Inter-ELM evolution of the edge current density profile on the ASDEX upgrade tokamak

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dc.check.embargoformatNot applicableen
dc.check.infoNo embargo requireden
dc.check.opt-outNoen
dc.check.reasonNo embargo requireden
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dc.contributor.advisorMcCarthy, Patrick J.en
dc.contributor.authorDunne, Michael G.
dc.date.accessioned2014-02-24T15:34:03Z
dc.date.available2014-02-24T15:34:03Z
dc.date.issued2013
dc.date.submitted2013
dc.description.abstractThe sudden decrease of plasma stored energy and subsequent power deposition on the first wall of a tokamak due to edge localised modes (ELMs) is potentially detrimental to the success of a future fusion reactor. Understanding and control of ELMs is critical for the longevity of these devices and also to maximise their performance. The commonly accepted picture of ELMs posits a critical pressure gradient and current density in the plasma edge, above which coupled magnetohy drodynamic peeling-ballooning modes become unstable. Much analysis has been presented in recent years on the spatial and temporal evolution of the edge pressure gradient. However, the edge current density has typically been overlooked due to the difficulties in measuring this quantity. In this thesis, a novel method of current density recovery is presented, using the equilibrium solver CLISTE to reconstruct a high resolution equilibrium utilising both external magnetic and internal edge kinetic data measured on the ASDEX Upgrade tokamak. The evolution of the edge current density relative to an ELM crash is presented, showing that a resistive delay in the buildup of the current density is unlikely. An uncertainty analysis shows that the edge current density can be determined with an accuracy consistent with that of the kinetic data used. A comparison with neoclassical theory demonstrates excellent agreement be- tween the current density determined by CLISTE and the calculated profiles. Three ELM mitigation regimes are investigated: Type-II ELMs, ELMs sup- pressed by external magnetic perturbations, and Nitrogen seeded ELMs. In the first two cases, the current density is found to decrease as mitigation on- sets, indicating a more ballooning-like plasma behaviour. In the latter case, the flux surface averaged current density can decrease while the local current density increases, providing a mechanism to suppress both the peeling and ballooning modes.en
dc.description.statusNot peer revieweden
dc.description.versionAccepted Version
dc.format.mimetypeapplication/pdfen
dc.identifier.citationDunne, M. G. 2013. Inter-ELM evolution of the edge current density profile on the ASDEX upgrade tokamak. PhD Thesis, University College Cork.en
dc.identifier.endpage166en
dc.identifier.urihttps://hdl.handle.net/10468/1409
dc.language.isoenen
dc.publisherUniversity College Corken
dc.rights© 2013, Michael Dunne.en
dc.rights.urihttp://creativecommons.org/licenses/by-nc-nd/3.0/en
dc.subjectMHDen
dc.subjectCurrent densityen
dc.subjectEdge localised modesen
dc.subjectTokamaken
dc.subjectLaboratory plasmaen
dc.subject.lcshPlasma diagnosticsen
dc.subject.lcshNuclear fusionen
dc.thesis.opt-outfalse
dc.titleInter-ELM evolution of the edge current density profile on the ASDEX upgrade tokamaken
dc.typeDoctoral thesisen
dc.type.qualificationlevelDoctoralen
dc.type.qualificationnamePhD (Science)en
ucc.workflow.supervisorpjm@ucc.ie
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