Speaker
Description
High magnetic fields of up to 20 T in tokamak-type fusion devices, such as in Central Solenoids of European DEMO and the Chinese BEST fusion reactors, require High-Temperature Superconductors (HTS) and a promising candidate is ReBCO tape. The large Lorentz forces occurring under these operating conditions may locally generate very high values of mechanical stress, which can irreversibly degrade the critical current of the superconductor. For the design of these cables, detailed structural finite element analysis (FEA) based on accurate material electromagnetic and mechanical properties under relevant electromagnetic load levels is needed for reliable and optimal operation. Knowledge of the axial tensile and compressive strain irreversibility limits for the critical current of ReBCO tapes is there for essential.
For this purpose, axial tensile stress–strain measurements have been performed on ReBCO tapes from several manufacturers in the upgraded TARSIS2 facility and compressive strain imposed by bending on different core diameters. The evolution of the critical current and n-value were measured at 77 K in self field for stepwise increasing tensile load and also cyclic loading conditions were studied. The tensile stress strain characteristics were also tested at room temperature.
Full-scale 3D FE models of the tapes have been developed and validated using electrical and mechanical material properties of the used superconducting tapes and simplified stress-strain relations are proposed. The model predictions are well in agreement with experimental results and will be used to predict quantitively the impact of Lorentz load on CORC-CICC design optimisation.
