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Miyamoto, Seiji; Sugihara, Masayoshi*; Shinya, Kichiro*; Nakamura, Yukiharu*; Toshimitsu, Shinichi*; Lukash, V. E.*; Khayrutdinov, R. R.*; Sugie, Tatsuo; Kusama, Yoshinori; Yoshino, Ryuji*
Fusion Engineering and Design, 87(11), p.1816 - 1827, 2012/11
Times Cited Count：15 Percentile：71.22(Nuclear Science & Technology)Nakamura, Yukiharu*; Pautasso, G.*; Sugihara, Masayoshi*; Miyamoto, Seiji; Toshimitsu, Shinichi; Yoshino, Ryuji; ASDEX Upgrade Team*
Proceedings of 37th European Physical Society Conference on Plasma Physics (EPS 2010) (CD-ROM), 4 Pages, 2010/06
Of particular importance for the assessment of electromagnetic loads on vacuum vessel and in-vessel components of ITER is the halo current which achieves a maximum during VDEs (VDE: vertical displacement event). However, halo current models have a limited development so far with a few exceptions such as a validation study of the JT-60U halo current modelling using the DINA code. Recently, several experimental groups have prepared systematic halo current data, and further model development and validation with these data need to be performed using an axisymmetric, two-dimensional, free boundary code, TSC. To enhance an understanding of the maximum halo current and large vertical shifts, a reference discharge was selected from those included in the ASDEX upgrade disruption database. Systematic TSC simulations were performed to mimic the observation of a slow VDE of hot plasma and an ensuing fast downward-going VDE during a subsequent plasma current quench. Careful parameter adjustment of the temperature and width of the halo region was examined to mimic measurements of the halo current. A spontaneous, downward-going VDE was reproduced accurately in a manner that closely resembled experimental observations.
electronic states in CeIrSi
studied by angle-resolved Ce 3
resonance photoemission spectroscopyOkochi, Takuo*; Toshimitsu, Takafumi*; Yamagami, Hiroshi; Fujimori, Shinichi; Yasui, Akira; Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; Fujimori, Atsushi; Miyauchi, Yuichiro*; et al.
Journal of the Physical Society of Japan, 78(8), p.084802_1 - 084802_6, 2009/08
Times Cited Count：10 Percentile：54.6(Physics, Multidisciplinary)We have applied angle-resolved Ce 3
4 resonance photoemission spectroscopy to the non-centrosymmetric pressure-induced superconductor CeIrSi and obtained the 4 band-structure and Fermi surfaces. We have found that the Ce 4 states are located mainly near the Fermi level and that the photoemission intensity derived from the dispersive conduction bands across the Fermi level shows considerable resonant enhancement. In addition, the band structure and Fermi surfaces of CeIrSi are different from those of the non- reference compound, LaIrSi and the difference is well explained by the band structure calculated within the local density approximation (LDA). These results strongly suggest that the Ce 4 electrons in CeIrSi are well hybridized with conduction bands and form itinerant electronic states.
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.
studied by angle-resolved soft X-ray photoemission spectroscopyOkochi, Takuo; Fujimori, Shinichi; Toshimitsu, Takafumi; Okane, Tetsuo; Saito, Yuji; Fujimori, Atsushi*; Yamagami, Hiroshi*; Haga, Yoshinori; Yamamoto, Etsuji; Ikeda, Shugo; et al.
no journal, ,
We investigated the temperature dependence of the density of states and the band structure of ferromagnetic uranium compound, UIr, by the soft X-ray angle integrated / resolved photoemission spectroscopy. We observed the exchange splitting of the density of states as well as the representative 5
band. These results suggest that the ferromagnetism of UIr is well explained by the Stoner model (itinerant-magnetism model).
studied by angle-resolved photoemisson spectroscopyOkochi, Takuo; Fujimori, Shinichi; Toshimitsu, Takafumi; Okane, Tetsuo; Saito, Yuji; Yamagami, Hiroshi; Fujimori, Atsushi; Haga, Yoshinori; Yamamoto, Etsuji; Ikeda, Shugo; et al.
no journal, ,
no abstracts in English
Miyamoto, Seiji; Hayashi, Nobuhiko; Oyama, Naoyuki; Takenaga, Hidenobu; Toshimitsu, Shinichi; Sugie, Tatsuo; Kusama, Yoshinori; Yoshino, Ryuji
no journal, ,
In the operation of ITER, transition from the high confinement (H) mode to the low confinement (L) mode (H-L transition) is serious disturbance to control system, and therefore it is an important issue in operation scenario development to model the plasma behavior during the transition. Especially, the analysis must include neutral particles in plasma behavior. In the ITER current ramp-down scenario, the plasma is kept in H-mode, and thereby in low internal inductance, to leave a control margin. Then the plasma goes to L-mode at the final stage of the discharge. When the plasma particles emitted at the H-L transition flow back to the plasma as neutrals, the discharge may lead to a radiation collapse if the pumping capacity is too low. It is therefore required to perform a simulation including a model of fueling and pumping system. We did not take into account the scrape-off-layer (SOL) and divertor models previously. However, these models influence the plasma particle behavior through neutralization of ions in front of the divertor target and re-ionization of neutrals in the SOL. In the presentation, we describe the implementation of the SOL and divertor models in the tokamak simulation code (TSC) and the effect on the plasma and neutral behavior.
Miyamoto, Seiji; Nakamura, Yukiharu*; Toshimitsu, Shinichi; Sugie, Tatsuo; Kusama, Yoshinori; Yoshino, Ryuji; Hayashi, Nobuhiko; Oyama, Naoyuki; Takenaga, Hidenobu; Oikawa, Toshihiro*
no journal, ,
Development of ITER operation scenario using TSC code in JAEA is reviewed. TSC is a numerical code to simulate plasma evolution solving the MHD equation in an axisymmetric cylindrical coordinates. We have incorporated numerical models of electron cyclotron heating (ECH) / current drive (ECCD) and neutral beam injection (NBI) heating / current drive into the TSC code. Using the incorporated ECH/ECCD model, flux saving during plasma current ramp-up by EC is discussed. It is shown that resistive flux is effectively reduced due to heating of electron by EC. Recently, we are incorporating a neutral particle fueling and pumping model for studying effect of H-L transition on the poloidal field coil system of ITER size machine. A plan of neutral model development in TSC is also presented.
Miyamoto, Seiji; Sugihara, Masayoshi*; Shinya, Kichiro*; Nakamura, Yukiharu*; Toshimitsu, Shinichi; Sugie, Tatsuo; Kusama, Yoshinori; Yoshino, Ryuji
no journal, ,
When Plasma Control System (PCS) generates wrong signal to the PF coils and in-vessel vertical stabilization (VS) coils, it could be happen that the vertical force somewhat larger than presently specified could be generated. Example is that though plasma moves downward, but PCS erroneously recognizes it is moving upward. Then PF coils start to generate the field pattern that tends to push plasma further downward and resultantly the force could be larger than the present specification, in which it is evaluated with the assumption that control system (PF coils) does nothing (i.e., short-circuited.) In fact, in the existing machines, this is the worst case. The DINA code is used to analyze the vertical force, which has been updated to incorporate the recent design change of the vacuum vessel and in-vessel VS coils. In the presentation, analysis of VS effect on the vertical force is discussed using the updated DINA code.
