SUPPRESSION OF THE EDGE TURBULENCE AT THE L-H TRANSITION IN DIII-D

A decrease in the edge magnetic and density fluctuations is always see n at the L-H transition in DIII-D. Also, a sudden change of the perpen dicular rotation v perpendicular-to in the edge has been observed at t he transition, which indicates the formation of shear in the radial el ectric field. This region coincides with the region where the density fluctuations are suppressed. These experimental observations are consi stent with recent theoretical models. Comparisons between the theories and the experimental observations will be discussed.