Local Cooling Effect of Rotation and Formation of Thermal Transport Barrier in Tokamaks

A simple model, rotation-inducing local cooling, for the mechanism on the formation of thermal transport barrier and the increase in rotation velocity is presented. It is shown that the sheared rotation can make electron temperature profile T_e(r) steepen near the rotation layer and ▽T_e > 0 on some location inside it, in agreement with the experimental observations in tokamaks, such as JT-60U with (poloidal or toroidal) sheared rotation and HL-1M with a biased electrode. Such temperature profile can remarkably improve the energy confinement in tokamaks.