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collapse after NBCD turn-off in JT-60U fully non-inductive reversed shear dischargesTakei, Nahoko; Nakamura, Yukiharu; Ushigome, Masahiro*; Suzuki, Takahiro; Aiba, Nobuyuki; Takechi, Manabu; Tobita, Kenji; Takase, Yuichi*; Fukuyama, Atsushi*; Jardin, S. C.*
Plasma Physics and Controlled Fusion, 49(3), p.335 - 345, 2007/03
Times Cited Count：7 Percentile：25.84(Physics, Fluids & Plasmas)Non-disruptive -collapses with a regular intermittency have been observed after a forced turn-off of neutral beam current drive (NBCD) in JT-60U fully non-inductive, reversed shear (RS) discharges. Self-consistent transport simulations with improved core confinement and linear MHD stability analysis have first clarified that redistribution of return current induced after the NBCD turn-off lowers the safety factor of magnetic shear reversal, leading to the n =1 kink-ballooning instability with localized modes around internal transport barrier (ITB). It was also pointed out that an increase of the bootstrap current under continuous NB heating can lead to ITB reconstruction and thus causes subsequent beta-collapses.
Ushigome, Masahiro*; Ide, Shunsuke; Ito, Satoshi*; Jotaki, Eriko*; Mitarai, Osamu*; Shiraiwa, Shunichi*; Suzuki, Takahiro; Takase, Yuichi*; Tanaka, Shigetoshi*; Fujita, Takaaki; et al.
Nuclear Fusion, 46(2), p.207 - 213, 2006/02
Times Cited Count：11 Percentile：37.01(Physics, Fluids & Plasmas)This papaer studies on tokamak plasma start-up completely without central solenoid (CS). On the JT-60 tokamak it is demonstrated that a completely CS-less Ip start-up to 100 kA was achieved even without any null-point by Electron cyclotron range of frequencies (ECRF) and outer PF coil current swing only. Necessary conditions (the EC power, the toroidal field etc.) were clarified. Moreover, it was succeded to maintain Ip = 260kA for 1 sec without CS by NB only. In addition Ip ramp-up by EC and NB only (without LHCD) from 215 to 310kA was achieved. In a high confinement reversed shear discharge, a result suggesting bootstrap over drive was obtained.
Takei, Nahoko; Ushigome, Masahiro*; Suzuki, Takahiro; Nakamura, Yukiharu; Takase, Yuichi*
Europhysics Conference Abstracts (CD-ROM), 30I, 4 Pages, 2006/00
no abstracts in English
Takei, Nahoko; Ushigome, Masahiro*; Suzuki, Takahiro; Takechi, Manabu; Aiba, Nobuyuki; Nakamura, Yukiharu; Takase, Yuichi*
no journal, ,
no abstracts in English
