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Kamiya, Kensaku; Oyama, Naoyuki; Ido, Takeshi*; Bakhtiari, M.*; JFT-2M Group
Physics of Plasmas, 13(3), p.032507_1 - 032507_9, 2006/03
Times Cited Count：17 Percentile：47.83(Physics, Fluids & Plasmas)Accompanying the HRS H-mode transition, the coherent magnetic fluctuations in the frequency range of the order of 10-100 kHz with significant variation are seen on the magnetic probes at the vessel wall. Above all, two types of edge MHD activities, which have associated toroidal mode number of n=1 and n
7, respectively, seem to be more important for the HRS H-mode plasmas. To investigate their interaction, bi-spectral analysis is applied for the magnetic probe data. It is found to be a powerful tool, exhibiting the phase-coupled oscillations between two types of edge MHD activities having n=1 and n7.
Kamiya, Kensaku; Oyama, Naoyuki; Miura, Yukitoshi; Hubbard, A. E.*
Plasma Physics and Controlled Fusion, 46(11), p.1745 - 1755, 2004/11
Times Cited Count：14 Percentile：40.72(Physics, Fluids & Plasmas)Recent experiments in the JFT-2M tokamak have concentrated on the studies of the access condition for the H-mode operation without any large ELMs, namely High Recycling Steady (HRS) H-mode regime in terms of the pedestal parameters. The HRS regime is more likely at the higher edge density and lower edge temperature, while the ELMy H-mode having large ELMs appears at the lower edge density and higher edge temperature. It is found that the ELMy/HRS operational boundary occurs at the normalized electron collisionality of 
*
1 in the plasma edge region, depending slightly on q
. A key feature of the HRS H-mode is the presence of the coherent magnetic fluctuations in the frequency range of the order of 10-100 kHz. It is suggested that the edge MHD activities may keep an edge pressure below a certain level needed to induce a large ELM.
Kawashima, Hisato; Uehara, Kazuya; Nishino, Nobuhiro*; Kamiya, Kensaku; Tsuzuki, Kazuhiro; Bakhtiari, M.; Nagashima, Yoshihiko*; Ogawa, Hiroaki; Hoshino, Katsumichi; Suzuki, Sadaaki; et al.
Purazuma, Kaku Yugo Gakkai-Shi, 80(11), p.907 - 908, 2004/11
A comparison of divertor heat load between ELMy and "High Recycling Steady" (HRS) H-mode was carried out by fast measurements of the two dimensional 
emission, and the divertor electron temperature and ion saturation current on JFT-2M. They brought an attractive feature of HRS H-mode that the heat load was reduced to the level on time average that for ELMy H-mode, being able to avoid the severe heat load during pulsed ELM event. It was also indicated that the HRS H-mode was dominated by an enhancement of particle transport, whereas both heat and particle transport increased abruptly at ELM event.
Kamiya, Kensaku; Bakhtiari, M.; Kasai, Satoshi; Kawashima, Hisato; Kusama, Yoshinori; Miura, Yukitoshi; Ogawa, Hiroaki; Oyama, Naoyuki; Sato, Masayasu; Shinohara, Koji; et al.
Plasma Physics and Controlled Fusion, 46(5A), p.A157 - A163, 2004/05
Times Cited Count：25 Percentile：59.78(Physics, Fluids & Plasmas)A new operating regime, High Recycling Steady (HRS) H-mode regime, has been discovered on JFT-2M, which is easily reproduced under the wall fueling from the boronized first wall. Accompanying the HRS H-mode transition, the coherent magnetic and floating potential fluctuations are seen on magnetic probes at vessel wall and Langmuir probe in SOL, respectively. These coherent fluctuations have a frequency of the order of 10-100 kHz with significant variation, which is recognized to be important to enhance the particle transport. The HRS can be seen even at 
3 with 
/
0.4 for the fixed delta0.4 in the standard single-null divertor configuration. Recent experimental results from JFT-2M show that the plasma shape also seems to play an important role in determining the type of ELMs. The HRS regime can be extended up to delta0.75 and 2.6 in the double-null configuration, while lower delta boundary exists at delta0.3 with moderate 4 even at high recycling and/or density condition of /0.4.
