Transport modelling of divertor bias experiments

A one-dimensional computer model of the transport in the scrape-off layer of a diverted tokamak is used to simulate the effects of applying a bias voltage to one of the neutralizer plates intercepting the separatrix. The transport is influenced by the classical ExB drift of the plasma. When the divertor plates are grounded, as in present experiments, an asymmetry of the temperature, energy flux and ion flux at the target plates is produced by the E x B drift, in agreement with experiments. Application of a bias to one target plate can substantially change these asymmetries, as well as the ion impact energy, the current and the total ion flux to the divertors. Some of the potential benefits to tokamak performance from divertor biasing are density control, impurity reduction, current profile control and radial electric field control.