Implications of convective scrape-off layer transport for fusion reactors with solid and liquid walls

Recent experimental observations in tokamaks indicate enhanced convection of plasma blobs toward the main chamber wall. Potential implications of these observations for reactors are examined here. Two-dimensional plasma edge calculations are performed with UEDGE, including convective transport consistent with present experiments. This is coupled to a kinetic neutral calculation using the code NUT, to compute the hot neutral flux to the wall. The inclusion of convection increases sputtering of the wall by roughly an order of magnitude. For tungsten walls, erosion (neglecting re-deposition) is estimated to be similar to.6 mm year(-1). The enhanced source of impurities for high Z walls requires an enhanced plasma screening factor to allow ignition. Low Z liquid materials enable acceptable plasma contamination with much lower screening factors. Rough estimates of dust generation from erosion rates with convection imply significant safety issues. Plasma transport via blobs can also strongly modify models of impurity screening and redeposition, and represents a potential feasibility issue in need of further research. (C) 2004 Elsevier B.V. All rights reserved.