On the dynamics of blobs in scrape‐off layer plasma: Model validation from two‐dimensional simulations and experiments in Tore Supra

Fedorczak, N.; Gallo, A.; Tamain, P.; Bufferand, Hugo; Ciraolo, Guido; Ghendrih, Ph.

doi:10.1002/ctpp.201700169

Cited by 9 publications

(20 citation statements)

References 12 publications

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“…We have then found a less intuitive picture of V that departs in particular from the straightforward scaling properties of the drift velocity. The latter features are reminiscent of the results for the SOL width scaling determined from a data base analysis of micro-turbulence simulations [96,97]. Since λ SOL /a ∝ qρ * appears to be a robust result, the change in V must therefore be associated to a change in the characteristic time, the latter then appearing as a key issue in understanding and modeling turbulent transport.…”

Section: Discussionmentioning

confidence: 63%

Self-consistent cross-field transport model for core and edge plasma transport

Baschetti

Bufferand²,

Ciraolo³

et al. 2021

Nucl. Fusion

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The 2D mean-field plasma edge transport description of plasma wall interaction is completed by a κ-ε model as in Reynolds Average Navier Stokes simulations for neutral fluids. The local evolution of the turbulent kinetic energy κ and its dissipation rate ε are revisited and slightly modified. It is shown that the κ-ε extends the quasilinear approach by self-consistently determining κ and the relevant time κ/ε leading to the diffusion coefficient κ 2 /ε. The κ-ε evolution is also shown to be equivalent to both coupled Ginzburg-Landau amplitude equations and predator-prey systems where κ is the prey and ε the predator. The dissipation process ε we enforce describes the small scale dissipation of Kolmogorov cascades. It depends on a free parameter akin to a velocity V . The chosen closure relates V to the the parallel connection time and the normalized Scrape-Off layer width qρ * , q is the safety factor and ρ * the ratio of the characteristic Larmor radius and plasma minor radius. A 1D model with κ-ε self-organized transport is used for comparison to empirical scaling laws of SOL width and energy confinement time in L-mode plasmas. Shortfalls of the scaling laws are analyzed. Possible changes of the closure for V are discussed. The 1D model is also used to test the transport response to a dependence of V to large scale velocity shear. Spontaneous confinement improvement when increasing the heating power 1 is observed with the development of an interface barrier at the separatrix. Plasma-wall interaction simulations for TCV and WEST are analyzed. A single scalar free parameter tunes the cross field transport. Experimental midplane and divertor profiles are compared to the simulations. Remarkable agreement is observed. The SOL width determined by the simulation for WEST is close to the experimental value with less than 20 % difference, while the scaling law for L-mode is off my more than a factor 3. The turbulent transport described by the κ-ε is not homogeneous, but ballooned as experimentally observed together with cross-field transport in the divertor SOL on the low field side, and nearly none in the private flux region.

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Section: Discussionmentioning

confidence: 63%

Self-consistent cross-field transport model for core and edge plasma transport

Baschetti

Bufferand²,

Ciraolo³

et al. 2021

Nucl. Fusion

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“…But so far, no theoretical model has shown an ability to predict these main SOL properties leading to the use of experimental scaling laws [1,2]. Numerical simulations are able to reproduce both the behavior of the intermittent turbulence and global features [3,4,5] such as the SOL width adimensioned by Larmor radii (ρ i ) in agreement with experimental measurements [6,7], e.g. 100ρ i in inner-limited plasma [8] and 1 − 10ρ L in diverted configurations.…”

Section: Introductionmentioning

confidence: 65%

“…Although 3D simulation codes have started to produce data to compare with experiments [16,17], cases are still spare and much more complex to interpret than simpler 2D simulations (transverse to magnetic field lines). In particular, 2D simulations have shown robust agreements against experimental observations [3,6,7]. The isothermal flux-driven TOKAM-2D code [3] is based on the continuity equation and on the total charge conservation, leading to density and vorticity conservation equations.…”

Section: A 2d Isothermal Model For Interchange Transportmentioning

confidence: 99%

“…The new equations for density and potential spectra (7,8) are meant to include an approximation of the non linear coupling with the dominant mode k 0 , that appears as a coupling between the density and potential equations through the wave number k 0 . In order to derive two independent expressions for the density and potential spectra, a first step is needed: derive the expressions of k 0 and Φ k 0 .…”

Section: The Spectral Filament Modelmentioning

confidence: 99%

“…The array consists in six protruding pins separated by 3mm that are alternatively floating or biased to -200V. Such system collects fluctuations of floating potential and saturation current at a frequency of 1MHz [7]. Unfortunately, it was not possible to coincide each tunnel probe reciprocation with a rake probe reciprocation.…”

Section: Validation Of the Sf Model Against Tore Supra Experimentsmentioning

confidence: 99%

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A spectral model for interchange transport in tokamak scrape-off layers

Peret¹,

Fedorczak²,

Tamain³

et al. 2021

Nucl. Fusion

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HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

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A self‐consistent mean‐field model for turbulent particle and heat transport in 2D interchange‐dominated electrostatic ExB turbulence in a sheath‐limited scrape‐off layer

Coosemans

Dekeyser

Baelmans

2022

Contributions to Plasma Physics

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In this paper, a self‐consistent model for the average radial turbulent transport of heat and particles in 2D anisothermal interchange‐dominated electrostatic ExB drift turbulence in sheath‐limited scrape‐off layers is presented. Diffusion models are used for the turbulent particle and heat fluxes, in which the transport coefficients scale with the square root of the turbulent kinetic energy (k⊥). The interchange drive proves to be the main source of turbulent kinetic energy, while the sheath term provides the main sink. These observations are qualitatively the same as for the isothermal case studied earlier. An analytical relation for the interchange term is derived, showing that the turbulent ExB thermal energy flux is the direct driver for k⊥ through the interchange source. A series decomposition of the sheath term in the k⊥ equation shows it includes a sink contribution that was also present in the isothermal case, but also a new source due to the sheath‐driven conducting‐wall (SCW) instability caused by electron temperature fluctuations. Using a simple regression model to close the total sheath term, a closed model for the turbulent transport is obtained. The interchange drive due to the ExB energy flux leads to a self‐saturation mechanism in the model, where the gradients and turbulence intensity increase until a sufficient transport level is reached to carry the power and particles across the field lines to find a balance with the sheath sink. An implementation of this model in a 1D mean‐field code approximates the profiles of the turbulence simulations with remarkable accuracy in part of the parameter space, while the error increases in parameter regimes where the relative importance of the SCW term is varied.

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On the dynamics of blobs in scrape‐off layer plasma: Model validation from two‐dimensional simulations and experiments in Tore Supra

Cited by 9 publications

References 12 publications

Self-consistent cross-field transport model for core and edge plasma transport

Self-consistent cross-field transport model for core and edge plasma transport

A spectral model for interchange transport in tokamak scrape-off layers

A self‐consistent mean‐field model for turbulent particle and heat transport in 2D interchange‐dominated electrostatic ExB turbulence in a sheath‐limited scrape‐off layer

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