Numerical investigation of isolated filament motion in a realistic tokamak geometry

Walkden, N.; Dudson, B.; Easy, Luke; Fishpool, G.; Omotani, John

doi:10.1088/0029-5515/55/11/113022

Cited by 23 publications

(34 citation statements)

References 64 publications

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“…In this form the floating potential appears explicitly in equation (27) and drives the growth of Ω e and consequently φ e thus producing a source of circulatory motion. This is analogous however to the isothermal 3D case where the Boltzmann response produces finite φ e thereby leading to circulatory motion [26]. Note that in the isothermal 2D limit V f T e,0 can be simply treated as a gauge for φ e .…”

Section: Velocity Scalingmentioning

confidence: 95%

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Dynamics of 3D isolated thermal filaments

Walkden

Easy

Militello

et al. 2016

Plasma Phys. Control. Fusion

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Abstract. Simulations have been carried out to establish how electron thermal physics, introduced in the form of a dynamic electron temperature, affects isolated filament motion and dynamics in 3D. It is found that thermal effects impact filament motion in two major ways when the filament has a significant temperature perturbation compared to its density perturbation: They lead to a strong increase in filament propagation in the bi-normal direction and a significant decrease in net radial propagation. Both effects arise from the temperature dependence of the sheath current which leads to a non-uniform floating potential, with the latter effect supplemented by faster pressure loss. The reduction in radial velocity can only occur when the filament cross-section loses angular symmetry. The behaviour is observed across different filament sizes and suggests that filaments with much larger temperature perturbations than density perturbations are more strongly confined to the near SOL region.

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Section: Velocity Scalingmentioning

confidence: 95%

“…Note that through E × B motion φ o produces radial motion of the filament whilst φ e produces circulatory motion about the filament centre. The decoupling technique is introduced and discussed in ref [26] and gives…”

Section: Velocity Scalingmentioning

confidence: 99%

Dynamics of 3D isolated thermal filaments

Walkden

Easy

Militello

et al. 2016

Plasma Phys. Control. Fusion

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“…The HESEL simulations predict an opposite trend with respect to the other codes. This is due to the fact that rotation is intrinsically linked to 3D effects, which play a dominant role in setting the bi-normal velocity [51].…”

Section: Comparison With the Experimentsmentioning

confidence: 99%

“…This effect is observed in STORM but not on GBS, probably due to the fact that GBS' parallel heat conduction term does not depend on the local temperature. In addition, Boltzmann spinning [51,53] induces a rotation of the filament on its axis, creating an annular density structure. A more theoretical analysis of the temperature effects can be found in [39].…”

Section: Additional Physics Insightmentioning

confidence: 99%

Multi-code analysis of scrape-off layer filament dynamics in MAST

Militello

Walkden

Farley

et al. 2016

Plasma Phys. Control. Fusion

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“…These models can also provide an estimate of the SOL width, a key quantity determining the heat load on the plasma-facing components, and of its scaling with parameters such as density, temperature, magnetic field and major radius 96 . They also provide some insights into the origin of the spontaneous toroidal plasma rotation 97 , the value of the electrostatic potential in the SOL 98,99 , and the dynamics of intermittent transport events 100,101 . As turbulence in the SOL is dominated by modes that are strongly elongated in the direction parallel to the magnetic field, one can simplify the 3D equations and construct a 2D model that evolves the plasma dynamics in a plane perpendicular to the magnetic field, INSIGHT | REVIEW ARTICLES employing simplified models of the ignored parallel direction.…”

Section: Edge Transport and Plasma-wall Interactionsmentioning

confidence: 99%

Computational challenges in magnetic-confinement fusion physics

et al. 2016

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Magnetic-fusion plasmas are complex self-organized systems with an extremely wide range of spatial and temporal scales, from the electron-orbit scales (⇠10 11 s, ⇠10 5 m) to the di usion time of electrical current through the plasma (⇠10 2 s) and the distance along the magnetic field between two solid surfaces in the region that determines the plasma-wall interactions (⇠100 m). The description of the individual phenomena and of the nonlinear coupling between them involves a hierarchy of models, which, when applied to realistic configurations, require the most advanced numerical techniques and algorithms and the use of state-of-the-art high-performance computers. The common thread of such models resides in the fact that the plasma components are at the same time sources of electromagnetic fields, via the charge and current densities that they generate, and subject to the action of electromagnetic fields. This leads to a wide variety of plasma modes of oscillations that resonate with the particle or fluid motion and makes the plasma dynamics much richer than that of conventional, neutral fluids.T he most straightforward way for describing plasmas would be the microscopic particle approach: solving the equations of motion for the many individual particles that form the plasma in externally imposed electromagnetic fields and in the fields that the particles themselves generate. However, this is computationally impossible to apply to realistic magnetic-fusion plasmas, which typically contain 10 22 -10 23 particles. (For a review of the basic concepts of magnetically confined fusion plasmas, see ref. 1.)A statistical treatment leads to the kinetic model, based on the Vlasov equation (equation (1)), essentially Liouville's theorem applied to the specific plasma environment, with interactions that are dominated by electromagnetic fields and a separation between particle collisions -that is, interactions at microscopic scales-and long-range fields. The Vlasov equation describes the evolution of f s (x,v,t), the single-particle phase-space distribution function of the species labelled 's' (electrons or ions), under the e ect of the longrange electric and magnetic fields E and B, which evolve according to Maxwell's equations with plasma charge and current densities as sources:Here, x, v, q s and m s stand for the position, velocity, charge and the mass of a particle of species 's' , respectively. In the Vlasov model, collisions are neglected, an approximation that is generally justified for fusion plasmas because small-scale e ects based on Coulomb interactions become very weak at high temperatures. In fact, Coulomb collisions' cross-sections for the exchange of momentum and energy, and related quantities such as the electrical resistivity ⌘, scale with T 3/2 . In ITER core plasmas (see ref. 1), for example, T ⇡ 10 keV (⇡10 8 K) and the electron-electron ('ee'), electron-ion ('ei') and ion-ion ('ii') collisional exchanges of momentum and energy ('E') occur over relatively long characteristic times:2)-justifying the collisi...

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Numerical investigation of isolated filament motion in a realistic tokamak geometry

Cited by 23 publications

References 64 publications

Dynamics of 3D isolated thermal filaments

Dynamics of 3D isolated thermal filaments

Multi-code analysis of scrape-off layer filament dynamics in MAST

Computational challenges in magnetic-confinement fusion physics

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