Damage Investigations in the HTS Cable Prototype After the Cycling Test in EDIPO

During the test of 60 kA high-temperature superconducting cable prototypes in the European DIPOle (EDIPO), the performance of the prototypes in the cycling test was gradually degrading with the increasing number of electromagnetic and warmup-cool-down cycles. At the end of the test, after about 2000 cycles, the performance drop of the SuperPower and SuperOx conductors reached 10% and 20%, respectively. After the strands were extracted from the SuperOx cable, the critical current of the strand sections that were located in a high-field zone of EDIPO was measured at 77 K /self-field. Reduction of I
_C
. was found not only in the loaded flat side of the cable, but also (and more evident) on the edges of the cable. Several strand sections with the highest degradation of I
_C
. were cut and desoldered. The results of the measurements on the extracted tapes demonstrate highly nonuniform distribution of the retained critical current. Additional investigations have been performed to investigate in details influence of such nonuniformity on the overall I
_C
performance of the strand. Based on the obtained results, concluding recommendations for the next cable prototypes are discussed.