Critical Current Distributions of Recent Bi-2212 Round Wires

Bi-2212 is the only high-field, high-temperature superconductor (HTS) capable of reaching a critical current density $J_{\text{c}}$(16 T, 4.2 K) 6500 $\mathrm{A\cdot mm^{-2}}$ in highly desirable round wire (RW) form. However, state-of-the-art conductors still have ($J_{\text{c}}$) to depairing ($J_{\text{d}}$) ratio around 20 30 times lower than that $\mathrm{Nb-Ti}$ or REBCO. Previously, we shown recent improvements RW $J_{\text{c}}$ are due improved connectivity associated with optimization heat treatment process, and most recently transition finer more uniform powder manufactured by Engi-Mat. One quantitative measure may be ($I_{\text{c}}$) distribution, since local $I_{\text{c}}$ can vary along length variable vortex-microstructure interactions factors such as filament shape variations, grain-to-grain variations blocking secondary phase distributions. Here compare $\sim$ 0.1 m distributions RWs very high-$J_{\text{c}}$ Engi-Mat older Nexans granulate powder. We do find spread for wires about twice relative standard well below $H_{\text{irr}}$. not yet see any obvious contribution anisotropy distribution rather encouraged these show too far from wires.