Faculty Profiles - OHNO, Noriyasu

Papers - OHNO, Noriyasu

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ELM propagation in the low- and high- filed-side Scrape-off Layer of the JT-60U tokamak Reviewed

N.Asakura, H.Kawashima, N.Ohno, G.Matsunaga, T.Nakano and N.Oyama

Journal of Physics; Conference Series Vol. 123 page： 012009(11pp) 2008

Statistical properties of edge plasma turbulence in the Large Helical Device Reviewed

J.M.Dewhurst, B.Hnat, N.Ohno, R.O.Dendy, S.Masuzaki, T.Morisaki and A.Komori

Plasma Physics and Controlled Fusion Vol. 50 page： 095013(15pp) 2008

Fluctuating Helium Emission in Optically Thick Divertor Plasmas Reviewed

F. B. Rosmej, N. Ohno, S. Takamura, S. Kajita

Contributions to Plasma Physics Vol. 48 page： 243-248 2008

Numerical Modeling of Behavior of Dust Made of Different Materials in Plasmas Reviewed

Y. Tanaka, A. Yu. Pigarov, R. D. Smirnov, S. I. Krasheninnikov, N. Ohno, Y. Uesugi

Contributions to Plasma Physics Vol. 48 page： 295-299 2008

Extended Self-Similarity in Edge Plasma Turbulence of Fusion Devices Reviewed

V. P. Budaev, N. Ohno, S. Takamura, S. Masuzaki, A. Komori, T. Morisaki

Contributions to Plasma Physics Vol. 48 page： 42-47 2008

Plasma Rotation Measurements by Passive Spectroscopic Method in the HYBTOK-II using a Dynamic Ergodic Divertor Reviewed

Y.Hasebe, M.Okamoto, S.Kajita, N.Ohno and S.Takamura

Plasma and Fusion Research Vol. 3 page： S1015 2008

ELM propagation in the low- and high-field-side scrape-off layer of the JT-60U tokamak Reviewed International journal

Asakura N., Kawashima H., Ohno N., Matsunaga G., Nakano T., Oyama N.

Journal of Physics: Conference Series Vol. 123 2008

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Physics: Conference Series

In JT-60U, the filament structure of Edge Localized Modes (ELMs) is measured at three poloidal locations, and their temporal evolution is investigated at the inner (high magnetic-field-side, HFS) SOL as well as outer (low magnetic-field-side, LFS) SOL. At the inner SOL, filament structure with 7-8 temporal multi-peaks in ion-saturation probe signals and other diagnostics is, for the first time, measured close to the sepatratrix. The delay of the first peak after the start of MHD activity is faster than the characteristic time of the parallel convection from the outer midplane, and the Mach numbers of the plasma parallel flow reach ion sonic levels. These results show that ELM filaments extend from the outer to the inner plasma edge, and that a part of the filaments are ejected into the inner SOL. The toroidal mode numbers (n) and poloidal width of the filaments (δz) are evaluated from the interval of the multi-peaks and duration of each peak, yielding n ∼ 18-44 and δz ∼ 2-6 cm on the HFS SOL, while n and δz are comparable on the LFS SOL. After the multi-peaks appear, flow reversal of the SOL plasma toward is observed over a wide region of the inner SOL. © 2008 IOP Publishing Ltd.

DOI： 10.1088/1742-6596/123/1/012009

Scopus

Plasma-assisted laser ablation of tungsten: Reduction in ablation power threshold due to bursting of holes/bubbles Reviewed International journal

Kajita S., Ohno N., Takamura S., Sakaguchi W., Nishijima D.

Applied Physics Letters Vol. 91 ( 26 ) 2007.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Applied Physics Letters

Nanosecond laser ablation of tungsten (W) exposed to helium plasma is investigated using optical emission spectroscopy. Submicrometer-sized holes/bubbles are formed on the surface of W when it was exposed to the helium plasma at a sufficiently high temperature (1500-1600 K). The emissions from a virgin W (before the helium plasma irradiation) cannot be detected when the fluence is <1 J cm2; however, the threshold fluence for the detection of neutral W emission after it was exposed to the helium plasma is ∼0.2 J cm2. The physical mechanism of laser-induced bursting of holes/bubbles is proposed for achieving a significant reduction in ablation power threshold. © 2007 American Institute of Physics.

DOI： 10.1063/1.2824873

Scopus

Effect of cross-field transport on H<sup>-</sup> density profile in magnetized plasmas: Comparison between measurement and simulation Reviewed International journal

Kajita S., Kado S., Ohno N., Takamura S., Kurihara K., Kuwahara Y.

Physics of Plasmas Vol. 14 ( 10 ) 2007.11

Language：English Publishing type：Research paper (scientific journal) Publisher：Physics of Plasmas

The radial density profile of negative hydrogen ions in magnetized plasma is investigated in the divertor simulator MAP (Material and plasma)-II [S. Kado et al., J. Plasma Fusion Res. 71, 810 (2005)] by measurement and numerical simulation. The laser photodetachment method is used to evaluate the H - density by considering the influence of the magnetic field. The density of H- has a hollow profile and exhibits a peak in the peripheral region, though the electron density and temperature exhibit a peak at the center of the plasma column. The density profile of H- does not agree with the calculation result obtained from, the rate equation, in which the local production and extinction rates are balanced, under the present experimental condition. To understand the behavior of negative ions, their trajectories are calculated by numerically solving the equation of motion by considering the effect of collisions. The negative ion density profile calculated from the particle simulation agrees well with the measured negative ion density profile. It is shown that the cross-field H- transport due to the radial electric field with the assistance of the elastic collisions plays an important role in enhancing the negative ion density in the peripheral region. © 2007 American Institute of Physics.

DOI： 10.1063/1.2789559

Scopus

Sub-ms Laser Pulse Irradiation on Tungsten Target Damaged by Exposure to Helium Plasma Reviewed

S.Kajita, S.Takamura, N.Ohno, D.Nishijima, H.Iwakiri, N.Yoshida

Nuclear Fusion Vol. 47 page： 1358 - 1366 2007.9

Integrated view of disruption dynamics on internal electromagnetic and plasma structures in the small tokamak HYBTOK-II Reviewed

M. Okamoto, S. Takamura, N. Ohno, S. Kajita, Y. Kikuchi, Y. Uesugi, T. Ozeki, Y. Kawano, M. Sugihara

Nuclear Fusion Vol. 47 page： 1106 - 1111 2007.8

Surface modification at tungsten and tungsten coated graphite due to low energy and high fluence plasma and laser pulse irradiation Reviewed International journal

Ohno N., Kajita S., Nishijima Dai, Takamura S.

JOURNAL OF NUCLEAR MATERIALS Vol. 363 page： 1153 - 1159 2007.6

Modeling of Dust-particle Behavior for Different Materials in Plasmas Reviewed

Y.Tanaka, A.Yu.Pigarov, R.D.Smirnov, S.I.Krasheninnikov, N.Ohno, Y.Uesugi

Physics of Plasmas Vol. 14 page： 52504 2007.5

Systematic Analysis of Current Decay Time during Disruption in HYBTOK-II Tokamak Reviewed

M.Okamoto, N.Ohno, S.Takamura

Plasma and Fusion Research Vol. 3 page： 6 2007

Effect of Cross-field Transport on H-Density Profile in Magnetized Plasmas: Comparison Between Measurement and Simulation Reviewed

S.Kajita, S.Kado, N.Ohno, K.Kurihara, Y.Kuwahara, S.Takamura

Physics of Plasmas Vol. 14 page： 103503 2007

Plasma-assisted Laser Ablaion of Tungsten: Reduction in Ablation Power Threshold Due to Bursting of Holes/Bubbles Reviewed

S.Kajita, N.Ohno, S.Takamura, W.Sakaguchi, D.Nishijima

Applied Physics Letters Vol. 9191 page： 261501 2007

Development of Tungsten Materials for Plasma Facing Components in Japan Reviewed

Y.Ueda, N.Ohno, S.Kajita, H.Kurishita, H.Iwakiri et al

Fusion Science and Technology Vol. 52 page： 513-520 2007

Overview of JT-60U results for the Development of a Steady-state Advanced Tokamak Scenario Reviewed

H.Takenaga, the JT-60 Team

Nuclear Fusion Vol. 47 page： S563-S578 2007

Structural Bifurcation of Microwave Helium Jet Discharge at Atmospheric Pressure Reviewed

S.TAKAMURA, M.KITOH, T.SOGA, H.TAKASHIMA, Y.NISHINO, S.HAYAKAWA, Y.BAN, T.YUHKI, M.KANDO, N.OHNO

Plasma and Fusion Research Vol. 3 page： 12 2007

High density plasma generation by RF ohmic discharge in toroidal divertor simulator NAGDIS-T Reviewed

M. Nagase, H. Masuda, N. Ohno, S. Takamura and M. Takagi

Journal of Nuclear Materials Vol. 363-365 page： 611-615 2007

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Papers - OHNO, Noriyasu