Experimental Modelling of Eddy Currents and Deflection for Tokamak Limiters

During plasma disruptions in a tokamak fusion reactor, eddy currents are induced in the limiters and other conducting structures surrounding the plasma. Interactions between these currents with the toroidal field causes deflection and stress in the structural components. The structural motion in the strong magnetic field induces additional eddy current opposing the initial eddy current and modifying subsequent structural dynamics. Therefore, the motion and current are coupled and must be solved simultaneously. The coupling between current and deflection in cantilevered beams was investigated experimentally. The beams provide a simple model for the limiter blade of a tokamak fusion reactor. Several test pieces and various magnetic field conditions were employed to study the extend of the coupling effect from weak to strong coupling. Experimental results were compared with analytical predictions.