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Urso, L.*; Zohm, H.*; Isayama, Akihiko; Maraschek, M.*; Poli, E.*; ASDEX Upgrade Team; JT-60 Team
Nuclear Fusion, 50(2), p.025010_1 - 025010_12, 2010/01
Times Cited Count:28 Percentile:71.87(Physics, Fluids & Plasmas)no abstracts in English
Isayama, Akihiko; Matsunaga, Go; Kobayashi, Takayuki; Moriyama, Shinichi; Oyama, Naoyuki; Sakamoto, Yoshiteru; Suzuki, Takahiro; Urano, Hajime; Hayashi, Nobuhiko; Kamada, Yutaka; et al.
Nuclear Fusion, 49(5), p.055006_1 - 055006_9, 2009/05
Times Cited Count:61 Percentile:89.55(Physics, Fluids & Plasmas)no abstracts in English
Urso, L.*; Zohm, H.*; Fischer, R.*; Isayama, Akihiko; Kamada, Yutaka; ASDEX Upgrade Team; JT-60 Team
Europhysics Conference Abstracts (CD-ROM), 32D, 4 Pages, 2008/00
no abstracts in English
Kobayashi, Noriyuki; Bigelow, T.*; Bonicelli, T.*; Cirant, S.*; Denisov, G.*; Heidinger, R.*; Henderson, M.*; Hogge, J.-P.*; Piosczyk, B.*; Ramponi, G.*; et al.
AIP Conference Proceedings 933, p.413 - 416, 2007/10
Since the EDA 2001, Design of Electron Cyclotron Heating and Current Drive (ECH&CD) System have been modified due to progress of physics understanding and change of interface. Nominal RF power 20 MW is injected by four upper launchers or one equatorial launcher. RF beams are steered by a front steering mirror. DCHV power supply will be composed of IGBT pulse step modulators because of high frequency modulation and design flexibility to three different types of 170 GHz gyrotrons from three parties. The RF power is transmitted by 63.5 mm dia corrugated waveguide and switched by a waveguide switch between the upper launcher and the equatorial launcher. A start-up system for initial discharge is composed of three 127.5 GHz gyrotrons and dedicated DCHV power supply. Three of transmission lines are shared between 170 GHz and 127.5 GHz gyrotrons to inject start-up RF beam through the equatorial launcher. R&Ds for high power long pulse have been on-going to obtain a reliable ITER ECH&CD system.
Hender, T. C.*; Wesley, J. C.*; Bialek, J.*; Bondeson, A.*; Boozer, A. H.*; Buttery, R. J.*; Garofalo, A.*; Goodman, T. P.*; Granetz, R. S.*; Gribov, Y.*; et al.
Nuclear Fusion, 47(6), p.S128 - S202, 2007/06
Times Cited Count:916 Percentile:100(Physics, Fluids & Plasmas)no abstracts in English
La Haye, R. J.*; Prater, R.*; Buttery, R. J.*; Hayashi, Nobuhiko; Isayama, Akihiko; Maraschek, M. E.*; Urso, L.*; Zohm, H.*
Proceedings of 21st IAEA Fusion Energy Conference (FEC 2006) (CD-ROM), 8 Pages, 2007/03
Resistive neoclassical tearing mode (NTM) islands will be the principal limit on stability and performance in ITER as beta is well below the ideal kink limit. NTM island control in ITER is predicted to be challenging both because of the relatively narrower marginal island widths and the relatively broader electron cyclotron current drive (ECCD). Measurements from ASDEX Upgrade, DIII-D, and JET in beta rampdown experiments are used to determine the marginal island size for m/n=3/2 NTM removal. This is compared to data from ASDEX Upgrade, DIII-D and JT-60U with elimination of the m/n=3/2 island by continuous ECCD at near constant beta. The empirical marginal island size is consistent in both sets of removal experiments and found to be about twice the ion banana width. A common methodology is developed for fitting the saturated m/n=3/2 island before (or without) ECCD in all four experimental devices. To this is added (and model tested to experiments) the effect of unmodulated co-ECCD on island stabilization including both replacing the missing bootstrap current and making the classical tearing stability index more negative. The experimentally benchmarked model is then used to evaluate ITER. The ITER ECCD upper launcher with up to 20 MW of injected power is appraised with or without modulation for both the m/n=3/2 mode and the m/n=2/1 NTM (which can lock to the resistive wall and induce disruption). An m/n=2/1 rotating island model with drag from eddy current induced in the resistive wall is used to predict the necessary ECCD to keep the island from locking as a function of the rotation in ITER. The planned relatively wide ECCD should be capable of regulating the island width to avoid mode locking with the anticipated rotation in ITER but there is little margin available for inevitable misalignment. Narrower ECCD of more power and/or more rotation in ITER would increase confidence in island control and successful operation.
La Haye, R. J.*; Prater, R.*; Buttery, R. J.*; Hayashi, Nobuhiko; Isayama, Akihiko; Maraschek, M. E.*; Urso, L.*; Zohm, H.*
Nuclear Fusion, 46(4), p.451 - 461, 2006/04
Times Cited Count:151 Percentile:97.55(Physics, Fluids & Plasmas)no abstracts in English
Zohm, H.*; Hayashi, Nobuhiko; La Haye, R. J.*; Isayama, Akihiko; Maraschek, M. E.*; Sauter, O.*; Urso, L.*
Proceedings of 14th Joint Workshop on Electron Cyclotron Emission and Electron Cyclotron Resonance Heating (EC-14), p.334 - 339, 2006/00
no abstracts in English
Zohm, H.*; Gantenbein, G.*; Isayama, Akihiko; Keller, A.*; La Haye, R. J.*; Maraschek, M.*; Mck, A.*; Nagasaki, Kazunobu*; Pinches, S. D.*; Strait, E. J.*
Plasma Physics and Controlled Fusion, 45(12A), p.A163 - A173, 2003/12
Times Cited Count:25 Percentile:59.85(Physics, Fluids & Plasmas)A review of magnetohydrodynamic limits to tokamak operation in terms of current, density and pressure is given. Although the current and density limits in a tokamak usually lead to disruptive termination of the discharge, it is argued that these can be avoided by staying away from the respective limits. This is especially true since operation close to these limits is not really desirable, due to the decreased confinement at very high density and the high disruptivity at low q. On the other hand, the limit to plasma pressure set by neoclassical tearing modes (NTMs) and resistive wall modes (RWMs) is too low to guarantee economic operation of future fusion reactors. Therefore, active control of these two instabilities is now being studied. Noticeable progress has been made by NTM stabilization with ECCD. Avoidance of NTMs and RWMs by tailoring sawteeth and spinning the plasma, shows promising results. Also, experiments on direct RWM stabilization by active coils are showing their first encouraging results.
Isayama, Akihiko; JT-60 Team; Urso, L.*; Zohm, H.*; Maraschek, M.*; Hobirk, J.*
no journal, ,
no abstracts in English
Ozeki, Takahisa; Suzuki, Yoshio; Totsuka, Toshiyuki; Iba, Katsuyuki*; Sakata, Shinya; Miyato, Naoaki; Isayama, Akihiko; Ide, Shunsuke; Urso, L.*; Behler, K.*; et al.
no journal, ,
Isayama, Akihiko; Matsunaga, Go; Kobayashi, Takayuki; Moriyama, Shinichi; Oyama, Naoyuki; Sakamoto, Yoshiteru; Suzuki, Takahiro; Urano, Hajime; Hayashi, Nobuhiko; Kamada, Yutaka; et al.
no journal, ,
no abstracts in English