Experimental and theoretical analyses of penetration processes of externally applied rotating helical magnetic perturbation fields in TEXTOR and HYBTOK-II

Penetration processes of rotating helical magnetic perturbation field into tokamak plasmas have been investigated by the dynamic ergodic divertor (DED) in TEXTOR. Experimental observations of the field penetration and field amplification are performed and the data are interpreted by theoretical analyses based on a linearized two-fluid plasma model. It is observed that the growth of the forced magnetic reconnection by the rotating DED-field is accompanied by a change in the plasma fluid rotation. The theoretical model is also applied to the DED experiment in the small tokamak device HYBTOK-II. It is confirmed that the theoretical analyses can explain the observed radial profiles of the DED-field in the plasma by inserting small magnetic pick-up coils in HYBTOK-II.