Particle flows in pumped DIII-D discharges

The dynamics of particle flows in the DIII-D tokamak for two divertor confi gurations is considered. Fuel and intrinsic carbon impurity flows are analy zed using experimental data and 2D fluid plasma simulations. The flows in p uff and pump experiments done in open and closed divertor geometries are de scribed, It is shown that the flow of fuel particles is sensitive to divert or geometry. The pumping efficiency of the DIII-D cryopumps is a factor of 2 higher in a closed geometry than an open. The core refueling rate of an o pen divertor is a factor of 2 higher than that of a closed divertor. In con trast, the flow of impurity carbon particles is insensitive to divertor geo metry, Both the core carbon content and the fraction of the carbon source w hich penetrates to the core are unchanged between open and closed diverters . In addition, the core impurity content is found to be insensitive to the amplitude of gas puffing in the simulations. (C) 2001 Elsevier Science B.V. All rights reserved.