Understanding L–H transition in tokamak fusion plasmas

Guosheng XU (徐国盛); Xingquan WU (伍兴权)

doi:10.1088/2058-6272/19/3/033001

Plasma Science and Technology > 2017 > 19(3): 33001-033001. > DOI: 10.1088/2058-6272/19/3/033001

Guosheng XU (徐国盛), Xingquan WU (伍兴权). Understanding L–H transition in tokamak fusion plasmas[J]. Plasma Science and Technology, 2017, 19(3): 33001-033001. DOI: 10.1088/2058-6272/19/3/033001

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Understanding L–H transition in tokamak fusion plasmas

Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, People’s Republic of China

Funds: This work was supported by National Magnetic Confinement Fusion Science Program of China under Contracts No. 2015GB101000, No. 2013GB106000, and No. 2013GB107000 and National Natural Science Foundation of China under Contracts No. 11575235 and No. 11422546.

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Received Date: May 05, 2016

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Abstract

Abstract

This paper reviews the current state of understanding of the L–H transition phenomenon in tokamak plasmas with a focus on two central issues: (a) the mechanism for turbulence quick suppression at the L–H transition; (b) the mechanism for subsequent generation of sheared flow. We briefly review recent advances in the understanding of the fast suppression of edge turbulence across the L–H transition. We uncover a comprehensive physical picture of the L–H transition by piecing together a number of recent experimental observations and insights obtained from 1D and 2D simulation models. Different roles played by diamagnetic mean flow, neoclassical-driven mean flow, turbulence-driven mean flow, and turbulence-driven zonal flows are discussed and clarified. It is found that the L–H transition occurs spontaneously mediated by a shift in the radial wavenumber spectrum of edge turbulence, which provides a critical evidence for the theory of turbulence quench by the flow shear. Remaining questions and some key directions for future investigations are proposed.
- L–H transition,
- E×B flow shear,
- turbulence suppression,
- zonal flows,
- Reynolds stress

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References (61)

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