• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.115.1-115.1
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• 2012

The Ultraviolet Coronagraph Spectrometer on board the Solar and Heliospheric Observatory (SOHO) observes low ionization state coronal mass ejection plasma at ultraviolet wavelengths. The CME plasmas are often detected in O VI ($3{\times}10^5K$), C III ($8{\times}10^4K$), $Ly{\alpha}$, and $Ly{\beta}$. Earlier in situ observations by the Solar Wind Ion Composition Spectrometer (SWICS) on board Advanced Composition Explorer (ACE) have shown mostly high ionization state plasmas in interplanetary coronal mass ejections (ICME) events, which implies that most CME plasma is strongly heated during its expansion in solar corona. In this analysis, we investigate whether the low ionization state CME plasmas observed by UVCS occupy small enough fractions of the CME volume to be consistent with the small fraction of ICMEs measured by ACE that show low ionization plasma, or whether the CME must be further ionized after passing the UVCS slit. To do this, we determine the covering factors of low ionization state plasma for 10 CME events. We find that the low ionization state plasmas in CMEs observed by UVCS show small covering factors. This result shows that the high ionization state ICME plasmas observed by the ACE results from a small filling factor of cool plasma. We also find that the low ionization state plasma volumes in faster CMEs are smaller than in slower CMEs. Most slow CMEs in this analysis are associated with a prominence eruption, while the faster CMEs are associated with X-class flares.

• Journal of Korean Vacuum Science & Technology
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• v.2 no.2
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• pp.122-132
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• 1998

Characteristics of inductively coupled Cl2/O2 and Cl2/N2 plasmas and their effects on the formation of submicron deep trench etching of single crystal silicon have been investigated using Langmuir probe, quadrupole mass spectrometer (QMS), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM), Also, when silicon is etched with oxygen added chlorine plasmas, etch products recombined with oxygen such as SiClxOy emerged and Si-O bondings were found on the etched silicon surface. However, when nitrogen is added to chlorine, no etch products recombined with nitrogen nor Si-N bondings were found on the etched silicon surface. When deep silicon trenches were teached, the characteristics of Cl2/O2 and Cl2/N2 plasmas changed the thickness of the sidewall residue (passivation layer) and the etch profile. Vertical deep submicron trench profiles having the aspect ratio higher than 5 could be obtained by controlling the thickness of the residue formed on the trench sidewall using Cl2(O2/N2) plasmas.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.56.2-56.2
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• 2015

Nonthermal Atmospheric Pressure Plasmas and their Applications to Plasma Bioscience and Medicines have been introduced for next generation human healthcare's quantum developments. Various kinds of nonthermal atmospheric pressure plasmas have been introduced and their electron temperature and plasma densities along with reactive oxygen and nitrogen species have been diagnosed and analyzed for biological cell interactions, especially, used in Plasma Bioscience Research Center (PBRC), Korea. Herein, we have also introduced the plasma-initiated ultraviolet photolysis, which might be a generation mechanism for the reactive oxygen and nitrogen species (RONS) intracellular and extracellular regions inside the liquid when the plasma has been bombarded onto the water. Finally we have investigated the interactions of these RONS with the various cancer cells resulting in apoptotic cell death.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.04c
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• pp.22-26
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• 2008

In this paper, we developed a hybrid simulation model of carbon laser ablation under the Ar plasmas consisted of fluid and particle methods. Three kinds of carbon particles, which are carbon atom, ion and electron emitted by laser ablation, are considered in the computation. In the present simulation, we adopt capacitively coupled plasma with asymmetrical electrodes. As a result, in Ar plasmas, carbon ion motions were suppressed by a strong electric field and were captured in Ar plasmas. Therefore, a low number density of carbon ions were deposited upon substrate. In addition, the plume motions in Ar gas atmosphere was also discussed.

• Journal of Astronomy and Space Sciences
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• v.15 no.1
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• pp.111-118
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• 1998

A method to determine normal vectors for boundaries of plasmas with a series of data acquired from a single spacecraft is investigated. The determination of the normal vector is possible through a set of Rankine-Hugoniot(R-H) relations that are conser-vation relations of plasmas across a boundary. It is assumed that the boundary is planar and that the structure of the boundary is not varing in the rest frame of plasmas. The present method utilizes a complete set of R-H relations and provieds self-consistent predictions of the plasma densities, bulk velocities, and temperatures a s well as mag-netic fields. It is expected that the present method provides a more accurate normal vector than the previous methods which employ only subsets of the available R-H relations.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.1
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• pp.56.3-56.3
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• 2018

The present study formulates the theory of spontaneously emitted electromagnetic fluctuations in magnetized plasmas containing particles with an anisotropic suparthermal (bi-Kappa) velocity distribution function. The formalism is general applying for an arbitrary wave vector orientation and wave polarization, and for any wave-frequency range. As specific applications, the high-frequency electromagnetic fluctuations emitted in the upper-hybrid and multiple harmonic electron cyclotron frequency range are evaluated. The fluctuations for low-frequency are also applied, which include the kinetic $Alfv\acute{e}n$, fast magnetosonic/whistler, kinetic slow mode, ion Bernstein cyclotron modes, and higher-order modes. The model predictions are confirmed by a comparison with particle-in-cell simulations. The study describes how energetic particles described by kappa velocity distribution functions influence the spectrum of high and low frequency fluctuations in magnetized plasmas. The new formalism provides quantitative analysis of naturally occurring electromagnetic fluctuations, and contribute to an understanding of the electromagnetic fluctuations observed in space plasmas, where kappa-distributed particles are ubiquitous.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.256-256
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• 2011

Using plasmas, hydrophobic surfaces are made on various substances such as polyimide films, filter paper, cotton clothes and multi-walled carbon nanotube (MWCNT) with hexamethyldisiloxane (HMDSO), trimethylchlorosilane (TMCS) and toluene reagents. Plasmas are easily and rapidly to change surface of hydrophilic materials into hydrophobic. We have also optimized processing time and maximized contact angle for super-hydrophobicity of MWCNT. Contact angles have been calculated by measuring between substance and probe liquid, and total surface free energies are determined by the Owens-Wendt equation. Figure 1 shows the measured contact angles with time and ratio of reagents on MWCNT.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.5
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• pp.492-497
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• 2006

The study on laser-ablation plasmas has been strongly interested in fundamental aspects of laser-solid interaction and consequent plasma generation. In particular, this plasma has been widely used for the deposition of thin solid films and applied to the semiconductors and insulators. In this paper, we developed and discussed the generation of carbon ablation plasmas emitted by laser radiation on a solid target, graphite. The progress of carbon plasmas by laser-ablation was simulated using Monte-Carlo particle model under the pressures of vacuum, 1 Pa, 10 Pa and 66 Pa. At the results, carbon particles with low energy were deposited on the substrate as the pressure becomes higher However, there was no difference of deposition distributions of carbon particles on the substrate regardless of the pressure.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.20-20
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• 2011

It has been known that, under certain conditions, application of low-temperature atmospheric-pressure plasmas can enhance proliferation of cells. In this study, conditions for optimal cell proliferation were examined for various cells relevant for orthopaedic applications. Plasmas used in our experiments were generated by dielectric barrier discharge (DBD) with a helium flow (of approximately 3 litter/min) into ambient air at atmospheric pressure by a 10 kV~20 kHz power supply. Such plasmas were directly applied to a medium, in which cells of interest were cultured. The cells examined in this study were human synoviocytes, rat mesenchymal stem cells derived from bone marrow or adipose tissue, a mouse osteoblastic cell line (MC3T3-E1), a mouse embryonic mesenchymal cell line (C3H-10T1/2), human osteosarcoma cells (HOS), a mouse myoblast cell line (C2C12), and rat Schwann cells. Since cell proliferation can be enhanced even if the cells are not directly exposed to plasmas but cultured in a medium that is pre-treated by plasma application, it is surmised that long-life free radicals generated in the medium by plasma application stimulate cell proliferation if their densities are appropriate. The level of free radical generation in the medium was examined by dROMs tests and correlation between cell proliferation and oxidative stress was observed. Other applications of plasma medicine in orthopaedics, such as plasma modification of artificial bones and wound healing effects by direct plasma application for mouse models, will be also discussed. The work has been done in collaboration with Prof. H. Yoshikawa and his group members at the School of Medicine, Osaka University.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.10
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• pp.1485-1490
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• 2014

$SF_6$ gas has been used for power transformers or gas insulated switchgears, because it has the superior insulation property and the stable structure chemically. It has been, however, one of global warming gases and required to reduce the its amount. Some papers have reported that its amount could be reduced by mixing with other gases, such as $N_2$, $CF_4$, $CO_2$ and $C_4F_8$ and their mixture gases would cause the synergy effect. In this paper, we investigated the characteristics of DC plasmas on $SF_6$ mixture gases with $N_2$ at atmospheric pressure. $N_2$ gas is one of cheap gases and has been reported to show the synergy effect with mixing $SF_6$ gas, even though $N_2$ plasmas have electron-positive characteristics. 38 kinds of $SF_6/N_2$ plasma particles, which consisted of an electron, two positive ions, five negative ions, 30 excitation and vibration particles, were considered in a one dimensional fluid simulation model with capacitively coupled plasma chamber. The results showed that the joule heating of $SF_6/N_2$ plasmas was mainly caused by positive ions, on the other hand electrons acted on holding the $SF_6/N_2$ plasmas stably. The joule heating was strongly generated near the electrodes, which caused the increase of neutral gas temperature within the chamber. The more $N_2$ mixed-ratio increased, the less joule heating was. And the power consumptions by electron and positive ions increased with the increase of $N_2$ mixed-ratio.