Speaker
Description
High magnetic fields of up to 20 T in tokamak-type fusion devices require High-Temperature Superconductors (HTS) and 50 kA/20 T class, full-size ReBCO Cable In Conduit Conductors (CICC). Conductors based on Conductor On Round Core (CORC®/HFRC) cables, are among others, proposed for the Central Solenoids of the European DEMO and the Chinese BEST fusion reactors. The large Lorentz forces occurring under these operating conditions may locally generate high mechanical stress, which can irreversibly degrade the critical current of the superconductor and may impact the contact resistance between tape layers in direct contact. For this reason, CORC® and HFRC cable samples, manufactured by Advanced Conductor Technologies and ASIPP (Hefei, China), have been tested under cyclic loading in the Twente Press. The samples have been loaded within geometric configurations resembling as close as possible the loading conditions of their respective CICC designs, recently tested in the Sultan facility. The critical currents, n-values and contact resistances of tapes selected from different layers have been measured at 77 K and in self field, at different loads and load cycling, beyond observed irreversible degradation.
In addition, detailed structural finite element analysis (FEA) of the conductors, based on measured material electromagnetic and mechanical properties, are compared with Twente Press experimental results and Lorentz loading conditions. An important input is the ReBCO mechanical properties and their tensile and compressive irreversibility limits, also measured at the University of Twente.
The model predictions agree with experimental results and are being used to predict quantitively which configurations can best withstand Lorentz load and what the impact is of proposed geometric and material design optimisations.
