Internal Transport Barrier for Electrons in JT-60U Reversed Shear Discharges [Phys. Rev. Lett. 78, 2377 (1997)]

Fujita, T.; Ide, S.; Shirai, Hiroshi; Kikuchi, M.; Naito, O.; Koide, Y.; Takeji, S.; Kubo, H.; Ishida, S.

doi:10.1103/physrevlett.78.4529

Cited by 128 publications

(205 citation statements)

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“…The common feature is a steep gradient of the T e profile in a core plasma region, just like an internal transport barrier ͑ITB͒ observed in tokamaks. 26 Thus, these profiles with the improvement of the electron transport observed in LHD are called electron-ITB here.…”

Section: Formation Of Electron Internal Transport Barriermentioning

confidence: 99%

Formation of electron internal transport barrier and achievement of high ion temperature in Large Helical Device

Takeiri¹,

Shimozuma²,

Kubo³

et al. 2003

Physics of Plasmas

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An internal transport barrier ͑ITB͒ was observed in the electron temperature profile in the Large Helical Device ͓O. Motojima et al., Phys. Plasmas 6, 1843 ͑1999͔͒ with a centrally focused intense electron cyclotron resonance microwave heating. Inside the ITB the core electron transport was improved, and a high electron temperature, exceeding 10 keV in a low density, was achieved in a collisionless regime. The formation of the electron-ITB is correlated with the neoclassical electron root with a strong radial electric field determined by the neoclassical ambipolar flux. The direction of the tangentially injected beam-driven current has an influence on the electron-ITB formation. For the counter-injected target plasma, a steeper temperature gradient, than that for the co-injected one, was observed. As for the ion temperature, high-power NBI ͑neutral beam injection͒ heating of 9 MW has realized a central ion temperature of 5 keV with neon injection. By introducing neon gas, the NBI absorption power was increased in low-density plasmas and the direct ion heating power was much enhanced with a reduced number of ions, compared with hydrogen plasmas.

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Section: Formation Of Electron Internal Transport Barriermentioning

confidence: 99%

Formation of electron internal transport barrier and achievement of high ion temperature in Large Helical Device

Takeiri¹,

Shimozuma²,

Kubo³

et al. 2003

Physics of Plasmas

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“…A number of facilities have recently added the capability to accuratelv measure the internal a Drofile evolution. and this has made possible systematic study of the production a n i performance of NCY regimes (Rice' 1996a(Rice' , 1996b(Rice' , 1996cLevinton 1995;Fujita 1997aFujita , 1997b.…”

Section: Negative Central Magnetic Shear (Ncs/lis/optimized Shear)mentioning

confidence: 99%

Physics of advanced tokamaks

Taylor¹

1997

Plasma Phys. Control. Fusion

204

153

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Significant reductions in the size and cost of a fusion power plant core can be realized if simultaneous improvements in the energy replacement time, τ E , and the plasma pressure or beta, β T = 2 µ 0 P /B 2 can be achieved in steady-state conditions with high selfdriven, bootstrap current fraction. Significant recent progress has been made in experimentally achieving these high performance regimes and in developing a theoretical understanding of the underlying physics. Three operational scenarios have demonstrated potential for steadystate high performance, the radiative improved mode, the high internal inductance or high i scenario, and the negative central magnetic shear, NCS (or reversed shear) scenario. In a large number of tokamaks, reduced ion thermal transport to near neoclassical values, and reduced particle transport have been observed in the region of negative or very low magnetic shear: the transport reduction is consistent with stabilization of microturbulence by sheared E × B flow. There is strong temporal and spatial correlation between the increased sheared E × B flow, the reduction in the measured turbulence, and the reduction in transport. The DIII-D tokamak, the JET tokamak and the JT-60U tokamak have all observed significant increases in plasma performance in the NCS operational regime. Strong plasma shaping and broad pressure profiles, provided by the H-mode edge, allow high beta operation, consistent with theoretical predictions; and normalized beta values up to β T /(I /aB) ≡ β N ∼ 4.5% m T MA −1 simultaneously with confinement enhancement over L-mode scaling, H = τ/τ ITER-89P ∼ 4, have been achieved in the DIII-D tokamak. In the JT-60U tokamak, deuterium discharges with negative central magnetic shear have reached equivalent breakeven conditions, Q DT (equiv) = 1.

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“…The slow transition to the improved transport mode [3], which is often observed in other types of improved modes or internal transport barrier (ITB) plasmas [4], is categorized as a type of second-order transition in contrast to a first-order transition such as the L/H transition [5][6][7]. In helical plasma, associated with the transition from ion-root to electron-root, an electron internal transport barrier (ITB) appears, when the heating power of the ECH exceeds a threshold power [8][9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Dynamic transport study of the plasmas with transport improvement in LHD and JT-60U

Ida¹,

Sakamoto²,

Inagaki³

et al. 2008

Nucl. Fusion

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Abstract.A transport analysis during the transient phase of heating (a dynamic transport study) applied to the plasma with internal transport barriers (ITBs) in the Large Helical Device (LHD) heliotron and JT-60U tokamak is described. In the dynamic transport study 1) a slow transition between two transport branches is observed, 2) the time of the transition from the L-mode plasma to the ITB plasma is clearly determined by the onset of the flattening of the temperature profile in the core region and 3) a spontaneous phase transition from a weak, wide ITB to a strong, narrow ITB and its back-transition are observed. The flattening of the core region of the ITB transition and the back-transition between a wide ITB and a narrow ITB suggest the strong interaction of turbulent transport in space, where turbulence suppression at certain locations in the plasma causes the enhancement of turbulence and thermal diffusivity nearby.

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Internal Transport Barrier for Electrons in JT-60U Reversed Shear Discharges [Phys. Rev. Lett. 78, 2377 (1997)]

Cited by 128 publications

References 0 publications

Formation of electron internal transport barrier and achievement of high ion temperature in Large Helical Device

Formation of electron internal transport barrier and achievement of high ion temperature in Large Helical Device

Physics of advanced tokamaks

Dynamic transport study of the plasmas with transport improvement in LHD and JT-60U

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