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

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dc.contributor.advisor McCarthy, Patrick J. en
dc.contributor.author Dunne, Michael G.
dc.date.accessioned 2014-02-24T15:34:03Z
dc.date.available 2014-02-24T15:34:03Z
dc.date.issued 2013
dc.date.submitted 2013
dc.identifier.citation Dunne, 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.endpage 166 en
dc.identifier.uri http://hdl.handle.net/10468/1409
dc.description.abstract The 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.format.mimetype application/pdf en
dc.language.iso en en
dc.publisher University College Cork en
dc.rights © 2013, Michael Dunne. en
dc.rights.uri http://creativecommons.org/licenses/by-nc-nd/3.0/ en
dc.subject MHD en
dc.subject Current density en
dc.subject Edge localised modes en
dc.subject Tokamak en
dc.subject Laboratory plasma en
dc.subject.lcsh Plasma diagnostics en
dc.subject.lcsh Nuclear fusion en
dc.title Inter-ELM evolution of the edge current density profile on the ASDEX upgrade tokamak en
dc.type Doctoral thesis en
dc.type.qualificationlevel Doctoral en
dc.type.qualificationname PhD (Science) en
dc.internal.availability Full text available en
dc.check.info No embargo required en
dc.description.version Accepted Version
dc.description.status Not peer reviewed en
dc.internal.school Physics en
dc.check.type No Embargo Required
dc.check.reason No embargo required en
dc.check.opt-out No en
dc.thesis.opt-out false
dc.check.embargoformat Not applicable en
ucc.workflow.supervisor pjm@ucc.ie
dc.internal.conferring Spring Conferring 2014 en


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© 2013, Michael Dunne. Except where otherwise noted, this item's license is described as © 2013, Michael Dunne.
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