Current density evolution in electron internal transport barrier discharges in TCV

Simulations of the plasma current density evolution in electron internal transport barrier discharges on the Tokamak a Configuration Variable (TCV) have been performed, in order to determine the relationship between the safety-factor profile and the electron transport improvement. The results show that the formation of the transport barrier is correlated with the shear reversal in all cases studied, regardless of the different heating and current drive schemes. No indications were found of discrete effects related to low-order rational q surfaces. On the contrary, the increase in confinement along with the negative shear is gradual, but constant, indicating that the transition is smooth, although it can be very fast.