Impact of Dynamic Ergodic Divertor on Plasma Rotation in the Small Tokamak HYBTOK-II

Plasma rotation or its shear is important on the formation of transport barrier. It is thought that the rotating helical magnetic field generated by Dynamic Ergodic Divertor (DED) could generate a rotational torque in tokamak plasmas and control rotation profiles as a result. In order to measure the plasma rotations and to investigate the effect of DED on them, we developed a passive spectroscopic measurement system for the small tokamak HYBTOK-II to measure plasma rotations. A spontaneous toroidal plasma rotation in co-current direction and the poloidal plasma rotation in electron diamagnetic drift direction have been observed without DED. Considerable changes of the plasma flow have been obtained with DED to show some reduction of toroidal and poloidal rotation velocity near the resonant magnetic surface. The modification of plasma rotation velocity was found to couple to the change of the radial electric field.