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Takenaga, Hidenobu; Miyo, Yasuhiko; Bucalossi, J.*; Marty, V.*; Urano, Hajime; Asakura, Nobuyuki; Nishiyama, Tomokazu; Sasajima, Tadayuki; Masaki, Kei; Kaminaga, Atsushi
Nuclear Fusion, 50(11), p.115003_1 - 115003_10, 2010/11
Times Cited Count：19 Percentile：57.62(Physics, Fluids & Plasmas)The supersonic molecular beam injection (SMBI) was successfully operated in JT-60U. Frequent density jumps were clearly observed in the main plasma against the SMBI pulses with the background gas pressure (
) of 2-6 bar. Fuelling efficiency exhibited weak dependence on and the injection direction (high- and low-field-side injections). The amount of the fuelling necessary for achieving the same density level is much smaller for the SMBI than for the gas-puffing. It is comparable for the SMBI and the pellet injection even with shallower penetration of the SMBI as discussed below. The SMBI ionization area was estimated based on emission measured using the fast TV camera with a time resolution of 0.167 ms. The estimations indicated similar penetration position for = 6 and 2 bar, although the ionization area was larger for 6 bar. This result supports the weak dependence of the fuelling efficiency. The front of the ionization area moved between first and second frames of the fast TV camera and it reached just inside the separatrix in the second frame. The ionization area was significantly expanded from the expected SMB size and the expansion was also enhanced between two frames. These relatively slow changes between two frames suggest that interaction between SMB and plasma significantly influences the fuelling characteristics.
Takenaga, Hidenobu; Oyama, Naoyuki; Urano, Hajime; Sakamoto, Yoshiteru; Asakura, Nobuyuki; Kamiya, Kensaku; Miyo, Yasuhiko; Nishiyama, Tomokazu; Sasajima, Tadayuki; Masaki, Kei; et al.
Nuclear Fusion, 49(7), p.075012_1 - 075012_11, 2009/07
Times Cited Count：9 Percentile：33.45(Physics, Fluids & Plasmas)Characteristics of internal transport barrier (ITB) have been investigated under reactor relevant condition with edge fuelling and electron heating in JT-60U weak shear plasmas. High confinement was sustained at high density with edge fuelling by shallow pellet injection or supersonic molecular beam injection (SMBI). The ion temperature (T
) in the central region inside the ITB decreased due to cold pulse propagation even with edge fuelling. By optimizing the injection frequency and the penetration depth, the decreased central T was recovered and good ITB was sustained with enhanced pedestal pressure. The T-ITB also degraded significantly with electron cyclotron heating (ECH), when stiffness feature was strong in the electron temperature (T
) profile. The ion thermal diffusivity in the ITB region increased with the electron thermal diffusivity, indicating existence of clear relation between ion and electron thermal transport. On the other hand, T-ITB unchanged or even grew, when stiffness feature was weak in the T profile. Density fluctuation level at ITB seemed to be unchanged during ECH, however, correlation length became longer in the T-ITB degradation case and shorter in the T-ITB unchanging case.
Takenaga, Hidenobu; Oyama, Naoyuki; Urano, Hajime; Sakamoto, Yoshiteru; Kamiya, Kensaku; Miyo, Yasuhiko; Nishiyama, Tomokazu; Sasajima, Tadayuki; Masaki, Kei; Kaminaga, Atsushi; et al.
Proceedings of 22nd IAEA Fusion Energy Conference (FEC 2008) (CD-ROM), 8 Pages, 2008/10
Characteristics of internal transport barrier (ITB) have been investigated under reactor relevant condition with edge fuelling and electron heating in JT-60U weak shear plasmas. High confinement was sustained at high density with edge fuelling by shallow pellet injection or supersonic molecular beam injection (SMBI). The ion temperature (
) in the central region decreased even with edge fuelling. The 
decrease with edge fuelling was larger inside the ITB than that outside the ITB, which can be described by cold pulse propagation using the ion thermal diffusivity (
) estimated from power balance analysis in the SMBI case. By optimizing the injection frequency and the penetration depth, the decreased was recovered and good ITB was sustained with enhanced pedestal pressure. The -ITB also degraded significantly when stiffness feature was strong in the electron temperature (
) profile against electron cyclotron heating (ECH). The value of in the ITB region increased with the electron thermal diffusivity (
), indicating existence of clear relation between ion and electron thermal transport. On the other hand, -ITB unchanged or even grew, when stiffness feature was weak in the profile. Density fluctuation level seemed to be unchanged during ECH, however, correlation length became longer in the -ITB degradation case and shorter in the -ITB unchanging case.
Miyo, Yasuhiko; Nishiyama, Tomokazu; Kaminaga, Atsushi; Takenaga, Hidenobu; Urano, Hajime; Sasajima, Tadayuki; Masaki, Kei; Bucalossi, J.*; Marty, V.*
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no abstracts in English
