• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.237-237
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• 2012

토파즈는 Al2SiO4 ((F,OH)2) 화학성분을 이루고 있는 광물로써 주로 Fe, Cr, V 등과 같은 불순물을 포함하고 있다. 토파즈는 colorless, blue, pink, yellow 등 다양한 컬러로 산출된다. 결정 내 Si4+ 가 있어야 할 자리에 Al3+ 가 치환되면 Al3+ 를 둘러싸고 있는 4개의 산소 중 하나의 최외각 전자가 전자가를 맞추기 위해 주변에 있던 수소와 결합하여 hole center를 형성한다. 이때 토파즈는 옅은 황색의 컬러를 발색하게 된다. 그 외 청색과 핑크색 등의 컬러는 Al3+ 자리에 치환된 Fe, Cr 등과 같은 불순물에 의해 발색을 일으킨다. 또한 토파즈는 인위적으로 감마선, 전자 빔, 양성자 빔, 중성자 빔을 통해서도 hole center를 형성시켜 컬러를 발색시킬 수 있다고 잘 알려져 있다. 본 연구에서는 총 8개의 무색 토파즈를 이용하여 다양한 조건(energy 및 dose)의 전자 빔 조사를 통해 각 조건 별 컬러변화 및 분광학적 특성변화를 관찰하였다. 모든 시료는 WD-XRF를 통해 정성분석을 하였고, 전자스핀공명(ESR)기기를 통해 전자 빔 조사 전과 후 전자의 스핀 특성 변화를 관찰하였다. 자외선-가시광선 분광분석결과 모든 시료는 전자빔 조사 후 황색과 관련이 있는 450 nm 부근의 파장 영역에서 흡수 peak가 증가하는 것을 확인할 수 있었다. 또한 전자 빔 조사 후 전자스핀공명 분석 결과에서도 Fe3+ 와 관련이 있는 g=3.5~4 영역은 감소하는 반면에 hole center와 관련이 있는 g=2.012 영역이 증가하는 향상을 보였다. 본 연구결과를 통해 우리는 전자 빔 조사 조건에 따라 토파즈의 결정 내부에 미치는 영향 및 컬러 변화와의 상관관계에 대해 확인할 수 있었다.

• Journal of the Korean Vacuum Society
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• v.19 no.6
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• pp.489-494
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• 2010

Enhance signal-to-noise ratio, slow positron coincidence Doppler Broadening method has been applied to study of characteristics of $Nb_3Ge$ superconductor film, which were performed from 20 K to 300 K sample temperature near Tc of it. In this investigation the numerical analysis of the Doppler spectra was employed to the determination of the shape parameter, S, defined as the ratio between the amount of counts in a central portion of the spectrum and the total counts of whole spectrum. The S-parameter values between 0.598 and 0.594 were decreased while the temperature were decreasing, that indicated the voids into the samples. The temperature dependence came from specific positron trapping rate into the vacancy-type defects. It is believed that the positrons annihilate with normal-electrons instead of super-electrons in the Nb3Ge superconductor.

• Journal of radiological science and technology
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• v.37 no.4
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• pp.253-259
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• 2014

Large volume of $6{\times}6{\times}12mm^3$ CdZnTe ${\gamma}$-ray detector was fabricated with CdZnTe single crystals grown by Traveling Heater Method (THM) to evaluate the energy resolution of 662 keV in $^{137}Cs$. Hole tailing effect which originated from the large mobility difference in electron and hole degrade energy resolution of radiation detector and its effects become more severe for a large volume detectors. Generally, single carrier collection technique is very useful method to remove/minimize hole tailing effect and thereby improvement in energy resolution. Virtual Frisch-grid technique is also one of single charge collection method through weighting potential engineering and it is very simple and easily applicable one. In this paper, we characterized CZT detector grown by THM and evaluated the effectiveness of virtual Frisch-grid technique for a high energy gamma-ray detector. The proper position and width of virtual Frisch-grid was determined from electric field simulation using ANSYS Maxwell ver. 14.0. Energy resolution of 2.2% was achieved for the 662 keV ${\gamma}$-peak of $^{137}Cs$ with virtual Frisch-grid CdZnTe detector.

• Analytical Science and Technology
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• v.16 no.5
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• pp.391-398
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• 2003

Basic research for the determination of boron content in biological sample has been carried out using the PGAA facility of the 24MW research reactor(HANARO). For investigation of characteristics for the measurement condition, neutron flux and its homogeneity were measured at irradiating geometry. The size of thermal neutron beam collimated from beam guide is $2{\times}2cm^2$ at the sample position. The neutron flux measured was the range of $1.0{\sim}6.5{\times}10^7n{\cdot}cm^{-2}{\cdot}s^{-1}$, and flux distribution from center within the radius of 4.5 mm and 9.0 mm was $5.77{\pm}0.71{\times}10^7n{\cdot}cm^{-2}{\cdot}s^{-1}$ and $4.68{\pm}1.64{\times}10^7n{\cdot}cm^{-2}{\cdot}s^{-1}$, respectively. Accordingly, sample size is adjusted within 10 mm for a homogeneous irradiation of high quality. Measurement system is designed to reduce the background source by Compton scattering and to improve the analytical sensitivity. To investigate the energy calibration and Compton suppression effect of gamma-ray counting system, the background conditions on both of Compton and single-mode were measured using NaCl standard. On the other hand, degree of spectral interference for sodium 472 keV peak as a matrix effect in the sample is established for an accurate boron analysis, and then boron content in three certified reference materials (NIST SRM 1570a, 1547, 1573a) was measured by using two modes and the results were compared with each other.

• Journal of the Korean Magnetics Society
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• v.15 no.2
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• pp.81-84
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• 2005

The origin for the charge disproportionation (CD) transition in polycrystalline $La_{1/3}Sr_{2/3}FeO_{2.96}$ was examined using X-ray diffraction and the external field $M\ddot{o}ssbauer$ssbauer spectroscopy. In order to see how the external magnetic field affects the CD state above its transition temperature, an external magnetic field of up to 6 T was applied either parallel or perpendicular to the $\gamma-ray$ direction with the sample temperature fixed at 225 K, which was above the CD transition temperature. Without an external magnetic field, a completely paramagnetic singlet was obtained in the temperature range of the averaged valence state above the transition temperature, which was interpreted as coming from the average valence $Fe^{3.6+}$. In the longitudinal geometry, a magnetic Zeeman with its intensity ratio 3:0:1:1:0:3 is superimposed to the central singlet. In the transverse geometry, however, the central singlet disappears and only a magnetic component with its intensity ratio 3:4:1:1:4:3 emerges. The existence of a singlet is understood as an evidence of the fast electron-transfer among Fe ions. Since the singlet still exists under the magnetic field, the application of an external field has little effect on the conduction mechanism of hopping electrons.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.336-336
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• 2012

수명 측정법과 동시 계수 도플러 넓어짐 양전자 소멸 분광법으로 p형과 n형 실리콘 시료에 0, 3.98 MeV 에너지를 가진 $0.0{\sim}20.0{\times}10^{13}$ protons/$cm^2$ 양성자 빔 조사에 의한 결함을 측정하여 실리콘 결함 특성에 대하여 조사하였다. 양전자와 전자의 쌍소멸로 발생하는 감마선 스펙트럼의 전자 밀도 에너지를 수리적 해석 방법인 S-변수와 열린 부피 결함에 대한 측정법으로서 양전자 수명 ${\tau}1$과 ${\tau}2$, 이에 따른 밀도 I1과 I2를 사용하여, 시료의 구조 변화를 측정하였다. 본 연구에서 측정된 S-변수와 양전자 수명은 시료에 조사된 양성자의 빔 에너지에 따라 변화하기보다 양성자 조사량의 변화에 따라 결함이 증가하였으며, 양전자 수명 측정과 같은 경향을 보여준다. SRIM의 결과로써, 양성자 조사 에너지에 따른 Bragg 피크 때문에 양성자는 시료의 특정 깊이에 주로 결함을 형성하여 시료 전체에는 결함으로 잘 나타나지 않기 때문이다. 빔의 조사량에 따른 결함의 영향이 더 큰 것으로 나타났다.

• Applied Chemistry for Engineering
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• v.18 no.4
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• pp.396-399
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• 2007

In present work, the anti-bacterial effect of silver/activated carbon (Ag/C) composites prepared by the ${\gamma}$-irradiation of $AgNO_3$ solution on Escherichia coli (E. coli) has been studied. Characteristics of the Ag/C composites were identified by scanning electron microscopy (SEM), X-ray diffraction (XRD) and atomic absorption spectroscopy (AAS). The inhibitory concentration of E. coli was found to be 0.387 ppm and the sterilizing concentration for the tested organism was 1.017 ppm. These results support the evidence that Ag/C composites have strong antibacterial activity to E. coli.

• Journal of the Korean Vacuum Society
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• v.17 no.2
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• pp.160-164
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• 2008

The Characterization of $MgB_2$ Thin Film by Slow Positron Annihilation Spectroscopy Enhance signal-to-noise ratio, slow positron coincidence Doppler Broadening method has been applied to study of characteristics of $MgB_2$ superconductor film, which were performed at 30 K and 50 K sample temperature near Tc of it. In this investigation the numerical analysis of the Doppler spectra was employed to the determination of the shape parameter, S, defined as the ratio between the amount of counts in a central portion of the spectrum and the total counts of whole spectrum. The S-parameter values were increased then decreased while the positron implantation energies were increasing, that indicated the diffusion into the samples. The S-parameters of the anisotropic 1 ${\mu}m$ $MgB_2$ thin film which were implanted by positrons at 10 keV are 0.567 at 30 K and 0.570 at 50 K. It is believed that the positrons annihilate with normal-electrons instead of super-electrons in the $MgB_2$ superconductor.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.1
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• pp.42-46
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• 2016

The radioactive iodine ($^{131}I$) presents in the environment through the excrete process of nuclear medicine patients. In the detecting of low level of $^{131}I$ in the public water, the counting uncertainty has an effect on the accuracy and reliability of detecting $^{131}I$ radioactivity concentration. In this study, the contribution of sample amount, radioactivity concentration and counting time to the uncertainty was investigated in the case of public water sample. Sampling points are public water and the effluents of a sewage treatment plant at Sapkyocheon stream, Geumgang river. In each point, 1, 10 and 20 L of liquid samples were collected and prepared by evaporation method. The HPGe (High Purity Germanium) detector was used to detect and analyze emitted gamma-ray from samples. The radioactivity concentration of $^{131}I$ were in the range of 0.03 to 1.8 Bq/L. The comparison of the counting uncertainty of the sample amount, 1 L sample is unable to verify the existence of the $^{131}I$ under 0.5 Bq/L radioactivity concentration. Considering the short half-life of $^{131}I$ (8.03 days), a method for measuring 1 L sample was used. However comparing the detecting and preparing time of 1, 10 L respectively, detecting 10 L sample would be an appropriate method to distinguish $^{131}I$ concentration in the public water.

• Clean Technology
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• v.22 no.2
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• pp.122-131
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• 2016

Caesium radioisotopes, ¹³⁴Cs and ¹³⁷Cs which come from the atmospheric nuclear tests and discharges from nuclear power plants, are very important to study artificial radioactivity. In this work, in order to lower the minimum detection activity (MDA) we investigated environmental radioactivity according to the Environment Measurement Laboratory procedure by ¹³⁷Cs and ¹³⁴Cs which is similar to chemical and environmental behaviors of ¹³⁷Cs. The environmental soils in high mountain areas near nuclear power plant were collected, and an Ammonium Molybdophosphate (AMP) precipitation method, which showed high selectivity toward Cs⁺ ions, was applied to chemically extract and concentrate Caesium radioisotopes. Radioactivity was estimated by a gamma-ray spectrometry. In gamma energy spectrum, with an increasing of ⁴⁰K radioactivity, it increased the MDA of ¹³⁴Cs and ¹³⁷Cs. Therefore, if the natural radionuclides were removed from the soil samples, the MDA of Caesium may be reduced, and the contents of ¹³⁷Cs of in the environmental soils can effectively be estimated. In the standard soil sample of Korea Institute of Nuclear Safety, radioactivity of ⁴⁰K was removed more than 84% on average, and the MDA of ¹³⁴Cs was reduced 2 times. The content of ¹³⁷Cs was recovered over 84%. On the other hand, in environmental soils, AMP precipitation method showed removal ratio of ⁴⁰K up to 180 times, which reduced the MDA about 5 times smaller than those of Direct method. ¹³⁷Cs recovery ratio showed from 54.54% to 70.06%. When considering the MDA and recovery ratio, AMP precipitation method is effective for detection of Caesium radioisotopes in low concentration.