Scaling of the energy confinement time with β and collisionality approaching ITER conditions

Cordey, J.G.; Thomsen, K.; Chudnovskiy, A. N.; Kardaun, O.; Takizuka, T.; Snipes, J. A.; Greenwald, M.; Sugiyama, L.; Ryter, F.; Kus, A.; Stöber, J.; DeBoo, J. C.; Petty, C. C.; Bracco, G.; Romanelli, M.; Cui, Z.Y.; Liu, Y.; McDonald, D. C.; Meakins, A.; Miura, Y.; Shinohara, K.; Tsuzuki, K.; Kamada, Y.; Urano, H.; Valovič, M.; Akers, R.; Brickley, C.; Sykes, A.; Walsh, M. J.; Kaye, S. M.; Bush, C. E.; Hogewei, D.; Martin, Yves; Cote, A.; Pacher, G.W.; Ongena, J.; Imbeaux, F.; Hoang, G. T.; Лебедев, С. В.; Leonov, V. M.

doi:10.1088/0029-5515/45/9/007

Cited by 51 publications

(81 citation statements)

References 12 publications

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“…Far more optimistic values for P aux and Q are obtained using a GyroBohm scaling [18] (Bτ E~β 0 ). The scaling proposed by Cordey [19] (Bτ E~β 0 ) would predict higher Q at high beta compared to the IPB98(y,2) scaling. …”

Section: Extrapolation To Itermentioning

confidence: 82%

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The performance of improved H-modes at ASDEX Upgrade and projection to ITER

et al. 2007

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Since 1998 ASDEX Upgrade has developed stationary H-modes that routinely obtain confinement enhancement factors H98(y,2) > 1 and normalized beta, βN = 2–3. These discharges are characterized by a q-profile with low magnetic shear in the centre and q(0) ∼ 1. New results presented here concentrate on extending the operational range of these improved H-modes at ASDEX Upgrade and extrapolating the results to ITER. Discharges are obtained at high density, over a wide range of plasma collisionality and with a first wall predominantly covered by tungsten coated carbon tiles. The performance is optimized for q95 ranging from 3 to 5. At q95 ∼ 3 real time control of βN is used and in some cases ECCD to suppress NTM activity at low βN ∼ 2. For the extrapolation to ITER, the fusion power is calculated using the same thermal beta (βN,th) and kinetic profile shapes as obtained in ASDEX Upgrade and setting ⟨ne⟩/nGW = 0.85. The fusion gain that could be obtained is evaluated using different confinement scaling expressions. The results indicate that improved H-modes are a candidate for an ITER hybrid scenario or could extend ITER operation beyond what is currently foreseen using standard H-modes.

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Section: Extrapolation To Itermentioning

confidence: 82%

“…The fusion gain and input power (P aux ) required have been calculated for three different energy confinement scalings [1,18,19]. For each scaling the respective H-values obtained at ASDEX Upgrade are taken.…”

Section: Extrapolation To Itermentioning

confidence: 99%

The performance of improved H-modes at ASDEX Upgrade and projection to ITER

et al. 2007

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“…However this could be due to a different β dependence in the H 98(y,2) scaling [25]. Neglecting this would lead to a scaling which is closer to gyro-Bohm scaling: B t × τ E-gyro-Bohm ∝ ρ * −3.0 .…”

Section: Confinement Scalingmentioning

confidence: 99%

Integrated scenario with type-III ELMy H-mode edge: extrapolation to ITER

Rapp¹,

Corre²,

Andrew³

et al. 2009

Nucl. Fusion

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One of the most severe problems for fusion reactors is the power load on the plasma facing components. The challenge is to develop operation scenarios, which combine sufficient energy confinement with benign heat loads to the plasma facing components. The radiative type-III ELMy H-mode seems a possible solution for such an integrated ITER scenario. Nitrogen seeded type-III ELMy H-modes for the standard inductive scenario and the high beta stationary hybrid scenario are investigated with respect to their transient and steady-state power fluxes to the divertor, confinement properties, edge operational space, core operational space, plasma purity and MHD behaviour. A large database of highly radiative type-III ELMy H-modes on JET is used for extrapolations to ITER. On this basis the transient heat load should be acceptable for ITER. It was found that the scaling of the confinement time with respect to the ion gyroradius is close to the gyro-Bohm scaling. Scalings with respect to the plasma collisionality suggest that the confinement will be good enough for an ITER scenario at 17 MA with a power amplification factor (Q) of 10 and might be marginally good enough for a Q = 10 scenario at 15 MA. Those extrapolations are supported by simulations with an integrated core/edge model COREDIV. In addition the hybrid scenario with type-III edge localized modes has been proven to have improved edge conditions without any modification of the central plasma current profile, indicating it is compatible with a high beta operation for a steady-state ITER Q = 5 scenario.

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“…This is in contrast to the ν * −0.4 e dependence seen at higher aspect ratio. 12 The result for the β T scaling is shown in Fig. 4b.…”

Section: Confinement Scalingmentioning

confidence: 99%

Confinement and local transport in the National Spherical Torus Experiment (NSTX)

et al. 2007

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NSTX operates at low aspect ratio (R/a∼1.3) and high beta (up to 40%), allowing tests of global confinement and local transport properties that have been established from higher aspect ratio devices. NSTX plasmas are heated by up to 7 MW of deuterium neutral beams with preferential electron heating as expected for ITER. Confinement scaling studies indicate a strong B T dependence, with a current dependence that is weaker than that observed at higher aspect ratio. Dimensionless scaling experiments indicate a strong increase of confinement with decreasing collisionality and a weak degradation with beta. The increase of confinement with B T is due to reduced transport in the electron channel, while the improvement with plasma current is due to reduced transport in the ion channel related to the decrease in the neoclassical transport level. Improved electron confinement has been observed in plasmas with strong reversed magnetic shear, showing the existence of an electron internal transport barrier (eITB). The development of the eITB may be associated with a reduction in the growth of microtearing modes in the plasma core. Perturbative studies show that while L-mode plasmas with reversed magnetic shear and an eITB exhibit slow changes of L T e across the profile after the pellet injection, H-mode plasmas with a monotonic q-profile and no eITB show no change in this parameter after pellet injection, indicating the existence of a critical gradient that may be related to the q-profile. Both linear and non-linear simulations indicate the potential importance of ETG modes at the lowest B T . Localized measurements of high-k fluctuations exhibit a sharp decrease in signal amplitude levels across the L-H transition, associated with a decrease in both ion and electron transport, and a decrease in calculated linear microinstability growth rates across a wide k-range, from the ITG/TEM regime up to the ETG regime.

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Scaling of the energy confinement time with β and collisionality approaching ITER conditions

Cited by 51 publications

References 12 publications

The performance of improved H-modes at ASDEX Upgrade and projection to ITER

The performance of improved H-modes at ASDEX Upgrade and projection to ITER

Integrated scenario with type-III ELMy H-mode edge: extrapolation to ITER

Confinement and local transport in the National Spherical Torus Experiment (NSTX)

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