Edge physics in reversed-field pinch and tokamak: similarities and differences

The edge-region properties of a reverse-field pinch (RFP) configuration are reviewed and a comparison with those of tokamaks is attempted. Despite the different magnetic configurations, many similarities have been observed. Among the similarities is the electrostatic nature of the particle transport and the structure of the plasma potential. In particular the radial electric field changes sign across the last closed flux surface and gives rise to an velocity shear layer. The anomalous transport driven by electrostatic and magnetic fluctuations is addressed and the regimes of improved confinement recently observed in RFPs are reviewed. The role of the velocity shear on turbulence stabilization in these regimes is discussed.