STOCHASTIC MAGNETIC AND AMBIPOLAR ELECTRIC-FIELDS IN THE PLASMA EDGE REGION OF RFX

The edge region of the reversed field pinch experiment RFX has been in vestigated with Langmuir and calorimetric probes. The energy flux meas urements reveal a spatial structure that is consistent with the presen ce of a superthermal tail in the energy distribution function of the e lectrons, as expected according to the kinetic dynamo theory (KDT). In the framework of this model, the value of the magnetic field line dif fusion coefficient in the edge region has been derived. The radial ele ctric field obtained from the plasma potential gradient is opposite in sign to the ambipolar electric field expected in a stochastic magneti c field. The discrepancy is discussed in terms of particle recycling a t the wall.