Scrape-off layer transport and deposition studies in DIII-D

Groth, M.; Allen, S. L.; Boedo, J. A.; Brooks, N.H.; Elder, J.D.; Fenstermacher, M.E.; Groebner, R. J.; Lasnier, C.J.; McLean, A.G.; Leonard, A.W.; Lisgo, S.; Porter, G. D.; Rensink, M.E.; Rognlien, T. D.; Rudakov, D.L.; Stangeby, P.C.; Wampler, W.R.; Watkins, J.G.; West, W.P.; Whyte, D.G.

doi:10.1063/1.2721978

Cited by 16 publications

(14 citation statements)

References 58 publications

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“…The injection of 13 CH 4 into the edge of tokamaks has been shown on TEXTOR [2], JET [3] and DIII-D [4,5], among others, to provide valuable opportunities for diagnosis of edge transport and carbon behavior. In the first DIII-D experiment, 13 CH 4 was puffed into a set of repeat, lower single-null (LSN), well-controlled, low power, 1 MW, L-mode discharges.…”

Section: Introductionmentioning

confidence: 99%

Indications of an inward pinch in the inner SOL of DIII-D from 13C deposition experiments

Elder

McLean

Stangeby

et al. 2009

Journal of Nuclear Materials

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a b s t r a c t 13 C methane puffing experiments were conducted on DIII-D in both L-and ELMy H-mode conditions. The puffing was toroidally symmetric into the crown of a series of well-characterized lower single-null discharges. The hydrocarbon breakup, carbon transport and deposition were modeled using the OEDGE interpretive code. Three separate hypotheses were tested using OEDGE to try to reproduce the experimental deposition: Radial variation of fast parallel flow, erosion of the puffed 13 C deposited in the divertor, and a pinch in the inner scrape off layer (SOL) towards the separatrix. A fast parallel flow was imposed for all hypotheses. The magnitude and the distribution of the 13 C deposition resulting from each hypothesis are compared. A fast parallel flow in the SOL toward the inner divertor combined with a pinch/drift of 10-30 m/s in the inner SOL towards the separatrix roughly reproduces the deposition in both the L-and H-mode experiments.

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Section: Introductionmentioning

confidence: 99%

Indications of an inward pinch in the inner SOL of DIII-D from 13C deposition experiments

Elder

McLean

Stangeby

et al. 2009

Journal of Nuclear Materials

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“…[25,26]) -perhaps a turbulent transport mechanism, akin to the 'blobs' that are found on the LFS. In addition, transport analysis of CH4 introduced into the DIII-D SOL and its deposition pattern in the inner divertor region suggest that some kind of inward transport mechanism is active there [27,28]. 3 Another complexity is the role that cross-field drifts (E r ×B and diamagnetic) play in the overall poloidal flow pattern.…”

Section: Introductionmentioning

confidence: 99%

Transport and drift-driven plasma flow components in the Alcator C-Mod boundary plasma

Smick¹,

LaBombard²,

Hutchinson³

2013

Nucl. Fusion

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Boundary layer flows in the Alcator C-Mod tokamak are systematically examined as magnetic topology (upper versus lower-null) and plasma density are changed. Utilizing a unique set of scanning Langmuir-Mach probes, including one on the high-field side midplane, the poloidal variation of plasma flow components in the parallel, diamagnetic and radial directions are resolved in detail. It is found that the plasma flow pattern can be decomposed into two principal parts: (1) a drift-driven component, which lies within a magnetic flux surface and is divergence-free and (2) a transport-driven component, which gives rise to near-sonic parallel flows on the high-field side scrape-off layer. Toroidal rotation, Pfirsch-Schlüter and transport-driven contributions are unambiguously identified. Transport-driven parallel flows are found to dominate the high-field side particle fluxes; the total poloidal-directed flow accounts for ~1/3 to all of the ion flux arriving on the inner divertor. As a result, heat convection is found to be an important player in this region, consistent with the observation of divertor asymmetries that depend on the direction of B ×∇B relative to the active x-point. In contrast, the poloidal projection of parallel flow in the low-field scrape-off layer largely cancels with E r ×B flow; toroidal rotation is the dominant plasma motion there. The magnitude of the transport-driven poloidal flow is found to be quantitatively consistent with fluctuation-induced radial particle fluxes on the low-field side, identifying this as the primary drive mechanism. Fluctuation-induced fluxes on the high-field side are found to be essentially zero, excluding turbulent inward transport as the mechanism that closes the circulation loop in this region.

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“…For model fidelity to experiments, it is important to carefully consider the vacuum assumption in the halo region relative to the dynamics of study. Edge modeling is likely sensitive to current and flows present in the scrape-off-layer (SOL) region [22], a subregion of the halo that directs the energy and particle exhaust from the hot plasma onto the divertor. Most published simulations to date are initialized from equilibrium that do not have current or flow in the halo region.…”

Section: Introductionmentioning

confidence: 99%

Effect of scrape-off-layer current on reconstructed tokamak equilibrium

et al. 2017

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Methods are described that extend fields from reconstructed equilibria to include scrape-off-layer current through extrapolated parametrized and experimental fits. The extrapolation includes both the effects of the toroidal-field and pressure gradients which produce scrape-off-layer current after recomputation of the Grad-Shafranov solution. To quantify the degree that inclusion of scrapeoff-layer current modifies the equilibrium, the χ-squared goodness-of-fit parameter is calculated for cases with and without scrape-off-layer current. The change in χ-squared is found to be minor when scrape-off-layer current is included however flux surfaces are shifted by up to 3 cm. The impact on edge modes of these scrape-off-layer modifications is also found to be small and the importance of these methods to nonlinear computation is discussed. Published version: Phys. Plasmas 24, 012504 (2017) [http://dx

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Scrape-off layer transport and deposition studies in DIII-D

Cited by 16 publications

References 58 publications

Indications of an inward pinch in the inner SOL of DIII-D from 13C deposition experiments

Indications of an inward pinch in the inner SOL of DIII-D from 13C deposition experiments

Transport and drift-driven plasma flow components in the Alcator C-Mod boundary plasma

Effect of scrape-off-layer current on reconstructed tokamak equilibrium

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