Reversed-shear experiments in the T-10 tokamak

Results from T-10 experiments in regimes with nonmonotonic plasma current p rofiles are presented. The possibility of controlling the current profile j (r) by electron-cyclotron current drive is demonstrated experimentally. Non monotonic q profiles with the reversed shear are obtained in which the q(mi n) value varies in a wide range, q(min) = 1-2.3. It is shown that the curre nt profiles with q(min) similar to 2 (in this case, there are two resonant magnetic surfaces q = 2 in the plasma) can cause the onset of MHD instabili ties. The possibility of the formation of an internal transport barrier in reversed-shear discharges in the T-10 tokamak is analyzed. In T-10, electro n transport is governed by short-wavelength electron turbulence. As a resul t, there is no clear evidence of the formation of an inner transport barrie r in these experiments. (C) 2000 MAIK "Nauka/lnterperiodica ".