Simulation of transient wall pumping, fuelling effects and density controlin tokamaks

dA dynamical model has been developed which solves a time-dependent coupled system of equations for the (I) plasma density and (2) hydrogenic concentr ations in the implantation layer of several representative plasma facing/li miting walls in tokamaks in order to examine the density behaviour during t he transient phase of discharges as well as long pulse discharges, which ar e dominated by the wall pumping/fuelling characteristics. A 1-D plasma part icle transport code including a model for the SOL and an analytical neutral transport model has been used to describe the plasma particle transport pr ocesses. The Local Mixing Model with some adaptations has been used to desc ribe the behaviour of the hydrogenic concentrations in the walls. The new m odel significantly improves the simulation of a Tore Supra experiment with a transition from limiting the plasma on the outer limiter to limiting the plasma on the inner wall compared our previous, more simple model. Long pul se discharges in Tore Supra are examined by the more simplified model to id entify the dominant mechanisms for the constant particle absorption mechani sms. (C) 1999 Elsevier Science B.V. All rights reserved.