The generation of poloidal pressure gradients in the SOL of TdeV by plate biasing

In the TdeV tokamak, the convection of the plasma towards the diverters can be studied by changing the radial electric field in the scrape-off-layer ( SOL) through biasing the divertor plates relative to the vacuum vessel wall . Electrostatic probes were used to determine the plasma parameters on both the outboard midplane and the bottom of the discharge. From these measurem ents, poloidal differences in the electron kinetic pressure were seen to ar ise due to the application of the biasing voltage on the neutralizer plates and that these pressure differences were correlated to the changing radial electric field. BS using a linear relation between the poloidal kinetic pr essure drop and the radial electric held averaged between the two observati on points, an experimental value of 8.8 x 10(-3) (Omega m)(-1) is obtained for the perpendicular conductivity. A comparison with current models would tend to favor inertia and viscosity over friction with neutrals to counterb alance the j x B force during biasing although the scaling of the conductiv ity with the toroidal magnetic field, plasma density and plasma current sho uld be verified to confirm this conclusion. (C) 1999 Elsevier Science B.V. All rights reserved.