On Filamentary Transport in the TCV Tokamak: Addressing the Role of the Parallel Connection Length

A set of experiments to address the role of parallel connection length in modifying Scrape Off Layer (SOL) filamentary transport has been performed on the TCV tokamak. The effort has been motivated by the well establish observations, supported by a variety of devices, of SOL density profile broadening in high density regimes, which has been attributed to an enhancement of cross-field filamentary transport with respect to parallel losses. The TCV's flexibility has been used for a scan of parallel connection length obtained through a modification of poloidal flux expansion (fx) at the target while keeping density and other macroscopic parameters identical during the scan, with the consequence of almost doubling L? at the two extremes of the scan. SOL profile evolution with fueling has also been investigated at different current levels and different magnetic equilibria (Lower/Upper Single Null and Double Null). These observations have been compared with the corresponding differences in filaments dynamics.