The impact of a biasing radial electric field on the scrape-off layer in a divertor tokamak

The issue of transport on open field lines is addressed using a fluid approach invoking anomalous inertia and viscosity. The emphasis of the model is on the transport of the toroidal momentum, which is notoriously anomalous. The model suggests that tokamaks with divertors may benefit from a significant amplification of the electric field. It is shown that biasing of the scrape-off layer (SOL) with respect to the grounded first wall results in fundamental phenomena, affecting the performance of a divertor. The theoretical model appears to be consistent with experimental results obtained on Tokamak de Varennes [Phys. Plasmas 1, 1485 (1994)].