The dynamic ergodic divertor (DED) was recently installed at the TEXTOR tokamak. One of the aims of the DED is to control and study heat and particle deposition on a plasma wall via modification of the plasma edge by external perturbation coils. Sixteen perturbation coils are mounted on the high-field side of the torus. The external magnetic perturbation creates a zone of chaotic field lines at the plasma edge by destroying several resonant surfaces. These structures have the properties of an open chaotic system while the field lines intersect the tokamak vessel. In order to study the topology of the field lines in different regimes, a set of tools called Atlas was created. Atlas uses a symplectic mapping technique to trace the magnetic field lines. The thermographic set-up is used to measure characteristic temperature patterns on the divertor target plates. The first measurements show the relation of the observed patterns with the results from the modelling with the Atlas codes.
Divertor heat load in ASDEX Upgrade L-mode in presence of external magnetic perturbation