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Miki, Kazuhiro; Diamond, P. H.*; Hahn, S.-H.*; Xiao, W. W.*; G
rcan, 
. D.*; Tynan, G. R.*
no journal, ,
A central issue in H-mode physics is to achieve control, not only understanding. Work in control has focused mainly on fueling by pellet injection at the near edge. We here introduce a developed one-dimensional mesoscale model, to report on the L-H transition stimulated by pellet injection. For highly heated plasmas, transition occurs spontaneously; when heat flux increases, a strong zonal flow is sufficiently excited, leading to I-phase oscillations or a single burst. When the zonal flow is excited, turbulence is reduced, allowing an ion pressure gradient to steepen. Then, mean flow shear increases to lock in the H-mode. On the other hand, studies reveal that L-H transition can be triggered by particle injection into a subcritical state. We also observe that zonal flows do not play a critical role in stimulated transitions.
Kamiya, Kensaku; Matsunaga, Go; Honda, Mitsuru; Miyato, Naoaki; Urano, Hajime; Kamada, Yutaka; Ida, Katsumi*; Ito, Kimitaka*
no journal, ,
no abstracts in English
Yoshida, Maiko; Ide, Shunsuke; Takenaga, Hidenobu; Honda, Mitsuru; Urano, Hajime; Kobayashi, Takayuki; Nakata, Motoki; Miyato, Naoaki; Kamada, Yutaka
no journal, ,
Temporal and spatial responses of electron channels (the electron density, ne and the electron temperature) and ion channels (the ion temperature, Ti and the toroidal rotation velocity) to central electron cyclotron heating (ECH) have been investigated in positive shear H-mode plasmas with relatively peaked Ti profile and internal transport barrier (ITB) plasmas on JT-60U.
Urano, Hajime
no journal, ,
The H-mode pedestal structure remains a critical subject for magnetic fusion plasma research because it governs overall energy confinement as well as affects strongly ELM features. The plasma pressure profile at the edge pedestal can simply be characterized by a right-angled triangle geometrically with three components of width, gradient, and height. While the steep edge pressure gradient in type-I ELMy H-modes is imposed in many cases by the peeling-ballooning stability limit, it has been observed in several tokamak devices that the spatial width of the edge pedestal is determined by 
where 
denotes the poloidal beta at the pedestal. The H-mode pedestal confinement can strongly be affected by the choice of first wall materials through plasma impurity composition and measures required to prevent first wall damage. Recently, the influence of the wall materials on the ELMy H-mode regime has intensively been studied in accordance with an issue of the possibile tungsten divertor in ITER. The reduction in the pedestal pressure can be overcome by seeding low-Z extrinsic impurities.
Honda, Mitsuru; Satake, Shinsuke*; Suzuki, Yasuhiro*; Matsunaga, Go; Shinohara, Koji; Ide, Shunsuke; Yoshida, Maiko; Urano, Hajime; Hayashi, Nobuhiko
no journal, ,
Aiba, Nobuyuki; Urano, Hajime
no journal, ,
Impact of plasma core profiles on MHD stability at tokamak edge pedestal is analyzed numerically with numerical codes MARG2D, MINERVA, and BETA. Based on pedestal prediction model EPED1, plasma current profile at edge pedestal can be changed by changing plasma core pressure profile even when pedestal width predicted with EPED1 is unchanged. Such a change of plasma current profile is due to varying bootstrap current, and affects an internal inductance. The MHD stability at edge pedestal is sensitive on current profile at edge pedestal, and we found that ideal ballooning mode, which is one of the strong candidates of small amplitude ELMs, can be unstable by increasing the internal inductance. This trend is consistent with the experimental results in JET, and indicates that plasma core profile affects the MHD stability at pedestal and will play important roles for realizing small amplitude ELMy H-mode.
Garcia, J.*; Hayashi, Nobuhiko; Baiocchi, B.*; Citrin, J.*; Giruzzi, G.*; Honda, Mitsuru; Ide, Shunsuke; Maget, P.*; Narita, Emi*; Schneider, M.*; et al.
no journal, ,