Transport Mechanisms in the Outer Region of RFX-mod

The edge region of the RFX-mod reversed field pinch experiment is shown to possess good flux surfaces, thanks to the action of the feedback system for the control of MHD modes, although the presence of m = 0 magnetic islands creates a complex magnetic structure. In Multiple Helicity conditions a localized plasma-wall interaction is still present, whereas when Quasi Single Helicity sets in a more widespread interaction takes place. Electron temperature profiles are determined by the m = 0 islands, being flat inside them. The particle diffusion coefficient and the thermal conductivity are 10 - 20m2/s and 100 - 200m2/s respectively in low-current MH discharges. The edge temperature gradient is found to grow linearly with plasma current. The presence of a double velocity shear layer, already observed in the old RFX, is confirmed, and is shown to be determined by a nonlinear interplay with edge turbulence through the electrostatic Reynolds stress. A dependence of the flow velocity on the density normalized to the Greenwald density is also found. Edge turbulence features coherent structures, which have the form of a pressure peak associated to an eddy in the perpendicular plane and to a parallel current density filament. These structures have a prominent role in determining the cross-field particle transport.