3D filamentary transport and the role of edge sheared radial electric fields in the RFX-mod tokamak

Sheared radial electric field is an important parameter in regulating cross-field transport in fusiondevices. The edge and scrape-off layer (SOL) turbulence coupling, as well as the parallel dissipation,are responsible for the SOL width maintenance, which, in turn, is a critical parameter for particle andenergy exhaustion in tokamaks \cite{Grenfell:2019}. This coupling is usually attributed to the trans-port of streamers or blobs (also called filaments). They are mostly created in the plasma edge, in highgradient free energy regions, and transported radially by ExB drift. The turbulent filaments prop-erties, e.g. velocity and size, and ultimately their penetration into the SOL, are defined by the typeof instability that generates them as well as how they interact with the background \cite{Myra:2013}.High beta filaments, on the other hand, tend to be more resilient to the background. This is thecase of the Edge-Localized Mode filaments in H-mode regimes, one of the current threats for thefeasibility of future fusion reactors. In this work, we study the filament or blob cross-field transportin the RFX-mod operating as tokamak in different plasma regimes by using a set of electrostatic andmagnetic probes \cite{Grenfell:2018}. It has been shown recently that H-mode ELM-free and ELMyare induced in the RFX-mod tokamak by electrode biasing technique \cite{Spolaore:2017}. We showthat the properties of filaments in these regimes, as well as in L-mode, are distinct. While in L-modeblobs propagate almost freely into the SOL scaling as sheath-connected filaments \cite{Manz:2013},in the ELM-free H-mode, filaments are trapped (their cross-field velocity approaches to zero) and dis-sipated around the plasma boundary, where the ExB shearing rate is marginally comparable to theireffective convective time \cite{Grenfell:2018}. ELMs filaments propagate further into the SOL carry-ing a larger parallel current density associated with the edge transport barrier relaxation.