Possible Effects of Drift Wave Turbulence on Magnetic Structure and Plasma Transport in Tokamaks PDF Download
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Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
A new mechanism is proposed by which low level, drift wave type fluctuations, such as those observed in the ATC and TFR experiments, can cause anomalous radial electron heat transport in tokamaks. The model is based on the fact that since transport processes parallel to the magnetic field are many orders of magnitude more rapid than perpendicular ones, very small helically resonant magnetic perturbations that cause field lines to move radially allow the parallel transport process to contribute to radial electron heat transport. It is hypothesized that the small magnetic perturbations accompanying drift waves at any nonzero plasma .beta. are large enough to produce significant effects in present tokamak experiments. The helical magnetic component of drift waves produces magnetic island structures whose spatial widths can easily exceed the ion gyroradius. In a drift wave oscillation period, electrons circumnavigate a magnetic island, whereas the slower moving ions see only a tilt of the magnetic field lines. Thus, electrons try to diffuse radially more rapidly than ions; however, a radialpotential builds up on a very short time scale to confine the electrons electrostatically and thereby keep the particle diffusion ambipolar. Nonetheless, this parallel electron diffusion process does cause net radial electron heat conduction through an ensemble of closely packed island structures. The heat conduction coefficient is estimated. Other effects that these magnetic flutters may have on plasma transport and runaway electron processes are also discussed.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
A new mechanism is proposed by which low level, drift wave type fluctuations, such as those observed in the ATC and TFR experiments, can cause anomalous radial electron heat transport in tokamaks. The model is based on the fact that since transport processes parallel to the magnetic field are many orders of magnitude more rapid than perpendicular ones, very small helically resonant magnetic perturbations that cause field lines to move radially allow the parallel transport process to contribute to radial electron heat transport. It is hypothesized that the small magnetic perturbations accompanying drift waves at any nonzero plasma .beta. are large enough to produce significant effects in present tokamak experiments. The helical magnetic component of drift waves produces magnetic island structures whose spatial widths can easily exceed the ion gyroradius. In a drift wave oscillation period, electrons circumnavigate a magnetic island, whereas the slower moving ions see only a tilt of the magnetic field lines. Thus, electrons try to diffuse radially more rapidly than ions; however, a radialpotential builds up on a very short time scale to confine the electrons electrostatically and thereby keep the particle diffusion ambipolar. Nonetheless, this parallel electron diffusion process does cause net radial electron heat conduction through an ensemble of closely packed island structures. The heat conduction coefficient is estimated. Other effects that these magnetic flutters may have on plasma transport and runaway electron processes are also discussed.
Author: Jan Weiland Publisher: Springer Science & Business Media ISBN: 1461437431 Category : Science Languages : en Pages : 235
Book Description
Stability and Transport in Magnetic Confinement Systems provides an advanced introduction to the fields of stability and transport in tokamaks. It serves as a reference for researchers with its highly-detailed theoretical background, and contains new results in the areas of analytical nonlinear theory of transport using kinetic theory and fluid closure. The use of fluid descriptions for advanced stability and transport problems provide the reader with a better understanding of this topic. In addition, the areas of nonlinear kinetic theory and fluid closure gives the researcher the basic knowledge of a highly relevant area to the present development of transport physics.
Author: Wendell Horton Publisher: World Scientific ISBN: 9814383546 Category : Science Languages : en Pages : 518
Book Description
The book explains how magnetized plasmas self-organize in states of electromagnetic turbulence that transports particles and energy out of the core plasma faster than anticipated by the fusion scientists designing magnetic confinement systems in the 20th century. It describes theory, experiments and simulations in a unified and up-to-date presentation of the issues of achieving nuclear fusion power.
Author: Gregory De Dominici Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
A model based on a model which natively contained turbulence and turbulence driven flow. It has been improved to include the diamagnetic effects, the magnetic fluctuations, and in this work, we study the parametric dependencies of the observed L-H transition power threshold with respect to the ion mass. By including the diamagnetic effects in our model, we allow the competition between the drift waves and the interchange instabilities. This competition is here studied using fixed gradient simulation. We show in this work that the diamagnetic effects are stabilizing for a resistivity close to experimental conditions. Electromagnetic effects lead to more unstable modes at realistic resistivities. Moreover, a quasilinear estimation of the turbulent flux is able to qualitatively grasp the competition between the drift waves and the interchange and the behaviour of the nonlinear electrostatic turbulent flux with resistivity and plasma beta. Another parametric dependency of the turbulence is studied, by changing the mass of the isotope. This is known as the isotope effect. We show here that the turbulence is reduced when the ion mass is increased. Finally, the characteristic times of the turbulence are studied.Magnetic fluctuations have a dramatic effect on correlation times of the turbulence, by drastically reducing them. Accounting for these results, we present in this work the auto-generation of a transport barrier with electromagnetic simulations of edge turbulence, when the heat power is higher than a threshold, using flux-driven simulations. We have then changed the isotope, and correspondingly to experiments, the power threshold is lower for higher isotope mass.
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Author: Ronald E. Waltz
Author: Jan Weiland
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Author: Anne A. Thoul
Author: Ing Hwie Tan
Author: Wendell Horton
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Author: Gregory De Dominici
Author: Christopher George Holland