Transport mechanisms and enhanced confinement studies in RFX

The results of an extensive study on transport mechanisms and on improved c onfinement scenarios in RFX are reported. The scaling of the thermal conduc tivity in the core with the Lundquist number indicates that the magnetic fi eld in this region is not fully stochastic, as proved by the existence of t hermal barriers observed in single helicity configurations. The electrostat ic transport at the edge has been proved to depend on the highly sheared E x B flow, which has been interpreted using fluid and Monte Carlo models. Re gimes of improved confinement have been obtained in the core by poloidal cu rrent drive techniques, and the electrostatic transport has been reduced at the edge by biasing experiments. A radiation mantle caused by impurity see ding has been found to successfully reduce the local plasma-wall interactio n without causing a significant deterioration in the plasma performance.