Faculty Profiles - OHNO, Noriyasu

Papers - OHNO, Noriyasu

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Field Emission Property of Nanostuructured Tungsten Formed by Helium Plasma Irradiation Reviewed

S.Kajita, N.Ohno, Y.Hirahata, M.Hiramatsu

Journal of Fusion Engineering and Design Vol. 88 page： 2842-2847 2013.6

Power Transmission Factor for Tungsten Target W/WO Fiber-form Nanostructure in He Plasmas with Hot Electron Component using Compact Plasma Device AIT-PID Reviewed

S.Takamura, T.Miyamoto, N.Ohno

Transactions of Fusion Science and Technology Vol. 63 page： 225-228 2013.5

Investigation of Advanced Divertor Magnetic Configuration for Demo Tokamak Reactor Reviewed

N.Asakura, K.Shinya, K.Tobita, K.Hoshino, K.Shimizu, H.Utoh, Y.Someya, M.Nakamura, N.Ohno, M.Kobayashi, H.Tanaka

Transactions of Fusion Science and Technology Vol. 63 ( 1T ) page： 70-75 2013.5

Impact of arcing on carbon and tungsten: from the observations in JT-60U, LHD and NAGDIS-II Reviewed

S.Kajita, M.Fukumoto, M.Tokitani, T.Nakano, Y.Noiri, N.Ohno, S.Masuzaki, S.Takamura, N.Yoshida, Y.Ueda

Nuclear Fusion Vol. 53 page： 053013(9 pp) 2013.4

Helium plasma implantation on metals: Nanostructure formation and visible-light photocatalytic response Reviewed Open Access

S.Kajita, T.Yoshida, D.Kitaoka, R.Etoh, M.Yajima, N.Ohno, H.Yoshida, N.Yoshida, Y.Terao

Journal of Applied Physics Vol. 113 page： 134301(8 pp) 2013.4

Assessment of multi-pulse laser-induced damage threshold of metallic mirrors for Thomson scattering system Reviewed Open Access

M.Sato, S.Kajita, R.Yasuhara, N.Ohno, M.Tokitani, N.Yoshida, Y.Tawara

Optics Express Vol. 21 ( 8 ) page： 9333-9342 2013.4

Comparison of damages on tungsten surfac exposed to noble gas plasmas Reviewed

M.Yajima, M.Yamagiwa, S.Kajita, N.Ohno et al.

Plasma Science & Technol. Vol. 15 page： 282-286 2013.3

Two-dimensional visualization of excitation temperature and chemical species in divertor plasmas: Trace CD molecules by chemical sputtering of fusion plasma reactor wall Reviewed

Z.Cui, K.Kodama, M.Yamamoto, Q.Shen, M.Yoshimi, S.Kajita, N.Ohno, K.Kitagawa

Microchemical Journal Vol. 106 page： 174-179 2013.1

Influence of the Probe Electrode on Probe Measurements for Atmospheric Pressure Microwave Plasma Torch Reviewed International journal

Ezumi N., Kodama N., Akahane K., Shiozawa S., Sawada K., Ohno N.

Contributions to Plasma Physics Vol. 53 ( 1 ) page： 81 - 85 2013.1

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Contributions to Plasma Physics

In this study, in order to clarify the influence of a probe electrode during probe measurements of an atmospheric pressure microwave plasma, simultaneous observations of probe current and the change of plasma shape using a high-speed camera have been done. Fast and random repetitions of attachment and detachment of the plasma torch to the probe electrode have been observed. It is found that the response time is related to ion sound speed. Different behaviors of the plasma torch for a floating metal electrode or an insulator have been observed. Probe current-voltage characteristics show asymmetric double probe shape © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOI： 10.1002/ctpp.201310014

Scopus

First Principles Investigation on Trapping of Multiple Helium Atoms within a Tungsten Monovacancy Reviewed

A.Takayama, A.M.Ito, S.Saito, N.Ohno, H.Nakamura

Japanese Journal of Applied Physics Vol. 52 page： 01AL03(4 pp) 2013

Intermittent transport in edge plasma with a 3-D magnetic geometry in the Large Helical Device Reviewed

H.Tanaka, S.Masuzaki, N.Ohno, T.Morisaki, Y.Tsuji, the LHD Experiment Group

Journal of Nuclear Materials Vol. 438 page： S563-S566 2013

Observation of Arc Spots Initiated on Nanostructured Tungsten Reviewed

S.Kajita, N.Ohno, S.Takamura

IEEE TRANSACTIONS ON PLASMA SCIENCE Vol. 41 ( 8, Part 2 ) page： 1889-1895 2013

Deuterium Atomic Density Estimation in Recombining Plasmas Using Self-Absorption Spectroscopy Reviewed

S.Kajita, T.Nishiwaki, N.Ohno, K.Sawada, M.Takagi

IEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING Vol. 8 ( 1 ) page： 1-6 2013

Extension of operation regimes and investigation of three-dimensional currentless plasmas in the Large Helical Device Reviewed Open Access

O.Kaneko, H.Yamada, S.Inagaki, M.Jakubowski, S.Kajita, et al.(N.Ohno is the 104th author))

Nucl. Fusion Vol. 53 page： 104015(11 pp) 2013

First-Principles Investigation on Trapping of Multiple Helium Atoms within a Tungsten Monovacancy Reviewed

A.Takayama, A.M.Ito, S.Saito, N.Ohno, H.Nakamura

Jpn. J. Appl. Phys. Vol. 52 page： 01AL023(4 pp) 2013

Effect of resistivity profile on current decay time of initial phase of current quench in neon-gas-puff inducing disruptions of JT-60U Reviewed

S.Kawakami, Y.Shibata, K.Y.Watanabe, N.Ohno, A.Isayama, T.Takizuka, Y.Kawano, M.Okamoto

Physics of Plasmas Vol. 20 page： 112507(6 pp) 2013

Degradation of optical reflectivity of in-vessel mirror materials by helium bombardment Reviewed Open Access

S.Kajita, M.Tokitani, T.Saekim N.Ohno, N.Yoshida

J. Nucl. Mater. Vol. 417 page： 838-841 2013

Behavior of Plasma Response Field in Detached Plasma Reviewed International journal

NARUSHIMA Yoshiro, KOBAYASHI Masahiro, AKIYAMA Tsuyoshi, SAKAKIBARA Satoru, MASUZAKI Suguru, ASHIKAWA Naoko, OHNO Noriyasu

Plasma and Fusion Research Vol. 8 ( 0 ) page： 1402058 - 1402058 2013

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：プラズマ・核融合学会

Sustaining a detached plasma is important for the reduction of the heat load on a divertor. The externally controlled methods such as gas puffing in the divertor region, etc. have been studied for maintaining detached plasmas. In the recent LHD experiments, a resonant magnetic perturbation (RMP) is utilized to establish the detached plasma, which is one of the candidates to reduce the divertor heat load. The finite plasma response field has been detected when the RMP is imposed, and its behavior is investigated from the viewpoint of the magnetic island dynamics. A parameter of the phase difference, Δθ (defined as the phase difference between the plasma response field and the RMP), changes from antiphase to in-phase while the plasma transits from the attached to the detached states. Finally, when the Δθ reaches at certain critical value, Δθcrit, the plasma enters the detached state. Since this critical value does not have a dependency on plasma beta and collisionality, Δθcrit seems to be a threshold to establish the detached plasma. From the viewpoint of magnetic island dynamics, the behavior of Δθ approaching in-phase implies the "trend" of island growth. The detached plasma might be established in the case of the tendency for the plasma response field to reinforce the island width.

DOI： 10.1585/pfr.8.1402058

CiNii Research

Thermal radiation characteristics and direct evidence of tungsten cooling on the way to nanostructure formation on its surface Reviewed International journal

Takamura S., Miyamoto T., Ohno N.

Journal of Nuclear Materials Vol. 438 ( SUPPL ) 2013

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Nuclear Materials

The physical properties of tungsten with nanostructure on its surface are investigated focusing on the thermal radiation and cooling characteristics. First, direct evidence of substantial W surface cooling has been clearly shown with use of a very thin thermocouple inserted into W target, which solves an uncertainty associated with a radiation thermometer. Second, the above measurements of W surface temperature make it possible to estimate quantitatively the total emissivity from which we may evaluate the radiative power through the Stefan-Boltzmann equation, which is very important for mitigation evaluation of a serious plasma heat load to the plasma-facing component. © 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jnucmat.2013.01.176

Scopus

Preliminary experiments on the vertical stability with helical coils in a small tokamak, HYBTOK-II Reviewed International journal

Hatakeyama S., Shibata Y., Kawakami S., Tsutsui H., Tsuji-Iio S., Shimada R., Ohno N., Akiyama T., Suzuki Y., Watanabe K.

39th EPS Conference on Plasma Physics 2012, EPS 2012 and the 16th International Congress on Plasma Physics Vol. 1 page： 285 - 288 2012.12

Language：English Publishing type：Research paper (international conference proceedings) Publisher：39th EPS Conference on Plasma Physics 2012, EPS 2012 and the 16th International Congress on Plasma Physics

In summary, we proposed saddle shaped stellarator system for vertical mode in toka-mak. These preliminary results demonstrate the feasibility of vertical stability, even if only two selected coils which are localized at one side of the torus. However as noted earlier, the experiment were conducted with the circular cross-section tokamak which is stable vertically. Further work is needed to confirm the improvement in the vertical stability in elongated tokamaks. In addition, very large coil current comparable to the plasma current are needed in our system. In order to reduce the current, future work also should focus on optimal configuration of the coils.

Scopus

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Papers - OHNO, Noriyasu