Effects of radial electric fields on the turbulence and transport in the TEXTOR edge and SOL plasma
Results are reported on the changes in edge transport in the presence of positive fields, below and above the H-mode threshold, induced in TEXTOR by means of a biasing electrode. Langmuir probes were used to measure the time-stationary convective and turbulent-driven particle transport. Experiments with normal and reversed toroidal field directions provided an indication of the spatial variation of the particle fluxes. The convective flux locally dominates the transport inside the limiter radius, but appears to be strongly position dependent, both in magnitude and direction. The turbulence-driven particle flux is spatially more uniform. With respect to a reference ohmic discharge, the convective flux strongly increases inside the limiter when positive bias is applied, with only small changes occurring at the H-mode transition. Radial fluxes as high as 2 x 1.0 E21 particles/m2.s, inward or outwardly directed, can be observed at the limiter radius. The turbulent flux inside the limiter during ohmic discharges is outwards, increases with a +250 bias voltage, but turns inwards in H-mode.
Bibliographic Reference: Report: UCLA-PPG-1432 EN (1992) 18 pp.
Availability: Available from University of California, Institute of Plasma and Fusion Research, Los Angeles (US)
Record Number: 199211272 / Last updated on: 1994-11-29
Original language: en
Available languages: en