Modelling of drifts and currents in the edge plasma

For the purpose of modelling the plasma transport in the boundary layer of limiter tokamaks, a complete set of multifluid equations is derived for general curvilinear coordinates, which are for TEXTOR or Tore Supra adapted to circular magnetic flux surfaces . The classical parallel and the anomalous radial and perpendicular viscosities are carefully taken into account . All drifts and electric currents are calculated and analyzed in detail . In the scrape-off layer the electric potential (and electric field) is essentially determined by the sheath potential drop at. the limiter surfaces, whereas in the transition layer inside the separatrix the global ambipolarity constraint and the perpendicular viscosity must be used, such that the problem is reduced to the solution of a second order differential equation for the radial electric field at. some poloidal reference position. The derivation of the coefficients and the numerical procedure is outlined