Faculty Profiles - OHNO, Noriyasu

Papers - OHNO, Noriyasu

Division display 221 - 240 of about 657 ／ All the affair displays >>

Surface modification of titanium using He plasma Reviewed

S.Kajita, D.Kitaoka, N.Ohno, R.Yoshihara, N.Yoshida, T.Yoshida

Applied Surface Science Vol. 303 page： 438-445 2014.3

Thermal response of nanostructured tungsten Reviewed

S.Kajita, G.De Temmerman, T.Morgan, S.van Eden, T. de Kruif, N.Ohno

Nuclear Fusion Vol. 54 page： 033005(10 pp) 2014.2

Helium plasma irradiation on single crystal tungsten and undersized atom doped tungsten alloys Reviewed International journal

Shin Kajita, Naoaki Yoshida, Noriyasu Ohno, Yuki Hirahata, Reiko Yoshihara

PHYSICA SCRIPTA Vol. 89 ( 2 ) 2014.2

Language：English Publishing type：Research paper (scientific journal) Publisher：IOP PUBLISHING LTD

Helium plasma irradiation leads to the formation of nanostructures on the surface when certain conditions are satisfied. The surface morphology changes due to helium plasma irradiation were investigated on single crystal tungsten samples with different crystal orientations. Differences in surface morphology changes were observed in (100) and (110) single crystal tungsten samples when the helium fluence was less than 10(25) m(-2). However, the differences disappeared as growth proceeded. Tungsten alloys were prepared in order to investigate the influence of the additional undersized atomic species on nanostructure growth. The influence of the doping of undersized atoms, i.e. 2 at% Fe doped and 2 at% Cr doped atoms, is presented.

DOI： 10.1088/0031-8949/89/02/025602

Web of Science

Scopus

Optical design for divertor Thomson scattering system for JT-60SA Reviewed

S.Kajita, A.Enokuchi, T.Hatae, K.Itami, T.Hamano, S.Kado, N.Ohno, N.Takeyama

Fusion Engineering and Design Vol. 89 ( 1 ) page： 69-76 2014.1

Helium plasma irradiation on single crystal tungsten and undersized atom doped tunsten alloys Reviewed

S.Kajita, N.Yoshida, N.Ohno, Y.Hirahata, R.Yoshihara

Phys. Scr. Vol. 89 page： 025602(7 pp) 2014.1

Modified Power Transmission Factor of Tungsten in Plasmas with Hot Electron Component Reviewed

S.Takamura, S.Ono, N.Ohno

Contrib. Plasma Phys. Vol. 54 ( 4-6 ) page： 474-478 2014

Transition in velocity and grouping of arc spot on different nanostructured tungsten electrodes Reviewed

Dogyun Hwangbo, Shin Kajita, Sergey A. Barengolts, Mikhail M. Tsventoukh, Noriyasu Ohno

RESULTS IN PHYSICS Vol. 4 page： 33 - 39 2014

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

Behavior of arc spots was investigated in detail using a nanostructured tungsten specimen with different thicknesses of the nanostructured layer. From the observation using a fast framing camera, it was found that the velocity of the arc spots significantly altered as passing the boundary of the two layers. The changes in spot velocity and spot width were discussed theoretically using the ecton model. The fractal dimension of the arc trail evaluated by using a box-counting method was significantly changed. Also, the width of arc trail was increased with the nanostructured layer thickness. From the SEM analysis of the specimen, the amount of tungsten eroded by arcing for two different thickness cases was estimated, and the erosion rates were discussed. (C) 2014 The Authors. Published by Elsevier B.V.

DOI： 10.1016/j.rinp.2014.03.001

Web of Science

Scopus

Spectroscopic Study and Motion Analysis of Arc Spot Initiated on Nanostructured Tungsten Reviewed

D.Hwangbo, S.Kajita, M.Osaka, N.Ohno

Jpn. J. Appl. Phys. Vol. 52 page： 11NC02(6 pp) 2013.11

Low-energy helium irradiation on in-vessel mirror materials Reviewed

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

Journal of Nuclear Materials Vol. 442 ( 1-3, Supplement 1 ) page： S515-S519 2013.11

Helium effects on tungsten surface morphology and deuterium retention Reviewed

Y.Ueda, H.Y.Peng, H.T.Lee, N.Ohno, S.Kajita, N.Yoshida, R.Doerner, G.De Temmerman, V.Alimov, G.Wright

Journal of Nuclear Materials Vol. 442 ( 1-3 ) page： S267-S272 2013.11

Properties of deposited layer formed by interaction with Be seede D-He mixture plasma and tungsten Reviewed

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

Journal of Nuclear Materials Vol. 442 ( 1-3 ) page： S313-S319 2013.11

Characterization of Gun Plasma Penetrated into a Steady State Plasma Device Reviewed

S.Kajita, T.Akiyama, T.Nihashi, M.Osaka, N. Ohno, Y.Kikuchi, I.Sakuma, M.Nagata

IEEE TRANSACTIONS ON PLASMA SCIENCE Vol. 41 ( 11 ) page： 3122-3128 2013.11

Field emission property of nanostructured tungsten formed by helium plasma irradiation Reviewed

Shin Kajita, Noriyasu Ohno, Yuki Hirahata, Mineo Hiramatsu

FUSION ENGINEERING AND DESIGN Vol. 88 ( 11 ) page： 2842 - 2847 2013.11

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE SA

Field emission property of nanostructured tungsten formed by the exposure to a helium plasma is measured to investigate the initiation process of arcing in nuclear fusion devices. Field emission current from the nanostructured tungsten and tungsten with helium bubbles was significantly higher than that from the polished tungsten specimen. However, field enhancement factor was on the order of 100, which was almost comparable to that of bulk tungsten; the increase in the field emission current is attributed to primarily an increase in the effective emission surface area. From the calculation of thermo-field emission current from a heated tungsten, it is thought that a significant current emission can be still initiated even when the field enhancement factor is not so high when tungsten is exposed to high density plasmas such as the one accompanied with ELMs. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.fusengdes.2013.05.014

Web of Science

Scopus

Progress of the JT-60SA project Reviewed International coauthorship International journal

Kamada Y., Barabaschi P., Ishida S., Abdel Maksoud W., Aiba N., Akino N., Akiyama T., Alonso J., Angioni C., Arai T., Arakawa H., Ardellier F., Artaud J., Asakawa S., Asakura N., Ashikawa N., Balaguer D., Barbato E., Barrera G., Baruzzo M., Baulaigue O., Bayetti P., Bécoulet M., Benkadda S., Benoit F., Besi U., Beurskens M., Boccaccini L., Bolzonella T., Borba D., Botija J., Bourdelle C., Brolatti G., Bruschi A., Bucalossi J., Cara P., Challis C., Chantant M., Chapman I., Chesny P., Chiba S., Ciayznski D., Cismondi F., Cocilovo V., Coletti R., Coletti A., Collins B., Conway G., Corato V., Costa P., Cucchiaro A., Dael A., Davis S., Day C., De Baar M., Decool P., Della Corte A., Delrez C., De Vries P., Decker J., Di Zenobio A., Di Pace L., Di Pietro E., Disset G., Donati A., Douai D., Dougnac H., Drotziger S., Duchateau J.L., Duglue D., Dumas N., Ejiri A., Endo Y., Farina D., Fernandez P., Ferro A., Fietz W., Figini L., Fslchetto G., Fujita T., Fukuda T., Fukumoto M., Fukuyama A., Furukawa M., Furukawa M., Gaio E., Garcia J., Garzotti L., Gauthier E., Genini L., Geraud A., Ginoulhiac G., Giruzzi G., Gomez Carrasco B., Gonde R., Goniche M., Gouat P., Gros G., Haga S.

Nuclear Fusion Vol. 53 ( 10 ) 2013.10

Language：English Publishing type：Research paper (scientific journal) Publisher：Nuclear Fusion

The JT-60SA project implemented by Japan and Europe is progressing on schedule towards the first plasma in March 2019. After careful R&D, procurements of the major components have entered their manufacturing stages. In parallel, disassembly of JT-60U has been completed on time, and the JT-60SA tokamak assembly is expected to start in January 2013. The JT-60SA device, a highly shaped large superconducting tokamak with a variety of plasma control actuators, has been designed in order to contribute to ITER and to complement ITER in all the major areas of fusion plasma development necessary to decide DEMO reactor construction. Detailed assessments and prediction studies of the JT-60SA plasma regimes have confirmed these capabilities: using ITER- and DEMO-relevant plasma regimes, heating conditions, and its sufficiently long discharge duration, JT-60SA enables studies on magnetohydrodynamic stability at high beta, heat/particle/momentum transport, high-energy ion physics, pedestal physics including edge localized mode control, and divertor physics. By integrating these studies, the project provides 'simultaneous and steady-state sustainment of the key performance characteristics required for DEMO' with integrated control scenario development.

DOI： 10.1088/0029-5515/53/10/104010

Scopus

Control of 3D edge radiation structure with resonant magnetic perturbation fields applied to the stochastic layer and stabilization of radiative divertor plasma in LHD Reviewed

M. Kobayashi, S. Masuzaki, I. Yamada, Y. Narushima, C. Suzuki, N. Tamura, B. J. Peterson, S. Morita, C. F. Dong, N. Ohno, S. Yoshimura, Y. Feng, M. Goto, K. Sato, T. Akiyama, K. Tanaka

Nuclear Fusion Vol. 53 ( 9 ) 2013.9

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

It is found that resonant magnetic perturbation (RMP) fields have a stabilizing effect on the radiating edge plasma, realizing stable sustainment of radiative divertor (RD) operation in the Large Helical Device (LHD). Without RMP, thermal instability leads to radiative collapse. Divertor power load is reduced by a factor of 3-10 during the RMP-assisted RD phase, while maintaining relatively good core plasma confinement with confinement enhancement factor . It has also been demonstrated that the RMP field itself can initiate transition to RD operation by increasing perturbation strength, while keeping constant density and injection power. The results show a possibility of a new control knob for divertor power load in a 3D magnetic field configuration. It is also found that after the transition to RD, the energy confinement enhancement factor based on ISS04 scaling increases by a factor of 1.4 compared with the attached phase. The operation range of the RMP-assisted RD is identified in terms of RMP strength and radial location of the resonance layer of the RMP. A 3D edge radiation structure is analysed using the edge transport code EMC3-EIRENE and the results are compared with experiments. The comparison indicates that the application of RMP modulates the 3D edge radiation structure such that an intense radiation appears around the X-point of the m/n = 1/1 island in the case with RMP, while it is located at the inboard side without RMP. © 2013 IAEA, Vienna.

DOI： 10.1088/0029-5515/53/9/093032

Scopus

Growth Annealing Equilibrium of Tungsten Nanostructures by Helium Plasma Irradiation in Non Eroding Regimes Reviewed

S.Kajita, N.Ohno, M.Yajima, J.Kato

Journal of Nuclear Materials Vol. 440 ( 1-3 ) page： 55-62 2013.9

Influence of crystal orientation on damages of tungsten exposed to helium plasma Reviewed

N.Ohno, Y.Hirahata, M.Yamagiwa, S.Kajita, M.Takagi, N.Yoshida, R.Yoshihara, T.Tokunaga, M.Tokitani

Journal of Nuclear Materials Vol. 438 page： S879-S882 2013.7

Study of Hydrogen Isotopes Behavior in Carbon Based Materials with In-Situ Ion Beam Analysis under Plasma Exposure Reviewed

Y.Nakamura, M.Yamagiwa, T.Kaneko, N.Matsunami, N.Ohno, S.Kajita, M.Takagi, M.Tokitani, S.Masuzaki

Journal of Nuclear Materials Vol. 438 page： S1036-S1039 2013.7

Tritium retention in nanostructured tungsten with large effective surface area Reviewed

M.Yajima, Y.Hatano, S.Kajita, J.Shi, M.Hara, N.Ohno

Journal of Nuclear Materials Vol. 438 page： S1142-S1145 2013.7

Development of steady/transient dual plasma irradiation device using a plasma gun Reviewed

S.Kajita, N.Ohno, T.Akiyama, T.Nihashi, T.Uchiyama, M.Osaka, Y.Kikuchi, M.Nagata

Journal of Nuclear Materials Vol. 438 page： S707-S710 2013.7

　 PREV - NEXT 　

<OHNO, Noriyasu>

Papers - OHNO, Noriyasu