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Journal Articles

Assessment of operational space for long-pulse scenarios in ITER

Polevoi, A. R.*; Loarte, A.*; Hayashi, Nobuhiko; Kim, H. S.*; Kim, S. H.*; Koechl, F.*; Kukushkin, A. S.*; Leonov, V. M.*; Medvedev, S. Yu.*; Murakami, Masakatsu*; et al.

Nuclear Fusion, 55(6), p.063019_1 - 063019_8, 2015/05

 Times Cited Count:23 Percentile:13.62(Physics, Fluids & Plasmas)

Journal Articles

Dynamics of energetic particle driven modes and MHD modes in wall-stabilized high-$$beta$$ plasmas on JT-60U and DIII-D

Matsunaga, Go; Okabayashi, Michio*; Aiba, Nobuyuki; Boedo, J. A.*; Ferron, J. R.*; Hanson, J. M.*; Hao, G. Z.*; Heidbrink, W. W.*; Holcomb, C. T.*; In, Y.*; et al.

Nuclear Fusion, 53(12), p.123022_1 - 123022_13, 2013/12

 Times Cited Count:2 Percentile:88.58(Physics, Fluids & Plasmas)

Journal Articles

Optimization of ITER operational space for long-pulse scenarios

Polevoi, A. R.*; Hayashi, Nobuhiko; Kim, H. S.*; Kim, S. H.*; Koechl, F.*; Kukushkin, A. S.*; Leonov, V. M.*; Loarte, A.*; Medvedev, S. Yu.*; Murakami, Masakatsu*; et al.

Europhysics Conference Abstracts (Internet), 37D, p.P2.135_1 - P2.135_4, 2013/07

Journal Articles

Dynamics of energetic particle driven modes and MHD modes in wall-stabilized high beta plasmas on JT-60U and DIII-D

Matsunaga, Go; Okabayashi, Michio*; Aiba, Nobuyuki; Boedo, J. A.*; Ferron, J. R.*; Hanson, J. M.*; Hao, G. Z.*; Heidbrink, W. W.*; Holcomb, C. T.*; In, Y.*; et al.

Proceedings of 24th IAEA Fusion Energy Conference (FEC 2012) (CD-ROM), 8 Pages, 2013/03

Journal Articles

Integrated modeling of steady-state scenarios and heating and current drive mixes for ITER

Murakami, Masanori*; Park, J. M.*; Giruzzi, G.*; Garcia, J.*; Bonoli, P.*; Budny, R. V.*; Doyle, E. J.*; Fukuyama, Atsushi*; Hayashi, Nobuhiko; Honda, Mitsuru; et al.

Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03

Journal Articles

MINERVA; Ideal MHD stability code for toroidally rotating tokamak plasmas

Aiba, Nobuyuki; Tokuda, Shinji; Furukawa, Masaru*; Snyder, P. B.*; Chu, M. S.*

Computer Physics Communications, 180(8), p.1282 - 1304, 2009/08

 Times Cited Count:22 Percentile:21.55(Computer Science, Interdisciplinary Applications)

A new linear MHD stability code MINERVA is developed for investigating a toroidal rotation effect on the stability of ideal MHD modes in tokamak plasmas. This code solves the Frieman-Rotenberg equation as not only the generalized eigenvalue problem but also the initial value problem. The parallel computing method used in this code realizes the stability analysis of both long and short wavelength MHD modes in short time. The results of some benchmarking tests show the validity of this MINERVA code. The numerical study with MINERVA about the toroidal rotation effect on the edge MHD stability shows that the rotational shear destabilizes the long/intermediate wavelength modes but stabilizes the short wavelength edge localized MHD modes, though the rotation frequency destabilizes both the long and the short wavelength MHD modes.

Journal Articles

Pedestal stability comparison and ITER pedestal prediction

Snyder, P. B.*; Aiba, Nobuyuki; Beurskens, M.*; Groebner, R. J.*; Horton, L. D.*; Hubbard, A. E.*; Hughes, J. W.*; Huysmans, G. T. A.*; Kamada, Yutaka; Kirk, A.*; et al.

Nuclear Fusion, 49(8), p.085035_1 - 085035_8, 2009/08

 Times Cited Count:146 Percentile:0.99(Physics, Fluids & Plasmas)

The pressure at the top of the edge transport barrier impacts fusion performance, while large ELMs can constrain material lifetimes. Investigation of intermediate wavelength MHD mode has led to improved understanding of the pedestal height and the mechanism for ELMs. The combination of high resolution diagnostics and a suite of stability codes has made edge stability analysis routine, and contribute both to understanding, and to experimental planning and performance optimization. Here we present extensive comparisons of observations to predicted edge stability boundaries on several tokamaks, both for the standard (Type I) ELM regime, and for small ELM and ELM-free regimes. We further discuss a new predictive model for the pedestal height and width (EPED1), developed by self-consistently combining a simple width model with peeling-ballooning stability calculations. This model is tested against experimental measurements, and used in initial predictions of the pedestal height for ITER.

Journal Articles

Pedestal stability comparison and ITER pedestal prediction

Snyder, P. B.*; Aiba, Nobuyuki; Beurskens, M.*; Groebner, R. J.*; Horton, L. D.*; Hubbard, A. E.*; Hughes, J. W.*; Huysmans, G. T. A.*; Kamada, Yutaka; Kirk, A.*; et al.

Proceedings of 22nd IAEA Fusion Energy Conference (FEC 2008) (CD-ROM), 8 Pages, 2008/10

Investigation of intermediate wavelength MHD modes has led to improved understanding of important constraints on the pedestal height and the mechanism for ELMs. The combination of high resolution pedestal diagnostics and a suite of highly efficient stability codes, has made edge stability analysis routine on several major tokamaks, contributing both to understanding, and to experimental planning and performance optimization. Here we present extensive comparisons of observations to predicted edge stability boundaries on several tokamaks, both for the standard ELM regime, and for small ELM and ELM-free regimes. We further use the stability constraint on pedestal height to test models of the pedestal width, and self-consistently combine a simple width model with MHD stability calculations to develop a new predictive model (EPED1) for the pedestal height and width. This model is tested against experimental measurements, and used in initial predictions of the pedestal height for ITER.

Journal Articles

Numerical method for the stability analysis of ideal MHD modes with a wide range of toroidal mode numbers in tokamaks

Aiba, Nobuyuki; Tokuda, Shinji; Fujita, Takaaki; Ozeki, Takahisa; Chu, M. S.*; Snyder, P. B.*; Wilson, H. R.*

Plasma and Fusion Research (Internet), 2, p.010_1 - 010_8, 2007/04

Numerical method for the stability analysis of ideal MHD modes is invented by using the physical model based on the two-dimensional Newcomb equation in combination with the conventional ideal MHD model. The MARG2D code built on this numerical method realizes to analyze the stability of wide $$n$$ range of ideal MHD modes. The validity of MARG2D has been confirmed with the benchmarking test with the DCON code by identifying the stability boundary of low-$$n$$ modes, and that with the ELITE code by comparing the growth rates of intermediate to high $$n$$ modes. With the MARG2D code, the edge stability of JT-60SA, the complementally experiment of ITER, is investigated.

Journal Articles

Edge pedestal physics and its implications for ITER

Kamada, Yutaka; Leonard, A. W.*; Bateman, G.*; Becoulet, M.*; Chang, C. S.*; Eich, T.*; Evans, T. E.*; Groebner, R. J.*; Guzdar, P. N.*; Horton, L. D.*; et al.

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

no abstracts in English

Journal Articles

Survey of type I ELM dynamics measurements

Leonard, A. W.*; Asakura, Nobuyuki; Boedo, J. A.*; Becoulet, M.*; Counsell, G. F.*; Eich, T.*; Fundamenski, W.*; Herrmann, A.*; Horton, L. D.*; Kamada, Yutaka; et al.

Plasma Physics and Controlled Fusion, 48(5A), p.A149 - A162, 2006/05

 Times Cited Count:40 Percentile:17.98(Physics, Fluids & Plasmas)

This report summarizes Type I edge localized mode (ELM) dynamics measurements from a number of tokamaks. Several transport mechanisms are conjectured to be responsible for ELM transport, including convective transport due to filamentary structures ejected from the pedestal, parallel transport due to edge ergodization or magnetic reconnection and turbulent transport driven by the high edge gradients when the radial electric field shear is suppressed. The experimental observations are assessed for their validation, or conflict, with these ELM transport conjectures.

Journal Articles

Energy loss for grassy ELMs and effects of plasma rotation on the ELM characteristics in JT-60U

Oyama, Naoyuki; Sakamoto, Yoshiteru; Isayama, Akihiko; Takechi, Manabu; Gohil, P.*; Lao, L. L.*; Snyder, P. B.*; Fujita, Takaaki; Ide, Shunsuke; Kamada, Yutaka; et al.

Nuclear Fusion, 45(8), p.871 - 881, 2005/08

 Times Cited Count:98 Percentile:4.57(Physics, Fluids & Plasmas)

The grassy ELM is characterized by the high frequency periodic collapse up to $$sim$$kHz, which is $$sim$$15 times faster than that for type I ELM. A divertor peak heat flux due to grassy ELMs is less than 10% of that for type I ELMs. This smaller heat flux is caused by narrower radial extent of the collapse of temperature pedestal. The different radial extent between type I ELMs and grassy ELMs qualitatively agrees with the different radial distribution of the eigen function of the ideal MHD stability analysis. The ratio of ELM energy loss for grassy ELMs to the pedestal stored energy was 0.4-1%. In high triangularity regime, ELM amplitude, frequency and type can be changed from type I ELM to high frequency grassy ELM as counter plasma rotation was increased. In low triangularity regime, on the other hand, the complete ELM suppression (QH-mode) has been achieved, when the plasma position is optimized with CTR-NBIs. The existence of the edge fluctuations localized in pedestal region may reduce the pedestal pressure, and therefore the QH-mode can be sustained for long time up to 3.4s.

Oral presentation

Dynamics of MHD modes in high-$$beta$$ tokamak plasmas

Matsunaga, Go; Okabayashi, Michio*; Aiba, Nobuyuki; Boedo, J. A.*; Ferron, J. R.*; Hanson, J. M.*; Hao, G. Z.*; Heidbrink, W. W.*; Holcomb, C. T.*; In, Y.*; et al.

no journal, , 

no abstracts in English

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