• Journal of Advanced Navigation Technology
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• v.20 no.5
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• pp.482-489
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• 2016

Detection of gamma ray can be available using optical fiber scintillator under radiation environment. It monitors the transfer energies of these ions by photodiodes and then convertes into currents. The module which converts those currents into voltages and processes signals is named fine current module TIA, and it is essentially important to convert currents into voltages with high linearity. We have studied and developed the TIA, improving converting linearity and minimizing noises and off-set voltages. Also, we have made efforts to develop precise and accurate current module in compliance with concerned requirements. First of all, we established developing theory, developed related circuits, and then made the current module. And, we confirmed its stability and linearity to be more excellent than any other equipment proposed by other references. We tested the developed fine current modules in the real radiation environment under authorized supervising, confirmed them to meet related requirements.

• Journal of Radiation Protection and Research
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• v.41 no.2
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• pp.87-91
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• 2016

Background: A hand-held detector for an emergency response was developed for nuclide identification and to estimate the information of the ambient dose rate in the scene of an accident as well as the radioactivity of the contaminants. Materials and Methods: To achieve this, the most suitable sensor was first selected as a cadmium zinc telluride (CZT) semiconductor and the signal processing unit from a sensor and the signal discrimination and storage unit were successfully manufactured on a printed circuit board. Results and Discussion: The performance of the developed signal processing unit was then evaluated to have an energy resolution of about 14 keV at 662 keV. The system control unit was also designed to operate the CZT detector, monitor the detector, battery, and interface status, and check and transmit the measured results of the ambient dose rate and radioactivity. In addition, a collimator, which can control the inner radius, and the airborne dust sampler, which consists of an air filter and charcoal filter, were developed and mounted to the developed CZT detector for the quick and efficient response of a nuclear accident. Conclusion: The hand-held CZT detector was developed to make the in-situ gamma-ray spectrometry and its performance was checked to have a good energy resolution. In addition, the collimator and the airborne dust sampler were developed and mounted to the developed CZT detector for a quick and efficient response to a nuclear accident.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.1
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• pp.34.2-34.2
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• 2017

A small wide-field imaging telescope is a powerful instrument to survey the Universe: wide-field image can monitor the variability of many sources at a time, e.g. young stellar objects and active galactic nuclei, and it can be an effective way to locate transient sources without precise positional information such as gravitational wave sources or some gamma-ray bursts. In February 2017, we installed a 0.25 m f/3.6 telescope on the McDonald 0.8 m telescope as a piggyback system. With a $4k{\times}4k$ CCD camera, the telescope has a $2.35{\times}2.35deg$ field-of-view. Currently, it is equipped with Johnson UBVRI filters and 3 narrow-band filters: $H{\alpha}$, OIII and SII. We will present the installation process, and the telescope performance such as detection limit and image quality based on the data from commissioning observations. We will also discuss possible scientific projects with this system.

• Journal of the Korean Society of Radiology
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• v.6 no.1
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• pp.79-82
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• 2012

Iodine is one of important nuclides to be checked for radiation exposure after nuclear power facility accidents. After Chernobyl accident, it was observed that there is a greater amount of organic iodine in the atmosphere than inorganic iodine. In this study, we not only varied the amount of sample being exposed to $^{131}I$ and the duration of exposure to $^{131}I$ but also diluted the sample in distilled water and mixed the sample in kelp and liquid $^{131}I$ to measure and analyze the radiation detection levels. We concluded that the radiation levels were not high enough to be harmful to human body. The radiation from $^{131}I$ decreased over time, and we calculated the half life at 7-9 days. We found that the radiation from any sample containing $^{131}I$ was halved by up to 7days.

• Journal of the Optical Society of Korea
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• v.20 no.6
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• pp.663-668
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• 2016

In single-photon-emission computed tomography (SPECT) with a pixelated semiconductor detector (PSD), not only pinhole collimators but also parallel-hole collimators are often used in preclinical nuclear-medicine imaging systems. The purpose of this study was to evaluate and compare pinhole and parallel-hole collimators in a PSD. For that purpose, we paired a PID 350 (Ajat Oy Ltd., Finland) CdTe PSD with each of the four collimators most frequently used in preclinical nuclear medicine: (1) a pinhole collimator, and (2) low-energy high-resolution (LEHR), (3) low-energy general-purpose (LEGP), and (4) low-energy high-sensitivity (LEHS) parallel-hole collimators. The sensitivity and spatial resolution of each collimator was evaluated using a point source and a hot-rod phantom. The highest sensitivity was achieved using LEHS, followed by LEGP, LEHR, and pinhole. Also, at a source-to-collimator distance of 2 cm, the spatial resolution was 1.63, 2.05, 2.79, and 3.45 mm using pinhole, LEHR, LEGP, and LEHS, respectively. The reconstructed hot-rod phantom images showed that the pinhole collimator and the LEHR parallel-hole collimator give a fine spatial resolution for preclinical SPECT with PSD. In conclusion, we successfully compared different types of collimators for a preclinical pixelated semiconductor SPECT system.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.82.1-82.1
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• 2012

GRB100205A is a Gamma Ray Burst (GRB) which is suspected to be at redshift z=11-13 due to its very red H-K color($(H-K)_{vega}=2.1{\pm}0.5$). We observed a field centered at GRB100205A with Wide Field Camera (WFCAM) at United Kingdom Infrared Telescope (UKIRT) in Hawaii, in order to search a quasar that could be located around the GRB. The images were obtained in J, H, and K filters covering a square area of $0.78deg^2$. Our J-, H-, and K-band data reach the depths of 22.5, 22.1, and 21.0 mag (Vega) at $5{\sigma}$, respectively. Also using z-band image observed by CFHT, we find 8 candidates that have colors consistent with a quasar at z=11-13(non-detection in z-, J-band and $(H-K)_{vega}$ > 1.6). However, the shallow depths of J-, H-band are not enough to verify their true nature. Instead, we identify many red objects to be old or dusty galaxies at $z{\geq}3$. The number density of such objects appears about twice or more than that of the field of Cosmological Evolution Survey (COSMOS) and Ultra Deep Survey (UDS) of UKIRT Infrared deep sky survey (UKIDSS). On scales between 0.18' and 15' the correlation function is well described by a power law with an exponent of ${\approx}-0.9$ and this implies that those objects are like galaxies. It is interesting that many red galaxies exist in the region where the GRB was detected.

• Journal of Biomedical Engineering Research
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• v.18 no.3
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• pp.307-313
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• 1997

he photoconductive gain mechanism in amorphus silicon devices was investigated in connection with applications to radiation detection. Various device types such as p-i-n, n-i-n and i-i-p-i-n structures were fabricated and tested. Photoconductive gain was measured in two time scales : one for short pulses of visible light(<$1{\mu}sec$) which simulate the transit of energetic charged particles or ${\gamma}$-rays, and the other for rather long pulses of light(1msec) which simulate x-ray exposure in medical imaging, We used two definitions of phtoconductive gain : current gain and charge gain which is an integration of the current gain. We obtained typical charge gains of 3~9 for short pulses and a few hundreds for long pulses at a dark current density level of 10mA/$cm^2$. Various gain results are discussed in terms of the device structure, applied bias and dark current density.

• Journal of Food Hygiene and Safety
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• v.28 no.2
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• pp.130-137
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• 2013

In this study, we investigated the applicability of the photostimulated luminescence (PSL), thermoluminescence (TL), electron spin resonance (ESR) and gas chromatography/mass spectrometry (GC/MS) methods for 5 seeds which are not allowed to be irradiated in Korea. All 5 seeds including evening primrose seed, safflower seed, rape seed, sunflower seed and flax seed were analyzed. Samples were irradiated at 1~10 kGy using a $^{60}Co$ gamma-ray irradiator. In PSL study, the photon counts of all the unirradiated samples showed negative (lower than 700). The photon counts of irradiated (1, 5, 10 kGy) samples showed positive (higher than 5,000). In TL analysis, results showed that it is possible to apply TL method to all foods containing minerals. In ESR measurements, the ESR signal (single-line) intensity of irradiated foods was higher than non-irradiated foods. The hydrocarbons 1,7-hexadecadiene ($C_{16:2}$) and 8-heptadecene ($C_{17:1}$) from oleic acid were detected only in the irradiated samples before and after the treatment at doses ${\geq}$ 1 kGy, but they were not detected in non-irradiated samples before and after treatment. These two hydrocarbons could be used as markers to identify irradiated safflower seed, rape seed, Sunflower seed and flax seed. And then, the hydrocarbons 1,7,10-hexadecatriene ($C_{16:3}$) and 6,9-heptadecadiene ($C_{17:2}$) from linoleic acid were detected in the evening primrose seed, safflower seed and sunflower seed. According to the results, PSL, TL and GC/MS methods were successfully applied to detect the irradiated foods. It is concluded that PSL, TL and GC/MS methods are suitable for detection of irradiated samples and a combined method is recommendable for enhancing the reliability of detection results.

• Food Science and Preservation
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• v.16 no.2
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• pp.211-216
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• 2009

This study determined the photostimulated luminescence(PSL), thermoluminescence(TL), and electron spin resonance(ESR) properties of wheat and corn irradiated with 0-10 kGy of gamma-ray or electron-beam. PSL values of both irradiated grains, regardless of radiation source, were 241-429 photons/sec in nonirradiated samples(negative values, defined as ${\leq}700$ photons/60 sec) and 5,528-40,870 photons/60 sec in irradiated ones(positive values, defined as ${\geq}5,000$ photons/sec), thereby distinguishing irradiated from nonirradiated samples. The TL glow curves($TL_1$) peaked at around $300^{\circ}C$ in nonirradiated samples, but at about $180^{\circ}C$ in irradiated samples, at high intensities, regardless of radiation source. The TL ratios($TL_1/TL_2$) calculated to strengthen $TL_1$ data reliability were less than 0.03 for nonirradiated samples and over 0.20 for irradiated materials, in good agreement with threshold values for nonirradiated(${\leq}0.1$) and irradiated(${\geq}0.1$) samples. ESR analysis was not applicable in identification of irradiated wheat and corn. Electron-beam irradiation resulted in higher PSL and TL signals than did gamma-rays, at the same applied doses.

• Food Science and Preservation
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• v.16 no.3
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• pp.371-375
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• 2009

Electron spin resonance (ESR) spectroscopy was used to detect radiation-induced signals from irradiated spices and ESR parameters were analyzed to define specific signals. Four powdered spices (red pepper, garlic, onion, and black pepper) were irradiated with 0, 1, 5, or 10 kGy at room temperature using a [60Co] gamma-ray irradiator prior to ESR analysis. Radiation-induced triplet signals, including those from the cellulose radical, which are center signals ($g_2=2.00673$) within the range of 3.0455 mT, were observed in all irradiated spice samples. The parameters g-value, center field, and signal range of hyperfine triplet ESR signals were constant in all irradiated samples, being specific for cellulose radicals and thereby distinguishing these signals from those of nonirradiated control samples. High positive correlation coefficients ($R^2=0.8452-0.9854$) were obtained between irradiation doses and corresponding ESR signal intensities. Thus, reliable detection of irradiated dried spices by measurement of ESR cellulose signals was confirmed by parameter analysis for the cellulose radical.