Perturbation field penetration into the TEXTOR tokamak and the resulting torque

Three model calculations for the reconnection of AC (frequency range: 1-10 kHz) magnetic field lines of the perturbation field of the TEXTOR dynamic ergodic divertor (DED) have been performed. The first model assumes that the shielding current fills the whole ergodic area (typically 2.5 cm wide), and the second one assumes that each resonant Fourier component of the magnetic field is shielded by currents flowing in its island (typically 0.5 cm wide). The last model also takes plasma flows into account, leading to a resonant interaction; the shielding width amounts to only 0.2 mm. Depending on the specific model assumptions, strong or mild shielding of the magnetic field lines is obtained. The dissipation process is also connected with a transfer of torque from the DED field to the plasma. The values depend on the frequency applied and on the model assumed; for all models, the obtainable forces are of the same order as those from NBI, allowing interesting sheared flow patterns to be imposed.