F. Militello J.T. Omotani
A theoretical framework is developed to clarify the relation between the profiles of density and temperature in the Scrape Off Layer (SOL) with the fluctuations (filaments) that generate them. The framework is based on the dynamics of independent filaments and on their statistical behaviour and can be used to rigorously understand the mechanisms th…
Preprint PublishedN. R. Walkden L. Easy F. Militello J. T. Omotani
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 per…
Preprint PublishedA. Geraldini F. I. Parra F. Militello
We develop a gyrokinetic treatment for ions in the magnetic presheath, close to the plasma-wall boundary. We focus on magnetic presheaths with a small magnetic field to wall angle, a << 1 (in radians). Characteristic lengths perpendicular to the wall in such a magnetic presheath scale with the typical ion Larmor orbit size, r
Preprint PublishedF. Militello N.R. Walkden T. Farley W.A. Gracias J. Olsen F. Riva L. Easy N. Fedorczak I. Lupelli J. Madsen A.H. Nielsen P. Ricci P. Tamain J. Young
Four numerical codes are employed to investigate the dynamics of Scrape-Off Layer filaments in tokamak relevant conditions. Experimental measurements were taken in the MAST device using visual camera imaging, which allows the evaluation of the perpendicular size and velocity of the filaments, as well as the combination of density and temperature as…
Preprint PublishedA. Kirk A.J. Thornton J.R. Harrison F. Militello N.R. Walkden The MAST Team The EUROfusion MST1 Team
Clear filamentary structures are observed at the edge of tokamak plasmas. These filaments are ejected out radially and carry plasma in the far Scrape Off Layer (SOL) region, where they are responsible for producing most of the transport. A study has been performed of the characteristics of the filaments observed in L-mode plasma on MAST, using visi…
Preprint PublishedJ.T. Omotani F. Militello L. Easy N.R. Walkden
A complete model of the dynamics of scrape-off layer filaments will be rather complex, including temperature evolution, three dimensional geometry and finite Larmor radius effects. However, the basic mechanism of E x B advection due to electrostatic potential driven by the diamagnetic current can be captured in a much simpler model; a complete unde…
Preprint PublishedF. Militello J.T. Omotani
A theoretical framework is developed to link the density profiles in the Scrape Off Layer (SOL) with the fluctuations (filaments) that generate them. The framework is based on the dynamics of independent filaments and their statistical behaviour and can be used to rigorously understand the mechanisms that lead to attending and broadening of the SOL…
Preprint PublishedF. Militello Y. Liu
Intrinsic Scrape Off Layer (SOL) instabilities are studied using flute approximation and incorporating the appropriate sheath boundary conditions at the target. The linear growth rate and the structure of the modes are obtained. The associated diffusion is estimated using a ?/k2? approach for the fastest growing modes. The model used includes curva…
Preprint PublishedL. Easy F. Militello J. Omotani N. R. Walkden B. Dudson
The propagation of filaments in the Scrape Off Layer (SOL) of tokamaks largely determines the plasma profiles in the region. In a conduction limited SOL, parallel temperature gradients are expected, such that the resistance to parallel currents is greater at the target than further upstream. Since the perpendicular motion of an isolated filament is…
Preprint PublishedL. Easy F. Militello J. Omotani B. Dudson E. Havlícková P. Tamain V. Naulin A. H. Nielsen
This paper presents simulations of isolated 3D filaments in a slab geometry obtained using a newly developed 3D reduced fluid code, written using the BOUT þþ framework. First, systematic scans were performed to investigate how the dynamics of a filament are affected by its amplitude, perpendicular size, and parallel extent. The perpendicular size…
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