Splice Resistance Measurements of REBCO Tapes for a REBCO Sextupole Magnet

The REBa2Cu3Oy (REBCO) superconducting magnet requires low-resistance and high-mechanical-strength splices from a standpoint of magnet manufacturing. In the previous study, we designed a prototype REBCO sextupole magnet. To fabricate the sextupole magnet, it is important to characterize low-temperature and high-magnetic-field performances of the splice resistance of REBCO tapes. For that reason, we measured the splice resistance of 4-mm-wide commercial REBCO tapes of three manufacturers at 77 and 4.2 K in this study. The magnetic field characteristics of the splice resistance was determined up to 10 T at 4.2 K. Parameters such as solder compositions and splicing orientations of two REBCO tapes were varied to clarify the impact of each on the splice resistance characteristics. The splice resistance was determined primarily by the splicing orientation of two REBCO tapes. The minimum splice resistance of the 40-mm-long joint was approximately 16.5 nΩ at 4.2 K and in self-field when REBCO layers of two tapes were in closest orientation. The critical current and n-value of the splice section showed no appreciable degradation compared to those of the original tape.