KR101204334B1 - Radiation Sensor Scintillator, and Method of Fabricating and Applying the Same - Google Patents

Abstract

There is provided a scintillator for a radiation sensor. This scintillator is cesium lithium cerium bromide (Cs ₂ LiCeBr ₆ ) scintillator based on cesium bromide (CsBr), lithium bromide (LiBr) and cerium bromide (CeBr ₃ ).

Description

Radiation Sensor Scintillator, and Method of Fabricating and Applying the Same}

The present invention relates to a scintillator for a radiation sensor, and a method of manufacturing and applying the same, and more particularly to a scintillator for cesium lithium cerium bromide radiation sensor, and a method of manufacturing and applying the same.
The present invention is derived from a study performed as part of the next generation new technology development project of the Ministry of Commerce, Industry and Energy. [Task control number: 200907190100, Title: Development of scintillator manufacturing technology for PET]

Scintillation is a phenomenon in which light is generated simultaneously with irradiation when the scintillator emits radiation such as X-rays. In this case, radiation information may be obtained by measuring the generated light using a suitable photoelectric element such as a photodiode or a photomultiplier tube (PMT). By processing the radiation information thus obtained in an appropriate manner, a radiographic image can be obtained.

Scintillator is composed of incident ultraviolet rays (UltraViolet ray (UV ray), X-ray, alpha ray (α-ray), beta ray (β-ray), electron ray, gamma ray (γ-ray) and neutron ray A radiation sensor that converts ionized radiation into light in the visible wavelength range, including Computed Tomography (CT) systems, Positron Emission Tomography (PET) systems, and single photon emission tomography ( Background Art It is widely used in various fields, such as medical imaging systems such as single photon emission computed tomography (SPECT) systems or gamma cameras called anger cameras, various radiation detectors, and industrial radiation sensors.

Scintillators having high radiation detection efficiency and short fluorescence decay time can be applied to various fields. Ideal scintillators for most applications require high density, high atomic number, high light output, no afterglow, and short fluorescence decay time. In addition, the scintillator must have a light emission wavelength consistent with the spectrum of the optoelectronic device while at the same time being mechanically robust, having a high degree of radiation hardness, and having a low price. However, because scintillators have their advantages and disadvantages, one scintillator may not be ideally suited for all applications.

Since the introduction of NaI: Tl scintillators by Hofstadter in 1948, scintillators have been developed and put into practical use as far as radiomedical, nuclear physics or high energy physics has developed. The main scintillators are based on NaI: Tl scintillators and alkali halide scintillators such as CsI, CsI: Tl, etc., BGO (Bi ₄ Ge ₃ O ₁₂ ), PbWO ₄ , LSO (Lu ₂ SiO ₅ ), etc. There are scintillators. Dense BGO scintillators are used in computed tomography systems, while PbWO ₄ scintillators are generally developed and utilized for high energy physics, and LSOs with good time resolution (τ = 40 ns) and good detection efficiency Scintillators have been utilized in positron emission tomography systems.

SUMMARY OF THE INVENTION An object of the present invention is to provide a scintillator for a radiation sensor having high sensitivity to radiation, high light output, and short fluorescence decay time.

Another object of the present invention is to provide a method for producing a scintillator for a radiation sensor having high sensitivity to radiation, high light output, and short fluorescence decay time.

Another object of the present invention is to provide a radiation sensor including a scintillator having high sensitivity to radiation, high light output, and short fluorescence decay time.

The problem to be solved by the present invention is not limited to the above-mentioned problems, and other tasks not mentioned will be clearly understood by those skilled in the art from the following description.

In order to achieve the above object, the present invention provides a scintillator for a radiation sensor. The scintillator may be a cesium lithium cerium bromide (CsLiCeBr ₆ ) scintillator based on cesium bromide (CsBr), lithium bromide (LiBr) and cerium bromide (CeBr ₃ ).

The cesium lithium cerium bromide scintillator may have an emission wavelength in the range of 370 to 460 nm and a peak wavelength of 420 nm.

The cesium lithium cerium bromide scintillator may have a size of at least 10 mm ³ .

Cesium lithium cerium bromide scintillators may have a powder, monocrystalline or polycrystalline form.

Moreover, in order to achieve the said another subject, this invention provides the manufacturing method of the scintillator for radiation sensors. The method may include preparing a parent cesium bromide (CsBr), lithium bromide (LiBr) and cerium bromide (CeBr ₃ ), and growing cesium lithium cerium bromide (CsLiCeBr ₆ ) from the parent.

Preparing the parent may be mixing cesium bromide, lithium bromide and cerium bromide in a 2: 1: 1 molar ratio.

The step of growing cesium lithium cerium bromide may be to use the choklasky method or bridgeman method.

The method may further include preparing the grown cesium lithium cerium bromide into a cylinder.

In addition, in order to achieve the above another object, the present invention provides a radiation sensor. This radiation sensor may comprise the cesium lithium cerium bromide (CsLiCeBr ₆ ) scintillator.

The radiation sensor may be used as a radiation detection device in the medical field or the industrial field.

It may be included in the medical field in Anger cameras, computerized tomography systems, positron emission tomography systems or single photon emission tomography systems.

In the industrial field, at least one radiation dose selected from X-rays, gamma rays, ultraviolet rays, electron beams, alpha particles, beta particles, and neutrons may be measured.

As described above, the cesium lithium cerium bromide scintillator having high sensitivity to radiation, high light output, and short fluorescence decay time can be provided according to the solution of the problem of the present invention. Accordingly, cesium lithium cerium bromide scintillators may be applied to medical imaging systems such as an Anger camera, a computed tomography system, a positron emission tomography system, or a single photon emission tomography system for obtaining radiographic images. In particular, cesium lithium cerium bromide scintillators are very suitable for positron emission tomography systems because of their very fast decay time characteristics.

In addition, cesium lithium cerium bromide scintillators may be applied to radiation sensors for measuring radiation doses for various radiations such as ultraviolet rays, X-rays, electron beams, alpha particles, beta particles, gamma rays, and neutrons. have. In particular, since lithium has a large thermal neutron capture cross-sectional area, the cesium lithium cerium bromide scintillator according to the embodiment of the present invention can be utilized for neutron detection.

1 is a light emission spectrum graph of a scintillator for a radiation sensor according to an embodiment of the present invention;
Figure 2 is a graph of the fluorescence decay time characteristic of the scintillator for a radiation sensor according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein but may be embodied in different forms. Rather, the embodiments disclosed herein are provided so that the disclosure can be thorough and complete, and will fully convey the concept of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In the present specification, the singular form includes plural forms unless otherwise specified in the specification. It is to be understood that the terms 'comprises' and / or 'comprising' as used herein mean that an element, step, operation, and / or apparatus is referred to as being present in the presence of one or more other elements, Or additions. In addition, since they are in accordance with the preferred embodiment, the reference numerals presented in the order of description are not necessarily limited to the order.

In addition, the embodiments described herein will be described with reference to cross-sectional views and / or plan views, which are ideal illustrations of the present invention. In the drawings, the size and / or thickness of the components are exaggerated for the effective description of the technical content. Thus, the shape of the illustrations may be modified by manufacturing techniques and / or tolerances. Accordingly, the embodiments of the present invention are not limited to the specific forms shown, but also include variations in forms generated by the manufacturing process. Accordingly, the components illustrated in the figures have schematic attributes, and the appearance of the components illustrated in the figures is intended to illustrate a particular form of component of the apparatus and is not intended to limit the scope of the invention.

The scintillator for a radiation sensor according to the embodiment of the present invention may be a cesium lithium cerium bromide (Cs ₂ LiCeBr ₆ ) scintillator. This cesium lithium cerium bromide scintillator can be based on cesium bromide (CsBr), lithium bromide (LiBr) and cerium bromide (CeBr ₃ ).

The method for producing cesium lithium cerium bromide scintillator may include preparing a matrix consisting of cesium bromide, lithium bromide and cerium bromide, and growing cesium lithium cerium bromide from the mother.

Preparing the parent may be mixing cesium bromide, lithium bromide and cerium bromide in a 2: 1: 1 molar ratio. The step of growing cesium lithium cerium bromide may use a Czochralski method or a bridgman method.

The growing of cesium lithium cerium bromide using the Bridgman method may include injecting the mixed cesium bromide, lithium bromide and cerium bromide into a quartz ampule with one end point in a vacuum atmosphere to seal. The vacuum atmosphere may be about 10 ⁻⁵ torr.

A single crystal of cesium lithium cerium bromide can be grown using a Bridgman electric furnace in a quartz ampoule sealing the mixed cesium bromide, lithium bromide and cerium bromide. The falling rate of the quartz ampoule and the temperature gradients of the crystal growth section were 0.2 mm / h and 10 ° C./cm, respectively, in the Bridgman electric furnace, which were the growth conditions of the single crystal cesium lithium cerium bromide according to the embodiment of the present invention. These growth conditions may vary depending on the amount of the mother or the size of the quartz ampoule, and the falling speed of the quartz ampule and the temperature gradient of the crystal growth part in the Bridgeman electric furnace are complementary to each other. The reason for using a quartz ampoule with one point is to easily generate a single crystal seed crystal for growing single crystal cesium lithium cerium bromide.

The growth of cesium lithium cerium bromide using the Czochralski method is carried out by mixing the mixed cesium bromide, lithium bromide and cerium bromide into the crucible, melting them in a Czochralski device, and then using a previously prepared single crystal seed crystal. It may be to grow cesium lithium cerium bromide of a single crystal. Crystal growth rate and crystal rotation speed, which are the growth conditions of the single crystal cesium cerium bromide according to the embodiment of the present invention, were 1.0 mm / h and 10 rpm, respectively. These growth conditions may vary depending on the amount of the parent or the size of the crystal, and in the Czochralski device, the crystal tensile speed and the crystal rotation speed are complementary to each other.

The method may further include preparing a single crystal cesium lithium cerium bromide into a cylinder. This may be to investigate the flash characteristics of the single crystal cesium lithium cerium bromide. After the single crystal cesium lithium cerium bromide is cut to a certain size, all surfaces may be polished to prepare a cylindrical cesium lithium cerium bromide scintillator. All surfaces of the single crystal cesium lithium cerium bromide can be polished by a polishing process using 0.02 μm aluminum oxide (Al ₂ O ₃ ) powder as an abrasive on a polishing cloth. The cesium lithium cerium bromide scintillator may have a size of at least 10 mm ³ .

Alternatively, the cesium lithium cerium bromide scintillator may also be prepared as a cesium lithium cerium bromide scintillator in powder form or polycrystal form.

The present invention can provide a radiation sensor comprising the cesium lithium cerium bromide scintillator. The radiation sensor may be used as a radiation detection device in the medical field or the industrial field. Radiation sensors, including cesium lithium cerium bromide scintillators, can be included in Anger cameras, computerized tomography systems, positron emission tomography systems or single photon emission tomography systems in the medical field, and in the industrial field include X-rays, gamma rays, ultraviolet rays, electron beams, At least one radiation dose selected from alpha particles, beta particles, and neutrons can be measured.

1 and 2 are light emission spectrum graphs and fluorescence decay time characteristic graphs of the scintillator for a radiation sensor according to an exemplary embodiment of the present invention, respectively.

Relative light output and fluorescence decay time at room temperature were measured with a pulse height analysis system using RbCs photomultipliers. The signal from the photomultiplier was amplified using an amplifier (× 10 or × 100), followed by a 400 MHz Flash Analog to Digital Converter (FADC), and then analyzed using a ROOT program.

Referring to Figure 1, the emission spectrum measured in the range of 380 ~ 480 nm using a spectrophotometer to determine the light output characteristics of the cesium lithium cerium bromide scintillator. As shown, the cesium lithium cerium bromide scintillator according to an embodiment of the present invention may have an emission wavelength in the range of 380 to 470 nm and a maximum peak wavelength of 420 nm. In addition, it can be seen that the light output of the cesium lithium cerium bromide scintillator is about 26,000 phs / MeV.

Referring to FIG. 2, fluorescence decay times measured by irradiating ¹³⁷ Cs 662 keV gamma rays to the cesium lithium cerium bromide scintillator are illustrated to determine the fluorescence decay time characteristic of the cesium lithium cerium bromide scintillator. The fluctuation lines in the graph are actual measurements, and the lines within the variability are trend lines of the actual measurements. As shown, it can be seen that the cesium lithium cerium bromide scintillator according to the embodiment of the present invention has three time components. The three time components are 86 ns fast time component (short dotted line), 444 ns intermediate time component (middle dotted line) and 3.8 μs slow time component (long dotted line). The fast time component 79 ns accounts for 76% of the total fluorescence, the medium time component 444 ns accounts for 8% of the total fluorescence, and the slow time component 3.8 μs accounts for 16% of the total fluorescence. Accordingly, it can be seen that the cesium lithium cerium bromide scintillator has a fast time characteristic of 86 ns.

Since the cesium lithium cerium bromide scintillator according to the embodiment of the present invention has high sensitivity to radiation, has a high light output of 26,000 phs / MeV, and shows a fast time characteristic of fluorescence decay time of 86 ns (76%), Gamma cameras, computerized tomography systems, positron emission tomography systems, or single photon emission tomography systems for obtaining radiographic images can be used. In particular, cesium lithium cerium bromide scintillators are very fast in time characteristics and are therefore suitable as scintillators for positron emission tomography systems. In addition, cesium lithium cerium bromide scintillator may be used in a radiation sensor for measuring the radiation dose for various radiations such as ultraviolet rays, X-rays, electron beams, alpha particles, beta particles, gamma rays and neutrons. In addition, since lithium ( ⁶ Li) has a large thermal neutron capture cross-sectional area, the rubidium lithium cerium bromide scintillator according to the embodiment of the present invention can be utilized for neutron detection.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be understood. It is therefore to be understood that the above-described embodiments are illustrative and non-restrictive in every respect.

Claims (9)

Cesium lithium cerium bromide scintillator based on cesium bromide, lithium bromide and cerium bromide. The method of claim 1,
Cesium lithium cerium bromide scintillator having a light emission wavelength in the range of 380 to 470 nm and peak wavelengths of 420 nm. The method of claim 1,
Cesium lithium cerium bromide scintillator having a size of 10 mm ³ or more. The method of claim 1,
Cesium lithium cerium bromide scintillator having a powder, monocrystalline or polycrystalline form. Preparing a matrix consisting of cesium bromide, lithium bromide and cerium bromide; And
Method of producing a cesium lithium cerium bromide scintillator comprising the step of growing cesium lithium cerium bromide from the parent. 6. The method of claim 5,
The preparing of the matrix may include cesium bromide, the lithium bromide and the cerium bromide in a 2: 1: 1 molar ratio. 6. The method of claim 5,
The step of growing the cesium lithium cerium bromide is a method of producing a cesium lithium cerium bromide scintillator, characterized in that using the Choklasky method or Bridgeman method. 6. The method of claim 5,
A method of producing a cesium lithium cerium bromide scintillator further comprising the step of producing a grown cesium lithium cerium bromide in a cylindrical shape. A radiation sensor comprising cesium lithium cerium bromide scintillator based on cesium bromide, lithium bromide and cerium bromide.

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