INTERACTION OF STOCHASTIC BOUNDARY-LAYER WITH PLASMA-FACING COMPONENTS

To alleviate the plasma-wall interaction problems in magnetic confinem ent devices, a stochastic layer is used at the edge of the Tore Supra tokamak (ergodic divertor). A very important point is to determine the power deposition on the plasma facing components. Two different kinds of transport can be identified in such a configuration: stochastic tr ansport surrounding the confined plasma, with a random walk process, a nd scrape-off layer (SOL) Like transport, a laminar transport, near th e plasma facing components. The laminar regime is investigated in term s of a simple criterion, namely that the power deposition is proportio nal to the radial penetration of the laminar zone flux tubes over a fi nite parallel length. The magnetic connection properties of the first wall components are then determined. The connection lengths are quanti fied with two characteristic scales. The larger corresponds to one pol oidal turn and appears to be the characteristic parallel length for la minar transport. A field line tracing code MASTOC (magnetic stochastic configuration) is used to compute the complex topology and the statis tics of the connection in the real tokamak geometry. The numerical sim ulations are then compared with the experimental heat deposition on th e modules and neutralizer plates of the Tore Supra ergodic divertor. G ood agreement is found. Further evidence of laminar transport is also provided by the tangential view of such structures revealed from H-alp ha structures in detached plasma experiments.