Blob dynamics in an inhomogeneous plasma

Bodi, K.; Krasheninnikov, S. I.; Smolyakov, Andrei

doi:10.1063/1.2993211

Cited by 13 publications

(16 citation statements)

References 22 publications

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“…247 As shown in Fig. 14 for the case of constant background density, the monopole density and dipole potential pattern predicted by simple theory 3,15,16 is obtained in this simulation.…”

Section: Blob Structure and Intermittencymentioning

confidence: 88%

Convective transport by intermittent blob-filaments: Comparison of theory and experiment

2011

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A blob-filament (or simply “blob”) is a magnetic-field-aligned plasma structure which is considerably denser than the surrounding background plasma and highly localized in the directions perpendicular to the equilibrium magnetic field B. In experiments and simulations, these intermittent filaments are often formed near the boundary between open and closed field lines, and seem to arise in theory from the saturation process for the dominant edge instabilities and turbulence. Blobs become charge-polarized under the action of an external force which causes unequal drifts on ions and electrons; the resulting polarization-induced E × B drift moves the blobs radially outwards across the scrape-off-layer (SOL). Since confined plasmas generally are subject to radial or outwards expansion forces (e.g., curvature and ∇B forces in toroidal plasmas), blob transport is a general phenomenon occurring in nearly all plasmas. This paper reviews the relationship between the experimental and theoretical results on blob formation, dynamics and transport and assesses the degree to which blob theory and simulations can be compared and validated against experiments.

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“…247 As shown in Fig. 14 for the case of constant background density, the monopole density and dipole potential pattern predicted by simple theory 3,15,16 is obtained in this simulation.…”

Section: Blob Structure and Intermittencymentioning

confidence: 88%

Convective transport by intermittent blob-filaments: Comparison of theory and experiment

2011

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“…The ellipticity of the filament can act to increase or decrease the radial velocity depending on the tilt of the ellipse [59]. And finally, recent works have also included the role of ion kinetic physics [60,61] and strong density gradients [62,63]. It is hoped that future models that use tested velocity scalings with some statistical spread due to these processes could be successful on increasing model predictability.…”

Section: Introductionmentioning

confidence: 99%

Filamentary velocity scaling validation in the TCV tokamak

et al. 2018

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A large database of reciprocating probe data from the edge plasma of TCV (Tokamak à Configuration Variable) is used to test the radial velocity scalings of filaments from analytical theory [J. R. Myra, D. A. Russell, and D. A. D'Ippolito, Phys. Plasmas 13, 112502 (2006)]. The measured velocities are mainly scattered between zero and a maximum velocity which varies as a function of size and collisionality in agreement with the analytical scalings. The scatter is consistent with mechanisms that tend to slow the velocity of individual filaments. While the radial velocities were mainly clustered between 0.5 and 2 km/s, a minority reached outward velocities as high as 5km/s or inward velocities as high as-4km/s. Inward moving filaments are only observed in regions of high poloidal velocity shear in discharges with Bx∇B away from the X-point, a new finding. The filaments have diameters clustered between 3 and 11mm, and normalized sizes â clustered between 0.3 and 1.1, such that most filaments populate the resistive-ballooning regime, therefore, most filaments in TCV have radial velocities with little or no dependence on collisionality. Improvements in crosscorrelation techniques and conditional averaging techniques are discussed which reduce the sizes determined for the largest filaments, including those larger than the scrape-off layer (SOL).

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“…The motion of the centroid of a blob is also affected by a velocity shear layer which can act to accelerate or decelerate it depending on the relative signs of vorticity of the shear layer and the blob [27]. Inhomogeneities in the background plasma modify both the blob motion and structure [27,28]. Finally, in the presence of toroidal rotation the blob-filaments, which have a density approximately constant along helical field lines, can acquire apparent poloidal motion when viewed at a fixed toroidal angle (the "barber pole" effect).…”

Section: Theoretical Backgroundmentioning

confidence: 99%

Comparison of edge turbulence imaging at two different poloidal locations in the scrape-off layer of Alcator C-Mod

et al. 2013

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This paper describes 2-D imaging measurements of plasma turbulence made in the scrape-off layer of the Alcator C-Mod tokamak simultaneously at two different poloidal locations, one near the outer midplane and the other near the divertor X-point region. These images were made with radial and poloidal resolution using two gas puff imaging (GPI) diagnostics, which were not directly connected along a B field line. The turbulence correlation structure has a significantly different tilt angle with respect to the local flux surfaces for the midplane and X-regions, and a slightly different ellipticity and size. The time-averaged turbulence velocities can be different in the midplane and Xregions, even within the same flux surface in the same shot, and in most cases the fluctuations in poloidal velocity in these two regions were not correlated. These structures are partially consistent with a magnetic flux tube mapping model, and the velocities are compared with various poloidal flow models.2

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Blob dynamics in an inhomogeneous plasma

Cited by 13 publications

References 22 publications

Convective transport by intermittent blob-filaments: Comparison of theory and experiment

Convective transport by intermittent blob-filaments: Comparison of theory and experiment

Filamentary velocity scaling validation in the TCV tokamak

Comparison of edge turbulence imaging at two different poloidal locations in the scrape-off layer of Alcator C-Mod

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