Collisionality dependent transport in TCV SOL plasmas

Results are presented from probe measurements at the outboard midplane scrapeoff layer region of TCV current scan experiments. It is shown that with decreasing plasma current, or increasing magnetic connection length, the radial particle density profile becomes broader and the fluctuation levels and turbulence driven radial transport increases. In the far scrape-off layer the fluctuations exhibit a high degree of statistical similarity. Together with previous TCV density scan experiments, this strongly indicates that plasma fluctuations and radial transport increases with plasma collisionality. Such a collisionality dependence is consistent with a recent theory for radial blob motion, which suggests that filamentary structures become electrically disconnected from the target sheaths at large collisionality and thus experience less sheath dissipation. This increases the radial convective transport and is likely linked to the discharge density limit. Collisionality dependent transport in TCV SOL plasmas 2