Comparison of plasma turbulence in the low- and high-field scrape-off layer in T-10

Experimental investigation of the scrape-off layer (SOL) turbulence and associated transport in high density regime in the T-10 tokamak is presented. Comparison of the plasma parameters measured at low- (LFS) and high-field side (HFS) of the tokamak shows that inboard turbulence essentially differs from outboard one. Turbulence has intermittent character but fluctuation level of the inboard ion saturation current is about two times lower than at the LFS. A radial turbulent particle flux and an effective perpendicular diffusion coefficient measured at the LFS are about 3-5 times higher than ones observed at the HFS. Enhanced perpendicular particle flux at the LFS is defined by the high density plasma structures formed in the vicinity of the last close flux surface (LCFS). A radial velocity of the plasma structures is directed towards the vacuum vessel both at the low-field side and at the high-field side. Analysis of experimental data allows us to conclude that enhanced plasma turbulence originates on the outboard part of the plasma and then plasma propagates to the inboard side. These experiments support the hypothesis that SOL parallel flow might be caused by an additional mechanism such as 'ballooning' transport which generates a larger flux of particles from the core into the SOL at the outer mid-plane. (author)