MHD activity and formation of the electron internal transport barrier in the T-10 tokamak

The plasma stability and confinement have been investigated through control of the safety factor profile q(r) by the electron cyclotron current drive in the T-10 tokamak. The regimes with dq/dr congruent to 0 and dq/dr < 0 in the plasma core were obtained. Various types of MHD activity were observed : ordinary sawtooth, saturated sawtooth, humpbacks, trills etc. It was show n that when the minimal value q(min) increases from q(min) < 1 to q(min) = 2 the plasma becomes strongly unstable due to the corresponding MHD activit y or passes to the steady-state improved confinement mode. The latter is re alized when the electron internal transport barrier (EITB) is formed. The c ondition for the appearance of the EITB is dq/dr congruent to 0, where q = m/n lies near a rational value for low m and n.