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Author(s):
J. Garcia, K. Yamazaki, J. Dies, J. Izquierdo
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Title:
Internal Transport Barrier Simulation in LHD
Date of publication:
June 2005
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Key words:
plasma transport simulation, internal transport barrier, electric field shear, Bohm diffusivity, GyroBohm diffusivity, neoclassical transport, LHD
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Abstract:
In order to study the electron heat transport channel and to clarify the electron thermal diffusivity dependence with some plasma parameters in LHD shots with internal transport barrier (ITB), some transport models have been added to TOTAL code. These models can be divided into two categories: Bohm and GyroBohm-like models and drift wave models. A sketch of mixed short and long wavelength models has been derived for this study as a good candidate for the ITB explaining. The effect of anomalous transport reduction by the electric field shear has been introduced by means of the factor (1+(tau omega_ExB)^gamma)^-1. This factor has been previously checked as a good candidate to drive anomalous transport in tokamak plasmas. Results show that a combination of short wavelength and long wavelength together with the electric field shear can explain the transition between non-ITB and ITB shots. The central temperature dependence with density is also well simulated. In the case of GyroBohm models, they fit also temperature profiles, although central temperature dependence with density is higher.
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