Scaling of density peaking in JET H-modes and implications for ITER

Weisen, H.; Zabolotsky, A.; Maslov, M.; Beurskens, M.; Giroud, C.; Mazon, D.; Contributors, Jet‐Efda

doi:10.1088/0741-3335/48/5a/s47

Cited by 55 publications

(119 citation statements)

References 14 publications

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“…On the other hand, it has been reported that the density becomes peaked with the decrease of collisionality [20]. In the ITER plasma, the collisionality will be much lower than the present plasmas and n e edge cannot rapidly increase compared with n e .…”

Section: Individual Density Dependencementioning

confidence: 68%

Power requirement for accessing the H-mode in ITER

Martin

Takizuka

2008

J. Phys.: Conf. Ser.

431

600

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Abstract. The input power requirements for accessing H-mode at low density and maintaining it during the density ramp in ITER is addressed by statistical means applied to the international H-mode threshold power database. Following the recent addition of new data, the improvement of existing data and the improvement of selection criteria, a revised scaling law that describes the threshold power required to obtain an L-mode to H-mode transition is presented. Predictions for ITER give a threshold power of ~52MW in a deuterium plasma at a line average density n e = 0.5×10 20 m -3 . At the nominal ITER H-mode density, n e = 1.0×10 20 m -3 , the threshold power required is ~86MW. Detailed analysis of data from individual devices suggests that the density dependence of the threshold power might increase with the plasma size and the magnetic field. On the other hand, the density at which the threshold power is minimal is found to decrease with the plasma size and increase with magnetic field. The influence of these effects on the accessibility of the H-mode regime in ITER plasmas is discussed. Analyses of the confinement database show that, in present day devices, H-modes are generally maintained with powers exceeding the threshold power by a factor larger than 1.5, and that, on the other hand, good confinement can be obtained close to the threshold power although rarely demonstrated.

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Section: Individual Density Dependencementioning

confidence: 68%

Power requirement for accessing the H-mode in ITER

Martin

Takizuka

2008

J. Phys.: Conf. Ser.

431

600

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“…This definition differs from the one used in previous publications [3,4], * = RS NBI /n e χ, where χ is the heat diffusivity. The definition adopted here makes the comparison with simulations straightforward, as explained later.…”

Section: Introductionmentioning

confidence: 93%

Density profile peaking in JET H-mode plasmas: experiments versus linear gyrokinetic predictions

et al. 2009

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As an independent complement to previous studies Unlike previous studies, this work focuses on low collisionality data as most representative of reactor conditions. The study confirms that collisionality is the most important parameter governing density peaking in H-mode, followed by the NBI particle flux and/or the T i /T e temperature ratio. For the first time in JET a modest, albeit significant dependence of peaking on internal inductance, or magnetic shear is seen. The experimental behaviour is compared with an extensive database of linear gyrokinetic calculations using the GS2 code. The predictions from GS2 simulations based on the highest linear growth rate mode are in good agreement with experimental observations. They are also corroborated by initial results from the non-linear code GYRO.

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“…It is usually difficult to separate the effect of density from the effect of the collisionality due to its co-linear behaviour [31]. However, careful analysis suggests the presence of an anomalous pinch leading to density peaking, which could increase the fusion power in ITER by almost 30% [31]. Figure 10 suggests a density peaking with decreasing collisionality; however figure 11 suggests that the density peaking is more related to the normalized density (and maybe underlying effects of core fuelling versus edge fuelling).…”

Section: Profile Peakingmentioning

confidence: 99%

“…The stronger correlation with the normalized density can result from the strong gas fuelling in those type-III ELMy H-mode discharges. Investigations on the density peaking are usually restricted to type-I ELMy H-modes without gas fuelling [31] and even the neutral beam fuelling is reduced to avoid any ambiguity in the determination of the inward pinch velocity resulting from particle sources [30]. However, the plasma core in type-I ELMy H-modes and type-III ELMy H-modes should behave similarly.…”

Section: Profile Peakingmentioning

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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Scaling of density peaking in JET H-modes and implications for ITER

Cited by 55 publications

References 14 publications

Power requirement for accessing the H-mode in ITER

Power requirement for accessing the H-mode in ITER

Density profile peaking in JET H-mode plasmas: experiments versus linear gyrokinetic predictions

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

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