Refine your search:     
Report No.
 - 
Search Results: Records 1-20 displayed on this page of 153

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

An Analytic formula for the relativistic incoherent Thomson backscattering spectrum for a drifting bi-Maxwellian plasma

Naito, Osamu

Physics of Plasmas, 22(8), p.084505_1 - 084505_5, 2015/08

 Times Cited Count:0 Percentile:0.01(Physics, Fluids & Plasmas)

An analytic formula has been derived for the relativistic incoherent Thomson backscattering spectrum for a drifting anisotropic plasma when the scattering vector is parallel to the drifting direction. The shape of the scattering spectrum is insensitive to the electron temperature perpendicular to the scattering vector, but its amplitude may be modulated. As a result, while the measured temperature correctly represents the electron distribution parallel to the scattering vector, the electron density may be underestimated when the perpendicular temperature is higher than the parallel temperature. Since the scattering spectrum in shorter wavelengths is greatly enhanced by the existence of drift, the diagnostics might be used to measure local electron current density in fusion plasmas.

Journal Articles

A GUI-based intuitive tool for analyzing formats and extracting contents of binary data in fusion research

Naito, Osamu

Fusion Engineering and Design, 92, p.1 - 7, 2015/03

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

An intuitive tool with graphical user interface (GUI) for analyzing formats and extracting contents of binary data in fusion research is presented. Users can examine structures of binary data at arbitrary addresses by selecting their type from a list of radio buttons in the data inspection window and checking their representations instantly on the computer screen. The result of analysis is saved in a file which contains the information such as name, data type, start address, and array size of the data. If the array size of some data depends on others that appear prior to the former and if the users specify their relation in the inspection window, the resultant file can also be used as a format template for the same series of data. By writing a simple script, the users can extract the contents of data either to a text or binary file in the format of their preference. As a real-life example, the tool is applied to the MHD equilibrium data at JT-60U, where poloidal flux data are extracted and converted to a format suitable for contour plotting in other data visualization program. The tool would be useful in collaborative fusion researches for exchanging relatively small-size data, which don't fit in well with the standard routine processes.

Journal Articles

A Model distribution function for relativistic bi-Maxwellian with drift

Naito, Osamu

Physics of Plasmas, 20(4), p.044501_1 - 044501_4, 2013/04

 Times Cited Count:5 Percentile:25.7(Physics, Fluids & Plasmas)

A model distribution function for relativistic bi-Maxwellian with drift is proposed, based on the maximum entropy principle and the relativistic canonical transformation. Since the obtained expression is compatible with the existing distribution functions and has a relatively simple form as well as smoothness, it might serve as a useful tool in the research fields of space or high temperature fusion plasmas.

Journal Articles

Characteristics of radiation distribution and divertor detachment in impurity seeding on JT-60U

Asakura, Nobuyuki; Nakano, Tomohide; Naito, Osamu; Oyama, Naoyuki

Journal of Nuclear Materials, 415(Suppl.1), p.S318 - S321, 2011/09

 Times Cited Count:4 Percentile:36.36(Materials Science, Multidisciplinary)

Impurity gas seeding is considered as the primary technique to decrease the heat loading to the divertor. Characteristics of the divertor plasma and radiation was investigated. Distribution of the impurity radiation in the edge and divertor was different depending on the impurity species. For Argon seeding, radiation loss in the main edge increased compared to Neon seeding cases. ELM characteristics changed from Type-I to Type-III for the intense Ar seeding, and detachment was produced. Dynamics of the transition from detachment to re-attachment was investigated. When the Ar gas puff rate was reduced, Type-I ELM activity appeared accompanied by a reduction in the edge radiation loss. Time scale of the re-attachment was short (0.4 s) compared to the transition from attached to detached divertor (1 s), which was affected by change in the edge transport barrier. In-out asymmetries in $$T$$$$_e^{div}$$ and ion flux became large in the re-attachment, and influence of the carbon-influx was increased.

Journal Articles

Architecture plan of the real-time diagnostic signals acquisition system toward JT-60SA project

Sakata, Shinya; Yamaguchi, Taiji; Sugimura, Toru; Kominato, Toshiharu; Kawamata, Yoichi; Totsuka, Toshiyuki; Sato, Minoru; Sueoka, Michiharu; Naito, Osamu

Fusion Science and Technology, 60(2), p.496 - 500, 2011/08

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

For a steady state operation of JT-60SA, a plasma feedback control using various diagnostic sensor signals plays an essential role. To realize this, Real Time Diagnostic Signals acquisition System, RTDS, which utilizes PC-based real-time OS "INtime", has been under consideration toward JT-60SA project. Moreover, long-time experiments more than 100 seconds will be planned in JT-60SA project. Therefore, real time monitoring will be required as an essential function that displays acquired diagnostic signals on real time during long-time experiment. This function will be also realized by utilizing RTDS.

Journal Articles

Development of PC-based control system in JT-60SA

Kawamata, Yoichi; Sugimura, Toru; Yamaguchi, Taiji; Sueoka, Michiharu; Sakata, Shinya; Totsuka, Toshiyuki; Sato, Minoru; Kominato, Toshiharu; Naito, Osamu

Fusion Science and Technology, 60(2), p.491 - 495, 2011/08

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

Journal Articles

An XML-based loose-schema approach to managing diagnostic data in heterogeneous formats

Naito, Osamu

Fusion Engineering and Design, 85(3-4), p.591 - 594, 2010/07

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

An approach to managing diagnostic data in heterogenous formats by using XML-based (eXtensible Markup Language) tag files is discussed. The tag file functions like header information in ordinary data formats but it is separate from the main body of data, human readable, and self-descriptive. Thus all the necessary information for reading the contents of data can be obtained without prior information or reading the data body itself. In this paper, modeling of diagnostic data and its representation in XML are studied and a very primitive implementation of this approach in C++ is presented. The overhead of manipulating XML in a proof-of-principle code was found to be small. The merits, demerits, and possible extensions of this approach are also discussed.

Journal Articles

Progress in development of the advanced Thomson scattering diagnostics

Hatae, Takaki; Howard, J.*; Ebizuka, Noboru*; Yoshida, Hidetsugu*; Nakatsuka, Masahiro*; Fujita, Hisanori*; Narihara, Kazumichi*; Yamada, Ichihiro*; Funaba, Hisamichi*; Hirano, Yoichi*; et al.

Journal of Physics; Conference Series, 227, p.012002_1 - 012002_6, 2010/06

 Times Cited Count:2 Percentile:69.52

Journal Articles

Optimization of optical filters for ITER edge Thomson scattering diagnostics

Kajita, Shin; Hatae, Takaki; Naito, Osamu

Fusion Engineering and Design, 84(12), p.2214 - 2220, 2009/12

 Times Cited Count:9 Percentile:56.98(Nuclear Science & Technology)

In ITER edge Thomson scattering measurement system, it is planned that polychromators by use of optical band-pass filters and avalanche photodiodes are used for the detection system. In this paper, the optimization of the filter transmission wavelength ranges is performed by minimizing the numerically calculated electron temperature error. The Thomson spectrum extends to considerably short wavelength range because high electron temperature measurement is required; therefore, it is important to eliminate the line emission from the plasma, such as $$D_{alpha}$$, in particular. It is shown that a filter, the transmission wavelength of which is shorter than $$D_{alpha}$$, becomes important to decrease the error in high temperature regime. Moreover, when the filter number is more than 7, it is found that a filter, the transmission wavelength of which is higher than the laser wavelength of 1064 nm, is useful to reduce the averaged error in wide temperature range.

Journal Articles

Development of advanced operation scenarios in weak magnetic-shear regime on JT-60U

Suzuki, Takahiro; Oyama, Naoyuki; Isayama, Akihiko; Sakamoto, Yoshiteru; Fujita, Takaaki; Ide, Shunsuke; Kamada, Yutaka; Naito, Osamu; Sueoka, Michiharu; Moriyama, Shinichi; et al.

Nuclear Fusion, 49(8), p.085003_1 - 085003_8, 2009/08

 Times Cited Count:7 Percentile:30.1(Physics, Fluids & Plasmas)

Fully non-inductive discharge having a relaxed current profile and high bootstrap current fraction f$$_{BS}$$=0.5 has been realized in the high-$$beta$$$$_{p}$$ ELMy H-mode discharge with weak magnetic-shear having q$$_{95}$$=5.8, qmin=2.1, and q(0)=2.4, where qmin and q(0) are the safety factor q at the minimum and the plasma center, respectively. The rest of the plasma current is externally driven by neutral beams (NBs) and lower-hybrid (LH) waves. The safety factor profile evaluated by the motional Stark effect (MSE) diagnostic is kept unchanged during 0.7 s at the end of the full current drive (CD) sustainment for 2 s (1.5 times the current relaxation time $$_{tau R}$$). The loop voltage profile is spatially uniform at 0 V at the end of the sustainment. This demonstration shows, for the first time, that the steady sustainment of ful-CD plasma is possible at high f$$_{BS}$$=0.5 and reasonably low q$$_{95}$$=5.8 regime and is stably controlled by appropriate external current drivers. On the other hand, when the combination of bootstrap current and externally driven current does not match to the steady current profile, slight change in the current profile due to current relaxation resulted in appearance of magnetohydrodynamic (MHD) instability, e.g. neo-classical tearing mode (NTM), in a high beta plasma. This discharge clarifies importance of the demonstration of steady current profile developed here. These discharges contribute to the ITER steady-state operation scenario development.

Journal Articles

Design study of the JT-60SA supervisory control system

Kawamata, Yoichi; Naito, Osamu; Kiyono, Kimihiro; Itami, Kiyoshi; Totsuka, Toshiyuki; Akasaka, Hiromi; Sueoka, Michiharu; Sato, Tomoki; Oshima, Takayuki; Sakata, Shinya; et al.

Fusion Engineering and Design, 83(2-3), p.198 - 201, 2008/04

 Times Cited Count:3 Percentile:25.63(Nuclear Science & Technology)

The design activity of JT-60SA (JT-60 Super Advanced) which is remodeled to a superconducting tokamak device has been starting under the JA-EU collaborative ITER-BA project. For the JT-60SA control system, the existing system should be reused as much as possible from the viewpoint of cost-effectiveness. We have just begun to discuss the configuration of the advanced Supervisory Control System (SVCS) including the following systems: (1) ultimately flexible real-time control system, (2) precise timing system enough to clarify cause and effect, and (3) safety shutdown control system. In this report, we present the design study of the JT-60SA SVCS with focusing on these systems.

Journal Articles

Off-axis current drive and real-time control of current profile in JT-60U

Suzuki, Takahiro; Ide, Shunsuke; Oikawa, Toshihiro; Fujita, Takaaki; Ishikawa, Masao; Seki, Masami; Matsunaga, Go; Hatae, Takaki; Naito, Osamu; Hamamatsu, Kiyotaka; et al.

Nuclear Fusion, 48(4), p.045002_1 - 045002_9, 2008/04

 Times Cited Count:35 Percentile:81.18(Physics, Fluids & Plasmas)

Aiming at optimization of current profile in high-b plasmas for higher confinement and stability, a real-time control system of the minimum of the safety factor ($$q$$$$_{rm min}$$) using the off-axis current drive has been developed. The off-axis current drive can raise safety factor in the center and help to avoid instability that limits performance of the plasma. The system controls injection power of lower-hybrid (LH) waves, and hence, its off-axis driven current in order to control $$q$$$$_{min}$$. The real-time control of $$q$$$$_{rm min}$$ is demonstrated in a high-$$beta$$ plasma, where $$q$$$$_{rm min}$$ follows the temporally changing reference $$q$$$$_{min,ref}$$ from 1.3 to 1.7. Applying the control to another high-$$beta$$ discharge ($$beta$$$$_{rm N}$$=1.7, $$beta$$$$_{rm p}$$=1.5) with $$m/n$$=2/1 neo-classical tearing mode (NTM), $$q$$$$_{rm min}$$ was raised above 2 and the NTM was suppressed. The stored energy increased by 16% with the NTM suppressed, since the resonant rational surface was eliminated. For the future use for current profile control, current density profile for off-axis neutral beam current drive (NBCD) is for the first time measured, using motional Stark effect (MSE) diagnostic. Spatially localized NBCD profile was clearly observed at the normalized $rm minor radius $rho$$ of about 0.6-0.8. The location was also confirmed by multi-chordal neutron emission profile measurement. The total amount of the measured beam driven current was consistent with the theoretical calculation using the ACCOME code. The CD location in the calculation was inward-shifted than the measurement.

Journal Articles

Development of polarization interferometer based on Fourier transform spectroscopy for Thomson scattering diagnostics

Hatae, Takaki; Howard, J.*; Hirano, Yoichi*; Naito, Osamu; Nakatsuka, Masahiro*; Yoshida, Hidetsugu*

Plasma and Fusion Research (Internet), 2, p.S1026_1 - S1026_5, 2007/11

A high-throughput polarization interferometer is being developed to demonstrate for the first time the utility of Fourier transform spectroscopy for Thomson scattering diagnostics of high temperature plasma. Target $$T$$$$_{e}$$ and $$n$$$$_{e}$$ ranges for the prototype polarization interferometer are $$<$$ 1 keV and $$>$$ 5$$times$$10$$^{18}$$ m$$^{-3}$$, respectively. This paper describes the design of the polarization interferometer and the results of initial tests.

Journal Articles

Ferritic insertion for reduction of toroidal magnetic field ripple on JT-60U

Shinohara, Koji; Sakurai, Shinji; Ishikawa, Masao; Tsuzuki, Kazuhiro*; Suzuki, Yutaka; Masaki, Kei; Naito, Osamu; Kurihara, Kenichi; Suzuki, Takahiro; Koide, Yoshihiko; et al.

Nuclear Fusion, 47(8), p.997 - 1004, 2007/08

 Times Cited Count:40 Percentile:80.59(Physics, Fluids & Plasmas)

Ferritic steel plates have been installed to improve the energetic ion confinement through reducing a toroidal magnetic field ripple. Aiming at cost-effective installation, orbit following calculations of energetic ions were performed for a design of ferritic installation on JT-60U by using the Fully three Dimensional magnetic field Orbit-Following Monte-Carlo (F3D OFMC) code. The installed ferritic steel adds the non-linear magnetic field on magnetic sensors for a plasma control and an equilibrium calculation. The code for a real-time control has been modified to take into account the magnetic field by ferritic steel. The plasma operation was successfully resumed and a real-time plasma control was successfully carried out after usual preparation processes. The heat load measurement indicates the improved confinement of energetic ions. These results are important for practical application of ferritic steel which is a leading candidate of a structural material on a demo reactor.

Journal Articles

Ferritic insertion for reduction of toroidal magnetic field ripple on JT-60U

Shinohara, Koji; Sakurai, Shinji; Ishikawa, Masao; Tsuzuki, Kazuhiro*; Suzuki, Yutaka; Masaki, Kei; Naito, Osamu; Kurihara, Kenichi; Suzuki, Takahiro; Koide, Yoshihiko; et al.

Proceedings of 21st IAEA Fusion Energy Conference (FEC 2006) (CD-ROM), 8 Pages, 2007/03

Ferritic steel plates have been installed to improve the energetic ion confinement through reducing a toroidal magnetic field ripple. Aiming at cost-effective installation, orbit following calculations of energetic ions were performed for a design of ferritic installation on JT-60U by using the Fully three Dimensional magnetic field Orbit-Following Monte-Carlo (F3D OFMC) code. The installed ferritic steel adds the non-linear magnetic field on magnetic sensors for a plasma control and an equilibrium calculation. The code for a real-time control have been modified to take into account the magnetic field by ferritic steel. The plasma operation was successfully resumed and a real-time plasma control was successfully carried out after usual preparation processes. The heat load measurement indicates the improved confinement of energetic ions. These results are important for practical application of ferritic steel which is a leading candidate of a structural material on a demo reactor.

Journal Articles

Off-axis current drive and current profile control in JT-60U

Suzuki, Takahiro; Ide, Shunsuke; Oikawa, Toshihiro; Fujita, Takaaki; Ishikawa, Masao*; Seki, Masami; Matsunaga, Go; Takechi, Manabu; Naito, Osamu; Hamamatsu, Kiyotaka; et al.

Proceedings of 21st IAEA Fusion Energy Conference (FEC 2006) (CD-ROM), 8 Pages, 2007/03

For the first time, we have measured the current density profile for off-axis neutral beam current drive (NBCD), using motional Stark effect (MSE) diagnostic. A spatially localized NBCD profile was clearly observed at $$rho=0.6-0.8$$. The location was also confirmed by neutron emission profile measurement. The total amount of the driven current (0.15MA) was consistent with the decrease in the surface loop voltage. The off-axis current drive can raise safety factor (q) in the center and help to avoid instability that limits performance of the plasma. We have developed a real-time control system of the minimum q (qmin), using the off-axis current drive. Injection power of lower hybrid (LH) waves, and hence, its off-axis driven current controls qmin. In a high $$beta$$ plasma ($$beta_{N}=1.7$$, $$beta_{p}=1.5$$), the system was adopted to control qmin. With the control, qmin was raised and MHD fluctuations were suppressed. The stored energy increased by 16% with the MHD fluctuations suppressed.

Journal Articles

Study on current drive capability of lower hybrid waves and neutral beam in an ITER steady state scenario

Oikawa, Toshihiro; Shimada, Michiya; Polevoi, A. R.*; Naito, Osamu; Bonoli, P. T.*; Hayashi, Nobuhiko; Kessel, C. E.*; Ozeki, Takahisa

Proceedings of 21st IAEA Fusion Energy Conference (FEC 2006) (CD-ROM), 7 Pages, 2007/03

The current drive capability of lower hybrid waves is assessed for an ITER steady state scenario using a relativistic, one-dimensional Fokker-Planck code and a toroidal ray tracing code. The present LH launcher design provides a current drive efficiency of 1.8$$times$$10$$^{19}$$AW$$^{-1}$$m$$^{-2}$$ and an off-axis profile of the driven current that is fovarable for a reversed magnetic shear configuration. Possible optimizations in the LH power spectrum are investigated. Neutral beam current drive (NBCD) is investigated with theoretical codes employing different approaches. An NBCD code employing the bounce-averaged Fokker-Planck equation to include orbit effects in a toroidal system shows a good agreement with an orbit following Monte-Carlo code.

Journal Articles

Progress in JT-60 joint research

Kimura, Haruyuki; Inutake, Masaaki*; Kikuchi, Mitsuru; Ogawa, Yuichi*; Kamada, Yutaka; Ozeki, Takahisa; Naito, Osamu; Takase, Yuichi*; Ide, Shunsuke; Nagasaki, Kazunobu*; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 83(1), p.81 - 93, 2007/01

no abstracts in English

Journal Articles

Applications of stimulated brillouin scattering phase conjugate mirror to Thomson scattering diagnostics in JT-60U and ITER

Hatae, Takaki; Naito, Osamu; Kitamura, Shigeru; Sakuma, Takeshi*; Hamano, Takashi*; Nakatsuka, Masahiro*; Yoshida, Hidetsugu*

Journal of the Korean Physical Society, 49, p.S160 - S164, 2006/12

no abstracts in English

Journal Articles

Applications of phase conjugate mirror to Thomson scattering diagnostics (invited)

Hatae, Takaki; Naito, Osamu; Nakatsuka, Masahiro*; Yoshida, Hidetsugu*

Review of Scientific Instruments, 77(10), p.10E508_1 - 10E508_6, 2006/10

 Times Cited Count:29 Percentile:77.96(Instruments & Instrumentation)

no abstracts in English

153 (Records 1-20 displayed on this page)