Parametric variation of the inboard field line pitch angle for the operation of the dynamic ergodic divertor

The dynamic ergodic divertor (DED) perturbation coil system of TEXTOR is designed to be resonant with the magnetic field lines of the q=3 surface at rres=43 cm and for βpol=1. These parameters determine the pitch of the perturbation coils. In this section the effect of a deviation from the design parameters is analyzed. It is found that—within reasonable limits—a deviation from the design parameters can be compensated by a repositioning of the plasma and–or a variation of the plasma current.