The role of turbulent transport in DIII-D edge and divertor plasmas

Reciprocating Langmuir probes have been used to investigate turbulent transport in DIII-D edge and divertor plasmas. The turbulent particle flux on the outboard midplane exceeds the particle flux from the 2-D local transport code UEDGE by a large enough factor to allow for substantial poloidal asymmetry in the turbulent transport. Changes in the turbulent effective diffusion coefficient in the edge agree qualitatively with particle confinement changes. Potential fluctuations (<e(phi)over tilde (f)/kT(e)>, in the divertor in attached ELM-free conditions are comparable to <e(phi)over tilde (f)/kT(e)> on the outboard midplane. ELMs transiently enhance <e(phi)over tilde (f)/kT(e)> to 2 in attached plasmas and to 2-20 in detached plasmas. Such strong turbulence (e<(phi)over tilde T-f(e)> > 1) in the divertor may affect the mean energy of ions striking the divertor target plates by altering the sheath potential and therefore affect target plate erosion rates.