Edge and scrape-off layer tokamak plasma turbulence simulation using two-field fluid model

Abstract

A novel two-dimensional (2D) fluid model is proposed for investigating flux-driven plasma turbulence in the tokamak edge and scrape-off layer (SOL). Unlike most previous turbulence simulations of this region, the 2D model treats the two regions in a consolidated manner with a smooth transition region in between. The unified 2D model is simpler and less computer intensive than 3D models, but captures most features of the 3D edge and 2D SOL turbulence. It also illustrates the influence of tokamak edge turbulence on the SOL transport, something not captured by earlier 2D SOL simulations. Existence of an equilibrium radial electric field in the edge and SOL regions has been found. Two different plasma conductivity models have been used for the simulations. Turbulence in the edge is characterized by radially elongated streamers and zonal flows. The streamer structures occasionally break mainly in a region where the radial electric field changes sign. A phenomenological condition for the breaking has been obtained. Effective diffusion co-efficient and density front propagation speed from the simulation have been calculated. Statistical properties of the particle transport obtained from this simulation are compared with earlier flux-driven 2D SOL turbulence simulations and also with Aditya tokamak results.