Filament simulations in regions of highly-varying parallel connection length

Shanahan, B.; Huslage, P.

doi:10.1017/s0022377820000562

Cited by 7 publications

(12 citation statements)

References 38 publications

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“…Similarly to the experimental investigations, the simulation of plasma dynamics in the stellarator boundary is still at a very early stage. The fluid code BOUT++ simulated seeded plasma filaments in a slab geometry that emulates the radially varying connection lengths of W7-X [20] and it was recently extended to simulate non-axisymmetric magnetic fields such as a lowfield-period rotating ellipse [21].…”

Section: Introductionmentioning

confidence: 99%

Global fluid simulation of plasma turbulence in a stellarator with an island divertor

et al. 2022

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Results of a three-dimensional, flux-driven, electrostatic, global, two-fluid turbulence simulation for a 5-field period stellarator with an island divertor are presented. The numerical simulation is carried out with the GBS code, recently extended to simulate plasma turbulence in non-axisymmetric magnetic equilibria. The vacuum magnetic field used in the simulation is generated with the theory of Dommaschk potentials, and describes a configuration with a central region of nested flux surfaces, surrounded by a chain of magnetic islands, similarly to the diverted configurations of W7-X. The heat outflowing from the core reaches the island region and is transported along the magnetic islands, striking the vessel walls, which correspond to the boundary of the simulation domain. The radial transport of particles and heat is found to be mainly driven by a field-aligned coherent mode with poloidal number $m=4$. The analysis of this mode, based on non-local linear theory considerations, shows its ballooning nature. In contrast to tokamak simulations and experiments, where blobs often contribute to transport, we do not observe the presence of intermittent transport events.

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Section: Introductionmentioning

confidence: 99%

Global fluid simulation of plasma turbulence in a stellarator with an island divertor

et al. 2022

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“…As such diffusion coefficients can emulate hidden physics, and thus allow analysis of experimental data. In order to gain predictive capabilities, the underlying physics need to be understood, to predict the diffusion coefficients [8,9,17] This work validates the diffusion-based anomalous transport of EMC3-EIRENE Highlighted are some fingers with their finger ID, that are also shown in fig. 3.…”

Section: Introductionmentioning

confidence: 55%

Parametrisation of target heat flux distribution and study of transport parameters for boundary modelling in W7-X

Bold,

Reimold,

Niemann

et al. 2022

Preprint

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Modelling the scrape-off layer of a stellarator is challenging due to the complex magnetic 3D geometry. The here presented study analyses simulations of the scrape-off layer (SOL) of the stellarator Wendelstein 7-X (W7-X) using the EMC3-EIRENE code for the magnetic standard configuration. Comparing with experimental observations, the transport model is validated. Based on the experimentally observed strike line width, the anomalous transport coefficients, used as input to the code are determined to around 0.2 m 2 /s. This is however in disagreement with upstream measurements, where such small cross-field transport leads to temperatures higher than measured experimentally. Agreement can be improved by using spatially varying transport coefficients. Various differences remain, even with spatially varying transport coefficients. The future implementation of drifts into the transport model are expected to help overcome the discrepancies, and thus the development of SOL transport models including drifts is a necessary next step to study the SOL transport of the W7-X stellarator.

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“…Periodic boundary conditions were imposed in Z (vertical, poloidal), such that a filament which propagates out of the top of the domain is returned to the bottom. The parallel dynamics are incorporated via sheath closures, detailed in [8,19]. Figure 1 illustrates the density (filled contours) and potential (white contour) for a filament as it propagates in a slab geometry, such that R is the direction of the polarizing force (radial, in cylindrical geometries), and Z is the binormal direction.…”

Section: Methodsmentioning

confidence: 99%

“…Nevertheless, filamentary structures have been observed in the SOL of the Wendelstein 7-X (W7-X) stellarator [8][9][10]. In terms of simulations, the numerical investigation of filaments often benefits from simplifying the geometry [11][12][13][13][14][15][16][17], which therefore becomes particularly relevant in the more complex stellarator situation [18,19].…”

Section: Introductionmentioning

confidence: 99%

Estimating the error in filament propagation measurement using a synthetic probe

Shanahan

Killer

Pechstein

et al. 2021

Plasma Phys. Control. Fusion

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Electric probe arrangements are a standard tool for investigating plasma filaments in the scrape-off layer of magnetic fusion experiments. In the Wendelstein 7-X stellarator, recent work has characterized plasma filaments using reciprocating electric probes and provided a comparison of filament scaling to simulated filaments, showing remarkable agreement (Killer et al 2020 Plasma Phys. Control. Fusion 62 085003). Here, such simulations are further employed to assess uncertainties inherent to probe measurements by introducing a synthetic probe diagnostic into the simulation. It is determined that filament diameters, and to a smaller degree radial filament velocities, are inherently underestimated in experiment when a filament is not centered on the probe tip. Filament velocity measurements are also sensitive to the alignment of the probes relative to the poloidal direction and the distance between pins. Floating potential pins which are spaced too far apart will underestimate filament velocity, whereas pins which are closely-spaced can overestimate the filament velocity. The sensitivity of the floating potential measurements—from which radial velocity is extracted—to temperature fluctuations is discussed. These investigations apply to measurements of filaments by electric probes in tokamaks as well and may serve as guidance for interpreting probe data and designing probe arrays.

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Filament simulations in regions of highly-varying parallel connection length

Cited by 7 publications

References 38 publications

Global fluid simulation of plasma turbulence in a stellarator with an island divertor

Global fluid simulation of plasma turbulence in a stellarator with an island divertor

Parametrisation of target heat flux distribution and study of transport parameters for boundary modelling in W7-X

Estimating the error in filament propagation measurement using a synthetic probe

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