Enhanced particle confinement and turbulence reduction due to E x B shear in the TEXTOR tokamak

Positive radial electric fields have been created at the edge of the TEXTOR tokamak plasma using an electrode. The electric field induces a thin (delt a r similar to 1.5 cm), E x B driven layer at the edge rotating poloidally at 12-20 km/s and featuring high shear. Concomitant changes in the density and poloidal electric field fluctuations and their cross-phase in the shear layer result in suppression of radial turbulent particle transport, even a t low radial electric field strength. Temperature fluctuations are reduced, resulting in diminished turbulent heat flux. As turbulent particle transpo rt is quenched, the particle confinement time tau(p) increases by a factor of 2 and the energy confinement time tau(E) by 20%. Turbulent transport acc ounts for similar to 50% of the total particle flux. Both the cross-phase a nd the density fluctuations are sensitive to the sign of del E-r.