Refine your search:     
Report No.
 - 
Search Results: Records 1-20 displayed on this page of 41

Presentation/Publication Type

Initialising ...

Refine

Journal/Book Title

Initialising ...

Meeting title

Initialising ...

First Author

Initialising ...

Keyword

Initialising ...

Language

Initialising ...

Publication Year

Initialising ...

Held year of conference

Initialising ...

Save select records

Journal Articles

Axial flow characteristics of bubbly flow in a vertical large-diameter square duct

Shen, X.*; Sun, Haomin; Deng, B.*; Hibiki, Takashi*; Nakamura, Hideo

Proceedings of 17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17) (USB Flash Drive), 14 Pages, 2017/09

An experimental study on the upward bubbly air-water flows in a vertical large-diameter square duct have been performed by using four-sensor probes. The four-sensor probe were applied in the local measurements at 3 axial positions along the flow direction to obtain interfacial area concentration, 3-D bubble velocity vector and bubble diameter. The obtained void fraction, interfacial area concentration, 3-D bubble velocity vector and bubble diameter provided valuable insight into the flow structure and will serve as a valuable database to develop the mechanistic models for interfacial area transport equation sources and sinks.

Journal Articles

Excavation damaged zone inferred by geophysical surveys on drift floor of Horonobe URL

Tokiwa, Tetsuya*; Aoyagi, Kazuhei; Fujita, Tomoo

Rock Mechanics and Rock Engineering; From the Past to the Future (EUROCK 2016), p.901 - 906, 2016/07

Journal Articles

Gas-liquid bubbly flow structure in a vertical large-diameter square duct

Shen, X.*; Sun, Haomin; Deng, B.*; Hibiki, Takashi*; Nakamura, Hideo

Progress in Nuclear Energy, 89, p.140 - 158, 2016/05

 Times Cited Count:9 Percentile:21.82(Nuclear Science & Technology)

An experimental study was performed on the local structure of upward air-water two-phase flow in a vertical large diameter square duct by using a four-sensor probe. The four-sensor probe method classifying spherical and non-spherical bubbles was applied as a key measurement way to obtain local parameters such as 3-D bubble velocity vector, bubble diameter and interfacial area concentration. Both the local void fraction and interfacial area concentration indicated radial core-peak and wall-peak distributions at low and high liquid flow rates respectively. The 2 components of the bubble velocity vector in the cross-section revealed that there exists a rotating secondary flow in the octant symmetric triangular area and the magnitude of the rotating secondary flow increases with the liquid flow rate. Some of constitutive correlations of drift-flux model and interfacial area concentration are reviewed to study their predictabilities against the present data.

Journal Articles

The Origin of beam non-uniformity in a large Cs-seeded negative ion source

Hanada, Masaya; Seki, Takayoshi*; Takado, Naoyuki; Inoue, Takashi; Mizuno, Takatoshi*; Hatayama, Akiyoshi*; Kashiwagi, Mieko; Sakamoto, Keishi; Taniguchi, Masaki; Watanabe, Kazuhiro

Nuclear Fusion, 46(6), p.S318 - S323, 2006/06

 Times Cited Count:28 Percentile:27.98(Physics, Fluids & Plasmas)

The origin of the beam non-uniformity, that is one of the key issues in large Cs-seeded negative ion sources for JT-60U and ITER, was experimentally examined by measuring correlations between the intensity of the H$$^{-}$$ ion beam and plasma parameters such as an electron temperature and plasma density in the JAERI 10 A negative ion source. From the correlation between the beam intensity and the plasma parameters, it was foreseen that the beam non-uniformity was due to the localization of the plasma and/or H0 atoms caused by B x $$nabla$$B drift of the fast electron from filaments. The filament position was modified to suppress the B x $$nabla$$B drift, and then the spatial uniformity of the beam intensity was examined. By this modification, the root-mean-square deviation of the spatial beam intensity from the averaged value deceased to a half of that before modification while the beam intensity integrated along the longitudinal direction was kept to be constant. From this result, it was confirmed that one of the origin of the beam non-uniformity was caused by plasma localization.

Journal Articles

Bispectral analysis applied to coherent floating potential fluctuations obtained in the edge plasmas on JFT-2M

Nagashima, Yoshihiko*; Ito, Kimitaka*; Ito, Sanae*; Fujisawa, Akihide*; Hoshino, Katsumichi; Takase, Yuichi*; Yagi, Masatoshi*; Ejiri, Akira*; Ida, Katsumi*; Shinohara, Koji; et al.

Plasma Physics and Controlled Fusion, 48(4), p.S1 - S15, 2006/04

 Times Cited Count:33 Percentile:22.98(Physics, Fluids & Plasmas)

This paper presents the results of bispectral analysis of floating potential fluctuations in the edge region of ohmically heated plasmas in the JFT-2M tokamak. Inside of the outermost magnetic surface,coherent modes were observed around the frequency of geodesic acoustic mode which is a kind of the zonal flow. The squared bicoherence shows significant nonlinear couplings between the coherent fluctuations and the background fluctuations (which are likely to contain drift wave turbulent fluctuations). The experimental results that the total bicoherence is proportional to the squared amplitude of the coherent fluctuation, and that the biphase of the coherent modes localizes around a constant value $$pi$$, are consistent with the theoretical prediction on the drift wave - zonal flow systems based on the Hasegawa-Mima model.

Journal Articles

Improvement of beam uniformity by magnetic filter optimization in a Cs-seeded large negative-ion source

Hanada, Masaya; Seki, Takayoshi*; Takado, Naoyuki*; Inoue, Takashi; Tobari, Hiroyuki; Mizuno, Takatoshi*; Hatayama, Akiyoshi*; Dairaku, Masayuki; Kashiwagi, Mieko; Sakamoto, Keishi; et al.

Review of Scientific Instruments, 77(3), p.03A515_1 - 03A515_3, 2006/03

 Times Cited Count:23 Percentile:26.26(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Observation of nonlinear coupling between small-poloidal wave-number potential fluctuations and turbulent potential fluctuations in Ohmically heated plasmas in the JFT-2M tokamak

Nagashima, Yoshihiko*; Hoshino, Katsumichi; Ejiri, Akira*; Shinohara, Koji; Takase, Yuichi*; Tsuzuki, Kazuhiro; Uehara, Kazuya; Kawashima, Hisato; Ogawa, Hiroaki; Ido, Takeshi*; et al.

Physical Review Letters, 95(9), p.095002_1 - 095002_4, 2005/08

 Times Cited Count:95 Percentile:6.79(Physics, Multidisciplinary)

By a reciprocating electrostatic probe, two types of low frequency coherent electrostatic modes (about1kHz and 10-15kHz) are found,for the first time, in the edge region of ohmically heated plasmas in the JFT-2M tokamak. These modes exists in the last closed surface. The higher frequency mode has features of the geodesic acoustic mode (GAM), though the low frequency mode is not identified yet. A bispectral analysis revealed that significant nonlinear couplings (parametric modulation) between these coherent fluctuations and broadband background turbulent potential fluctuations occur. In the other words, the GAM and the back ground turbulence are modulated by the newly found low frequency electrostatic mode (further, the GAM modulates the background turbulence, also) for the first time. The newly found low frequency mode (frequency about 1kHz) is supposed to contribute to the turbulent diffusion nonlinearly.

Journal Articles

Recent progress of SOL and divertor plasma studies in Tokamaks

Asakura, Nobuyuki

Purazuma, Kaku Yugo Gakkai-Shi, 80(3), p.190 - 200, 2004/03

Understanding of the divertor and Scrape-off Layer (SOL) plasmas has been progressed during improvements of the compact- and closed-geometry tokamak divertors. Developments of new diagnostics viewing the SOL and upstream of the divertor target (with the finest spatial and/or time resolutions) have contributed to understand the physics mechanisms under large variations of the plasma along and perpendicular to the field lines. Four topics: (i) heat and particle transports upstream of the divertor plate, (ii) burst transport of heat and particles towards the divertor, (iii) SOL plasma flow, and (iv) plasma diffusion in SOL, were reviewed.

Journal Articles

JT-60U plasma current measurement by an optical current transformer

Arai, Takashi; Nishiyama, Tomokazu; Yagyu, Junichi; Kasai, Satoshi; Sone, Isamu*; Abe, Mitsushi*; Miya, Naoyuki

Fusion Science and Technology, 45(1), p.65 - 68, 2004/01

 Times Cited Count:2 Percentile:81.64(Nuclear Science & Technology)

In a nuclear fusion experiment device, a plasma discharge is to be sustained for a long time in steady state operation. In such a device an electromagnetic sensor that has a signal integrator to measure direct currents will cause a technical problem of zero point drift on signals. So, the detection device using new technology for direct current measurement, optical current transformer (optical CT), was developed. The device has an optical fiber specified for 1550nm (wavelength) was manufactured, and was applied to JT-60U experiments. A gamma ray irradiation examination was also done to the optical CT

Journal Articles

Drift stabilization of internal resistive-wall modes in tokamaks

Konovalov, S. V.; Mikhailovskii, A. B.*; Tsypin, V. S.*; Galv$~a$o, R. M. 0.*; Nascimento, I. C.*

Plasma Physics Reports, 29(9), p.779 - 784, 2003/09

 Times Cited Count:2 Percentile:93.13(Physics, Fluids & Plasmas)

The problem of drift stabilization of internal resistive-wall modes (RWMs) in tokamaks is theoretically investigated. The basic assumption of our model is that these modes are unstable in the absence of a conducting wall and stable in the presence of a close-fitting ideally conducting wall, when drift effects are neglected. Stability of the internal RWMs, was estimated for several existing tokamaks contributing to the ITER data base, namely, AUG (ASDEX-Upgrade), DIII-D, JET, TFTR and JT-60U, as well as for the projected ITER-FEAT. It is concluded that although drift effects do not stabilize the internal RWMs in current devices, they should be effective for suppressing these modes in reactor-grade tokamaks.

Journal Articles

Study on gas-liquid two-phase flow distribution in a tight-lattice rod bundle

Onuki, Akira; Shibata, Mitsuhiko; Tamai, Hidesada; Akimoto, Hajime; Yamauchi, Toyoaki*; Mizokami, Shinya*

Nippon Konsoryu Gakkai Nenkai Koenkai 2003 Koen Rombunshu, p.35 - 36, 2003/07

Analytical evaluation of maximum critical power by so-called subchannnel code is indispensable for design of reduced moderation water reactor. In this study, two-phase flow distribution in a tight-lattice rod bundle is investigated using 19-rod bundle experimental rig and subchannnel analysis code NASCA. The flow distribution was measured under so-called churn flow regime and the predictive capability of NASCA was assessed. NASCA can predict the flow distribution qualitatively depending on local pressure drop. Quantitative prediction is also reasonable for liquid phase but the gas phase distribution was underestimated. Void-drift model has a dominant contribution and we should improve the model for the tight-lattice rod bundle.

Journal Articles

Stabilization of cyclotron magnetic field strength by means of magnet temperature control

Okumura, Susumu; Kurashima, Satoshi; Ishimoto, Takayuki*; Yokota, Wataru; Arakawa, Kazuo; Fukuda, Mitsuhiro; Nakamura, Yoshiteru; Ishibori, Ikuo; Nara, Takayuki; Agematsu, Takashi; et al.

Proceedings of 13th Symposium on Accelerator Science and Technology, p.283 - 285, 2001/00

no abstracts in English

Journal Articles

Computational studies on ion source plasmas of the neutral beam injection system

Kashiwagi, Mieko; Ido, Shuji*; Okumura, Yoshikazu

Review of Scientific Instruments, 71(2), p.747 - 750, 2000/02

 Times Cited Count:2 Percentile:72.51(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Some results of the summer 1999 JAERI-FERHRI expedition

Tkalin, A. V.*; Aramaki, Takafumi; Togawa, Orihiko; Volkov, Y. N.*

Proceedings of International Symposium on Oceanography of the Japan Sea (CREAMS-2000), p.181 - 187, 2000/00

no abstracts in English

Journal Articles

Water structure and currents in the north-west Japan sea in May of 1999

Danchenkov, M. A.*; Togawa, Orihiko; Hong, G. H.*

Proceedings of International Symposium on Oceanography of the Japan Sea (CREAMS-2000), p.188 - 192, 2000/00

no abstracts in English

JAEA Reports

ETC-Rel code; Orbit trace code of relativistic electrons in a tokamak

Tokuda, Shinji; *

JAERI-Data/Code 98-032, 36 Pages, 1998/11

JAERI-Data-Code-98-032.pdf:1.93MB

no abstracts in English

Journal Articles

Effects of radial gradient of the Shafranov shift on the kinetic ballooning and drift-type modes in high-performance tokamaks

*; Yamagiwa, Mitsuru

Canadian Journal of Physics, 75(9), p.599 - 604, 1997/09

no abstracts in English

Journal Articles

Poloidal shear flow effect on toroidal ion temperature gradient mode; A Theory and simulation

J.Y.Kim*; Kishimoto, Yasuaki; Wakatani, Masahiro*; Tajima, Toshiki*

Physics of Plasmas, 3(10), p.3689 - 3695, 1996/10

 Times Cited Count:47 Percentile:18.27(Physics, Fluids & Plasmas)

no abstracts in English

JAEA Reports

Magnetic sensor for steady state tokamak

Neyatani, Yuzuru; Mori, Katsuharu*; *; Kikuchi, Mitsuru

JAERI-Research 96-026, 25 Pages, 1996/06

JAERI-Research-96-026.pdf:1.06MB

no abstracts in English

Journal Articles

Theory of self-organized critical transport in tokamak plasmas

Kishimoto, Yasuaki; Tajima, Toshiki*; W.Horton*; LeBrun, M. J.*; J.Y.Kim*

Physics of Plasmas, 3(4), p.1289 - 1307, 1996/04

 Times Cited Count:67 Percentile:11.63(Physics, Fluids & Plasmas)

no abstracts in English

41 (Records 1-20 displayed on this page)