Faculty Profiles - OHNO, Noriyasu

Papers - OHNO, Noriyasu

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Anisotropic Graphite Erosion in Low-Temperature and high-Density Deuterium Plasma Reviewed

M.Teraoka, N.Ohno, S.Kajita, T.Nishiwaki, A.M.Ito, H.Nakamura

Jpn. J. Appl. Phys. Vol. 51 page： 01AB03 (5pp) 2012.1

Near Infrared Radiation from Heated Nanostructured Tungsten Reviewed

S.Kajita, T.Yokochi, N.Ohno, T.Kumano

Jpn. J. Appl. Phys. Vol. 51 page： 01AJ03 (5pp) 2012.1

Measurement of ion and electron temperatures in plasma blobs by using an improved ion sensitive probe system and statistical analysis methods Reviewed International journal

K. Okazaki, H. Tanaka, H. Tanaka, N. Ohno, N. Ezumi, Y. Tsuji, S. Kajita

Review of Scientific Instruments Vol. 83 2012.1

Language：English Publishing type：Research paper (scientific journal)

We have measured ion temperature as well as electron temperature in plasma blobs observed in a linear plasma device by using an improved ion sensitive probe. Current-voltage characteristics of the ion sensitive probe inside and outside plasma blobs were re-constructed with a conditional sampling method. It is clearly found that both ion and electron temperatures in plasma blobs decrease more slowly in a cross-field direction than those in a bulk plasma without plasma blobs. © 2012 American Institute of Physics.

DOI： 10.1063/1.3681778

Scopus

Electric Field at a Plasma-Facing Wall for a Two-Temperature Electron Distribution Reviewed

Y.Tomita, G.Kawamura, M.Ueno, N.Ohno, Z.H.Huang, Y.D.Pan, L.W.Yan

Contrib. Plasma Phys. Vol. 52 ( 5-6 ) page： 484-489 2012

Thermionic Energy Converter System Using Heat Flux in Divertor Region Reviewed

D.Oikawa, N.Ohno, S.Kajita, M.Takagi, S.Masuzaki, M.Tokitani, K.Asano

Plasma and Fusion Research Vol. 7 page： 1405050(8 pages) 2012

Conditions for the Release of a Metallic Dust Particle from a Plasma-Facing Wall Reviewed

M.Ueno, N.Ohno, Y.Tomita, G.Kawamura

Contrib. Plasma Phys. Vol. 52 ( 5-6 ) page： 478-483 2012

Effects of fibre-form nanostructures on particle emissions from a tungsten surface in plasmas Reviewed

S.Takamura, T.Miyamoto, N.Ohno

Nuclear Fusion Vol. 52 page： 123001(8 pages) 2012

Validation of the current decay model in the initial phase of current quench in high disruptive discharges of JT-60U Reviewed International journal

Shibata Y., Watanabe K., Ohno N., Okamoto M., Isayama A., Kurihara K., Oyama N., Nakano T., Kawano Y., Sugihara M.

38th EPS Conference on Plasma Physics 2011, EPS 2011 - Europhysics Conference Abstracts Vol. 35 2 page： 1628 - 1631 2011.12

Language：English Publishing type：Research paper (scientific journal) Publisher：38th EPS Conference on Plasma Physics 2011, EPS 2011 - Europhysics Conference Abstracts

The validation of current decay model during the current quench was investigated in high (3p disruptive discharges on JT-60U. It is experimentally confirmed that the electron temperature does not play an important role in the determination of the current decay time in the initial phase of current quench and that values obtained from L/R model are two orders of magnitude larger than the experimental current decay time. The current decay time predicted by the modified L/R model, in which the time derivative of plasma inductance is taken into account, is in fairly good agreement with the experimental data. In future work, we need to perform the MHD equilibrium code for free-boundary condition such as DINA [5] and TSC [6] code under the axisymmetric assumption in order to clear up the determination mechanism of time derivative of plasma inductance.

Scopus

Recent progress of tungsten R&D for fusion application in Japan Reviewed International journal

Ueda Y., Lee H.T., Ohno N., Kajita S., Kimura A., Kasada R., Nagasaka T., Hatano Y., Hasegawa A., Kurishita H., Oya Y.

Physica Scripta T Vol. T145 2011.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Physica Scripta T

The status of ongoing research projects of tungsten R&D in Japan is summarized in this paper. For tungsten material development, a new improved fabrication technique, the so-called superplasticity-based microstructural modification, is described. This technique successfully improved fracture strength and ductility at room temperature. Recent results on vacuum plasma spray W coating and W brazing on ferritic steels and vanadium alloys are explained. Feasibility of these techniques for the manufacture of the blanket is successfully demonstrated. The latest findings on the effect of neutron damage in tungsten on T retention and on the change in mechanical and electrical properties are described. Retention characteristics for neutron-damaged W were different compared to those for ion-damaged W. Upon neutron irradiation, tungsten alloys containing transmutation elements of W (Re and Os) show changes in properties that are different compared with those shown by pure W. The effects of mixed plasma exposure (D/He/C) are described. Both D/He and D/C mixed ion irradiations significantly affect ion-driven permeation in W. He bubble dynamics play a key role in nano-structure formation on the W surface. © 2011 The Royal Swedish Academy of Sciences.

DOI： 10.1088/0031-8949/2011/T145/014029

Scopus

Deuterium retention in Fe <inf>2</inf>O <inf>3</inf> under low-energy deuterium-plasma exposure Reviewed International journal

Matsunami N., Sogawa T., Sakuma Y., Ohno N., Tokitani M., Masuzaki S.

Physica Scripta T Vol. T145 2011.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Physica Scripta T

Stainless steel (SUS) is used as the structure material in nuclear fusion devices. Heating and O 2 plasma discharge are considered for the removal of tritium. Oxide layer growth is anticipated on heating SUS at a high temperature in low-pressure residual O 2 gas. When O 2 plasma discharge is performed, oxygen plasma reaches the structure material and iron oxides such as Fe 2O 3 are formed. Thus, a knowledge of the retention behavior of hydrogen isotopes or deuterium (D) in the oxide layers is important in designing the devices. We investigated D retention in Fe 2O 3 films and the influence of Fe 2O 3 crystal structure on D retention and found that D retention in γ-Fe 2O 3 (cubic-maghemite) is larger than that in α-Fe 2O 3 (hexagonal-hematite). The results for Fe 2O 3 are compared with those for SUS and Fe. © 2011 The Royal Swedish Academy of Sciences.

DOI： 10.1088/0031-8949/2011/T145/014042

Scopus

TEM observation of the growth process of helium nanobubbles on tungsten: Nanostructure formation mechanism Reviewed International journal

Kajita Shin, Yoshida Naoaki, Yoshihara Reiko, Ohno Noriyasu, Yamagiwa Masato

JOURNAL OF NUCLEAR MATERIALS Vol. 418 ( 1-3 ) page： 152 - 158 2011.11

Helium bubble formation on tungsten in dependence of fabrication method Reviewed International journal

Yamagiwa Masato, Kajita Shin, Ohno Noriyasu, Takagi Makoto, Yoshida Naoaki, Yoshihara Reiko, Sakaguchi Wataru, Kurishita Hiroaki

JOURNAL OF NUCLEAR MATERIALS Vol. 417 ( 1-3 ) page： 499 - 503 2011.10

Nanoscale surface morphology of tungsten materials induced by Be-seeded D-He plasma exposure Reviewed International journal

Tokunaga K., Baldwin M. J., Doerner R. P., Nishijima D., Kurishita H., Fujiwara T., Araki K., Miyamoto Y., Ohno N., Ueda Y.

JOURNAL OF NUCLEAR MATERIALS Vol. 417 ( 1-3 ) page： 528 - 532 2011.10

Exfoliation of the tungsten fibreform nanostructure by unipolar arcing in the LHD divertor plasma Reviewed International journal

Tokitani M., Kajita S., Masuzaki S., Hirahata Y., Ohno N., Tanabe T.

NUCLEAR FUSION Vol. 51 ( 10 ) 2011.10

Development of Nanostructured Black Metal by Self-Growing Helium Bubbles for Optical Application Reviewed International journal

S.Kajita, T.Saeki, Y.Hirahata, M.Yajima, N.Ohno, R.Yoshihara, N.Yoshida

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 50 ( 8 ) page： 08JG01 2011.8

Investigation on the effect of temperature excursion on the helium defects of tungsten surface by using compact plasma device Reviewed

S.Takamura, T.Miyamoto, Y.Tomida, T.Minagawa, N.Ohno

Journal of Nuclear Materials Vol. 415 page： S100-S103 2011.8

Exposure of tungsten nano-structure to TEXTOR edge plasma Reviewed International coauthorship

Y.Ueda, K.Miyata, Y.Ohtsuka, H.T.Lee, M.Fukumoto, S.Brezinsek, J.W.Coenen, A.Kreter, A.Litnovsky, V.Philipps, B.Schweer, G.Sergienko, T.Hirai, A.Taguchi, Y.Torikai, K.Sugiyama, T.Tanabe, S.Kajita, N.Ohno, The TEXTOR team

Journal of Nuclear Materials Vol. 415 ( 1 ) page： S92 - S95 2011.8

Divertor simulation experiment and its future research plan making use of a large tandem mirror device Reviewed International journal

Nakashima Y., Takeda H., Hosoi K., Yonenaga R., Katanuma I., Ichimura K., Ichimura M., Imai T., Ishii T., Kariya T., Kiwamoto Y., Minami R., Miyata Y., Ozawa H., Shidara H., Yamaguchi Y., Yoshikawa M., Asakura N., Hatayama A., Higashizono Y., Kado S., Masuzaki S., Nishino N., Ohno N., Ueda Y.

Journal of Nuclear Materials Vol. 415 ( 1 SUPPL ) 2011.8

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

Divertor simulation study has been started as a new research plan, by making best use of a large linear plasma device. The experiment of generating the plasma flow with high heat and particle flux was successfully performed at an end-mirror exit of the GAMMA 10 tandem mirror. In typical hot-ion-mode plasmas, the heat-flux density of 0.6 MW/m2 and the particle-flux density of 1022 particles/s m2 were simultaneously achieved in the case of only ICRF heating and superimposing the 300 kW ECH pulse attained the peak value of the net heat-flux up to 8 MW/m2 on axis. The above experimental results and the simulation analysis of ICRF heating using the Fokker-Planck code give a clear prospect of generating the required performance for divertor studies by building up the plasma heating systems to the end-mirror cell. Detailed behavior of the plasma flow and the future research plan are also described. © 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jnucmat.2010.11.081

Scopus

Motion of unipolar arc spots ignited on a nanostructured tungsten surface Reviewed

S.Kajita, S.Takamura, N.Ohno

Plasma Physics and Controlled Fusion Vol. 53 ( 7 ) page： 074002 2011.5

Molecular Dynamics Simulation of Hydrogen Injection onto Diamond Surfaces Reviewed

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

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 50 ( 1 ) page： 01AB04(4 pages) 2011.1

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Papers - OHNO, Noriyasu