KR20120008873A - Radiation Sensor Scintillator, and Method of Fabricating and Applying the Same - Google Patents

Abstract

PURPOSE: A radiation sensor scintillator is provided to have a high sensitivity to radiation, high optical power, and short phosphor decay time. CONSTITUTION: A radiation sensor scintillator comprises cesium bromide, sodium bromide, and gadolinium bromide as base material, and is doped by cerium. The manufacturing method of the radiation sensor scintillator comprises a step of manufacturing the base material comprising cesium bromide, sodium bromide, and gadolinium bromide; a step of adding cerium bromide as a doping material into the base material; and a step of growing the cerium-doped cesium sodium gadolinium bromide from the base material, and the doped material.

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 sodium gadolinium bromide radiation sensor doped with cerium, and a method of manufacturing and applying the same.

The present invention is derived from the research carried out as part of the next generation new technology development project of the Ministry of Commerce, Industry and Energy [task management number: 200907190100, name of the project: the development of the 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 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. This scintillator is cerium doped cesium sodium gadolinium bromide (Cs ₂ NaGdBr ₆ : Ce) scintillator doped with cerium (Ce) doped with cesium bromide (CsBr), sodium bromide (NaBr) and gadolinium chloride (GdBr ₃ ). have.

The doping concentration of cerium may be up to 50 mol%.

The cesium sodium gadolinium bromide scintillator doped with cerium may have an emission wavelength in the range of 345 to 465 nm, and peak wavelengths of 375 and 407 nm.

Cesium sodium gadolinium bromide scintillator doped with cerium may have a size of at least 10 mm ³ .

Cesium sodium gadolinium bromide scintillator doped with cerium 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. This method comprises the steps of preparing a matrix of cesium bromide (CsBr), sodium bromide (NaBr) and gadolinium chloride (GdBr ₃ ), adding cerium bromide (CeBr ₃ ) as the doping material, and cerium from the mother and doping materials And growing the doped cesium sodium gadolinium bromide (Cs ₂ NaGdBr ₆ : Ce).

The step of preparing the mother may be mixing cesium bromide, sodium bromide and gadolinium chloride in a 2: 1: 1 molar ratio.

The step of growing cesium sodium gadolinium bromide doped with cerium may be performed using the Choklasky method or the Bridgeman method.

The method may further include preparing the grown cerium doped cesium sodium gadolinium bromide into a cylinder.

In addition, in order to achieve the above another object, the present invention provides a radiation sensor. The radiation sensor may comprise cesium sodium gadolinium bromide (Cs ₂ NaGdBr ₆ : Ce) scintillator doped with the cerium.

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 sodium gadolinium bromide scintillator doped with cerium doped with high radiation sensitivity, high light output, and short fluorescence decay time can be provided according to the solution of the problem of the present invention. Accordingly, cesium sodium gadolinium bromide scintillator doped with cerium 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, cerium doped cesium sodium gadolinium bromide scintillators are very suitable for positron emission tomography systems because of their very fast decay time characteristics.

In addition, cesium sodium gadolinium bromide scintillator doped with cerium 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 May be applied.

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. Advantages and features of the present invention, and methods of achieving the same will become apparent with reference to the embodiments described below in detail together with 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 introduced herein are provided so that the disclosure may be made thorough and complete, and to fully convey the spirit of the invention to those skilled in the art, and the invention is defined only 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 and / or plan views, which are ideal exemplary views 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. Accordingly, shapes of the exemplary views 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 an embodiment of the present invention may be a cesium sodium gadolinium bromide (Cs ₂ NaGdBr ₆ : Ce) scintillator. The CE is a cesium, sodium gadolinium bromide scintillator doped cesium bromide (CsBr), sodium bromide (NaBr) and gadolinium bromide to cerium bromide (CeBr ₃₎ to (GdBr ₃₎ as a matrix is added to the doping material may be doped with cerium have.

The process for preparing cesium sodium gadolinium bromide scintillator doped with cerium includes the steps of preparing a matrix of cesium chloride, cesium bromide, sodium bromide and gadolinium bromide, adding cerium bromide as the doping material, and Growing doped cesium sodium gadolinium bromide.

Preparing the parent may be mixing cesium chloride, cesium bromide, sodium bromide and gadolinium bromide in a 2: 1: 1 molar ratio. The step of growing cesium sodium gadolinium bromide doped with cerium may use a Czochralski method or a Bridgman method.

The growth of cerium-doped cesium sodium gadolinium bromide using the Bridgman method adds cerium bromide as a doping material to the mixed cesium chloride, cesium bromide, sodium bromide and gadolinium bromide, which is then pointed at one end in a vacuum atmosphere. Injecting into the ampule (ampule) may include the step of sealing. The vacuum atmosphere may be about 10 ⁻⁵ torr.

The mixed cesium chloride containing cesium bromide, cesium bromide, sodium bromide and gadolinium bromide as the doping material may be used to grow cesium sodium gadolinium bromide doped with single crystal cerium using Bridgman electric furnace. The falling rate of the quartz ampoule and the temperature gradients of the crystal growth portion were 0.2 mm / h and 20 ° C./cm, respectively, in Bridgman electric furnaces for growing conditions of cesium sodium gadolinium bromide doped with single crystal cerium according to an 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 cesium sodium gadolinium bromide doped with single crystal cerium.

The growth of cerium-doped cesium sodium gadolinium bromide using the Czochralski method is carried out in a crucible with mixed cesium chloride, cesium bromide, sodium bromide and gadolinium bromide containing cerium bromide as the doping material, and After melting in, it may be to grow cesium sodium gadolinium bromide doped with cerium of the single crystal using a seed crystal of a single crystal prepared in advance. Crystal growth rates and crystal rotation speeds of growth conditions of cesium sodium gadolinium bromide doped with single crystals of cerium according to an 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 cerium doped cesium sodium gadolinium bromide into a cylinder. This may be to investigate the flash characteristics of cesium sodium gadolinium bromide doped with single crystal cerium. The cesium sodium gadolinium bromide doped with a single crystal of cerium may be cut to a certain size, and then all surfaces may be polished to prepare a cesium sodium gadolinium bromide scintillated doped with a cylindrical cerium. All surfaces of cesium sodium gadolinium bromide doped with single crystals of cerium can be polished on a polishing cloth using a polishing process using aluminum oxide (Al ₂ O ₃ ) particles of 0.02 μm in size. Cesium sodium gadolinium bromide scintillator doped with cerium may have a size of at least 10 mm ³ .

Alternatively, the cesium sodium gadolinium bromide scintillator doped with cerium may also be prepared as a cesium sodium gadolinium bromide scintillator doped with cerium in powder or polycrystal form.

The present invention may provide a radiation sensor comprising the cesium sodium gadolinium bromide scintillator doped with the cerium. The radiation sensor may be used as a radiation detection device in the medical field or the industrial field. Radiation sensors, including cesium doped cesium sodium gadolinium 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. At least one radiation dose selected from ultraviolet rays, electron beams, alpha particles, beta particles, and neutrons may 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, measured in the range 300 ~ 600 nm using a spectrometer to determine the light output characteristics of cesium sodium gadolinium bromide scintillation doped with cerium doped concentration of 1 mol%, 5 mol% and 10 mol%, respectively One emission spectrum is shown. As shown, the cesium sodium gadolinium bromide scintillator doped with cerium according to an embodiment of the present invention may have an emission wavelength in the range of 345 to 465 nm, and maximum peak wavelengths of 375 and 407 nm. In addition, the relative emission intensity of the peak wavelengths may vary according to the mol% of the doped cerium, the position of the peak wavelengths or the emission wavelength range showed similar results. In addition, it can be seen that the light output of cesium sodium gadolinium bromide scintillator doped with cerium is about 20,000 phs / MeV.

Referring to FIG. 2, the doping concentrations of 1 mol% (red), 5 mol% (blue), and 10 mol% (black), respectively, were used to determine the fluorescence decay time characteristics of the cesium sodium gadolinium bromide scintillator doped with cerium. Fluorescence decay times measured by irradiating ¹³⁷ Cs 662 keV gamma rays to cerium doped cesium sodium gadolinium bromide scintillators are shown. The fluctuation lines in the graph are actual measurements. As shown, the difference in the fluorescence decay time may appear according to the mol% of the doped cerium, it can be seen that the cesium doped cesium sodium gadolinium bromide scintillators according to an embodiment of the present invention has three time components . In particular, cesium sodium gadolinium bromide scintillation doped with cerium doped concentrations of 10 mol% has a fast time component of 72 ns, an intermediate time component of 226 ns and a slow time component of 698 ns. 67% of the fluorescence, 226 ns of the intermediate time component, 22%, and 698 ns of the slow time component account for 11% of the total fluorescence. Accordingly, it can be seen that the cesium sodium gadolinium bromide scintillator doped with cerium has a fast time characteristic of 72 ns.

Cerium doped cesium sodium gadolinium bromide scintillator according to the embodiment of the present invention has high sensitivity to radiation, high light output of 20,000 phs / MeV, and fast fluorescence decay time of 72 ns (67%). Since it can be used in a gamma camera, a computed tomography system, a positron emission tomography system or a single photon emission tomography system for obtaining a radiographic image. In addition, cerium-doped cesium sodium gadolinium bromide scintillator may be included in a radiation sensor for measuring radiation dose for various radiations such as ultraviolet rays, X-rays, electron beams, alpha particles, beta particles, gamma rays, and neutrons.

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 (10)

Cesium sodium gadolinium bromide scintillator doped with cerium doped with cesium bromide, sodium bromide and gadolinium bromide. The method of claim 1,
A doped cesium sodium gadolinium bromide scintillator characterized in that the doping concentration of cerium is 50 mol% or less. The method of claim 1,
A cerium doped cesium sodium gadolinium bromide scintillator characterized by having an emission wavelength in the range of 345 to 465 nm, and peak wavelengths of 375 and 407 nm. The method of claim 1,
Cerium doped cesium sodium gadolinium bromide scintillator having a size of at least 10 mm ³ . The method of claim 1,
Cesium sodium gadolinium bromide scintillator doped with cerium in the form of a powder, monocrystalline or polycrystalline form. Preparing a matrix consisting of cesium bromide, sodium bromide and gadolinium bromide;
Adding cerium bromide as a doping material to the matrix; And
A method for producing cerium-doped cesium sodium gadolinium bromide scintillator comprising the step of growing cerium-doped cesium sodium gadolinium bromide from the parent and the doping material. The method of claim 6,
The preparing of the matrix may include cesium bromide, sodium bromide and gadolinium bromide at a 2: 1: 1 molar ratio. The method of claim 6,
The step of growing the cerium-doped cesium sodium gadolinium bromide is a method of producing a cerium-doped cesium sodium gadolinium bromide scintillator, characterized in that using the Choklasky method or Bridgeman method. The method of claim 6,
A method of producing a cerium-doped cesium sodium gadolinium bromide scintillator, characterized by further comprising the step of cylindrically grown cerium-doped cesium sodium gadolinium bromide. A radiation sensor comprising cesium sodium gadolinium bromide scintillator doped with cesium bromide, sodium bromide and gadolinium bromide.

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