Particle collection and exhaust in ergodic divertor experiments on Tore Supra

The particle exhaust in ergodic divertor (ED) configuration has been enhanced by inserting the outboard pump limiter (OPL) in the ergodic layer. The influence on the edge parameters (electron density and temperature) induced by the insertion of the OPL at different positions in the ergodic layer is reported in this paper. The additional pumping delivered by the OPL is shown to improve by about 50% the plasma density control while low impurity (carbon) concentration, characteristic of the ED shots, is also obtained for high plasma density in spite of proximity of the OPL to the bulk plasma