A scrape-off layer based model for Hugill-Greenwald type density limits

Borraß, K.; Schneider, R.; Farengo, Ricardo

doi:10.1088/0029-5515/37/4/i10

Cited by 41 publications

(47 citation statements)

References 21 publications

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“…The onset of the X-point MARFE in deuterium density limits has been described successfully by a model based on divertor detachment [8]. Although the difference in the onset of the X-point MARFE between deuterium and helium is relatively small, the scaling of the X-point MARFE onset predicted by [8], n n ðq 95 RÞ À1:3 would lead to a reasonable fit of the experimental data.…”

Section: à0:73mentioning

confidence: 85%

“…Although the difference in the onset of the X-point MARFE between deuterium and helium is relatively small, the scaling of the X-point MARFE onset predicted by [8], n n ðq 95 RÞ À1:3 would lead to a reasonable fit of the experimental data. Although Bohm-like transport would be consistent with this scaling, a larger dependence on the edge safety factor remains.…”

Section: à0:73mentioning

confidence: 93%

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Density limits in helium plasmas at JET

Rapp

Huber

Ingesson

et al. 2003

Journal of Nuclear Materials

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Recently at JET a pure helium campaign has been performed. The exploration of the density limit in L-mode limiter as well as L-mode and H-mode diverted plasmas was one of the main objectives. In L-mode plasmas the density can be increased until the total radiated power equals the heating power, hence the density limit is determined by a radiative collapse. When compared to deuterium plasmas the L-mode density limit in helium is twice as high. In H-mode no significant difference in the density limit process has been observed. The pedestal density just before the H to L-mode back transition is the same in deuterium and helium plasmas. The H to L-mode back transition is followed by a development of a MARFE [J. Nucl. Mater. 145-147 (1987) 15] which eventually leads to a density limit disruption.

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Section: à0:73mentioning

confidence: 85%

Section: à0:73mentioning

confidence: 93%

Density limits in helium plasmas at JET

Rapp

Huber

Ingesson

et al. 2003

Journal of Nuclear Materials

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“…Note that it is plausible that the density limit in tokamaks is related to the edge phenomena at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0022377817000654 including divertor plasma detachment (Borrass, Schneider & Farengo 1997b;Maingi et al 1999;Greenwald 2002). …”

Section: Mechanisms Of Divertor Plasma Detachmentmentioning

confidence: 99%

Physics of ultimate detachment of a tokamak divertor plasma

Krasheninnikov¹,

2017

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The basic physics of the processes playing the most important role in divertor plasma detachment is reviewed. The models used in the two-dimensional edge plasma transport codes that are widely used to address different issues of the edge plasma physics and to simulate the experimental data, as well as the numerical schemes and convergence issues, are described. The processes leading to ultimate divertor plasma detachment, the transition to and the stability of the detached regime, as well as the impact of the magnetic configuration and divertor geometry on detachment, are considered. A consistent, integral physical picture of ultimate detachment of a tokamak divertor plasma is developed.

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“…ELMs are discussed in references 7,12 to trigger the HDL: The pedestal might be more eroded by high frequency ELMs than can be recovered in the short inter-ELM phase.…”

Section: Elmsmentioning

confidence: 99%

The H-mode density limit in the full tungsten ASDEX Upgrade tokamak

Bernert

Eich

Kallenbach

et al. 2014

Plasma Phys. Control. Fusion

120

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The high confinement mode (H-mode) is the operational scenario foreseen for ITER, DEMO and future fusion power plants. At high densities, which are favorable in order to maximize the fusion power, a back transition from the H-mode to the low confinement mode (L-mode) is observed. In present tokamaks, this H-mode density limit (HDL) occurs at densities on the order of, but below, the Greenwald density.In gas ramp discharges at the fully tungsten covered ASDEX Upgrade tokamak (AUG), four distinct operational phases are identified in the approach towards the HDL. These phases are a stable H-mode, a degrading H-mode, the breakdown of the H-mode and an L-mode. They are reproducible, quasi-stable plasma regimes and provide a framework in which the HDL can be further analyzed. During the evolution, energy losses are increased and a fueling limit is encountered. The latter is correlated to a plateau of electron density in the scrape-off layer (SOL). The well-known extension of the good confinement at high density with high triangularity is reflected in this scheme by extending the first phase to higher densities.In this work, two mechanisms are proposed, which can explain the experimental observations. The fueling limit is most likely correlated to an outward shift of the ionization profile. The additional energy loss channel is presumably linked to a regime of increased radial filament transport in the SOL. The SOL and divertor plasmas play a key role for both mechanisms, in line with the previous hypothesis that the HDL is edgedetermined.The four phases are also observed in carbon covered AUG, although the HDL density exhibits a different dependency on the heating power and plasma current. This can be attributed to a changed energy loss channel in the presented scheme.

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A scrape-off layer based model for Hugill-Greenwald type density limits

Cited by 41 publications

References 21 publications

Density limits in helium plasmas at JET

Density limits in helium plasmas at JET

Physics of ultimate detachment of a tokamak divertor plasma

The H-mode density limit in the full tungsten ASDEX Upgrade tokamak

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