Effect of Selectively Electrodeposited Stabilizer Thickness on AC Loss Behavior of Fully-Filamentized HTS Wire

The influence of thickness of stabilizer layer on fully-filamentized RE-Ba-Cu-O (REBCO, RE = rare earth) coated conductors fabricated by using our recently developed selective electroplating technique on magnetization ac losses is investigated over a frequency range of 40 to 500 Hz at ~ 77 K. The results showed no significant loss contribution by the increasing thickness of the stabilizer in fully-filamentized or decoupled 12-filament tape. The losses for 12-filament decoupled tapes were found to be almost 15 times lower than that for nonstriated reference at relatively high field amplitudes and low frequencies while this number is slightly reduced at high frequencies. Furthermore, magnetization ac losses of partially- and fully-coupled tape structure were investigated since excessive deposition of electroplated copper results in merging of the metal in the middle of the groove, which eventually bridges the superconducting filaments. Such structures resulted in a drastic increase in the losses, and the filamentization became ineffective above the penetration field to an extent that the losses exceeded that of a nonstriated reference tape at relatively low field amplitudes. The thickness for the selectively-coated copper stabilizer on filaments without bridges that leads coupling was achieved to be 30 μm and estimated up to 35 to 40 μm for a groove width of 40 to 55 μm.