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>Role of the radial electric field in the transition from L (low) mode to H (high) mode to VH (very high) mode in the DIIIhyphen;D tokamak@f
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Role of the radial electric field in the transition from L (low) mode to H (high) mode to VH (very high) mode in the DIIIhyphen;D tokamak@f
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机译：Role of the radial electric field in the transition from L (low) mode to H (high) mode to VH (very high) mode in the DIIIhyphen;D tokamak@f
The hypothesis of stabilization of turbulence by shear in theEtimes;Bdrift speed successfully predicts the observed turbulence reduction and confinement improvement seen at the L (low)ndash;H (high) transition; in addition, the observed levels ofEtimes;Bshear significantly exceed the value theoretically required to stabilize turbulence. Furthermore, this same hypothesis is the best explanation to date for the further confinement improvement seen in the plasma core when the plasma goes from the H mode to the VH (very high) mode. Consequently, the most fundamental question for Hhyphen;mode studies now is: How is the electric fieldErformedquest; The radial force balance equation relatesErto the main ion pressure gradientnabla;Pi, poloidal rotationvthgr;i, and toroidal rotationvfgr;i. In the plasma edge, observations shownabla;Piandvthgr;iare the important terms at the Lndash;H transition, withnabla;Pibeing the dominant, negative term throughout most of the H mode. In the plasma core,Eris primarily related tovfgr;i. There is a clear temporal and spatial correlation between the change inEtimes;Bshear and the region of local confinement improvement when the plasma goes from the H mode to the VH mode. Direct manipulation of thevfgr;iandEtimes;Bshear using the drag produced by a nonaxisymmetric magnetic perturbation has produced clear changes in local transport, consistent with theEtimes;Bshear stabilization hypothesis. The implications of these results for theories of the Lndash;H and Hndash;VH transitions will be discussed.
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