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Abstract

Microinstabilities date to explain anomalous transport and thus gave been extensively investigated. In particular, Ion Temperature Gradient modes seem to play an important part in ion confinement. These modes have been thoroughly studied, first through dispersion relations [1]-[2] and ballooning representation [3]-[7].
Recently some evidence has been noticed that sheared E×B flows could be responsible for creation of internal transport barriers in fusion devices, thus improving confinement [8]. If so, these flows should strongly affect the ITG instability. So far, their effect in tokamaks has only been studied via ballooning representation [9] although it has been established [10] that this representation breaks down for strong values of these flows.
Therefore, in the present work we study E×B flows with a global fluid model for ions and adiabatic electrons. %Results show an important effect of these flows; they reduce the overall maximum growth rate of the instability and they contract the radial extent of the convective cells. Both effects tend to reduce the linear estimate for transport. We have also studied the effect of negative magnetic shear in combination with poloidal flows and in the absence of these flows.Negative magnetic shear does not exhibit a systematic effect on the growth rates of the unstable modes, but it also tends to reduce the linear estimate for transport. .

Additional information

Authors: MACCIO M, Centre de Recherches en Physique des Plasmas Ecole Polytechnique Federale (CH);VACLAVIK J, Centre de Recherches en Physique des Plasmas Ecole Polytechnique Federale (CH);VILLARD L, Centre de Recherches en Physique des Plasmas Ecole Polytechnique Federale (CH)
Bibliographic Reference: Article: Papers on Theory of Fusion Plasmas, (1998)
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