Energy transport and magnetic stochasticity at the edge of a plasma in RFP configuration

The energy flux carried by energetic electrons at the edge of the RFP experiment ETA BETA II has been derived by comparing the total heat collected by calorimetric probes oriented parallel and antiparallel to the magnetic field. Assuming that the energetic electrons flow along the stochastic magnetic field lines without undergoing collisions, the magnetic diffusion coefficient has been inferred from the radial behaviour of the energy flux. The diffusion coefficient is then compared with the magnetic fluctuation amplitude measured at the edge for different reversal of the toroidal field at the wall. It is found that the magnetic diffusion coefficient increases with magnetic fluctuations and the energy flux carried by energetic electrons decreases with Theta.