Dudson, B.

Easy, L.

Havlícková, E.

Madsen, Jens

Militello, F.

Naulin, Volker

Nielsen, Anders Henry

Omotani, J.

Tamain, P.

Online Research Database In Technology

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Downloaded from orbit.dtu.dk on: Dec 20, 20173D Simulations of Plasma Filaments in the Scrape Off LayerEasy, L.; Militello, F.; Omotani, J.; Dudson, B.; Tamain, P.; Havlícková, E.; Naulin, Volker; Nielsen,Anders Henry; Madsen, JensPublished in:Proceedings of the 19th Joint EU-US Transport Task Force MeetingPublication date:2014Link back to DTU OrbitCitation (APA):Easy, L., Militello, F., Omotani, J., Dudson, B., Tamain, P., Havlícková, E., ... Madsen, J. (2014). 3D Simulationsof Plasma Filaments in the Scrape Off Layer. In Proceedings of the 19th Joint EU-US Transport Task ForceMeeting3D Simulations of Plasma Filaments in the Scrape Off LayerL. Easy1, 2, F. Militello2, J. Omotani2, B. Dudson1,P. Tamain 3, E. Havl´ıcˇkova´ 2,V. Naulin4, A. H. Nielsen4, J. Madsen4,1Department of Physics, University of York, Heslington, York, YO10 5DD, UK2CCFE, Culham Science Centre, Abingdon, OX14 3DB, UK3CEA, IRFM, F-13108 Saint-Paul-lez-Durance, France4 DTU, Department of Physics, DK-2800 Kgs. Lyngby, DenmarkAbstractThe scrape off layer (SOL) of magnetic confinement devices is inherently turbulent. Both inL- and H-mode, anomalous transport of particles and energy perpendicular to the magnetic fieldis dominated by the propagation of coherent field aligned filamentary structures. Understandingtheir dynamics is essential for successful operation of future fusion experiments, as they determine,among other relevant SOL features, SOL widths and particle and heat fluxes to the first wall.We present results from a newly developed non-linear 3D reduced fluid code for filament andturbulence studies using the BOUT++ framework. Using this code, the motions of isolated filamentstructures in a local slab geometry have been studied. First, systematic scans were performed,that investigated how the dynamics of a filament is affected by its amplitude, perpendicular size,parallel extent, and the strength of the magnetic curvature that it is subject to. The perpendicularsize was found to have a strong influence on the motion of the blob, as it determined the relativeimportance of polarisation currents to parallel currents in the filament, whilst drift wave turbulencewas observed if the initial amplitude of the blob was increased sufficiently.Next, the 3D simulations were compared to 2D simulations using different parallel closures;namely, the sheath dissipation closure [1], and the vorticity advection closure [2], which neglectsthe influence of parallel currents. The vorticity advection closure was found to not replicate the 3Dperpendicular dynamics and over estimated the initial radial acceleration of all the filaments studied.In contrast, a more satisfactory comparison with the sheath dissipation closure was obtained,even against 3D filaments with significant parallel gradients, where the closure is no longer valid.Specifically it captured the contracting dynamics of filaments with different perpendicular sizesthat were observed in the 3D simulations which the vorticity advection closure failed to replicate.However, neither closure successfully replicated the Boltzmann spinning effects and associatedpoloidal drift of the blob upwards that was observed in the 3D simulations.It is concluded that the sheath dissipation closure was more successful in replicating the 3Ddynamics, because significant parallel currents closed through the sheath were observed to occureven for ballooned filaments simulations. Nevertheless it is possible that the vorticity closure bemay be relevant for situations where the parallel current is inhibited from closing through thesheath due to effects such as strong magnetic shear around X points.References[1] G Q Yu and Sergei I Krashenninikov. “Dynamics of blobs in scrape-off-layer/shadow regions of tokamaks and lineardevices”. In: Phys. Plasmas (2003).[2] O E Garcia et al. “Computations of Intermittent Transport in Scrape-Off Layer Plasmas”. In: Phys. Rev. Lett.(2004).This work was funded by the RCUK Energy Programme [grant number EP/I501045] and by the European Union’s Horizon2020 research and innovation programme. To obtain further information on the data and models underlying this paper pleasecontact PublicationsManager@ccfe.ac.uk. The views and opinions expressed herein do not necessarily reflect those of the EuropeanCommission. In addition, this work was carried out also using the Plasma HEC Consortium EPSRC grant number EP/L000237/1and the HELIOS supercomputer system at Computational Simulation Centre of International Fusion Energy Research Centre(IFERC-CSC), Aomori, Japan, under the Broader Approach collaboration between Euratom and Japan, implemented by Fusionfor Energy and JAEA.

3D Simulations of Plasma Filaments in the Scrape Off Layer

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3D Simulations of Plasma Filaments in the Scrape Off Layer

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