Consequences of charge exchange in plasmas and the intrinsic rotation of KSTAR

Ion gyro-center shift induced by the charge exchange reaction between ion and neutral atom is analyzed to explain the electric field formations and turbulence suppression in various plasmas including Er of tokamak edge, H-mode transition, reversed motion of arc discharge, E-fields of equatorial electro-jet (EEJ), black aurora, and Bohm diffusions. [1][2] And new intrinsic plasma rotation analysis is developed based on the unbalanced ion-electron momentum exchange induced by the ion-neutral charge exchanges. The origin of intrinsic rotation has been researched for decades because the plasma rotation controls the MHD instabilities. However, no quantitative agreement is available thus far. Very strong counter-current intrinsic rotation is induced on KSTAR when the ion-neutral collision frequency is comparable to the electron-ion collision frequency, especially at the edge of tokamak. The comparison of experimental observations on KSTAR and VEST is well agreed with the analysis based on this charge exchange effect. The magnitude and time evolution of the intrinsic rotations agrees for the cases with different plasma parameters. It is also found that the neutral density is not sensitive to the intrinsic rotation and the impurity concentration is an important parameter for the intrinsic rotation.