Efficiency of transport suppression due to E x B flow shear - A parameter study

Turbulence suppression by shear in the E x B flow is a widely accepted mechanism. Edge polarization experiments on TEXTOR-94 have been used to study the dependence on the toroidal magnetic field, plasma current and plasma composition of the critical E x B shear, defined as the highest rate of change in the diffusion coefficient with shear. Our experiments show that an increase of the isotopic mass and/or a decrease of the toroidal magnetic field leads to higher critical E x B flow shear, whereas a change of the plasma current seems to have no effect.