Analysis of EAST’s New Tungsten Divertor and Cooling System During a Disruption with Halo Currents

Chinese Academy of Sciences Institute of Plasma Physics (ASIPP) Experimental Advanced Superconducting Tokamak (EAST) has designed and built a new outer divertor with an ITER-like cooling system. As part of a joint collaboration, the Plasma Science and Fusion Center at MIT performed analyses on the EAST design to determine loading, stresses and deflections due to the eddy currents and halo currents occurring during a disruption. The analysis was done using the finite element program COMSOL using techniques developed at MIT to recreate actual tokamak discharges from measured data. This technique has been used successfully to recreate discharges from Alcator C-Mod, a high field tokamak with TZM tiles at the Plasma Science Fusion Center at MIT, and allows us to recreate the fields for any disruption from the EAST data base. For the new divertor, an upward moving disruption was chosen as the design scenario.

The plasma filament model predicts fields, eddy currents and loads due to a disruption, but the divertor will also be exposed to halo currents. The new EAST divertor borrows its cooling system design from ITER where the plasma facing tungsten tiles are water cooled by a CuCrZr manifold and pipes attached to the tiles. Halo currents traveling down these tubes and crossing the toroidal field will result in large loads in these components, and COMSOL is used to predict the stresses and deflections. The model predicts that the EAST divertor will survive the combined loading due to the eddy and halo currents.