillation detectors are the most commonly used detectors at present, the scintillation detectors are strictly divided into liquid scintillation detectors and solid scintillation detectors, the portability of the liquid scintillation detectors is far worse than that of the solid scintillation detectors, the solid detectors for measuring radiation by utilizing scintillation crystals are the most studied types in the field basically used for laboratory research.

A typical structure of the traditional scintillation crystal radiation measuring device is shown in fig. 1, a scintillation crystal is used as a detection crystal, a reflection layer is arranged on the surface facing an emission source and the periphery of the scintillation crystal, the rest surface is an excitation light emergent surface, the excitation light emergent surface is connected with a photosensor (typically, a photomultiplier) through an optical coupling structure, and the photosensor photomultiplier is respectively connected with 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 a 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 as the most widely used detector.

The known reflecting layer material is usually polytetrafluoroethylene or barium sulfate, the setting mode of the reflecting layer is usually wrapping or filling, but the mode is not ideal for the protection and reflection effect of the scintillation crystal, the requirement of developing a high-performance detector cannot be met, the further improvement of energy resolution and time resolution becomes difficult, on the basis, researchers further propose a film plating mode, including a mode of plating MgF2/CeO2 dielectric film/metallic aluminum film on the surface of the crystal, the higher reflectivity at a specific wavelength is realized, the design of adopting the high-reflection design of two materials of Ta2O5/SiO2 and the concept of providing the combination of three materials of HfO2/TiO2/SiO2 is designed, even the scheme design of 48 layers of film plating layers is provided for achieving the effect of total reflection, but the method is only theoretically feasible, the more actual film plating layers have larger errors, and the effect of improving after a certain degree of film plating is also insignificant.

The concept of film coating still opens a new idea for a person skilled in the art, however, the film coating scheme needs to overcome various problems, firstly, the film coating can be easily coated on the scintillation crystal, the coating has enough firmness, and the film layer and even the crystal are not affected by the environment, for example, the problems of oxidation, deliquescence and the like need to be avoided, and the performance of the detector can not be further obviously improved through the existing design of the film layer no matter the selection of materials.

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, the technical team of the applicant invests a lot of funds through careful research, by means of a high-flux test instrument, a high-flux linear test method is breakthrough designed in a lot of test data, and a plurality of groups of feasible coating schemes (a plurality of groups of patent layouts are planned to be carried out on different scintillation crystals) are obtained, so that the technology team of the applicant relates to a detection system of one coating scheme, and other detector systems of other coating schemes are applied for in another way.

It should be noted that, after the technical team of the applicant has studied this field for more than three years, a plurality of technical achievements are obtained, in order to avoid that the prior application may become the prior art or contradictory application of the later application, the technical achievements are purposely combined with different technologies of the application filed on the same day to form a patent layout, and the corresponding prior art mentioned in the background art is not necessarily the technology disclosed to the public, and some is the prior art which is not disclosed when the technical team of the applicant researches the corresponding technology, so that the prior art mentioned in the background art or the claimed prior art cannot be taken as the evidence that the related technology is known by the public, and cannot be the evidence of the common general knowledge.

Disclosure of Invention

Aiming at the problems and bottlenecks 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 extraction rate based on the corresponding total reflection coating scheme, and mainly aims to provide a structure capable of further improving the light extraction rate when developing a high-performance radiation detector so as to improve the detection efficiency and the detection precision.

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

the utility model provides a radiation detector with special play plain noodles scintillation crystal, includes scintillation crystal, light sensor, pre-amplification circuit and multichannel analyzer, and scintillation crystal surface is provided with reflector layer and reflection-reducing layer, and the reflector layer sets up at the surface except that scintillation light exit face, and reflection-reducing layer sets up at scintillation light exit face, scintillation crystal is adulterated thallium cesium iodide crystal, and scintillation crystal and light sensor set up in encapsulation casing, its characterized in that: the reflection layer is a reflection enhancing film layer, the reflection rate of the reflection enhancing film layer on the scintillation light of the scintillation crystal is more than 99%, and the number of the film layers is less than 10;

further, the reflection enhancing film layer is a multi-layer film, and the film layers are yttrium oxide (Y2O 3), magnesium fluoride (MgF 2), hafnium dioxide (HfO 2), silicon dioxide (SiO 2), titanium dioxide (TiO 2), aluminum (Al) and yttrium oxide (Y2O 3) in sequence from the contact surface of the scintillation crystal, wherein the film thicknesses of the yttrium oxide (Y2O 3) and the silicon dioxide (HfO 2), the silicon dioxide (SiO 2), the titanium dioxide (TiO 2) and the aluminum (Al) are respectively 30nm,150nm,30nm,40 nm and 20nm;

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

further, the physical deposition mode is specifically electron beam evaporation.

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

the invention provides a concept of purposefully designing a film layer for the main emergent wave band of a scintillation crystal, overcomes the difficulty of excessively large research data volume of the film and difficult analysis, obtains a proper reflective film layer material, has good adhesion with thallium-doped cesium iodide crystals, has less film layer number and is easy to realize, and the overall design of the detector based on the concept can obviously improve the light yield of the scintillation crystal and correspondingly improve the time resolution and measurement accuracy.

Drawings

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

FIG. 2 is a schematic diagram of a radiation detector according to the present invention;

FIG. 3 is a graph showing the bandpass test results of the highly reflective film of the present invention;

in the figure: r: radiation source S1: scintillation crystal light exit face S2: scintillation crystal light reflection surface S3: light receiving surface 1 of photomultiplier: scintillation crystal 2: light sensor 3: internal circuit 4: the detector package housing 5: an external power source and circuitry.

Detailed Description

The invention is further described below with reference to the accompanying drawings, as shown in fig. 2, a radiation detector with a scintillation crystal with a special light-emitting surface comprises a scintillation crystal 1, a photosensor 2, a pre-amplifying circuit and a multi-channel analyzer 3, wherein the surface of the scintillation crystal is provided with a reflecting layer and an anti-reflection layer, the reflecting layer is arranged on a surface S2 except a scintillation light-emitting surface, the anti-reflection layer is arranged 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 arranged in a packaging shell 4.

The 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 isotropically distributed, and only photons can be detected when the photons are emitted from an emitting surface S1, the invention is redesigned by deviating from the traditional conception of stacking a periodic film material with one optical thickness, and a film layer with unexpected effect is found from mass data through high-flux experiments, so that the film layer is easy to plate on the crystal surface, has good adhesion capability and environmental adaptability and is not easy to be influenced by the environment, and the reflecting layer is specifically designed as follows:

the reflecting layer uses a reflection enhancing film layer which is a multilayer film, and the film layers from the contact surface of the scintillation crystal sequentially comprise yttrium oxide (Y2O 3), magnesium fluoride (MgF 2), hafnium dioxide (HfO 2), silicon dioxide (SiO 2), titanium dioxide (TiO 2), aluminum (Al) and yttrium oxide (Y2O 3), wherein the film thicknesses of the film layers are 30nm,150nm,30nm,40 nm and 20nm respectively.

Although the film layer composition of the invention is original, each film layer is a common material, and the film layer plating can be realized by using a conventional film plating method, wherein the common film deposition method comprises a sol-gel method, a physical vapor deposition method, a chemical vapor deposition method, an atomic layer deposition method, an electroplating method, a pulse laser deposition method and the like.

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 precisely process a scintillation crystal, in the process, firstly, an alumina hard abrasive with graded grain size is adopted to grind step by step to rapidly remove crystal surface defects, the light emergent surface of the crystal is ground into a designed shape according to the design, then cerium oxide polishing solution is adopted to precisely polish the crystal, the surface roughness of the crystal after processing can reach the nano level, preferably less than 1nm, then a corresponding film layer material is added into thermal evaporation coating equipment (a commercially available conventional electron beam evaporation coating machine) to carry out coating, evaluation on the aspects of surface quality of a reflecting film, mechanical properties (hardness, film base binding force and the like) is carried out after coating is completed, and after the basic use condition can be reached, the light reflecting performance test is carried out, and the test result is shown in figure 3:

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

The foregoing is merely illustrative of the present invention, and the present invention is not limited thereto, and any person skilled in the art will readily recognize that variations or substitutions are within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. The utility model provides a thallium doped cesium iodide scintillation crystal radiation detector with high light yield, includes scintillation crystal, photosensor, pre-amplification circuit and multichannel analyzer, and scintillation crystal surface is provided with reflector layer and antireflection layer, and the reflector layer setting is at the surface except scintillation light exit face, and the antireflection layer setting is at scintillation light exit face, scintillation crystal is thallium doped cesium iodide crystal, and scintillation crystal and photosensor set up in encapsulation casing, its characterized in that: the reflection layer is a reflection enhancement film layer, the reflection enhancement film layer has more than 99% of reflection rate of scintillation light of the scintillation crystal, the number of film layers is less than 10, the reflection enhancement film layer is a multilayer film, the multilayer film is obtained through a physical deposition mode, the film layers are yttrium oxide (Y2O 3), magnesium fluoride (MgF 2), hafnium dioxide (HfO 2), silicon dioxide (SiO 2), titanium dioxide (TiO 2), aluminum (Al) and yttrium oxide (Y2O 3) from the contact surface of the scintillation crystal in sequence, and the film thicknesses are 30nm,150nm,30nm,40 nm and 20nm respectively in sequence.

2. The radiation detector of claim 1, wherein: the physical deposition mode is specifically electron beam evaporation.