An upgrade of the magnetic diagnostic system of the DIII-D tokamak for non-axisymmetric measurements.

King, J D,Strait, E J,Boivin, R L,Taussig, D,Watkins, M G,Hanson, J M,Logan, N C,Paz-Soldan, C,Pace, D C,Shiraki, D,Lanctot, M J,La Haye, R J,Lao, L L,Battaglia, D J,Sontag, A C,Haskey, S R,Bak, J G American Institute of Physics 2014 Review of scientific instruments Vol.85 No.8

<P>The DIII-D tokamak magnetic diagnostic system [E. J. Strait, Rev. Sci. Instrum. 77, 023502 (2006)] has been upgraded to significantly expand the measurement of the plasma response to intrinsic and applied non-axisymmetric '3D' fields. The placement and design of 101 additional sensors allow resolution of toroidal mode numbers 1 n 3, and poloidal wavelengths smaller than MARS-F, IPEC, and VMEC magnetohydrodynamic model predictions. Small 3D perturbations, relative to the equilibrium field (10(-5) < δB/B0 < 10(-4)), require sub-millimeter fabrication and installation tolerances. This high precision is achieved using electrical discharge machined components, and alignment techniques employing rotary laser levels and a coordinate measurement machine. A 16-bit data acquisition system is used in conjunction with analog signal-processing to recover non-axisymmetric perturbations. Co-located radial and poloidal field measurements allow up to 14.2 cm spatial resolution of poloidal structures (plasma poloidal circumference is ~500 cm). The function of the new system is verified by comparing the rotating tearing mode structure, measured by 14 BP fluctuation sensors, with that measured by the upgraded B(R) saddle loop sensors after the mode locks to the vessel wall. The result is a nearly identical 2/1 helical eigenstructure in both cases.</P>

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>

Physical and rheological properties of xanthan gum agglomerated in fluidized bed: Effect of HPMC as a binder

Jeong, G.Y.,Bak, J.H.,Yoo, B. Elsevier 2019 INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES Vol.121 No.-

<P><B>Abstract</B></P> <P>Physical and rheological properties of agglomerated xanthan gum (XG), commonly used as a food thickener for the management of the patients with dysphagia (swallowing difficulty), were investigated at different concentrations (0, 2, 4, and 6% w/w) of hydroxypropyl methylcellulose (HPMC) as a binder in the fluidized bed agglomeration process. Flow characteristics of agglomerated XG powder were evaluated using Carr index (CI) and Hausner ratio (HR). The agglomerated XG powders obtained by HPMC binder exhibited a better flowability and higher porosity than the agglomerated powder without binder due to the size enlargement of XG powder. Dynamic moduli (G′ and G”) of agglomerated XG powders at 2% and 4% HPMC were significantly higher than those of other powders. The tan δ values of agglomerated powders with HPMC binder were much lower than that of an agglomerated powder without HPMC, indicating that their elastic properties were enhanced because of the addition of HPMC binder. Results suggest that the use of HPMC in agglomeration process could considerably enhance the flow characteristics and rheological properties of XG powder.</P>

^19F(p, αγ)^16O 반응의 α-γ 각상관

박상태,김기동,이대원,정운혁,노태익,정성채,이종환,나상균 동의대학교 기초과학연구소 1994 基礎科學硏究論文集 Vol.4 No.1

The α-γ angular correlations in the ^19F(p, αγ)^16O reaction have been measured using a 500 keV VDG accelerator at E_p=340 keV and a CaF₂ taget prepared by evaporation in vaccum. The measurement of the α-γ angular correlation between the α-rays from the decay of ^20Ne into ^16O and the γ-rays from ^16O has been performed using a Si surface barrier detector and a NaI(TI) detector to determine the spin of the 13.196 MeV level in ^20Ne, and those of the 6.14 MeV and the ground level in ^16O, together with the orbital angular momentum of the emitted α's. The α-γ angular correlations in the ^19F(p, αγ)^16O reaction have been also calculated for the assumed spins of the 13.196 MeV level in ^20Ne, and those of the 6.14 MeV and ground level in ^16O. The spins of the levels under condsideration have been determined by comparison of the calculated values with experimental value. The result makes a good agreement to Arnold's data.

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.

Plastic 섬광검출기의 감마선 스펙트럼에 대한 unfolding 분석

김기동,박상태,최선수,이대원,정운혁,이종환,노태익 동의대학교 기초과학연구소 1995 基礎科學硏究論文集 Vol.5 No.1

The γ-ray pulse height spectra from ^137Cs and ^22Na were measured with a plastic scintillation detector for the unfolding analysis of the γ-ray spectra. The energy deposition spectra were calculated using the Compton deposition cross section. The energy dependent resolution and its corresponding response matrix were determined by comparing the measured γ-ray pulse height spectra with the calculated energy deposition spectra. The energy spectra were obtained by unfolding the measured pulse height spectra with the response matrix.

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>

Fast Reciprocating Probe Assembly for the KSTAR

Bak, J. G.,Lee, S. G.,KSTAR project team WILEY-VCH Verlag 2006 CONTRIBUTIONS TO PLASMA PHYSICS Vol.46 No.5

<P>A fast reciprocating probe assembly (FRPA) that can scan a distance of up to 32.5 cm with a maximum speed of 1.7 m/s was fabricated to obtain the spatial profile of basic plasma parameters in the edge region of the KSTAR plasma during a plasma discharge of 20 s. The probe driving mechanism consists of two parts; first a slow movement driven by a servo motor system and then a fast reciprocating movement actuated by a pneumatic system. A performance test of the drive system, which is remotely controlled by a PC, was carried out. The prototype of the probe head for the KSTAR FRPA was fabricated as a modular type for easy replacement. It was installed in the fast injection probe assembly (FIPA) in the Hanbit magnetic mirror device, and a radial plasma parameter profile measurement was carried out. The performance test results of the drive system and the profile measurements using the probe head are presented. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</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.

Restriction of Fourier transforms to curves: An endpoint estimate with affine arclength measure

Bak, J.-G.,Oberlin, D.M.,Seeger, A. WALTER DE GRUYTER 2013 Journal für die reine und angewandte Mathemat Vol.2013 No.682