Edge turbulence scaling in RFX-mod as measured using GPI diagnostic

The nature of plasma edge turbulence has been studied in the Reversed Field Pinch (RFP) RFX-mod, making use of a Gas Puffing Imaging (GPI) diagnostic, with high time (2 MHz) and space (5 mm) resolution. The edge turbulence has been characterized in terms of toroidal phase velocity of fluctuations, v(phi), of the. width of emission structures, 2 sigma, and of their linear density in the toroidal direction. The packing fraction f(p) of intermittent structures has been estimated as the fraction of occupied area in a plane perpendicular to the magnetic field. The behaviors of v(phi),f(p), and 2 sigma are reported as functions of the density normalized to its Greenwald value, n/n(G). A comparison at different plasma regimes of an effective diffusion coefficient D(p) due to the plasma trapped in coherent structures has been discussed. A decreasing trend of D(p)with n/n(G) values has been guessed. (C) 2009 Elsevier B.V. All rights reserved.