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

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dc.contributor.advisor McCarthy, Patrick J. en Curran, Diarmuid B. 2015-11-06T09:22:47Z 2015-11-06T09:22:47Z 2014 2014
dc.identifier.citation Curran, 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.endpage 248
dc.description.abstract The 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.sponsorship European Commission (EURATOM) en
dc.format.mimetype application/pdf en
dc.language.iso en en
dc.publisher University College Cork en
dc.rights © 2014, Diarmuid B. Curran. en
dc.rights.uri en
dc.subject Alfvén eigenmode en
dc.subject Kinetic en
dc.subject Plasma en
dc.subject Tokamak en
dc.subject Nuclear fusion en
dc.subject BAE en
dc.title The influence of thermal plasma profiles on low-frequency Alfvén eigenmode dynamics in a 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 No embargo required en
dc.description.version Accepted Version
dc.contributor.funder Irish Research Council for Science Engineering and Technology en
dc.contributor.funder European Commission en
dc.description.status Not peer reviewed en Physics en
dc.check.type No Embargo Required
dc.check.reason No embargo required en
dc.check.opt-out Not applicable en
dc.thesis.opt-out false
dc.check.embargoformat Not applicable en
dc.internal.conferring Spring Conferring 2015

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© 2014, Diarmuid B. Curran. Except where otherwise noted, this item's license is described as © 2014, Diarmuid B. Curran.
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