Bifurcation theory for the L-H transition in magnetically confined fusion plasmas

Weymiens, W Wolf; Blank, HJ de; Hogeweij, G. M. D.; Valença, Joeri C. de

doi:10.1063/1.4739227

Cited by 11 publications

(14 citation statements)

References 22 publications

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“…Extended predator-prey models predict both an oscillatory limit-cycle (LCO) type predator-prey transition 8 and a sharp transition [9][10][11] triggered by a single burst of axisymmetric sheared turbulence-driven E Â B flow (known as zonal flow). Turbulent fluid simulations have shown evidence for some of this phenomenology.…”

Section: Introductionmentioning

confidence: 99%

A fast low-to-high confinement mode bifurcation dynamics in the boundary-plasma gyrokinetic code XGC1

et al. 2018

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Article:Ku, S., Chang, C. S., Hager, R. et al. (9 more authors) (2018) A fast low-to-high confinement mode bifurcation dynamics in the boundary-plasma gyrokinetic code XGC1. Physics of Plasmas. 056107. ISSN 1089-7674 https://doi.org/10.1063/1.5020792 eprints@whiterose.ac.uk https://eprints.whiterose.ac.uk/ Reuse Items deposited in White Rose Research Online are protected by copyright, with all rights reserved unless indicated otherwise. They may be downloaded and/or printed for private study, or other acts as permitted by national copyright laws. The publisher or other rights holders may allow further reproduction and re-use of the full text version. This is indicated by the licence information on the White Rose Research Online record for the item. TakedownIf you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing eprints@whiterose.ac.uk including the URL of the record and the reason for the withdrawal request.A fast low-to-high confinement mode bifurcation dynamics in the boundary-plasma gyrokinetic code XGC1 A fast low-to-high confinement mode bifurcation dynamics in the boundary-plasma gyrokinetic code XGC1 A fast edge turbulence suppression event has been simulated in the electrostatic version of the gyrokinetic particle-in-cell code XGC1 in a realistic diverted tokamak edge geometry under neutral particle recycling. The results show that the sequence of turbulent Reynolds stress followed by neoclassical ion orbit-loss driven together conspire to form the sustaining radial electric field shear and to quench turbulent transport just inside the last closed magnetic flux surface. The main suppression action is located in a thin radial layer around w N ' 0:96-0:98, where w N is the normalized poloidal flux, with the time scale $0:1ms.Published by AIP Publishing. https://doi

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Section: Introductionmentioning

confidence: 99%

A fast low-to-high confinement mode bifurcation dynamics in the boundary-plasma gyrokinetic code XGC1

et al. 2018

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“…Extended predator-prey models predict both oscillatory limit-cycle (LCO) type predator-prey transition [8] and a sharp transition [9,10,11] triggered by a single burst of axisymmetric sheared turbulence-driven ExB flow (known as zonal flow). Turbulent fluid simulations have shown evidence for some of this phenomenology [24][25][26].…”

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confidence: 99%

Fast Low-to-High Confinement Mode Bifurcation Dynamics in a Tokamak Edge Plasma Gyrokinetic Simulation

Chang

Tynan

et al. 2017

Phys. Rev. Lett.

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Transport barrier formation and its relation to sheared flows in fluids and plasmas are of fundamental interest in various natural and laboratory observations and of critical importance in achieving an economical energy production in a magnetic fusion device. Here we report the first observation of an edge transport barrier formation event in electrostatic gyrokinetic simulation carried out in a realistic diverted tokamak edge geometry under strong forcing by a high rate of heat deposition. The results show that turbulent Reynoldsstress driven sheared ExB flows act in concert with neoclassical orbit loss to quench turbulent transport and form a transport barrier just inside the last closed magnetic flux surface.

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“…1(b) the possible edge states of the radial electric field for Zohm's model are reproduced from Ref. 10. The structure of the solutions of both models is qualitatively the same, and therefore the same arguments can be applied to find the bifurcations of this new model.…”

Section: Bifurcation Analysismentioning

confidence: 75%

“…However, general bifurcation theory implies that the dynamics corresponding to the L-H transition occurs in the neighborhood of the cusp bifurcation. 10 This cusp-bifurcation transition behaviour can only occur around an inflection point of this nonlinear function of the radial electric field. Therefore, to describe the transition behaviour it is sufficient to Taylor expand this function of many terms around its inflection point to be able to describe its L-H transition behavior.…”

Section: Transport Model For the L-h Transitionmentioning

confidence: 99%

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Bifurcation theory of a one-dimensional transport model for the L-H transition

2013

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Transitions between low and high-confinement (L-H transitions) in magnetically confined plasmas can appear as three qualitatively different types: sharp, smooth, and oscillatory. Bifurcation analysis unravels these possible transition types and how they are situated in parameter space. In this paper the bifurcation analysis is applied to a 1-dimensional model for the radial transport of energy and density near the edge of magnetically confined plasmas. This phenomenological L-H transition model describes the reduction of the turbulent transport by E Â B-flow shear selfconsistently with the evolution of the radial electric field. Therewith, the exact parameter space, including the threshold values of the control parameters, of the possible L-H transitions in the model is determined. Furthermore, a generalised equal area rule is derived to describe the evolution of the transport barrier in space and time self-consistently. Applying this newly developed rule to the model analysed in this paper reveals a naturally occurring transition to an extra wide transport barrier that may correspond to the improved confinement known as the very-high-confinement mode. [http://dx

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Bifurcation theory for the L-H transition in magnetically confined fusion plasmas

Cited by 11 publications

References 22 publications

A fast low-to-high confinement mode bifurcation dynamics in the boundary-plasma gyrokinetic code XGC1

A fast low-to-high confinement mode bifurcation dynamics in the boundary-plasma gyrokinetic code XGC1

Fast Low-to-High Confinement Mode Bifurcation Dynamics in a Tokamak Edge Plasma Gyrokinetic Simulation

Bifurcation theory of a one-dimensional transport model for the L-H transition

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