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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:170 Percentile:98.64(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

Experimental tests of paleoclassical transport

Callen, J. D.*; Anderson, J. K.*; Arlen, T. C.*; Bateman, G.*; Budny, R. V.*; Fujita, Takaaki; Greenfield, C. M.*; Greenwald, M.*; Groebner, R. J.*; Hill, D. N.*; et al.

Nuclear Fusion, 47(11), p.1449 - 1457, 2007/11

 Times Cited Count:7 Percentile:25.84(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Characteristics of the H-mode pedestal in improved confinement scenarios in ASDEX Upgrade, DIII-D, JET and JT-60U

Maggi, C. F.*; Groebner, R. J.*; Oyama, Naoyuki; Sartori, R.*; Horton, L. D.*; Sips, A. C. C.*; Suttrop, W.*; ASDEX Upgrade Team; Leonard, A.*; Luce, T. C.*; et al.

Nuclear Fusion, 47(7), p.535 - 551, 2007/07

 Times Cited Count:63 Percentile:88.45(Physics, Fluids & Plasmas)

Pedestal and global plasma parameters are compared in ELMy H-modes and improved confinement discharges from ASDEX Upgrade (AUG), DIII-D, JET and JT-60U with varying net input power. The pedestal top pressure increases moderately with power, in broad agreement with the power dependence of the H98(y,2) scaling. For all machines and all scenarios a robust correlation between the total and the pedestal thermal stored energy is observed. In AUG the improved confinement is due to improved pedestal confinement in improved H-modes with early heating and to both improved pedestal and core confinement in improved H-modes with late heating. In DIII-D the increase in confinement is due to improved confinement in the plasma core. JT-60U reversed shear H-modes have strong internal transport barriers and thus improved core performance. In all four tokamaks improved edge stability is correlated with increasing total $$beta_{p}$$ and H98(y,2) increases with pedestal $$beta_{p}$$.

Journal Articles

Progress in the ITER physics basis, 1; Overview and summary

Shimada, Michiya; Campbell, D. J.*; Mukhovatov, V.*; Fujiwara, Masami*; Kirneva, N.*; Lackner, K.*; Nagami, Masayuki; Pustovitov, V. D.*; Uckan, N.*; Wesley, J.*; et al.

Nuclear Fusion, 47(6), p.S1 - S17, 2007/06

 Times Cited Count:744 Percentile:99.93(Physics, Fluids & Plasmas)

The Progress in the ITER Physics Basis document is an update of the ITER Physics Basis (IPB), which was published in 1999. The IPB provided methodologies for projecting the performance of burning plasmas, developed largely through coordinated experimental, modeling and theoretical activities carried out on today's tokamaks (ITER Physics R&D). In the IPB, projections for ITER (1998 Design) were also presented. The IPB also pointed out some outstanding issues. These issues have been addressed by the International Tokamak Physics Activities (ITPA), which were initiated by the European Union, Japan, Russia and the U.S.A.. The new methodologies of projection and control developed through the ITPA are applied to ITER, which was redesigned under revised technical objectives, but will nonetheless meet the programmatic objective of providing an integrated demonstration of the scientific and technological feasibility of fusion energy.

Journal Articles

Progress in the ITER physics basis, 4; Power and particle control

Loarte, A.*; Lipschultz, B.*; Kukushkin, A. S.*; Matthews, G. F.*; Stangeby, P. C.*; Asakura, Nobuyuki; Counsell, G. F.*; Federici, G.*; Kallenbach, A.*; Krieger, K.*; et al.

Nuclear Fusion, 47(6), p.S203 - S263, 2007/06

 Times Cited Count:859 Percentile:98.25(Physics, Fluids & Plasmas)

Progress, since the ITER Physics Basis publication (1999), in understanding the processes that will determine the properties of the plasma edge and its interaction with material elements in ITER is described. Significant progress in experiment area: energy and particle transport, the interaction of plasmas with the main chamber material elements, ELM energy deposition on material elements and the transport mechanism, the physics of plasma detachment and neutral dynamics, the erosion of low and high Z materials, their transport to the core plasma and their migration at the plasma edge, retention of tritium in fusion devices and removal methods. This progress has been accompanied by the development of modelling tools for the physical processes at the edge plasma and plasma-materials interaction. The implications for the expected performance in ITER and the lifetime of the plasma facing materials are discussed.

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

Characteristics of the H-mode pedestal in improved confinement scenarios in ASDEX Upgrade, DIII-D, JET and JT-60U

Maggi, C. F.*; Groebner, R. J.*; Oyama, Naoyuki; Sartori, R.*; Horton, L. D.*; Sips, A. C. C.*; Suttrop, W.*; ASDEX Upgrade Team; Leonard, T.*; Luce, T. C.*; et al.

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

Pedestal and global plasma parameters are compared in ELMy H-mode discharges from ASDEX Upgrade (AUG), DIII-D, JET and JT-60U. The increase in pedestal pressure (p$$^{PED}$$) with power is continuous, reflecting the continuous transition from "standard H-mode" to "improved confinement scenario". In AUG improved H-modes p$$^{PED}$$ increases with power due to an increase of both pedestal top density and temperature. In DIII-D p$$^{PED}$$ increases primarily due to an increase of the pedestal temperature. In JT-60U high $$beta_{pol}$$ H-modes at $$q_{95}$$ = 6.5 and high $$delta$$ the improved confinement is due to an increase of $$W_{PED}$$, while in reversed shear H-modes to an increase of $$W_{core}$$. In JET hybrid discharges at 1.4 MA $$W_{th}$$ increases with power and $$delta$$ due to an increase of $$W_{PED}$$. In all four tokamaks improved edge stability is correlated to increasing total $$beta_{pol} $$ and H98(y,2) increases with pedestal $$beta_{pol}$$.

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:78.1(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

Progress in physics basis and its impact on ITER

Shimada, Michiya; Campbell, D.*; Stambaugh, R.*; Polevoi, A. R.*; Mukhovatov, V.*; Asakura, Nobuyuki; Costley, A. E.*; Donn$'e$, A. J. H.*; Doyle, E. J.*; Federici, G.*; et al.

Proceedings of 20th IAEA Fusion Energy Conference (FEC 2004) (CD-ROM), 8 Pages, 2004/11

This paper summarises recent progress in the physics basis and its impact on the expected performance of ITER. Significant progress has been made in many outstanding issues and in the development of hybrid and steady state operation scenarios, leading to increased confidence of achieving ITER's goals. Experiments show that tailoring the current profile can improve confinement over the standard H-mode and allow an increase in beta up to the no-wall limit at safety factors $$sim$$ 4. Extrapolation to ITER suggests that at the reduced plasma current of $$sim$$ 12MA, high Q $$>$$ 10 and long pulse ($$>$$1000 s) operation is possible with benign ELMs. Analysis of disruption scenarios has been performed based on guidelines on current quench rates and halo currents, derived from the experimental database. With conservative assumptions, estimated electromagnetic forces on the in-vessel components are below the design target values, confirming the robustness of the ITER design against disruption forces.

Journal Articles

Edge localized mode physics and operational aspects in tokamaks

B$'e$coulet, M.*; Huysmans, G.*; Sarazin, Y.*; Garbet, X.*; Ghendrih, P.*; Rimini, F.*; Joffrin, E.*; Litaudon, X.*; Monier-Garbet, P.*; An$'e$, J.-M.*; et al.

Plasma Physics and Controlled Fusion, 45(12A), p.A93 - A113, 2003/12

 Times Cited Count:84 Percentile:91.17(Physics, Fluids & Plasmas)

no abstracts in English

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