Electric Probe Measurements at Edge Region During H‐Mode Discharges in KSTAR

Bak, J.G.,Oh, Y.S.,Kim, H.S.,Hahn, S.H.,Yoon, S.W.,Jeon, Y.M.,Xiao, W.W.,Ko, W.H.,Kim, W.C.,Kwak, J.G.,Woo, H.J.,Chung, K.S.,the KSTAR project team, WILEY‐VCH Verlag 2013 Contributions to plasma physics Vol.53 No.1

<P><B>Abstract</B></P><P>Electrical probe measurements are carried out at the scrape‐off‐layer (SOL) and divertor regions in order to investigate the characteristics of edge plasmas during H‐mode discharges in the Korea Superconducting Tokamak Advanced Research (KSTAR) device. Radial profiles of plasma parameters such as electron temperature T<SUB><I>e</I></SUB>, plasma density n<SUB><I>e</I></SUB>, and parallel flow velocity v<I><SUB>‖</SUB></I> are measured by using a fast reciprocating Langmuir probe assembly (FRLPA) at the SOL region. From the FRLPA measurements, it is found that the decay length of temperature λ<I><SUB>Te</SUB></I> and that of density λ<I><SUB>ne</SUB></I> are 2 <I>∼</I> 4 cm and 1 <I>∼</I> 3 cm, respectively. The magnitude of v<I><SUB>‖</SUB></I> near the last closed flux surface (LCFS) is 4 <I>∼</I> 15 km/s. The radial flux due to edge turbulence at the SOL region is investigated by using spectra analysis on electrostatic fluctuation levels such as ion saturation current Ĩ<I><SUB>is</SUB></I> and floating potential <TEX>$ \tilde{\rm V}_f$</TEX> obtained from the FRLPA measurement. The value of the flux is estimated as <I>∼</I> 10<SUP>20</SUP> particle m<SUP>−2</SUP> s <SUP>−1</SUP> near the LCFS. The poloidal distribution of the ion saturation current density j<I><SUB>is</SUB></I> is measured by fixed edge Langmuir probe array (ELPA) at the divertor region, and it is found that the positions of strike points from the ELPA measurement agree well with those reconstructed from the EFIT result using magnetic diagnostic data. From the spectrum analysis on the ELPA measurements at the divertor region during edge localized modes (ELMs) control in the H‐mode discharges, it is observed that the magnitude of <TEX>$ \tilde{\rm j}_{is}$</TEX>(<I>ω</I>) near strike point decreases when the ELMs are suppressed or mitigated (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)</P>

Key Features in the Operation of KSTAR

Jong-Gu Kwak,Oh, Y. K.,Kim, K. P.,Kim, S. W.,Hong, S. H.,Chu, Y.,Lee, H. J.,Kim, Y. O.,Kim, J.,Park, S. L.,Hahn, S. H.,Park, M. K.,Kim, H. K.,Bak, J. G.,Bae, Y. S.,Ko, W. H.,Lee, S. G.,Lee, J. H.,Jung IEEE 2012 IEEE transactions on plasma science Vol.40 No.3

<P>The Korea Superconducting Tokamak Advanced Research (KSTAR) device is aimed at advanced tokamak (AT) research. Three years have passed since it achieved its first plasma in 2008. Because it is a superconducting machine and is working toward AT research, it has unique features in terms of the machine engineering and operation. The toroidal field (TF) magnet coils are made of Nb<SUB>3</SUB>Sn, which provide high TFs up to 3.5 T, and have been fully tested. The poloidal field (PF) magnet coils, consisting of both Nb<SUB>3</SUB>Sn and NbTi, which have a maximum current of 25 kA in their design, were tested up to 15 kA. A thermal hydraulic analysis is being conducted for PF magnet coil operation. All plasma-facing components (PFCs) are equipped with water cooled graphite tiles and have the capability of being baked up to 350°C. A startup scenario, which considered both the effect of the ferromagnetic material in the cable in conduit conductor jacket of the magnet coils as well as a nonferromagnetic up-down asymmetry in the cryostat structure, was developed and demonstrated its effectiveness by the last two year's reliable operations. Passive stabilizers and in-vessel control coils (IVCCs) are key components to realize AT operation in KSTAR. The segmented IVCC coils were connected to form circular coils for internal vertical control in 2010, and diverted plasmas with high elongation (κ~1.8, δ>;0.6) were achieved. A neutral beam injection (NBI) system was developed aiming at 2 MW, 300 s per ion source which meets the long-pulse requirement of KSTAR. An NBI ion source with a power of 1.7 MW at 100 kV has been commissioned for 10 s. Finally, ELMy H-modes were successfully produced with 1.3-MW NBI power at a plasma current of 0.6 MA in the 2010 campaign. The first H-mode discharge (#4200) in KSTAR was achieved one year earlier than officially planned and was done at B<SUB>T</SUB> = 2 T with I<SUB>p</SUB> = 0.6 MA in a well-balanced double null configuration after boronization on the PFC. Successful operations in the early days of KSTAR including H-mode experiments revealed the capability of advanced and steady-state operation which is essential for the international thermonuclear experimental reactor (ITER) and future fusion reactors.</P>

VIBRATION REDUCTION OF H/SHAFT USING AN ELECTROMAGNETIC DAMPER WITH MODE CHANGE

K. H. LEE,J. H. BAK,J.-L. PARK,C. H. Lee 한국자동차공학회 2017 International journal of automotive technology Vol.18 No.2

The objective of this study is to develop a damper that can reduce the amplitude of vibration in various frequency ranges. Previous H/Shaft vibration reduction methods work in a passive way. A dynamic damper reduces the amplitude of vibration at its first mode, but vibration still appears at the second mode. A mass damper or hollow shaft can shift the natural frequency to a lower or higher region. The fixed operating frequency prevents vibration from being reduced outside the operating frequency range. The proposed damper uses electromagnets as either masses or actuators to change the damper mode between dynamic damper mode and mass damper mode. The electromagnetic damper (EMD) can change its mode to respond to the vibration excitation at both low and high frequencies. The vibration reduction performance was evaluated by FRF tests in laboratory and vehicle conditions. The results were compared with those of a dynamic damper and indicate that the amplitude of vibration is reduced by 95.6 % when the EMD is implemented on an H/Shaft, whereas only 61.9 % vibration reduction is achieved by the dynamic damper.

처리방법별 농산물중의 잔류농약 제거에 관한 연구

박주성,강희곤,오준세,이규희,성창근,김성애,오만진 충남대학교 환경문제연구소 2000 環境硏究 Vol.18 No.-

The removal rates of pesticide residues on agricultural products by washing with tap water, washing with detergent, heating and dipping with ozonized water were analyzed. The removal rates of organophosphorous pesticide residues on perilla leaves and Korean cabbage were shown as 25.7-71.9% level by washing with tap water and 72.4%-82.0% level by washing with detergent. However, those on Angelica keiskei were shown as 44.6-64.7% level by washing with tap water and 72.4-82.0% by washing with detergent. Those on perilla leaves and Korean cabbage were shown as 61.1%-91.1% and 74.8-95.4% levels by heating, respectively. Also, the removal rates of organochlorine pesticide residues on perilla leaves and Aster scaber were shown as 55.6-66.3% level by washing with tap water, 85.8-93.0% level by washing with detergent and 54.1-63.6% level by heating. Therefore, the organochlorine pesticide residues was shown the highest removal rate by washing with detergent and not significance between washing with tap water and heating. When the grape was processed as jam, the removal rates of organophosphorous pesticide residues were shown as below 50% level and those of organochlorine were shown as 22.3-60.2% level with difference according to variety of pesticides. Also, the decomposition effects of pesticides by dipping in ozonized water were analyzed. The various solvents were tested for the most effective recovery of pesticides on agricultural products. The benzene contained 20% dichloromethane was shown the most effective recovery rate for organophosphorous pesticides as 105.4-113.8% level. Hexan was the most effective for organochlorine as 67.7-91.3% level. As the result by dipping with ozonized water, the changes of pesticide content levels according to dipping and dipping time in ozonized water were not shown significance.

Neuroprotective Effects of Acetyl-L-Carnitine Against Oxygen-Glucose Deprivation-Induced Neural Stem Cell Death

Bak, S. W.,Choi, H.,Park, H. H.,Lee, K. Y.,Lee, Y. J.,Yoon, M. Y.,Koh, S. H. Humana Press 2016 Molecular Neurobiology Vol. No.

<P>Deprivation of oxygen and glucose is the main cause of neuronal cell death during cerebral infarction and can result in severe morbidity and mortality. In general, the neuroprotective therapies that are applied after ischemic stroke have been unsuccessful, despite many investigations. Acetyl-L-carnitine (ALCAR) plays an important role in mitochondrial metabolism and in modulating the coenzyme A (CoA)/acyl-CoA ratio. We investigated the protective effects of ALCAR against oxygen-glucose deprivation (OGD) in neural stem cells (NSCs). We measured cell viability, proliferation, apoptosis, and intracellular signaling protein levels after treatment with varying concentrations of ALCAR under OGD for 8 h. ALCAR protected NSCs against OGD by reducing apoptosis and restoring proliferation. Its protective effects are associated with increases in the expression of survival-related proteins, such as phosphorylated Akt (pAkt), phosphorylated glycogen synthase kinase 3b (pGSK3b), B cell lymphoma 2 (Bcl-2), and Ki-67 in NSCs that were injured by OGD. ALCAR also reduced the expression of death-related proteins, such as Bax, cytosolic cytochrome C, cleaved caspase-9, and cleaved caspase-3. We concluded that ALCAR exhibits neuroprotective effects against OGD-induced damage to NSCs by enhancing the expression of survival signals and decreasing that of death signals.</P>

Investigation of SOL parameters and divertor particle flux from electric probe measurements in KSTAR

Bak, J.G.,Kim, H.S.,Bae, M.K.,Juhn, J.W.,Seo, D.C.,Bang, E.N.,Shim, S.B.,Chung, K.S.,Lee, H.J.,Hong, S.H. Elsevier 2015 Journal of Nuclear Materials Vol.463 No.-

<P><B>Abstract</B></P> <P>The upstream scrape-off layer (SOL) profiles and downstream particle fluxes are measured with a fast reciprocating Langmuir probe assembly (FRLPA) at the outboard mid-plane and a fixed edge Langmuir probe array (ELPA) at divertor region, respectively in the KSTAR. It is found that the SOL has a two-layer structure in the outboard wall-limited (OWL) ohmic and L-mode: a near SOL (∼5mm zone) with a narrow feature and a far SOL with a broader profile. The near SOL width evaluated from the SOL profiles in the OWL plasmas is comparable to the scaling for the L-mode divertor plasmas in the JET and AUG. In the SOL profiles and the divertor particle flux profile during the ELMy H-modes, the characteristic e-folding lengths of electron temperature, plasma density and particle flux during an ELM phase are about two times larger than ones at the inter ELM.</P>

SOL Parameters, and Particle and Heat Fluxes at Divertor Targets from Electric Probe Measurements in KSTAR

J. G. Bak,H. S. Kim,J. Kim,K. I. You,S. H. Hong,M. K. Bae 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.8

The plasma parameters in the scrape-off layer (SOL) region and the particle flux at the divertortarget are measured by using a fast reciprocating Langmuir probe assembly (FRLPA) and a fixededge Langmuir probe array (ELPA) in the KSTAR. The e-folding lengths of the plasma density (ne)and the electron temperature (Te), ne and Te, are obtained from the radial profile measurementusing the FRLPA at the outboard mid-plane during ohmic and H-mode discharges. Particle fluxesmeasured by using the ELPA at the divertor target are mapped to the outboard mid-plane, and thefluxes are quite well matched to the radial profile of the particle flux from the FRLPA measurement. Finally, the peak heat flux at the divertor target during edge localized modes (ELMs) can beestimated to be up to 1.0 MWm−2 for the neutral beam power of 2.7 MW by using Te at theseparatrix and Te from the FRLPA measurements. In this work, the experimental results fromthe probe measurements in the KSTAR are presented.

一部 農村住民의 母子保健센타 施設分娩의 利用要園에 對한 豫備調査

박기흠,김병성,이종호,조홍준,김창엽,김정숙,허봉렬 의학교육출판사 1987 Korean Journal of Family Medicine Vol.8 No.3

Electric probe diagnostics for measuring SOL parameters, wall and divertor fluxes in KSTAR

Kim, H.S.,Bak, J.G.,Bae, M.K.,Chung, K.S.,Hong, S.H. North-Holland ; Elsevier Science Ltd 2016 Fusion engineering and design Vol.109 No.1

Some components in electric probe diagnostics (EPDs) are improved in order to investigate characteristics of edge plasmas in the upstream scrape-off-layer (SOL) region and to measure wall and divertor fluxes during L-mode and H-mode plasma discharges in the Korea Superconducting Tokamak Advanced Research (KSTAR). From the upgrades in the EPDs, the measured error of the elapsed distance for the evaluation of the SOL profiles can be reduced up to 1% and the ion saturation current of up to 1.0A near an outer strike point (OSP) can be measured at the divertor region. In the SOL profile measurements during L-mode and inner wall limited plasma (B<SUB>T</SUB>=2.0T, I<SUB>p</SUB>=0.4MA), the e-folding lengths in the main SOL region λ<SUB>Te</SUB> and λ<SUB>ne</SUB> are evaluated as 3.5cm and 2.1cm, respectively. From particle flux measurement at the far SOL region during a diverted ELMy H-mode discharge (B<SUB>T</SUB>=1.8T, I<SUB>p</SUB>=0.65MA), peaked heat flux toward to outboard wall during ELM bursts is estimated up to ~20kWm<SUP>-2</SUP>, which may be less than 1% of the peaked divertor heat flux expected for the neutral beam (NB) heating power P<SUB>NB</SUB> of ~2.66MW and stored energy W<SUB>TOT</SUB> of ~0.38MJ. In addition, the movement of the OSP during a diverted H-mode plasma (B<SUB>T</SUB>=2.4T, I<SUB>p</SUB>=0.5 MA) can be detected from the divertor probe measurement and peaked heat flux near the OSP is estimated as few MWm<SUP>-2</SUP> for P<SUB>NB</SUB>=3.0 MW, W<SUB>TOT</SUB>=~0.25MJ. In this work, the technical details of the EPDs including its upgrades and some experimental results from EPD measurements are presented.

1996년도 제35차 대한소화기학회 추계학술대회 / Helicobacter pylon 박멸에 proton pump inhibitor-amoxicillin 이중요법과 proton pump inhibitor-amoxicillin-clarithromycin 삼중요법의 효과

연종은(J . E . Yeon),박영태(Y . T . Bak),김진호(J . H . Kim),이창홍(C . H . Lee),임형준(H . J . Kim),김종극(J . K . Kim),김재선(J . S . Kim) 대한소화기학회 1996 대한소화기학회지 Vol.28 No.1