The electrostatic turbulence in the edge plasma of the RFX reversed field pinch experiment has been studied using Langmuir probes and a homodyne reflectometer. The radial particle flux driven by electrostatic fluctuations has been measured in the region where a double E × B velocity shear layer occurs. It is found that almost 100% of the particle flux at the edge is driven by electrostatic fluctuations. The naturally occurring E × B velocity shear has been shown to be close to that required Biglari-Diamond-Terry criterion for turbulence radial decorrelation

The first evidence of an electrostatic potential well at the edge of plasmas confined in a reversed field pinch configuration is reported, based on measurements made on the RFX experiment. The radial width of the well decreases with plasma current, whereas the potential drop is a few times the electron temperature at the edge, almost independent of plasma current. The resulting radial electric field points inward at the edge and this behavior has been related to finite Larmor radius losses as in tokamaks. Because of the spatial structure of the plasma potential, a naturally occurring double velocity shear layer has been identified at the edge with a shear value comparable to that of tokamaks and stellarators

The E × B velocity and its shear have been modified in the edge of the RFX reversed field pinch experiment by a biasing experiment performed with electrodes inserted into the plasma. Causality between an increase in the E × B velocity shear and a decrease of the particle flux driven by electrostatic turbulence has been observed. The decrease of the particle flux has been found to be mainly due to a change of the relative phase between density and plasma potential fluctuations. The results confirm the role of sheared flow in transport suppression in reversed field pinches and show remarkable similarities with those found in other magnetic configurations.

The edge region of the reversed field pinch experiment RFX has been investigated with Langmuir and calorimetric probes. The energy flux measurements reveal a spatial structure that is consistent with the presence of a superthermal tail in the energy distribution function of the electrons, as expected according to the kinetic dynamo theory (KDT). In the framework of this model, the value of the magnetic field line diffusion coefficient in the edge region has been derived. The radial electric field obtained from the plasma potential gradient is opposite in sign to the ambipolar electric field expected in a stochastic magnetic field. The discrepancy is discussed in terms of particle recycling at the wall.

The electron energy flux driven by electrostatic turbulence has been measured for the first time in the edge region of the RFX reversed field pinch experiment using triple Langmuir probes. The energy flux has been found to be almost entirely convective. The total energy loss due to electrostatic turbulence has been estimated to account for 30% of the overall transport losses.