Turbulence induced particle and heat load on the first wall in different confinement regimes

The turbulent dynamics in the edge and scrape-off layer (SOL) regions determines the particle and heat fluxes at the tokamak divertor and first wall. This presentation summarizes the work carried out within a doctoral research project at Consorzio RFX, Padua, Italy. Herein, the SOL transport properties have been studied by means of two extensive high-density H-mode datasets on TCV, where either the gas fuelling rate or the plasma shaping have been varied at constant plasma current, toroidal field and auxiliary heating power. The features of the SOL profiles and fluctuations have been correlated with the αt turbulence control parameter defined in [Eich et al 2020 Nucl. Fusion 60056016], quantifying the level of resistive ballooning turbulence relative to drift wave transport. Like in previous work, at high upstream density and high upper triangularity a transition has been obtained from a type-I ELMy regime to the Quasi-continuous exhaust (QCE) scenario. Within both datasets, an increase in αt has been correlated with a continuous broadening of both the divertor heat load footprint and the near SOL upstream density profile. This is associated with the progressive formation of a density shoulder in the far SOL. These behaviours have been linked to an enhancement of the radial filamentary transport level towards the first wall. Within the gas fuelling scan database, at higher αt larger filaments travel radially faster towards the midplane first wall, propagating mostly within the resistive X-point or resistive ballooning regimes. Within the shaping scan database, the average, the standard deviation, and the frequency of fast fluctuation measurements increase towards high δup. From low to high shaping, midplane neutral pressure measurements do not suggest a significant variation in the local ionization sources, whereas the total core radiated power increases, possibly owing to a higher first wall carbon intake due to changes in magnetic topology.