B. Hnat S. Gadgil A. Kirk F. Militello N. Walkden The MAST Team
Reciprocating Mach probe data is used to estimate the radial wave number of oscillatory zonal flows in Ohmic MAST plasma. An intermittent 10kHz mode is detected in the wavelet decomposition and windowed spectra of plasma potential fluctuations of the MAST tokamak edge plasma. Previously, this mode has been identified as a Geodesic Acoustic Mode (GA…
Preprint PublishedN.R. Walkden A. Wynn F. Militello B. Lipschultz G. Matthews C.Guillemaut J. Harrison D. Moulton JET Contributors
Statistical analysis of the ion flux to the JET outer-wall is conducted in outer-wall limiter mounted Langmuir probe (OLP) time-series across a wide range of plasma current and line-averaged density during Ohmically heated horizontal target L-mode plasmas. The mean, _, and the standard deviation, _, of the ion-saturation current measured by the OLP…
Preprint PublishedA. R. Field I. Balboa P. Drewelow J. Flanagan C. Guillemaut J. R. Harrison A. Huber V. Huber B. Lipschultz G. Matthews A. Meigs J. Schmitz M. Stamp N. Walkden JET contributors
The dynamics and stability of divertor detachment in N2 seeded, type-I, ELMy H-mode plasmas with dominant NBI heating in the JET-ILW device is studied by means of an integrated analysis of diagnostic data from several systems, classifying data relative to the ELM times. It is thereby possible to study the response of the detachment evolution to the…
Preprint PublishedS. Murphy-Sugrue J. Harrison N. Walkden P. Bryant J. W. Bradley
Ball-pen probes have been deployed in the SOL of numerous magnetic confinement experiments to make direct measurements of the plasma potential. They have also been used simultaneously with Langmuir probes to make fast measurements of the electron temperature. Despite strong empirical evidence for the success of the BPP it lacks a theoretical underp…
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 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 PublishedS. Elmore S.Y. Allan G. Fishpool A. Kirk A.J. Thornton N.R. Walkden J.R. Harrison The MAST Team
In future nuclear fusion reactors high heat load events, such as edge-localised modes (ELMs), can potentially damage divertor materials and release impurities into the main plasma, limiting plasma performance. The most difficult to handle are type I ELMs since they carry the largest fraction of energy from the plasma and therefore deposit the large…
Preprint PublishedN. R. Walkden B. D. Dudson L. Easy G. Fishpool J. T. Omotani
This paper presents a numerical investigation of isolated filament dynamics in a simulation geometry representative of the scrape-off layer (SOL) of the Mega Amp Spherical Tokamak (MAST) previously studied in [N.R.Walkden et.al, Plasma Phys. Control. Fusion, 55 (2013) 105005]. This paper focuses on the evolution of filament cross-sections at the ou…
Preprint Published