Formation of internal and edge transport barriers in JT-60U

Koide, Y.; Kikuchi, M.; Ishida, S.; Mori, Masahiro; Tsuji, S.; Asakura, N.; Kamada, Y.; Nishitani, T.; Kawano, Y.; Hatae, T.; Fujita, T.; Fukuda, T.; Sakasai, A.; Kondoh, T.; Yoshino, R.; Neyatani, Y.

doi:10.1088/0741-3335/36/7a/027

Cited by 37 publications

(31 citation statements)

References 12 publications

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“…A growth rate γ of the n = 1 mode is about 430 s -1 in the early phase and is about 1,020 s -1 at t ≈ 6.322 s. Since the estimated τ w of the JT-60U vacuum vessel is ≈ 10 ms, the growth rate of 430 s -1 corresponds to ≈ 4 τ w -1 . Toroidal rotation velocity of the ohmic discharges is nearly zero within the uncertainty of the measurement by a charge-exchange recombination spectroscopy (CXRS) [21]. The diamagnetic drift is a dominant fluid drift in the poloidal direction in such ohmic discharges and its velocity is typically ≈ 5 km/s.…”

Section: Rwms Associated With Current-driven Kink Modesmentioning

confidence: 95%

Observation of Resistive Wall Modes in JT-60U.

Takeji¹,

Tokuda²,

Kurita³

et al. 2002

J. Plasma Fusion Res.

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Resistive wall modes (RWM) associated with ideal magnetohydrodynamic current-driven (β N < 0.2) and pressure-driven (β N > 2.4) kink modes with low toroidal mode number n (n = 1) have been identified in JT-60U. The pressure-driven RWM occurs at the plasma toroidal rotation of about 1% the Alfvén speed without clear continuous slowing down of the plasma toroidal rotation. Occurrence of n = 1 RWMs result in thermal quench accompanied by higher n (n ≥ 2) modes. In the case of current-driven (~ zero β) RWMs, a thermal quench occurs only at the peripheral region just after the RWM. In contrast, a thermal quench occurs in the whole plasma region following a drastic increase in the growth rate of the RWM from the order of τ w -1 (τ w is the resistive diffusion time of the wall) to larger than 10 2 τ w -1 in the case of pressure-driven (high β ) RWMs.

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Section: Rwms Associated With Current-driven Kink Modesmentioning

confidence: 95%

Observation of Resistive Wall Modes in JT-60U.

Takeji¹,

Tokuda²,

Kurita³

et al. 2002

J. Plasma Fusion Res.

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“…Figure 10 (a) shows a close correlation of ∆W ELM /W ped with a v T,ped under a P SEP ∼ 5-6 MW at each configuration, showing similar slopes in the dependence of ∆W ELM /W ped on v T,ped . A reason for the narrower dynamic range toward the co-direction in the v T,ped for the larger volume configuration is due to an offset toroidal rotation towards the counter-direction at the plasma's edge region due to larger losses of fast ions from perpendicular NBI [11][12][13]. As shown in Fig.…”

Section: Effects Of Toroidal Field Ripple On Elmsmentioning

confidence: 93%

“…discharge at a given P SEP as shown in Fig. 8, which is related to the losses of fast ions due to perpendicular NBI and the formation of negative E r [11,12]. From the results described above, it 005-4 is suggested that the effect of the resultant toroidal rotation at the plasma edge caused by the losses of the fast ions due to the TF-ripple on ELMs is also an interesting edge phenomenon, which may also provide a controllable parameter for ELM mitigation.…”

Section: Effects Of Toroidal Field Ripple On Elmsmentioning

confidence: 99%

“…These plasmas show a toroidal rotation at the plasma edge, v T,ped , in the direction counter to the plasma current, providing a controllable parameter through which ELMs can be controlled, though underlying physics of this phenomenon is not yet well understood. Furthermore, the behavior of ELMs with the change in the power of neutral beam injection (NBI) in the JT-60U exhibited a complex nature, since the negative radial electric field, E r , formation due to losses of fast ions originating mainly from the perpendicular NBI as well as the v T,ped could vary with external momentum input from tangential NBI [11,12].…”

Section: Introductionmentioning

confidence: 99%

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Roles of Toroidal Rotation at the Plasma Edge, Toroidal Field Ripple and Configuration on ELMs in the JT-60U Tokamak

Kamiya

Urano

Oyama

et al. 2007

Plasma and Fusion Research

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Recent experimental studies are presented regarding ELMy H-mode plasma having Type-I Edge Localized Modes (ELMs) in the JT-60U. Toroidal rotation scan experiments in inward-shifted, small-volume plasma show that the ELM energy loss decreases as the toroidal rotation at the plasma edge increases in the direction counter to the plasma current. Specifically for a large volume plasma having a toroidal field ripple of ∼2% at the plasma edge, small Type-I ELMs are observed whose ELM energy loss normalized by the pedestal stored energy is smaller than that of an acceptable ELM size in the ITER. However, the pedestal pressure tends to decrease when plasma volume increases. No remarkable effect of reduced toridal field ripple due to the installation of Ferritic Steel Tile (FSTs) inside the vacuum vessel on the JT-60U on ELMs for large volume plasma is seen in the ELM energy loss normalized by the pedestal stored energy. These new findings suggest that the toroidal field ripple itself may not directly affect the normalized ELM energy loss, and that toroidal rotation at the plasma edge as well as plasma configuration might play important roles in the prediction of ELM size in future devices.

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“…Ion temperature profiles, T i , were measured by charge-exchange recombination spectroscopy (CXRS) of carbon [27]. The effective charge number, Z eff , was estimated using visible bremsstrahlung, and its profile was assumed to be spatially uniform so that these values were capable of reproducing the measured neutron emission rate, S n [28].…”

Section: Experiments Of High-triangularity Elmy H-modementioning

confidence: 99%

Deactivation of 3s levels of the neon atom by collisions with neon, argon, krypton, and xenon

1995

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High-triangularity ELMy H-mode experiments (δ x ∼ 0.45) have been carried out in JT-60U. In the low-density regime (n e /n GW < 0.5), the discharges are characterized by type-I ELMs and high-triangularity plasmas produced higher H-mode pedestal pressure than low-triangularity plasmas (δ x ∼ 0.20). In the high-density regime (n e /n GW > 0.5), at fixed neutral beam heating power type-III ELMs are generated and the pedestal pressure reduces gradually with density whereas the ELM frequency at low triangularity is much lower at a given density. Compared to low-triangularity plasmas at low densities, higher pedestal temperature was obtained at high triangularity and the core temperature was also improved by almost the same factor. The profiles of temperature are stiff in the sense that there seems to exist a minimum scale length of temperature gradient. Since plasma shaping affects strongly the peripheral region of toroidal magnetic flux surfaces, the improvement of the edge stability by triangularity leads to higher pedestal temperature, which in turn raises the core temperature. * This paper is an extended version of a contribution to the 28th EPS

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Formation of internal and edge transport barriers in JT-60U

Abstract: Spontaneous formation of intemal transport barrier was observed in JT-60U high-& discharges, where q=3 surface is the most likely explanation for its radial location. Further improved confinement was brought about by the subsequent transition to the edge nansport barrier.

Cited by 37 publications

References 12 publications

Observation of Resistive Wall Modes in JT-60U.

Observation of Resistive Wall Modes in JT-60U.

Roles of Toroidal Rotation at the Plasma Edge, Toroidal Field Ripple and Configuration on ELMs in the JT-60U Tokamak

Deactivation of 3s levels of the neon atom by collisions with neon, argon, krypton, and xenon

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