Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.668935
Title: Modelling and interpreting the coupling between coherent nonlinear structures and ambient turbulence in fusion plasmas using approaches derived from the Lotka-Volterra equations
Author: Zhu, Hao
ISNI:       0000 0004 5368 0329
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2015
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Abstract:
Turbulent transport in magnetized plasmas is one of the fundamental issues in fusion plasma physics. It is recognized that the interactions between zonal flows(ZFs) and micro-scale drift wave turbulence can influence plasma transport in both Tokamaks and Stellarators. These interactions are believed to play a significant role in the transition from low energy confinement regime(L-mode) to high confinement regime(H-mode). In the desired H-mode, the temperatures and densities are higher than those in L-mode, and this can typically generate a doubling of the confinement time. Anomalous, turbulent-linked transport between the plasma edge and the core is also significant in fusion plasma physics. Heat pulse experiments, which involve strongly nonlinear localised perturbation of the plasma, probe the character of anomalous transport in both Tokamaks and Stellarators. In this thesis, we interpret the zonal ow-turbulence interactions in terms of the Lotka-Volterra model, which is derived in ecology and is widely utilized in many fields of science. We discover a novel limit cycle manifold for the plasma state as characterised by micro-scale drift wave turbulence, the electron temperature gradient and the energy of meso-scale structures such as zonal flows. In fusion experiments, an apparent limit cycle manifold called the I-phase has been found in many Tokamaks during L-H transitions. We investigate the possible links between this phenomenology and our model, and also report transitions between different confinement regimes in the model. Finally, we describe heat pulse propagation experiments in Large Helical Device(LHD), which is a Stellarator, in terms of a new model for anomalous transport phenomena from the plasma edge to the core.
Supervisor: Not available Sponsor: Engineering and Physical Sciences Research Council ; Research Councils UK ; European Commission ; Culham Laboratory ; Japan Society of Plasma Science and Nuclear Fusion Research ; Nihon Gakujutsu ShinkĊkai
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.668935  DOI: Not available
Keywords: QC Physics
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