The effects of rotation, electric field, and recycling neutrals on determining the edge pedestal density profile

Stacey, Weston M.

doi:10.1063/1.3431092

Cited by 3 publications

(7 citation statements)

References 17 publications

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“…The radial and toroidal momentum balance equations ( 2) and (3) may be combined to define a force-balance constraint that must be satisfied by the radial ion particle flux [24,25]…”

Section: Momentum Transport and Particle Pinchmentioning

confidence: 99%

“…The density, temperature, radial electric field and carbon (C) toroidal rotation velocity are measured, and ν DC can be calculated using the measured density and temperature. The momentum transfer frequencies for deuterium (ν dD ) and carbon (ν dC ) can also be inferred from experimental data by solving the coupled toroidal momentum balance equations (2) for the two species 'backwards', using the measured rotation velocities as known inputs, to obtain [24,25]…”

Section: Momentum Transport and Particle Pinchmentioning

confidence: 99%

“…There have been suggestions of a pinch since the earliest days of tokamak research on T3 [16,17], continuing through ASDEX-U [18], JET [19,20], DIII-D [21], TCV [22] and Tore-Supra [23]. Analysis of the momentum balance equations has shown that the force balance among the pressure gradient and electromagnetic forces in fact requires that the radial particle flow in the edge plasma satisfies a 'pinch-diffusion' relationship [24,25].…”

Section: Introductionmentioning

confidence: 99%

“…In order to further test the pinch-diffusion relation for the radial particle flux, as well as to further elucidate the evolution of edge pedestal parameters, time-dependent edge pedestal data over the interval between ELMs, in which the steep gradients first collapse following an ELM and then build back up prior to the next ELM, have been prepared for this H-mode DIII-D shot that the HEP benchmarking collaboration is analyzing. The principal objective of this paper is to present an interpretation of the observed evolution of edge pedestal data based on the force balance (pinch-diffusion particle flux methodology [24,25,29] previously developed for the interpretation of edge pedestal (non-MHD) phenomena). We note that we have previously examined [30] the evolution of the experimentally inferred thermal diffusivity between ELMs in this same DIII-D discharge.…”

Section: Introductionmentioning

confidence: 99%

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Evolution of the H-mode edge pedestal between ELMs

Stacey

Groebner

2011

Nucl. Fusion

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The evolution of edge pedestal parameters between edge-localized modes (ELMs) is analyzed for an H-mode DIII-D (Luxon 2002 Nucl. Fusion 42 612) discharge. Experimental data are averaged over the same sub-intervals between successive ELMs to develop data that characterize the evolution of density, temperature, rotation velocities, etc over the interval between ELMs. These data are interpreted within the context of the constraints imposed by particle, momentum and energy balance, in particular in terms of the pinch-diffusion relation for radial particle flux that is required by momentum balance. It is found that in the edge pedestal there is an increase in both inward (pinch) electromagnetic and outward (diffusive) pressure gradient forces over the inter-ELM interval.

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“…The radial and toroidal momentum balance equations ( 2) and (3) may be combined to define a force-balance constraint that must be satisfied by the radial ion particle flux [24,25]…”

Section: Momentum Transport and Particle Pinchmentioning

confidence: 99%

Section: Momentum Transport and Particle Pinchmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Evolution of the H-mode edge pedestal between ELMs

Stacey

Groebner

2011

Nucl. Fusion

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“…Anomalous transport in the plasma edge region has been analyzed previously, and it has been found that par- ticle pinches may have an important role in the pedestal region 16,17 . Experimental observations and some analytical models suggest that anomalous transport in scrapeoff layer may be intermittent and significantly larger than in the pedestal region.…”

Section: Finding Anomalous Transport Profiles Which Yield Xgc0 Pmentioning

confidence: 99%

Kinetic modeling of divertor heat load fluxes in the Alcator C-Mod and DIII-D tokamaks

et al. 2015

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The guiding-center kinetic neoclassical transport code, XGC0, [C.S. Chang et. al, Phys. Plasmas 11, 2649] is used to compute the heat fluxes and the heat-load width in the outer divertor plates of Alcator C-Mod and DIII-D tokamaks. The dependence of the width of heat-load fluxes on neoclassical effects, neutral collisions and anomalous transport is investigated using the XGC0 code. The XGC0 code includes realistic Xpoint geometry, a neutral source model, the effects of collisions, and a diffusion model for anomalous transport. It is observed that width of the XGC0 neoclassical heat-load is approximately inversely proportional to the total plasma current I p . The scaling of the width of the divertor heat-load with plasma current is examined for an Alcator C-Mod discharge and four DIII-D discharges. The scaling of the divertor heat-load width with plasma current is found to be weaker in the Alcator C-Mod discharge compared to scaling found in the DIII-D discharges. The effect of neutral collisions on the 1/I p scaling of heat-load width is shown not to be significant. Although inclusion of poloidally uniform anomalous transport results in a deviation from the 1/I p scaling, the inclusion of the anomalous transport that is driven by ballooning-type instabilities results in recovering the neoclassical 1/I p scaling. The Bohm or Gyro-Bohm scalings of anomalous transport does not strongly affect the dependence of the heat-load width on plasma current. The inclusion of anomalous transport, in general, results in widening the width of neoclassical divertor heat-load and enhances the neoclassical heat-load fluxes on the divertor plates. Understanding heat transport in the tokamak scrape-off layer plasmas is important for strengthening the basis for predicting divertor conditions in ITER.

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Semi-analytical study of the tokamak pedestal density profile in a single-null diverted plasma with puffing–recycling gas sources

Shi¹

2010

Plasma Phys. Control. Fusion

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The tokamak pedestal density structure is generally studied using a diffusiondominant model. Recent investigations (Stacey and Groebner 2009 Phys. Plasmas 16 102504) from first principle based physics have shown a plausible existence of large inward convection in the pedestal region. The diffusionconvection equation with rapidly varying convection and diffusion coefficients in the near edge region and model puffing-recycling neutral particles is studied in this paper. A peculiar property of its solution for the existence of the large convection case is that the pedestal width of the density profile, qualitatively different from the diffusion-dominant case, depends mainly on the width of the inward convection and only weakly on the neutral penetration length and its injection position.

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The effects of rotation, electric field, and recycling neutrals on determining the edge pedestal density profile

Cited by 3 publications

References 17 publications

Evolution of the H-mode edge pedestal between ELMs

Evolution of the H-mode edge pedestal between ELMs

Kinetic modeling of divertor heat load fluxes in the Alcator C-Mod and DIII-D tokamaks

Semi-analytical study of the tokamak pedestal density profile in a single-null diverted plasma with puffing–recycling gas sources

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