Tokamak edge plasma simulation including anomalous cross-field convective transport

Abstract

Multi-fluid two-dimensional transport models such as the UEDGE code model [T. D. Rognlien et al., J. Nucl. Mater. 196–198, 34 (1992)] are widely used in the simulation of tokamak edge plasmas. Usually these models are based on the assumption of anomalous plasma diffusion in the direction perpendicular to magnetic field lines. As will be shown, the pure diffusive cross-field transport model is inadequate and fails to match properly plasma parameters measured both in the scrape-off layer (SOL) and in the divertor of the DIII-D tokamak. Recently it has been suggested that specific nondiffusive transport occurs in the edge plasma [S. I. Krasheninnikov, Phys. Lett. A 283, 368 (2001)]. The nondiffusive transport is incorporated to the UEDGE model by adding the anomalous cross-field convective velocity for plasma species and by prescribing a specific two-dimensional profile to this velocity. A series of highly radiative discharges obtained on the DIII-D tokamak is analyzed using the UEDGE code with the hybrid, convective and diffusive, cross-field transport model. For these discharges, anomalous convective velocity profiles are adjusted until the simulated radial profiles agree with measurements in the SOL and in the divertor. It is found that in order to reproduce most of the extensive experimental data, anomalous plasma convection should play the dominant role in the outboard edge-plasma region.