Computational assessment of effects of electric fields and currents in tokamak edge plasmas

In recent experiments, changes in plasma behaviour turned out to be influenced by the application of electrostatic fields in both divertor and limiter configurations. In order to investigate the impact of biassing on scrape-off layer profiles, the B2 code is extended to compute electric fields, electric currents and diamagnetic and E × B particle drifts. As a consequence of improved numerical treatment the extended B2 code (EB2) is now able to provide stable and converged solutions with only a slight increase of computing time. In this paper the effect of the additional variables for grounded, floating and poloidally biassed divertor plates is investigated for a low power divertor configuration. In addition, the introduction of a neoclassical expression for the radial current density provides the opportunity to obtain the electric potential inside the last closed flux surface.