A new paradigm for plasma transport and zonal flows

Journal Article · Mon May 15 04:00:00 EDT 2006 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.2196267· OSTI ID:20783123

Sen, A K; Sokolov, V; Wei, X ^[1]

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1. Plasma Physics Laboratory, Columbia University, New York, New York 10027 (United States)

Most tokamak experimental results indicate dependence of the ion thermal conductivity on the isotopic mass close to {chi}{sub perpendicular}{approx}m{sub i}{sup -0.5}, i.e., inverse gyro-Bohm. This is in stark contradiction to most present theoretical models predicting Bohm (m{sub i}{sup 0}) or gyro-Bohm (m{sub i}{sup 0.5}) scaling. A basic physics isotopic scaling experiment [V. Sokolov and A. K. Sen, Phys. Rev. Lett. 89, 095001 (2002)] on the anomalous ion thermal conduction due to ion temperature gradient (ITG) instabilities in two different gases (hydrogen and deuterium) closely confirms the tokamak results. Another series of experiments designed to explore the physics basis of this scaling appears to lead to a new model for this scaling based on 3-wave coupling of two ITG radial harmonics and an IA wave. The resulting isotopic scaling of transport is {approx}m{sub i}{sup -0.5} dictated primarily by the IA damping. This basic physics may be extrapolated to tokamaks resolving the paradox [V. Sokolov and A. K. Sen, Phys. Rev. Lett. 92, 165002 (2004)]. Last, the much discussed theoretical role of zonal flows in transport regulation is critically examined by another set of experiments. A novel diagnostic has been developed on the basis of the observation that the effect of zonal flow can be seen in the FM modulation (at zonal flow frequency) of the carrier frequency of the large equilibrium Doppler shift frequency of ITG modes both in tokamaks and in the Columbia Linear Machine [V. Sokolov, X. Wei, and A. K.Sen, APS DPP meeting, Savannah (2004)]. The present results indicate zonal flow levels close to the theoretical prediction, but its shear is much lower than that predicted by theory for transport regulation.

• OSTI ID: 20783123
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 5 Vol. 13; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
COUPLING
DAMPING
DEUTERIUM
DOPPLER EFFECT
ELECTRON TEMPERATURE
HYDROGEN
ION ACOUSTIC WAVES
ION TEMPERATURE
IONS
MODULATION
PLASMA
PLASMA CONFINEMENT
PLASMA DIAGNOSTICS
PLASMA INSTABILITY
RADIATION TRANSPORT
SHEAR
TEMPERATURE GRADIENTS
THERMAL CONDUCTION
THERMAL CONDUCTIVITY
TOKAMAK DEVICES