• Journal of Radiation Protection and Research
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• v.11 no.1
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• pp.51-56
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• 1986

It is important to measure and protect from the radiation space dose and induced activity at the high energy medical linear accelerator facilities. These are to consider the additional risk to patients undergoing treatment, machine operators and staff members. Measurements of the space dose distribution and induced radioactivity at the 18 MeV medical linear accelerator facility in the Yonsei Cancer Center. 1. Exposure space dose for 300 rads monitor doses of 18 MeV electron are measured as 50 mR at 1 meter from patients. 2. Exposure space dose for 300 rads monitor doses of 10 MV X-ray are detected as 350 mR at 1 meter from phantom. 3. Induced radioactivity by photonuclear reaction was measured as 0.65 mR/hr from collimater after 30 Gy(3,000 rads) irradiated. 4. Analyzing the decay curves and energy spectrum of induced radioactivity, detected a few materials to be activated by photoneutron reaction, $^{65}Cu({\gamma}{\cdot}n)\;^{64}Cu,\;^{186}W({\gamma}{\cdot}n)\;^{185}W,\;^{181}Ta({\gamma}{\cdot}n)\;^{180}Ta,\;^{199}Au({\gamma}{\cdot}n)\;^{198}Au$.

• Journal of the Korean Electrochemical Society
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• v.3 no.1
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• pp.5-10
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• 2000

In the present work, corrosion rate W and corrosion potential tow were simultaneously measured as a function of relative humidity RH employing the electrochemical wet and dry method as an accelelated atmospheric corrosion method. The W versus (vs.) RH curve is classified into .three regions, namely, the first W plateau region, the second region of the linear relationship between logarithmic W and RH, finally, followed by an abrupt decay region. Based upon the atmospheric corrosion mechanism of mild steel, we introduced another diagram of $\varepsilon_{corr}$ vs. RH which is divided into three regions. In the first region, the corrosion scales are composed of single lepidocrocite-phase $(\gamma-FeOOH)$; in the second region, $\gamma-FeOOH$-phase coexists with magnetite-phase $(Fe_3O_4)$ in the scales and finally the oxide scales change into a single Fe304-phase in the third region. The three distinct regions of both representations share almost each other, which is validated by FT-IR (Fourier transform infra-red) analysis and surface observation. Both representations prove to be convenient and complementary for surveying the spectrum of the atmospheric corrosion of mild steel.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.17 no.3
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• pp.321-328
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• 2019

The detection performances of the NaI(Tl), $LaBr_3$(Ce) and $CeBr_3$ scintillation detectors, which can be used to rapidly evaluate the major artificial radionuclides deposited on the soil surface in a nuclear accident or radiological emergency, were compared. Detection performance was assessed by calculating the minimum detectable activity (MDA). The detection efficiency of each detector for artificial radionuclides was semi-empirically determined using mathematical modelling and point-like sources having certified radioactivity. The background gamma-ray energy spectrum for MDA evaluation was obtained from relatively wide and flat grassland, and the MDA values of each detector for the major artificial radionuclides that could be released in nuclear accidents were calculated. As a result, the relative MDA values of each detector regarding surface deposition distribution at normal environmental radiation level were evaluated as high in the order of the NaI(Tl), $LaBr_3$(Ce), and $CeBr_3$ detectors. These results were compared based on each detector's intrinsic and measurement environment background, detection efficiency, and energy resolution for the gamma-ray energy region of the radionuclide of interest.

• Journal of the Korean Society of Radiology
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• v.15 no.2
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• pp.257-263
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• 2021

This study derives the relative cross-section for the natW(p,xn)176Re nuclear reaction by measuring the gamma rays generated from the nuclear reaction with natural tungsten using a 100 MeV linear accelerator of the Korea Multi-purpose Accelerator Complex in the Korea Atomic Energy Research Institute. In general, research on isotopes with a short half-life always shows a tendency that the intensity of radioactivity decreases rapidly within a short period of time, making it very difficult to measure itself. In particular, 176Re is one of the relatively short radionuclides with a half-life of 5.3 minutes. In this study, 109.08 keV gamma rays generated from the 176Re isotope having such a short half-life were measured using a high-purity Ge detector(HPGe detector). The obtained relative measurements were the results in the 8 to 14 MeV proton energy domain published by Richard G. in 1967, and the TENDL-2019 value, which was the result of A. J. Koning in 2019, which evaluated the nuclear reaction cross-section by calculation based on this comparative analysis was performed. The results of this study are expected to be usefully applied to the design of nuclear fusion reactor which is known as future energy sources, elements ratio for the nuclear synthesis of astrophysics.

• Journal of the Korean Vacuum Society
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• v.22 no.6
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• pp.341-347
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• 2013

The n-type and p-type silicon samples were exposed by 40.0, 3.98 MeV proton beams ranging between 0 to $20.0{\times}10^{13}protons/cm^2$. Coincidence Doppler Broadening Positron Annihilation Spectroscopy (CDBPAS) were applied to study of defect characteristics of p type and n type silicon samples. In this investigation the numerical analysis of the 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 gamma spectrum and the total counts of whole gamma spectrum. The S-parameter values strongly depend on the irradiated proton beam that indicated the defects generate more, rather than the energy intensity. 40 MeV irradiated proton beam in the n-type silicon at $20.0{\times}10^{13}protons/cm^2$ was larger defects than 3.98 MeV irradiated proton beam. It was analysis between the proton irradiation beams and the proton intensities of the irradiation. Because of the Bragg peak, SRIM results shows mainly in a certain depth of the sample to form the defect by the proton irradiation, rather than the defects to appear for the entire sample.

• Nuclear Engineering and Technology
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• v.55 no.10
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• pp.3907-3912
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• 2023

Radiation portal monitors (RPMs) installed at airports and harbors to prevent illicit trafficking of radioactive materials generally use large plastic scintillators. However, their energy resolution is poor and radionuclide identification is nearly unfeasible. In this study, to improve isotope identification, a RPM system based on a multi-array plastic scintillator and convolutional neural network (CNN) was evaluated by measuring the spectra of radioactive sources. A multi-array plastic scintillator comprising an assembly of 14 hexagonal scintillators was fabricated within an area of 50 × 100 cm². The energy spectra of ¹³⁷Cs, ⁶⁰Co, ²²⁶Ra, and ⁴K (KCl) were measured at speeds of 10-30 km/h, respectively, and an energy-weighted algorithm was applied. For the CNN, 700 and 300 spectral images were used as training and testing images, respectively. Compared to the conventional plastic scintillator, the multi-arrayed detector showed a high collection probability of the optical photons generated inside. A Compton maximum peak was observed for four moving radiation sources, and the CNN-based classification results showed that at least 70% was discriminated. Under the speed condition, the spectral fluctuations were higher than those under dwelling condition. However, the machine learning results demonstrated that a considerably high level of nuclide discrimination was possible under source movement conditions.

• Journal of Sensor Science and Technology
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• v.12 no.1
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• pp.1-9
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• 2003

CsI single crystals doped with lithium, potassium or rubidium were grown by using Czochralski method at Ar gas atmosphere. The energy resolutions of CsI(Li:0.2 mole%), CsI(K:0.5 mole%) and CsI(Rb:1.5 mole%) scintillators were 14.5%, 15.9% and 17.0% for $^{137}Cs$(0.662 MeV), respectively. The energy calibration curves of CsI(Li), CsI(K) and CsI(Rb) scintillators were linear for $\gamma$-ray energy. The time resolutions of CsI(Li:0.2 mole%), CsI(K:0.5 mole%) and CsI(Rb:1.5 mole%) scintillators measured by CFT(constant-fraction timing method) were 9.0 ns, 14.7 ns and 9.7 ns, respectively. The fluorescence decay times of CsI(Li:0.2 mole%) scintillator had a fast component and slow one of ${\tau}_1=41.2\;ns$ and ${\tau}_2=483\;ns$, respectively. The fluorescence decay times of CsI(K:0.5 mole%) scintillator were ${\tau}_1=47.2\;ns$ and ${\tau}_2=417\;ns$. And the fluorescence decay times of CsI(Rb:1.5 mole%) scintillator were ${\tau}_1=41.3\;ns$ and ${\tau}_2=553\;ns$. The phosphorescence decay times of CsI(Li:0.2 mole%), CsI(K:0.5 mole%) and CsI(Rb:1.5 mole%) scintillators were 0.51 s, 0.57 s and 0.56 s, respectively.

• Journal of Sensor Science and Technology
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• v.10 no.1
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• pp.62-70
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• 2001

The ZnSe sample grown by chemical bath deposition (CBD) method were annealed in Ar gas at $45^{\circ}C$. Using extrapolation method of X-ray diffraction pattern, it was found to have zinc blend structure whose lattice parameter $a_o$ was $5.6687\;{\AA}$. From Hall effect, the mobility was likely to be decreased by impurity scattering at temperature range from 10 K to 150 K and by lattice scattering at temperature range from 150 K to 293 K. The band gap given by the transmission edge changed from $2.700{\underline{5}}\;eV$ at 293 K to $2.873{\underline{9}}\;eV$ at 10 K. Comparing photocurrent peak position with transmission edge, we could find that photocurrent peaks due to excition electrons from valence band, ${\Gamma}_8$ and ${\Gamma}_7$ and to conduction band ${\Gamma}_6$ were observed at photocurrent spectrum. From the photocurrent spectra by illumination of polarized light on the ZnSe thin film, we have found that values of spin orbit coupling splitting ${\Delta}so$ is $0.098{\underline{1}}\;eV$. From the PL spectra at 10K, the peaks corresponding to free bound excitons and D-A pair and a broad emission band due to SA is identified. The binding energy of the free excitons are determined to be $0.061{\underline{2}}\;eV$ and the dissipation energy of the donor -bound exciton and acceptor-bound exciton to be $0.017{\underline{2}}\;eV$, $0.031{\underline{0}}\;eV$, respectively.

• Journal of the Korean Society of Radiology
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• v.7 no.1
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• pp.31-36
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• 2013

The radioactive gas radon ($^{222}Rn$), which is generated from the decay process of uranium ($^{238}U$) originating from the soil of more than 85 percent higher the porosity of the soil, the soil can radiate out the possibility that many isotopes. In order to protect the human body from radon, above all, the development of accurate measurement techniques to formulate appropriate measures should be followed. This study Gamma-ray spectrometry using a high purity germanium (HPGe) detector, if you want to measure radon unstable the nature radiation of the background problems can be reduced, radium and radon daughter nuclides after radioactive equilibrium leads to Radon concentration was measured, the soil samples from the Gamma-ray emitting nuclides, and the energy spectrum is analyzed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.179-180
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• 2007

Single crystal $AgGaSe_2$ layers were grown on thoroughly etched semi-insulating GaAs(100) substrate at $420^{\circ}C$ with hot wall epitaxy (HWE) system by evaporating $AgGaSe_2$ source at $630^{\circ}C$. The crystalline structure of the single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of single crystal $AgGaSe_2$ thin films measured with Hall effect by van der Pauw method are $4.05{\times}\;10^{16}/cm^3$, $139\;cm^2/V{\cdot}s$ at 293 K. respectively. The temperature dependence of the energy band gap of the $AgGaSe_2$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)=1.9501\;eV\;-\;(8.79{\times}10^{-4}\;eV/K)T^2$/(T + 250 K). The crystal field and the spin-orbit splitting energies for the valence band of the $AgGaSe_2$ have been estimated to be 0.3132 eV and 0.3725 eV at 10 K, respectively, by means of the phcitocurrent spectra and the Hopfield quasicubic model. These results indicate that the splitting of the ${\Delta}So$ definitely exists in the $\Gamma_5$ states of the valence band of the $AgGaSe_2$. The three photocurrent peaks observed at 10 K are ascribed to the $A_1$-, $B_1$-, and $C_1$-exciton peaks for n = 1.