• Nuclear Engineering and Technology
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• v.55 no.3
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• pp.1045-1051
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• 2023

In this study, we fabricated a liquid light-guide-based radiation sensor with a LaBr₃:Ce scintillator for remote gamma-ray spectroscopy. We acquired the energy spectra of Cs-137 and Co-60 using the proposed sensor, estimated the energy resolutions of the full energy peaks, and compared the scintillation light output variations. The major peaks of the radionuclides were observed in each result, and the estimated energy resolutions were similar to that of a general NaI(Tl) scintillation detector without a liquid light guide. Moreover, we showed the relationships of energy resolution and analog-to-digital channel regarding the number of photoelectrons produced and confirmed the effects of light guide length on remote gamma-ray spectroscopy. The proposed sensor is expected to be utilized to perform remote gamma-ray spectroscopy for distances of 3 m or more and would find application in many fields of nuclear facilities and industry.

• Journal of the Korean Ceramic Society
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• v.40 no.11
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• pp.1058-1061
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• 2003

Gallium Nitride (GaN) powders were synthesized by calcining a gallium(III) sulfate salt in flowing ammonia in the temperature range 500-1100$^{\circ}C$. The process of conversion of the salt to GaN was monitored by X-Ray Diffraction (XRD). The salt decomposed to ${\gamma}$-Ga$_2$O$_3$ and then converted to GaN without ${\gamma}$-${\beta}$Ga$_2$O$_3$ phase transition. Variations in XRD patterns and weight loss of samples with temperature indicate that the conversion of ${\gamma}$-Ga$_2$O$_3$ to GaN does not proceed through Ga$_2$O but stepwise via amorphous gallium oxynitride (GaO$\_$x/N$\_$y/) as intermediates. Room-temperature photoluminescence spectra of GaN powders obtained showed the emission peak at 363 nm and no yellow band.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.8
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• pp.716-719
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• 2007

The effects of the evaporation rate of MgO films using an electron beam on the MgO properties and the discharge characteristics of a plasma display panel (PDP) were investigated and analyzed. MgO films were deposited with the various MgO evaporation rates. The MgO properties such as the crystal orientation, the surface roughness, and the film structure were inspected using XRD (X-ray diffraction), AFM (atomic force microscopy). From the experiments and Paschen law, the maximum value of the secondary electron emission coefficient $({\gamma})$ was obtained at the evaporation rate of $5{\AA}/sec$. The XRD results and cathode-luminescence (CL) spectra show the ${\gamma}$ values are correlated with F/F+ centers of the molecular structure of MgO films. The minimum firing voltage and the maximum luminous efficiency were obtained at an evaporation rate of $5{\AA}/sec$. In the MgO film deposited at $5{\AA}/sec$, the (200) orientation and F+ center were most intensive.

• Bulletin of the Korean Chemical Society
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• v.15 no.9
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• pp.752-758
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• 1994

Several one-electron reduction products of ${\gamma}$(1,2)-[$H_nSiV_2W_{10}O_{40}]^{(6-n)-}$ were separated by precipitating or coprecipitating with diamagnetic host compounds at different pH. Mono-and diprotonated species, 1 and 2, in powder samples exhibit aPR spectra characteristic of a mononuclear oxovanadium species, indicating that the unpaired electron is trapped at one vanadium atom. The EPR spectrum of the unprotonated species 0 shows 15 parallel lines, indicating that the unpaired electron interacts equally with two vanadium atoms. While different species were precipitated depending upon the pH of the solution and the charge of the host anion, only one species 1' was formed in the frozen solutions at pH 3.2-4.7. The EPR spectrum of 1' indicates that the unpaired electron is trapped at one vanadium atom and 1/16 of the spin density is delocalized onto the second vanadium atom. The species 1' is probably another form of the monoprotonated species. The EPR spectra show that some of 2 transform into 1 and some of 0 transform into 1' in the solid state at low temperatures. It is suggested that proton transfer between the heteropolyanion and water molecues in the solid state is involved in these transformations.

• Nuclear Engineering and Technology
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• v.54 no.10
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• pp.3833-3840
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• 2022

A method for calibrating the energy scale and detection efficiency of stilbene scintillators is presented herein. This method can be used to quantitatively analyze the Compton continuum of gamma-ray spectra obtained using such scintillators. First, channel-energy calibration was conducted by fitting a semi-empirical equation for the Compton continuum to the acquired energy spectrum and a new method to evaluate the intrinsic detection efficiency, called intrinsic Compton efficiency, of stilbene scintillators was proposed. The validity of this method was verified by changing experimental conditions such as the number of sources being measured simultaneously and the detector-source distance. According to the energy calibration, the standard error for the estimated Compton edge position was ±1.56 keV. The comparison of the intrinsic Compton efficiencies calculated from the single- and two-source spectra showed that the mean absolute difference and the mean absolute percentage difference are 0.031 %p and 0.557%, respectively, demonstrating reasonable accuracy of this method. The feasibility of the method was confirmed for an energy range of 0.5-1.5 MeV, showing that stilbene scintillators can be used to quantitatively analyze gamma rays in mixed-radiation fields.

• Nuclear Engineering and Technology
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• v.55 no.7
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• pp.2432-2437
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• 2023

Methodology for suppressing or recovering the distorted spectra, which may occur due to mutual non-uniformity and nonlinear response when a multi-detector is simultaneously operated for gamma spectroscopy, is presented with respect to its applicability to stabilization of spectra having the non-identical feature using modified full spectrum reallocation method. The modified full-spectrum reallocation method is extended to provide multiple coefficients that describe the gain drift for multi-division of the spectrum and they were incorporated into an optimization process utilizing a random sampling algorithm. Significant performance improvements were observed with the use of multiple coefficients for solving partial peak dislocation. In this study, our achievements to confirm the stabilization of spectrum having differences in moments and modify the full spectrum reallocation method provide the feasibility of the method and ways to minimize the implication of the non-linear responses normally associated with inherent characteristics of the detector system. We believe that this study will not only simplify the calibration process by using an identical response curve but will also contribute to simplifying data pre-processing for various studies as all spectra can be stabilized with identical channel widths and numbers.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.2
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• pp.232-237
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• 1999

The relationship between structure and contractile activity was studied on the three neuropeptide $\gamma$ (mammalian-, bowfin-, shark-NP$\gamma$) that were synthesized by the solid-phase method. Circular dichroism spectra showed that mammalian-, bowfin- and shark-neuropeptide $\gamma$ took an unordered structure in buffer solution and artificial liposome. The intestinal motility response was investigated with guinea-pig ileum, rat duodenum and carp intestine. In case of carp intestine, contractile activity was as follows; bowfin-NP$\gamma$> shark-NP$\gamma$>mammalian-NP$\gamma$, On the other hand, the contractile activity of mammalian-neuropeptide $\gamma$ was more potent than those of bowfin-, shark-neuropeptide $\gamma$ in the guinea-pig ileum and rat duodenum. These results suggest that NP$\gamma$ show the species-specific activity.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.2
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• pp.284-290
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• 2014

A fiber-optic beta/gamma dual detector system with two types of sensing probes was fabricated to detect the beta- and gamma-rays simultaneously. As scintillators of the sensing probe type 1, two different inorganic scintillators, $CaF_2(Eu)$ and LYSO(Ce) crystals, were used to obtain the each scintillating efficiency with respect to beta-and gamma-rays and the inherent energy spectra of radioactive isotopes. In the case of the sensing probe type 2, which is composed of two identical inorganic scintillators and a beta shielding material based on the lead, it could discriminate beta- and gamma-rays using a subtraction method. In conclusion, we demonstrated that the proposed fiber-optic beta/gamma dual detector could measure and discriminate beta- and gamma-rays using both energy spectroscopy and subtraction method.

• Journal of Astronomy and Space Sciences
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• v.31 no.4
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• pp.317-323
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• 2014

Odyssey, one of the NASA's Mars exploration program and SELENE (Kaguya), a Japanese lunar orbiting spacecraft have a payload of Gamma-Ray Spectrometer (GRS) for analyzing radioactive chemical elements of the atmosphere and the surface. In these days, gamma-ray spectroscopy with a High-Purity Germanium (HPGe) detector has been widely used for the activity measurements of natural radionuclides contained in the soil of the Earth. The energy spectra obtained by the HPGe detectors have been generally analyzed by means of the Window Analysis (WA) method. In this method, activity concentrations are determined by using the net counts of energy window around individual peaks. Meanwhile, an alternative method, the so-called Full Spectrum Analysis (FSA) method uses count numbers not only from full-absorption peaks but from the contributions of Compton scattering due to gamma-rays. Consequently, while it takes a substantial time to obtain a statistically significant result in the WA method, the FSA method requires a much shorter time to reach the same level of the statistical significance. This study shows the validation results of FSA method. We have compared the concentration of radioactivity of $^{40}K$, $^{232}Th$ and $^{238}U$ in the soil measured by the WA method and the FSA method, respectively. The gamma-ray spectrum of reference materials (RGU and RGTh, KCl) and soil samples were measured by the 120% HPGe detector with cosmic muon veto detector. According to the comparison result of activity concentrations between the FSA and the WA, we could conclude that FSA method is validated against the WA method. This study implies that the FSA method can be used in a harsh measurement environment, such as the gamma-ray measurement in the Moon, in which the level of statistical significance is usually required in a much shorter data acquisition time than the WA method.

• Journal of Radiation Protection and Research
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• v.41 no.4
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• pp.378-383
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• 2016

Background: Radiation dose rates in PRIDE facility is evaluated quantitatively for assessing radiation safety of workers because of large amounts of depleted uranium being handled in PRIDE facility. Even if direct radiation from depleted uranium is very low and will not expose a worker to significant amounts of external radiation. Materials and Methods: ORIGEN-ARP code was used for calculating the neutron and gamma source term being generated from depleted uranium (DU), and the MCNP5 code was used for calculating the neutron and gamma fluxes and dose rates. Results and Discussion: The neutron and gamma fluxes and dose rates due to DU on spherical surface of 30 cm radius were calculated with the variation of DU mass and density. In this calculation, an imaginary case in which DU density is zero was added to check the self-shielding effect of DU. In this case, the DU sphere was modeled as a point. In case of DU mixed with molten salt of 50-250 g, the neutron and gamma fluxes were calculated respectively. It was found that the molten salt contents in DU had little effect on the neutron and the gamma fluxes. The neutron and the gamma fluxes, under the respective conditions of 1 and 5 kg mass of DU, and 5 and $19.1g{\cdot}cm^{-3}$ density of DU, were calculated with the molten salt (LiCl+KCl) of 50 g fixed, and compared with the source term. As the results, similar tendency was found in neutron and gamma fluxes with the variation of DU mass and density when compared with source spectra, except their magnitudes. Conclusion: In the case of the DU mass over 5 kg, the dose rate was shown to be higher than the environmental dose rate. From these results, it is concluded that if a worker would do an experiment with DU having over 5 kg of mass, the worker should be careful in order not to be exposed to the radiation.