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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

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:150 Percentile:98.87(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

Experimental studies of ITER demonstration discharges

Sips, A. C. C.*; Casper, T.*; Doyle, E. J.*; Giruzzi, G.*; Gribov, Y.*; Hobirk, J.*; Hogeweij, G. M. D.*; Horton, L. D.*; Hubbard, A. E.*; Hutchinson, I.*; et al.

Nuclear Fusion, 49(8), p.085015_1 - 085015_11, 2009/08

 Times Cited Count:48 Percentile:87.48(Physics, Fluids & Plasmas)

Key parts of the ITER scenarios are determined by the capability of the proposed poloidal field (PF) coil set. They include the plasma breakdown at low loop voltage, the current rise phase, the performance during the flat top (FT) phase and a ramp down of the plasma. The ITER discharge evolution has been verified in dedicated experiments. New data are obtained from C-Mod, ASDEX Upgrade, DIII-D, JT-60U and JET. Results show that breakdown for $$E$$$$_{axis}$$ $$<$$ 0.23-0.33 V m$$^{-1}$$ is possible unassisted (ohmic) for large devices like JET and attainable in devices with a capability of using ECRH assist. For the current ramp up, good control of the plasma inductance is obtained using a full bore plasma shape with early X-point formation. This allows optimization of the flux usage from the PF set. Additional heating keeps $$l$$$$_{i}$$(3) $$<$$ 0.85 during the ramp up to $$q$$$$_{95}$$ = 3. A rise phase with an H-mode transition is capable of achieving $$l$$$$_{i}$$(3) $$<$$ 0.7 at the start of the FT. Operation of the H-mode reference scenario at $$q$$$$_{95}$$ $$sim$$ 3 and the hybrid scenario at $$q$$$$_{95}$$ = 4-4.5 during the FT phase is documented, providing data for the $$l$$$$_{i}$$(3) evolution after the H-mode transition and the $$l$$$$_{i}$$(3) evolution after a back-transition to L-mode. During the ITER ramp down it is important to remain diverted and to reduce the elongation. The inductance could be kept $$leq$$ 1.2 during the first half of the current decay, using a slow $$I$$$$_{p}$$ ramp down, but still consuming flux from the transformer. Alternatively, the discharges can be kept in H-mode during most of the ramp down, requiring significant amounts of additional heating.

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

Progress in the ITER physics basis, 2; Plasma confinement and transport

Doyle, E. J.*; Houlberg, W. A.*; Kamada, Yutaka; Mukhovatov, V.*; Osborne, T. H.*; Polevoi, A.*; Bateman, G.*; Connor, J. W.*; Cordey, J. G.*; Fujita, Takaaki; et al.

Nuclear Fusion, 47(6), p.S18 - S127, 2007/06

no abstracts in English

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

Pedestal conditions for small ELM regimes in tokamaks

Oyama, Naoyuki; Gohil, P.*; Horton, L. D.*; Hubbard, A. E.*; Hughes, J. W.*; Kamada, Yutaka; Kamiya, Kensaku; Leonard, A. W.*; Loarte, A.*; Maingi, R.*; et al.

Plasma Physics and Controlled Fusion, 48(5A), p.A171 - A181, 2006/05

 Times Cited Count:65 Percentile:90.57(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Comparisons of small ELM H-mode regimes on the Alcator C-Mod and JFT-2M tokamaks

Hubbard, A. E.*; Kamiya, Kensaku; Oyama, Naoyuki; Basse, N.*; Biewer, T.*; Edlund, E.*; Hughes, J. W.*; Lin, L.*; Porkolab, M.*; Rowan, W.*; et al.

Plasma Physics and Controlled Fusion, 48(5A), p.A121 - A129, 2006/05

 Times Cited Count:15 Percentile:49.06(Physics, Fluids & Plasmas)

Dedicated experiments were carried out to compare the properties, fluctuation behaviour and access conditions of these regimes. A common shape was developed which scaled the plasma boundary except for aspect ratio. Scans of density and input power were carried out at several values of q95, so as to achieve ranges of dimensionless parameters. A striking similarity of access conditions was seen. These results suggest common physical mechanisms for the H-mode regimes, which do not depend critically on aspect ratio over this range. On the other hand, several differences in the details of the edge fluctuations were found, and will be reported. The effect of wall conditioning via boronization on the H-mode regimes will also be discussed.

Journal Articles

Pedestal characteristics in JFT-2M HRS H-mode plasma

Kamiya, Kensaku; Oyama, Naoyuki; Miura, Yukitoshi; Hubbard, A. E.*

Plasma Physics and Controlled Fusion, 46(11), p.1745 - 1755, 2004/11

 Times Cited Count:13 Percentile:42.46(Physics, Fluids & Plasmas)

Recent experiments in the JFT-2M tokamak have concentrated on the studies of the access condition for the H-mode operation without any large ELMs, namely High Recycling Steady (HRS) H-mode regime in terms of the pedestal parameters. The HRS regime is more likely at the higher edge density and lower edge temperature, while the ELMy H-mode having large ELMs appears at the lower edge density and higher edge temperature. It is found that the ELMy/HRS operational boundary occurs at the normalized electron collisionality of $$nu$$*$$_{e}$$$$sim$$1 in the plasma edge region, depending slightly on q$$_{95}$$. A key feature of the HRS H-mode is the presence of the coherent magnetic fluctuations in the frequency range of the order of 10-100 kHz. It is suggested that the edge MHD activities may keep an edge pressure below a certain level needed to induce a large ELM.

Journal Articles

Understanding of the H mode pedestal characteristics using the multimachine pedestal database

Hatae, Takaki; Sugihara, Masayoshi; Hubbard, A. E.*; Igitkhanov, Y.*; Kamada, Yutaka; Janeschitz, G.*; Horton, L. D.*; Oyabu, Nobuyoshi*; Osborne, T. H.*; Osipenko, M.*; et al.

Nuclear Fusion, 41(3), p.285 - 293, 2001/03

 Times Cited Count:39 Percentile:75.89(Physics, Fluids & Plasmas)

no abstracts in English

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