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Author(s):
K. Itoh, M. Yagi, S.-I. Itoh, A. Fukuyama, H. Sanuki and M. Azumi
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Title:
Anomalous Transport Theory for Toroidal Helical Plasmas
Date of publication:
Aug. 1994
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Key words:
anomalous transport, stellarator, heliotron, torsatron, improved confinement, nonlinear simulation, current diffusivity, self-sustained turbulence
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Abstract:
Anomalous transport coefficients in toroidal helical plasmas are studied, based on the innovative theoretical method. The self-sustained turbulence is analyzed by balancing the nonlinear growth due to the current diffusivity with the nonlinear damping by the ion viscosity and thermal conductivity. Interchange and ballooning mode turbulence is investigated, and the geometrical dependence of the anomalous transport coefficient is clarified. Variation of transport owing to the geometrical difference in toroidal helical plasmas is illustrated. The mechanism for confinement improvement is searched for. To verify the nonlinear destabilization and the self-sustained state, the nonlinear simulation of the interchange mode turbulence is performed in sheared slab. It is demonstrated that the nonlinear enhancement of the growth rate occurs when the fluctuation amplitude exceeds the critical level. In the saturation stage, the fluctuation level becomes higher associated with the enhanced nonlinear growth.
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