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Journal Articles

Soft, skin-interfaced microfluidic systems with integrated immunoassays, fluorometric sensors, and impedance measurement capabilities

Kim, S.*; Lee, B.*; Reeder, J. T.*; Seo, S. H.*; Lee, S.-U.*; Hourlier-Fargette, A.*; Shin, J.*; Sekine, Yurina; Jeong, H.*; Oh, Y. S.*; et al.

Proceedings of the National Academy of Sciences of the United States of America, 117(45), p.27906 - 27915, 2020/11

 Times Cited Count:9 Percentile:76.81(Multidisciplinary Sciences)

In this study, we present a wireless, battery-free, skin-interfaced microfluidic system that combines lateral flow immunoassay for sweat cortisol assay, fluorometric imaging of glucose and ascorbic acid (vitamin C) assays, and digital tracking of sweat rate using electrodes that measure skin galvanic response. Systematic benchtop testing and on-body field studies on human subjects exercising in a gym environment highlight the key multifunctional features of this platform in tracking the biochemical correlates of physical stress.

Journal Articles

Comparison of dislocation density, twin fault probability, and stacking fault energy between CrCoNi and CrCoNiFe medium entropy alloys deformed at 293 and 140K

Woo, W.*; Naeem, M.*; Jeong, J.-S.*; Lee, C.-M.*; Harjo, S.; Kawasaki, Takuro; He, H.*; Wang, X.-L.*

Materials Science & Engineering A, 781, p.139224_1 - 139224_7, 2020/04

 Times Cited Count:6 Percentile:76.25(Nanoscience & Nanotechnology)

Journal Articles

Stacking fault energy analyses of additively manufactured stainless steel 316L and CrCoNi medium entropy alloy using in situ neutron diffraction

Woo, W.*; Jeong, J.-S.*; Kim, D.-K.*; Lee, C. M.*; Choi, S.-H.*; Suh, J.-Y.*; Lee, S. Y.*; Harjo, S.; Kawasaki, Takuro

Scientific Reports (Internet), 10(1), p.1350_1 - 1350_15, 2020/01

 Times Cited Count:10 Percentile:82.97(Multidisciplinary Sciences)

Journal Articles

First online multireflection time-of-flight mass measurements of isobar chains produced by fusion-evaporation reactions; Toward identification of superheavy elements via mass spectroscopy

Schury, P.*; Wada, Michiharu*; Ito, Yuta*; Kaji, Daiya*; Arai, Fumiya*; MacCormick, M.*; Murray, I.*; Haba, Hiromitsu*; Jeong, S.*; Kimura, Sota*; et al.

Physical Review C, 95(1), p.011305_1 - 011305_6, 2017/01

AA2016-0638.pdf:0.71MB

 Times Cited Count:33 Percentile:96.3(Physics, Nuclear)

Using a multireflection time-of-flight mass spectrograph located after a gas cell coupled with the gas-filled recoil ion separator GARIS-II, the masses of several $$alpha$$-decaying heavy nuclei were directly and precisely measured. The nuclei were produced via fusion-evaporation reactions and separated from projectilelike and targetlike particles using GARIS-II before being stopped in a helium-filled gas cell. Time-of-flight spectra for three isobar chains, $$^{204}$$Fr-$$^{204}$$Rn-$$^{204}$$At-$$^{204}$$Po, $$^{205}$$Fr- $$^{205}$$Rn-$$^{205}$$At-$$^{205}$$Po-$$^{205}$$Bi, and $$^{206}$$Fr-$$^{206}$$Rn-$$^{206}$$At, were observed. Precision atomic mass values were determined for $$^{204-206}$$Fr, $$^{204,205}$$Rn, and $$^{204,205}$$At. Identifications of $$^{205}$$Bi, $$^{204,205}$$Po, $$^{206}$$Rn, and $$^{206}$$At were made with N$$leq$$10 detected ions, representing the next step toward use of mass spectrometry to identify exceedingly low-yield species such as superheavy element ions.

Journal Articles

Spontaneous decays of magneto-elastic excitations in non-collinear antiferromagnet (Y,Lu)MnO$$_{3}$$

Oh, J.*; Le, M. D.*; Nahm, H.-H.*; Sim, H.*; Jeong, J.*; Perring, T. G.*; Woo, H.*; Nakajima, Kenji; Kawamura, Seiko; Yamani, Z.*; et al.

Nature Communications (Internet), 7, p.13146_1 - 13146_6, 2016/10

 Times Cited Count:38 Percentile:85.96(Multidisciplinary Sciences)

Magnons and phonons are fundamental quasiparticles in a solid and can be coupled together to form a hybrid quasi-particle. However, detailed experimental studies on the underlying Hamiltonian of this particle are rare for actual materials. Moreover, the anharmonicity of such magnetoelastic excitations remains largely unexplored, although it is essential for a proper understanding of their diverse thermodynamic behaviour and intrinsic zero-temperature decay. Here we show that in non-collinear antiferromagnets, a strong magnon phonon coupling can significantly enhance the anharmonicity, resulting in the creation of magnetoelastic excitations and their spontaneous decay. By measuring the spin waves over the full Brillouin zone and carrying out anharmonic spin wave calculations using a Hamiltonian with an explicit magnon phonon coupling, we have identified a hybrid magnetoelastic mode in (Y,Lu)MnO$$_{3}$$ and quantified its decay rate and the exchange-striction coupling termrequired to produce it.

Journal Articles

Direct measurement of nanoscale lithium diffusion in solid battery materials using radioactive tracer of $$^{8}$$Li

Ishiyama, Hironobu*; Jeong, S.-C.*; Watanabe, Yutaka*; Hirayama, Yoshikazu*; Imai, Nobuaki*; Jung, H. S.*; Miyatake, Hiroari*; Oyaizu, Mitsuhiro*; Osa, Akihiko; Otokawa, Yoshinori; et al.

Nuclear Instruments and Methods in Physics Research B, 376, p.379 - 381, 2016/06

 Times Cited Count:6 Percentile:61.4(Instruments & Instrumentation)

Journal Articles

Nanoscale diffusion tracing by radioactive $$^{8}$$Li tracer

Ishiyama, Hironobu*; Jeong, S.-C.*; Watanabe, Yutaka*; Hirayama, Yoshikazu*; Imai, Nobuaki*; Miyatake, Hiroari*; Oyaizu, Mitsuhiro*; Katayama, Ichiro*; Osa, Akihiko; Otokawa, Yoshinori; et al.

Japanese Journal of Applied Physics, 53(11), p.110303_1 - 110303_4, 2014/11

 Times Cited Count:4 Percentile:21.42(Physics, Applied)

Journal Articles

Characteristics of global energy confinement in KSTAR L- and H-mode plasmas

Kim, H.-S.*; Jeon, Y. M.*; Na, Y.-S.*; Ghim, Y.-C.*; Ahn, J.-W.*; Yoon, S. W.*; Bak, J. G.*; Bae, Y. S.*; Kim, J. S.*; Joung, M.*; et al.

Nuclear Fusion, 54(8), p.083012_1 - 083012_11, 2014/08

 Times Cited Count:4 Percentile:24.21(Physics, Fluids & Plasmas)

We evaluate the characteristics of global energy confinement in KSTAR ($$tau_{E, rm KSTAR}$$) quantitatively by comparing it with multi-machine scalings, by deriving multiple regression equations for the L- and the H-mode plasmas, and evaluating confinement enhancement of the H-mode phase compared with the L-mode phase in each discharge. From the KSTAR database, $$tau_{E, rm KSTAR}$$ of L-mode plasmas exhibits $$sim 0.04$$ s to $$sim 0.16$$ s and $$tau_{E, rm KSTAR}$$ of H-mode plasmas $$sim 0.06$$ s to $$sim 0.19$$ s. The multiple regression equations derived by statistical analysis present the similar dependency on PL and slightly higher dependency on IP compared with the multi-machine scalings, however the dependency on elongation $$kappa$$ in both L- and H-mode plasmas draw the negative power dependency of $$kappa^{-0.68}$$ and $$kappa^{-0.76}$$ for H-mode and for L- mode database, respectively on the contrary to the positive dependency in all multi-machine empirical scalings. Although the reason is not clear yet, two possibilities are addressed. One is that the wall condition of KSTAR was not clean enough. The other is that striking points on the divertor plate were uncontrolled. For these reasons, as $$kappa$$ increases, the impurities from the wall can penetrate into plasmas easily. As a consequence, the confinement is degraded on the contrary to the expectation of multi-machine scalings.

Journal Articles

Development of high voltage power supply for the KSTAR 170 GHz ECH and CD system

Jeong, J. H.*; Bae, Y. S.*; Joung, M.*; Kim, H. J.*; Park, S. I.*; Han, W. S.*; Kim, J. S.*; Yang, H. L.*; Kwak, J. G.*; Sakamoto, Keishi; et al.

Fusion Engineering and Design, 88(5), p.380 - 387, 2013/06

 Times Cited Count:1 Percentile:12.53(Nuclear Science & Technology)

Journal Articles

First neutral beam injection experiments on KSTAR tokamak

Jeong, S. H.*; Chang, D. H.*; Kim, T. S.*; In, S. R.*; Lee, K. W.*; Jin, J. T.*; Chang, D. S.*; Oh, B. H.*; Bae, Y. S.*; Kim, J. S.*; et al.

Review of Scientific Instruments, 83(2), p.02B102_1 - 02B102_3, 2012/02

 Times Cited Count:20 Percentile:68.57(Instruments & Instrumentation)

The first NB (neutral beam) injection system of the KSTAR tokamak was partially completed in 2010 with only 1/3 of its full design capability, and NB heating experiments were carried out during the 2010 KSTAR operation campaign. The ion source is composed of a JAEA bucket plasma generator and a KAERI large multi-aperture accelerator assembly. Before the beam injection experiments, characteristics of the ion source were investigated. A minimum beam divergence angle was 0.8 $$^{circ}$$. The ion species ratio was D$$^{+}$$:D$$_{2}$$$$^{+}$$:D$$_{3}$$$$^{+}$$=75:20:5. The arc efficiency is more than 1.0 A/kW. In the 2010 KSTAR campaign, the deuterium NB power of 0.7-1.5 MW was successfully injected into the KSTAR plasma with the beam energy of 70-90 keV. L-H transitions were observed within a wide range of beam powers relative to a threshold value. In every deuterium NB injection, a burst of D-D neutrons was recorded, and increases in the ion temperature and the plasma stored energy were found.

Journal Articles

Arc discharge characteristics of a long pulse ion source for the KSTAR neutral beam injector

Chang, D. H.*; Jeong, S. H.*; Jin, J. T.*; Chang, D. S.*; Kim, T. S.*; Lee, K. W.*; In, S. R.*; Oh, B. H.*; Bae, Y. S.*; Kim, J. S.*; et al.

Journal of the Korean Physical Society, 59(2), p.275 - 280, 2011/08

 Times Cited Count:3 Percentile:29.52(Physics, Multidisciplinary)

A long pulse ion source (LPIS) for the neutral beam injector (NBI) has been developed for the Korea Superconducting Tokamak Advanced Research (KSTAR) superconducting tokamak. The arc discharge characteristics of the ion source were investigated on the first KSTAR neutral beam injector (NBI-1). The ion source consists of a magnetic bucket plasma generator with multi-pole cusp fields and a set of prototype tetrode accelerators with circular apertures. Stable and efficient arc plasmas up to an arc power of 70 kW have been produced by using a constant power-mode operation of the arc power supply. The reliable operation region of the arc discharges has been investigated for various filament heating voltages, arc powers, and amounts of injected deuterium gas.

Journal Articles

Results of beam extraction performance for the KSTAR neutral beam injector

Chang, D. H.*; Jeong, S. H.*; Kim, T. S.*; Lee, K. W.*; In, S. R.*; Jin, J. T.*; Chang, D. S.*; Oh, B. H.*; Bae, Y. S.*; Kim, J. S.*; et al.

Japanese Journal of Applied Physics, 50(6), p.066302_1 - 066302_7, 2011/06

 Times Cited Count:9 Percentile:41.24(Physics, Applied)

A stable ion beam extraction of the LPIS-1 was achieved up to 85 kV/32 A for a 5 s pulse length and 80 kV/25 A for a 14 s pulse length. An optimum beam perveance of 1.15 $$mu$$perv was observed at an acceleration voltage of 60 kV. Neutralization efficiency was measured by a water-flow calorimetry (WFC) method using a calorimeter and the operation of a bending magnet. The full-energy species of ion beams were detected by using the diagnostic method of optical multichannel analyzer (OMA). An arc efficiency of the LPIS was 0.6-1.1 A/kW depending on the operating conditions of arc discharge. A neutral beam power of 1.0 MW must be sufficiently injected into the KSTAR plasmas from the LPIS-1 at a beam energy of 80 keV.

Journal Articles

Development of a plasma generator for a long pulse ion source for neutral beam injectors

Watanabe, Kazuhiro; Dairaku, Masayuki; Tobari, Hiroyuki; Kashiwagi, Mieko; Inoue, Takashi; Hanada, Masaya; Jeong, S. H.*; Chang, D. H.*; Kim, T. S.*; Kim, B. R.*; et al.

Review of Scientific Instruments, 82(6), p.063507_1 - 063507_6, 2011/06

 Times Cited Count:15 Percentile:61.15(Instruments & Instrumentation)

A long pulse plasma generator for neutral beam injectors has been developed. The plasma generator was designed to produce 65 A at 120 keV from a beam extraction area of 12 cm $$times$$ 46 cm. A type of the plasma generator is a multi-cusp plasma generator with SmCo permanent magnets. A long pulse test of the plasma generator was performed at the KSTAR NBI test stand in Korea under the Japan - Korea Fusion collaboration. It was successfully demonstrated of the long pulse operation of the plasma generator for 200 s at an arc discharge power of 70 kW which can produce 65 A beams. Plasma spatial uniformity at the beam extraction area was confirmed to be smaller than $$pm$$ 8% of the deviation from an averaged ion saturation current density. A high arc efficiency of 0.9-1.1 A/kW was obtained at the beam extraction with 73 keV, 41 A for 5 sec. From these experimental studies, a performance of this plasma generator for long pulse ion sources was confirmed.

Journal Articles

Commissioning results of the KSTAR neutral beam system

Bae, Y. S.*; Park, Y. M.*; Kim, J. S.*; Han, W. S.*; Kwak, S. W.*; Chang, Y. B.*; Park, H. T.*; Song, N. H.*; Chang, D. H.*; Jeong, S. H.*; et al.

Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 9 Pages, 2011/03

The neutral beam injection (NBI) system is designed to provide the ion heating and current drive for the high performance operation and long pulse operation of the Korean Superconducting Tokamak Advanced Research (KSTAR). The KSTAR NBI consists of two beam lines. Each beam line contains three ion sources of which one ion source has been designed to deliver more than 2.5 MW of deuterium neutral beam power with maximum 120-keV beam energy. Consequently, the final goal of the KSTAR NBI system aims to inject more than 14 MW of deuterium beam power with the two beam lines. According to the planned NBI system, the first NBI system is to demonstrate the beam injection from one ion source into the KSTAR tokamak plasma in 2010 campaign including the system commissioning of each components and subsystems. In this paper, the construction and the commissioning of the first NBI system with one ion source is presented.

Journal Articles

Status and result of the KSTAR upgrade for the 2010's campaign

Yang, H. L.*; Kim, Y. S.*; Park, Y. M.*; Bae, Y. S.*; Kim, H. K.*; Kim, K. M.*; Lee, K. S.*; Kim, H. T.*; Bang, E. N.*; Joung, M.*; et al.

Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03

Because the 2010 operation of Korea Superconducting Tokamak Advanced Research (KSTAR) mainly aims to achieve strongly elongated and diverted plasma, all the necessary hardware systems to provide an essential circumstance for the plasma shaping were newly installed and upgraded in 2010. In this paper, general configuration of the upgraded systems described earlier will be outlined. Moreover, several key performances and test results of the systems will be also reported in summary.

Journal Articles

ECRH assisted plasma start-up with toroidally inclined launch; Multi-machine comparison and perspectives for ITER

Stober, J.*; Jackson, G. L.*; Ascasibar, E.*; Bae, Y.-S.*; Bucalossi, J.*; Cappa, A.*; Casper, T.*; Cho, M. H.*; Gribov, Y.*; Granucci, G.*; et al.

Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2010/10

Journal Articles

Efficient production of a collimated MeV proton beam from a Polyimide target driven by an intense femtosecond laser pulse

Nishiuchi, Mamiko; Daido, Hiroyuki; Yogo, Akifumi; Orimo, Satoshi; Ogura, Koichi; Ma, J.-L.; Sagisaka, Akito; Mori, Michiaki; Pirozhkov, A. S.; Kiriyama, Hiromitsu; et al.

Physics of Plasmas, 15(5), p.053104_1 - 053104_10, 2008/05

 Times Cited Count:40 Percentile:84.02(Physics, Fluids & Plasmas)

High-flux energetic protons whose maximum energies are up to 4 MeV are generated by an intense femtosecond Titanium Sapphire laser pulse interacting with a 7.5, 12.5, and 25$$mu$$m thick Polyimide tape targets. The laser pulse energy is 1.7 J, duration is 34 fs, and intensity is 3$$times$$10$$^{19}$$Wcm$$^{-2}$$. The amplified spontaneous emission (ASE) has the intensity contrast ratio of 4$$times$$10$$^{-8}$$. The conversion efficiency from laser energy into proton kinetic energies of $$sim$$3% is achieved, which is comparable or even higher than those achieved in the previous works with nanometer-thick targets and the ultrahigh contrast laser pulses ($$sim$$10$$^{-10}$$).

Journal Articles

Simultaneous proton and X-ray imaging with femtosecond intense laser driven plasma source

Orimo, Satoshi; Nishiuchi, Mamiko; Daido, Hiroyuki; Yogo, Akifumi; Ogura, Koichi; Sagisaka, Akito; Li, Z.*; Pirozhkov, A. S.; Mori, Michiaki; Kiriyama, Hiromitsu; et al.

Japanese Journal of Applied Physics, Part 1, 46(9A), p.5853 - 5858, 2007/09

 Times Cited Count:16 Percentile:55.33(Physics, Applied)

A laser-driven proton beam with a maximum energy of a few MeV is stably obtained using an ultra-short and high-intensity Titanium Sapphire laser. At the same time, keV X-ray is also generated at almost the same place where protons are emitted. Here, we show the successful demonstration of simultaneous proton and X-ray projection images of a test sample placed close to the source with a resolution of $$sim$$10$$mu$$m, which is determined from the source sizes. Although the experimental configuration is very simple, the simultaneity is better than a few hundreds of ps. A CR-39 track detector and imaging plate, which are placed as close as possible to the CR-39, are used as detectors of protons and X-ray. The technique is applicable to the precise observation of microstructures.

Journal Articles

Status of KSTAR electron cyclotron heating system

Bae, Y. S.*; Na, Y. S.*; Oh, Y. K.*; Kwon, M.*; Bak, J. S.*; Lee, G. S.*; Jeong, J. H.*; Park, S. I.*; Cho, M. H.*; Namkung, W.*; et al.

Fusion Science and Technology, 52(2), p.321 - 333, 2007/08

 Times Cited Count:21 Percentile:81.84(Nuclear Science & Technology)

An 84-GHz, 500-kW gyrotron system have been installed at KSTAR, and the initial test of the gyrotron has been carried out with 20 $$mu$$sec-pulse and an output RF power of 500 kW. The launcher system having with a highly flexible steering mirror was fabricated and would inject 500-kW rf power into the KSTAR plasma. KSTAR will employ 170-GHz EC current drive (CD) in ITER-relevant experiments such as the suppression of the neoclassical tearing modes and the creation of an electron internal transport barrier. A JAEA 170-GHz, 1-MW gyrotron on loan in accordance with a Korea-Japan fusion collaboration agreement, and it will be used for the 170-GHz, 1-MW ECCD system in 2010. This paper describes the current status of the installation and initial conditioning tests of the 84-GHz gyrotron system as well as the development plan of the 170-GHz ECH and CD system. Also, this paper discusses the CD efficiency and the steering range of the second-harmonic X-mode injection.

Journal Articles

Development of laser driven proton sources and their applications

Daido, Hiroyuki; Sagisaka, Akito; Ogura, Koichi; Orimo, Satoshi; Nishiuchi, Mamiko; Mori, Michiaki; Ma, J.-L.; Pirozhkov, A. S.; Kiriyama, Hiromitsu; Kanazawa, Shuhei; et al.

Proceedings of 7th Pacific Rim Conference on Lasers and Electro-Optics (CLEO-PR 2007) (CD-ROM), p.77 - 79, 2007/00

We are developing a proton accelerator using an intense lasers with a focused intensity of $$>$$ 10$$^{17}$$ W/cm$$^{2}$$. To monitor proton energy spectra as well as plasma parameters at each laser shot, we are using real time detectors. The proton energy of MeV is stably obtained for applications.

28 (Records 1-20 displayed on this page)