Transport reduction in the edge of the RFX reversed-field pinch

Magnetic field lines and particle orbits are calculated with the code \textsc{Orbit} for a typical multiple helicity (MH) chaotic field, provided by a MHD numerical simulation of the reversed-field pinch (RFP). The result (confirmed by an analytical Hamiltonian calculation) is that $m=0$ and $m=1$ modes allow for the formation of magnetic islands which induce transport barriers at $r/a \simeq 0.7 \div 0.8$. This model has been cross-checked with experimental data coming from the Padua experiment RFX. A particle transport analysis has been done, by means of the 1D transport code TED, to investigate the dependence of the particle diffusion coefficient $D$ on mode amplitude. TED runs show that there is a decrease of $D$ at $r/a \simeq 0.7$. \textsc{Orbit} runs are consistent with TED results. Finally, we present preliminary data showing the active control of $m=0$ modes in the recently rebuilt RFX-mod, aiming at reproducing (with a suitable choice of externally applied $m=0$ amplitudes and phases) an ideal no-resonance, no-island condition, which corresponds, in the Hamiltonian formulation, to the presence of good flux surfaces at the $q=0$ radius.