The influence of thermal plasma profiles on low-frequency Alfvén eigenmode dynamics in a tokamak

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dc.check.embargoformatNot applicableen
dc.check.infoNo embargo requireden
dc.check.opt-outNot applicableen
dc.check.reasonNo embargo requireden
dc.check.typeNo Embargo Required
dc.contributor.advisorMcCarthy, Patrick J.en
dc.contributor.authorCurran, Diarmuid B.
dc.contributor.funderIrish Research Council for Science Engineering and Technologyen
dc.contributor.funderEuropean Commissionen
dc.date.accessioned2015-11-06T09:22:47Z
dc.date.available2015-11-06T09:22:47Z
dc.date.issued2014
dc.date.submitted2014
dc.description.abstractThe confinement of fast particles, present in a tokamak plasma as nuclear fusion products and through external heating, will be essential for any future fusion reactor. Fast particles can be expelled from the plasma through their interaction with Alfvén eigenmode (AE) instabilities. AEs can exist in gaps in the Alfvén continuum created by plasma equilibrium non-uniformities. In the ASDEX Upgrade tokamak, low-frequency modes in the frequency range from f ≈ 10 − 90kHz, including beta-induced Alfvén eigenmodes (BAEs) and lower frequency modes with mixed Alfvén and acoustic polarisations, have been observed. These exist in gaps in the Alfvén continuum opened up by geodesic curvature and finite plasma compressibility. In this thesis, a kinetic dispersion relation is solved numerically to investigate the influence of thermal plasma profiles on the evolution of these low-frequency modes during the sawtooth cycle. Using information gained from various experimental sources to constrain the equilibrium reconstructions, realistic safety factor profiles are obtained for the analysis using the CLISTE code. The results for the continuum accumulation point evolution are then compared with experimental results from ASDEX Upgrade during periods of ICRH only as well as for periods with both ICRH and ECRH applied simultaneously. It is found that the diamagnetic frequency plays an important role in influencing the dynamics of BAEs and low-frequency acoustic Alfvén eigenmodes, primarily through the presence of gradients in the thermal plasma profiles. Different types of modes that are observed during discharges heated almost exclusively by ECRH were also investigated. These include electron internal transport barrier (eITB) driven modes, which are observed to coincide with the occurrence of an eITB in the plasma during the low-density phase of the discharge. Also observed are BAE-like modes and edge-TAEs, both of which occur during the H-mode phase of the discharge.en
dc.description.sponsorshipEuropean Commission (EURATOM)en
dc.description.statusNot peer revieweden
dc.description.versionAccepted Version
dc.format.mimetypeapplication/pdfen
dc.identifier.citationCurran, D. B. 2014. The influence of thermal plasma profiles on low-frequency Alfvén eigenmode dynamics in a tokamak. PhD Thesis, University College Cork.en
dc.identifier.endpage248
dc.identifier.urihttps://hdl.handle.net/10468/2039
dc.language.isoenen
dc.publisherUniversity College Corken
dc.rights© 2014, Diarmuid B. Curran.en
dc.rights.urihttp://creativecommons.org/licenses/by-nc-nd/3.0/en
dc.subjectAlfvén eigenmodeen
dc.subjectKineticen
dc.subjectPlasmaen
dc.subjectTokamaken
dc.subjectNuclear fusionen
dc.subjectBAEen
dc.thesis.opt-outfalse
dc.titleThe influence of thermal plasma profiles on low-frequency Alfvén eigenmode dynamics in a tokamaken
dc.typeDoctoral thesisen
dc.type.qualificationlevelDoctoralen
dc.type.qualificationnamePhD (Science)en
ucc.workflow.supervisorpjm@ucc.ie
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