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 l ocal transport code UEDGE by a large enough factor to allow for substa ntial poloidal asymmetry in the turbulent transport. Changes in the tu rbulent effective diffusion coefficient in the edge agree qualitativel y with particle confinement changes. Potential fluctuations (<e(phi)ov er tilde (f)/kT(e)>, in the divertor in attached ELM-free conditions a re 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 attach ed 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 energ y of ions striking the divertor target plates by altering the sheath p otential and therefore affect target plate erosion rates.