Calculation of 2D profiles for the plasma and electric field in the boundary layer of the TEXTOR-94 Tokamak

An improved version of the 2D multifluid code TECXY is used to study the plasma parameters and the electric field in the boundary layer of the TEXTOR-94 tokamak. An anomalous perpendicular shear viscosity η⊥ is incorporated into the ion momentum balance which allows to fulfil the global (magnetic surface averaged) ambipolarity constraint for the radial electric current, and to determine the electric field in the transition layer by a second-order ordinary differential equation for Er(r). The code modelling results suggest the existence of a narrow global circulation layer for the poloidal plasma velocity just inside the separatrix which is connected with a negative electric field spike. A proper choice of η⊥ gives better agreement with experimental velocity profiles.