REBCO (REBa₂Cu₃O_7-δ) coated conductor with J_e > 1000 A/mm² at operating condition has a wide range of applications in fusion and high-field magnets. We have demonstrated short REBCO samples with J_e ~ 4,600 A/mm² (based on 0.1 mm thick tape) at 4.2 K, 20 T using Advanced metal-organic chemical vapor deposition (A-MOCVD). In order to achieve such high performance uniformly over long tapes, defective regions in thick films need to be avoided. In this work, we investigated which parameter causes dropout or variation in the critical current along the length of long tapes made by A-MOCVD. By addressing the engineering challenges of growing 4+ µm thick REBCO films in a single pass, 10+ m long tapes with high critical current that varies < 5% along the length have been fabricated.

Keywords: REBCO tapes, Defect, Microstructure, MOCVD