Curr. Appl. Phys. 2023; 55: 16-21

Published online November 30, 2023

Copyright © The Korean Physical Society.

Intrinsic rotation of fusion plasmas induced by the ion-neutral charge exchanges

Lee, Kwan Chul; Lee, Sang Gon

Korea Institute of Fusion Energy, Daejeon, 34133, South Korea

Correspondence to:K.C. Lee; Korea Institute of Fusion Energy, Daejeon, 34133, South Korea; email:


A quantitative driving mechanism of the spontaneous plasma rotation is analyzed by the plasma collisions with the neutrals. The origin of the plasma rotation on fusion devices without external momentum input has been an intensive research subject for more than two decades and no quantitative explanation is available so far. This new intrinsic rotation analysis finds that there is an unbalanced electrical force exchange between the ion and the electron induced by the ion-neutral charge exchange reactions. The electrons give most of the electrical force induced by the toroidal E-field to the ions, but the ions give a significant part of the electrical force to the neutrals. This unbalanced force generates toroidal rotation of ions in a counter-current direction. The rotation magnitude is determined by the frequencies of collisions between plasma and neutrals. A calculation method for the intrinsic rotation based on the measured parameters and simulated unknown parameters is established. The evolution of calculated intrinsic rotation by this method is well agreed with the experimental measurement on KSTAR. It is also found that the most determinant parameter for the intrinsic rotation is the impurity concentration and the variation by the neutral density change is relatively small. © 2023 The Authors

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