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Miyamoto, Seiji; Nakamura, Yukiharu*; Hayashi, Nobuhiko; Oyama, Naoyuki; Takenaga, Hidenobu; Sugie, Tatsuo; Kusama, Yoshinori; Yoshino, Ryuji
Proceedings of 36th European Physical Society Conference on Plasma Physics (CD-ROM), 4 Pages, 2009/07
The neutral dynamics including fueling, divertor pumping, charge exchange penetration, wall retention and so on would complicate the analysis of ITER plasma behavior such as H-L back transition during plasma current ramp-down. Recently, a relatively simple model of neutral dynamics was developed by us with TSC code to describe the plasma behavior during L-H and H-L transition phase. This model is compared with a JT-60U shot, in which it is possible to extract the effect of particle confinement change on neutral because H-mode discharge is switched on/off according to EC injection and thereby particle source density is kept constant during transition. It is shown that TSC simulation can account the behavior of neutral inferred from the experimental D
signal. It is concluded that this model is applicable to scenario development of the ITER.
Nakamura, Yukiharu*; Miyamoto, Seiji; Toshimitsu, Shinichi; Sugie, Tatsuo; Kusama, Yoshinori; Yoshino, Ryuji
Proceedings of 36th European Physical Society Conference on Plasma Physics (CD-ROM), 4 Pages, 2009/07
The ITER termination scenario from 15 MA to 1.5 MA (500 s 
t 
700 s) was reviewed by self-consistent simulations with the TSC code, comprised of newly developed D-T fuelling and pumping-out system. At 600 s, when the plasma current decreased to 10 MA, auxiliary NB heating was switched off to cease fusion 
-heating. Simultaneously, the energy confinement switches H to L mode by intentionally removing the H mode pedestal of edge transport barrier. The H to L mode transition dynamics, 
reduction in the plasma density while building-up of in-vessel neutral gas, disappearance of the edge BS current and consequent jump in the internal inductance 
, were investigated to assess performance of the ITER pump-out system. It was newly shown that the forced H to L mode transition may trigger a radiation collapse, consequently terminating the discharge. It was also demonstrated that EC heating with 170 GHz O-mode wave after the H to L mode transition provides an effective control means to hedge risk of the radiation collapse.
Urano, Hajime; Sakamoto, Yoshiteru; Oyama, Naoyuki; Kamiya, Kensaku; Kojima, Atsushi; Hayashi, Nobuhiko; Aiba, Nobuyuki; Kamada, Yutaka; JT-60 Team
Proceedings of 36th European Physical Society Conference on Plasma Physics (CD-ROM), 4 Pages, 2009/07
In JT-60U, the physics basis and control of the H-mode pedestal have been studied. Frequency of type-I ELMs becomes higher with increasing counter toroidal rotation. Fast recovery of density pedestal was observed after the ELM crash. ELM perturbation profile of density and temperature extends inward with co-NBI. In grassy ELM regime, ELM frequency increases with counter-toroidal rotation independently of 
. The amplitude of grassy ELM decreases as edge collisionality decreases. QH-mode was obtained at nearly zero or slightly co-toroidal rotation at the plasma edge. Scaling of pedestal width was examined by using hydrogen/deuterium discharges. It was found that dependence of pedestal width on the Larmor radius is weak.
