JET-P(98)01

The Scaling of the Edge Electron Temperature at the L-H Transition Based on the Alfvén Drift-Wave Instability

The stability theory of Alfven drift-waves shows that with increasing plasma pressure the Alfven waves get coupled to electron drift waves. This instability can be characterised by two significant parameters, i.e. the normalised plasma beta and the normalised collision frequency. The resulting turbulent transport coefficient is suppressed when the normalised beta is greater than a critical value, i.e. βn > 1 + νn2/3 , which depend on the normalised collision frequency νn. The transport coefficients change their dependence on plasma parameters at this threshold. The Alfven drift-wave model predicts the scaling of the electron edge temperature at the L-H transition with respect to the toroidal field, plasma current, density and other plasma parameters. The experimental data corresponding to the L-H transition on different tokamaks exhibit a similar behaviour in the T0 – n0 diagram, in particular a weak dependence of T0 on the density at high densities but a more pronounced increase at low densities.
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JETP98001 274.80 Kb