KR20090119033A - Radiation sensor scintillator, and method of fabricating and applying the same - Google Patents

Abstract

PURPOSE: A scintillator for a radiation sensor and a manufacturing and applying method thereof are provided to apply a scintillator to a radiation sensor for measuring radiation dose like an ultraviolet ray, an X-ray, an electron beam, alpha and beta particles, a gamma-ray, and a neutron. CONSTITUTION: A scintillator for a radiation sensor has a rubidium bromide and a cerium bromide as a matrix. The rubidium cerium bromide scintillator has a light emitting wavelength of 360~440nm and the maximum peak wavelength of 390.5nm. The rubidium cerium bromide scintillator is formed as a powder, a single crystal, or a poly crystal.

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 a rubidium cerium bromide radiation sensor, and a method of manufacturing and applying the same.

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. 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 of manufacturing 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.

In order to achieve the above object, the present invention provides a scintillator for a radiation sensor. The scintillator may be a rubidium cerium bromide (Rb ₂ CeBr ₅ ) scintillator based on rubidium bromide (RbBr) and cerium bromide (CeBr ₃ ).

The rubidium cerium bromide scintillator may have an emission wavelength in the range of 360-440 nm and a maximum peak wavelength of 390.5 nm.

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

The rubidium cerium bromide scintillator 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 matrix consisting of rubidium bromide (RbBr) and cerium bromide (CeBr ₃ ) and growing rubidium cerium bromide (Rb ₂ CeBr ₅ ) from the parent.

The preparation of the mother may include mixing rubidium bromide and cerium bromide in a 2: 1 molar ratio and injecting the mixed rubidium bromide and cerium bromide into a quartz ampoule in a vacuum atmosphere to seal the mixture.

The quartz ampoule may have a pointed shape at one end.

The step of growing rubidium cerium bromide may use the bridge-only method.

The method may further include preparing the grown rubidium cerium 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 the above rubidium cerium bromide (Rb ₂ CeBr ₅ ) 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, according to the problem solving means of the present invention, a rubidium cerium bromide scintillator having high sensitivity to radiation, high light output, and short fluorescence decay time can be provided. Accordingly, rubidium cerium bromide scintillators can be applied to medical imaging systems such as an angle camera, computerized tomography system, positron emission tomography system, or single photon emission tomography system for obtaining radiographic images. Since the decay time characteristic is very fast, it is suitable for positron emission tomography systems. In addition, the present invention may be applied to 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.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other 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. Therefore, the shape of the elements in the drawings are exaggerated to emphasize a clearer description. In addition, since reference is made to the preferred embodiment, reference numerals presented in the order of description are not necessarily limited to the order. In the drawings, like reference numerals designate like elements that perform the same function.

The scintillator for a radiation sensor according to an embodiment of the present invention may be a rubidium cerium bromide (Rb ₂ CeBr ₅ ) scintillator. This rubidium cerium bromide scintillator can be based on rubidium bromide (RbBr) and cerium bromide (CeBr ₃ ).

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

The preparation of the matrix may include mixing rubidium bromide and cerium bromide in a 2: 1 molar ratio and injecting the mixed rubidium bromide and cerium bromide into a quartz ampoule with one end point in a vacuum atmosphere and sealing it. Can be. The vacuum atmosphere may be about 10 ⁻⁵ torr.

Growing rubidium cerium bromide may use a bridgman method. A single crystal of rubidium cerium bromide can be grown using a Bridgman electric furnace in a quartz ampoule sealing the mixed rubidium bromide and cerium bromide. The falling rate of the quartz ampoule and the temperature gradient of the crystal growth section were 0.18 mm / h and 10 ° C./cm, respectively, in the Bridgman electric furnace, which were the growth conditions of the single crystal rubidium 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 why one end of the quartz ampoule is used is to easily generate a single crystal seed crystal for growing single crystal rubidium cerium bromide.

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

Alternatively, the rubidium cerium bromide scintillator can also be made of rubidium cerium bromide scintillator in powder form or polycrystal form.

The present invention can provide a radiation sensor comprising the rubidium 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 rubidium 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, alpha. At least one radiation dose selected from particles, beta particles and neutrons can be measured.

1 to 3 are graphs showing emission spectra, fluorescence decay time characteristics, and energy resolution graphs for ¹³⁷ Cs 662 keV gamma rays 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 FIG. 1, the emission spectrum measured in the range of 300 to 500 nm using a spectrometer is shown to determine the light output characteristics of the rubidium cerium bromide scintillator. As shown, the rubidium cerium bromide scintillator according to the embodiment of the present invention may have an emission wavelength in the range of 360 to 440 nm and a maximum peak wavelength of 390.5 nm. In addition, it can be seen that the light output of the rubidium cerium bromide scintillator is about 40,000 phs / MeV.

Referring to FIG. 2, the fluorescent decay times measured by irradiating ¹³⁷ Cs 662 keV gamma rays to the rubidium cerium bromide scintillator are illustrated to determine the fluorescence decay time characteristic of the rubidium cerium bromide scintillator. The thin solid line in the graph is the actual measurement value, and the thick solid line is the trend line of the actual measurement values. As shown, it can be seen that the rubidium cerium bromide scintillator according to an embodiment of the present invention has two time components. The two time components are a fast time component of 56.1 ns and a slow time component of 329.9 ns, respectively. The fast time component 56.1 ns accounts for 98.8% of the total fluorescence and the slow time component 329.9 ns accounts for 1.2% of the total fluorescence. Accordingly, it can be seen that the rubidium cerium bromide scintillator has a fast time characteristic of 56.1 ns.

Referring to FIG. 3, values of scintillation phenomena measured by irradiating ¹³⁷ Cs 662 keV gamma rays on the rubidium cerium bromide scintillator are illustrated to determine the energy resolution of the rubidium cerium bromide scintillator. The thin solid line in the graph is the actual measurement, and the thick solid line is the statistically calculated line of the actual measurement. As shown, it can be seen that the rubidium cerium bromide scintillator according to the embodiment of the present invention has an energy resolution of about 11.82% for ¹³⁷ Cs 662 keV gamma rays.

Since the rubidium cerium bromide scintillator according to the embodiment of the present invention has high sensitivity to radiation, has a high light output of 40,000 phs / MeV, and shows a fast time characteristic with a fluorescence decay time of 56.1 ns (98.9%), Gamma cameras, computerized tomography systems, positron emission tomography systems or single photon emission tomography systems for obtaining images can be used. In particular, because of their very fast time characteristics, they are suitable as scintillators for positron emission tomography systems. In addition, it may be included in the radiation sensor for measuring the radiation dose for a variety of radiation, such as ultraviolet rays, X-rays, electron beams, alpha particles, beta particles, gamma rays and neutrons.

Although the present invention has been described using the above-described exemplary preferred embodiments, the scope of the present invention is not limited to the disclosed embodiments. Rather, the scope of the present invention is intended to include various modifications and similar constructions. Accordingly, the claims should be construed as broadly as possible to encompass all such variations and similar constructions.

1 is a light emission spectrum graph of a scintillator for a radiation sensor according to an embodiment of the present invention;

2 is a graph of fluorescence decay time characteristics of a scintillator for a radiation sensor according to an embodiment of the present invention;

Figure 3 is a graph of energy resolution of 137Cs 662keV gamma rays of the scintillator for radiation sensors according to an embodiment of the present invention.

Claims (10)

Rubidium cerium bromide scintillator based on rubidium bromide and cerium bromide. The method of claim 1, A rubidium cerium bromide scintillator having an emission wavelength in the range of 360 to 440 nm and a maximum peak wavelength of 390.5 nm. The method of claim 1, Rubidium cerium bromide scintillator having a size of 10 mm ³ or more. The method of claim 1, A rubidium cerium bromide scintillator having a powder, monocrystalline or polycrystalline form. Preparing a matrix consisting of rubidium bromide and cerium bromide; And A method for producing a rubidium cerium bromide scintillator comprising the step of growing rubidium cerium bromide from the parent. The method of claim 5, Preparing the matrix is: Mixing the rubidium bromide and the cerium bromide in a 2: 1 molar ratio; And A method for producing a rubidium cerium bromide scintillator comprising the step of injecting the mixed rubidium bromide and cerium bromide into a quartz ampoule in a vacuum atmosphere. The method of claim 6, The quartz ampoule has a pointed shape at one end, characterized in that the rubidium cerium bromide scintillator manufacturing method. The method of claim 5, The step of growing the rubidium cerium bromide is a method of manufacturing a rubidium cerium bromide scintillator, characterized in that using the Bridgeman method. The method of claim 5, A method for producing a rubidium cerium bromide scintillator further comprising the step of producing the grown rubidium cerium bromide in a cylindrical shape. A radiation sensor comprising a rubidium cerium bromide scintillator based on rubidium bromide and cerium bromide.

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