Magnetic and electrostatic structures measured in the edge region of the RFX-mod experiment

Spolaore, M.; Vianello, N.; Agostini, M.; Cavazzana, R.; Martines, E.; Serianni, G.; Scarin, P.; Spada, E.; Zuin, M.; Antoni, V.

doi:10.1016/j.jnucmat.2009.01.132

Cited by 21 publications

(26 citation statements)

References 30 publications

(24 reference statements)

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“…The filament propagation behavior has been proved both by electrostatic probes, Gas Puffing Imaging diagnostic 34 and through the observation of the perpendicular propagation of their magnetic fingerprints 20 . A direct estimate of the vorticity represents an intrinsic 2D information of the blob 29 and it was found that the vorticity fluctuation is consistent with the reconstructed 2D floating potential map corresponding to a filament. This further confirms the reliability of the underlying frozen turbulent hypothesis 35 , that allows the time-space conversion of single measurement points.…”

Section: Filament Em Experimental Measurementsmentioning

confidence: 56%

“…RFX-mod RFX-mod: Reversed Field Pinch RFX-mod Reversed Field Pinch experiment was one of the first fusion relevant plasmas providing direct measurements of the electromagnetic features associated to plasma blobs 8 . We would like here to summarize the main experimental observation already reported in several publications 8,20,29 .…”

Section: Filament Em Experimental Measurementsmentioning

confidence: 87%

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Electromagnetic turbulent structures: A ubiquitous feature of the edge region of toroidal plasma configurations

et al. 2015

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Electromagnetic features of turbulent filaments, emerging from a turbulent plasma background, have been studied in four different magnetic configurations: the stellarator TJ-II, the Reversed Field Pinch RFX-mod, a device that can be operated also as a ohmic tokamak, and the Simple Magnetized Torus, TORPEX. By applying an analogous diagnostic concept in all cases, direct measurements of both field-aligned current density and vorticity were performed inside the filament. The inter-machine comparison reveals a clear dependence of the filament vorticity upon the local timeaveraged E × B flow shear. Furthermore, a wide range of local beta was explored allowing concluding that this parameter plays a fundamental role in the appearance of filament electromagnetic features.

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Section: Filament Em Experimental Measurementsmentioning

confidence: 56%

Section: Filament Em Experimental Measurementsmentioning

confidence: 87%

Electromagnetic turbulent structures: A ubiquitous feature of the edge region of toroidal plasma configurations

et al. 2015

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“…192,193 The pressure peak of the blob was associated with a current filament aligned along B and moving with the E Â B flow. Somewhat similar results were obtained on the MST field-reversed pinch.…”

Section: F Potential and Magnetic Fieldmentioning

confidence: 99%

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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“…This probe consists of two boron nitride arms, each of them equipped with 25 electrostatic pins. 30,31 Fifteen of the pins are used as three five-pin triple probes, 32 allowing simultaneous measurements of ion saturation, I sat , plasma density, n, electron temperature, T e , and floating potential, V fl , while ten others are in the floating mode and used to obtain direct measurements of V fl . The time resolution of the measurements is 0.2 ls.…”

Section: à3mentioning

confidence: 99%

Three-dimensional simulations of plasma turbulence in the RFX-mod scrape-off layer and comparison with experimental measurements

et al. 2018

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The tokamak scrape-off layer (SOL) plasma dynamics is investigated in a circular limiter configuration with a low edge safety factor. Focusing on the experimental parameters of two ohmic tokamak inner-wall limited plasma discharges in RFX-mod [Sonato et al., Fusion Eng. Des. 74, 97 (2005)], nonlinear SOL plasma simulations are performed with the GBS code [Ricci et al., Plasma Phys. Controlled Fusion 54, 124047 (2012)]. The numerical results are compared with the experimental measurements, assessing the reliability of the GBS model in describing the RFX-mod SOL plasma dynamics. It is found that the simulations are able to quantitatively reproduce the RFX-mod experimental measurements of the electron plasma density, electron temperature, and ion saturation current density (jsat) equilibrium profiles. Moreover, there are indications that the turbulent transport is driven by the same instability in the simulations and in the experiment, with coherent structures having similar statistical properties. On the other hand, it is found that the simulation results are not able to correctly reproduce the floating potential equilibrium profile and the jsat fluctuation level. It is likely that these discrepancies are, at least in part, related to simulating only the tokamak SOL region, without including the plasma dynamics inside the last close flux surface, and to the limits of applicability of the drift approximation. The turbulence drive is then identified from the nonlinear simulations and with the linear theory. It results that the inertial drift wave is the instability driving most of the turbulent transport in the considered discharges.

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Magnetic and electrostatic structures measured in the edge region of the RFX-mod experiment

Cited by 21 publications

References 30 publications

Electromagnetic turbulent structures: A ubiquitous feature of the edge region of toroidal plasma configurations

Electromagnetic turbulent structures: A ubiquitous feature of the edge region of toroidal plasma configurations

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

Three-dimensional simulations of plasma turbulence in the RFX-mod scrape-off layer and comparison with experimental measurements

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