Structural Modeling of HTS Cable-in-Conduit Conductor With Helically Slotted Aluminum Core for High-Field Magnet Applications

A structural model has been developed for a Cable-in-Conduit Conductor (CICC) made with 2G HTS superconductors inserted in a helically slotted aluminum core. The cable is particularly suited for high-field applications and consists of a twisted aluminum core and five helical slots. Each slot accommodates a stack of twenty REBCO tapes. The cable is equipped with a central cooling channel and an aluminum jacket. In this work, finite element analysis was used to predict the electrical performance of the cable as a function of the bending diameter. The model consists of three parts: compaction of the aluminum jacket on the slotted core (each slot filled with the HTS stack of tapes), cable's bending and thermal cooldown (from room temperature to 77 K). It was found that the compaction process affects the performance for the top and bottom tapes of the stack. To mitigate this effect, a new design option which includes one structural tape (either copper or stainless steel) on the top and bottom of the stack was evaluated, showing a significant reduction of the strain in those tapes. By adding the strain results generated by the three processes (compaction, bending and cooldown), the normalized critical current was calculated as a function of the bending diameter and compared with experimental data. With a friction coefficient of 0.02 between the tapes, the agreement between model and experimental data is good. The numerical modeling presented here will provide important information on the strain state of the tape-stacks and can be used to investigate the behavior of more recently developed cable designs and optimize future configurations.