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Description
This study explores the angular ($\theta$) dependence of the critical current $I_c(B,T,\theta)$ in REBCO coated conductors using a torque magnetometer (US Patent) optimized for high magnetic fields ($B$) and low temperatures ($T$)—a critical regime for magnet development and pinning mechanism studies, where high $I_c$ complicates transport measurements.
Data from over 200 samples reveal significant $I_c$ variations, even among samples fabricated to the same specifications. When $B$ is near the ab-plane,
strong pinning dominates and $I_c$ exhibits exponential and stretched exponential decays ($I_c\propto\exp(-B)\exp[-(T)^s]$, $s\approx2$). When $B$ is away from the ab plane, $I_c$ shows power-law and simple exponential decays ($I_c\propto B^{-\alpha}\exp(-T)$, $\alpha\lesssim1$) This enables clear assessment of different pinning contributions into $I_c(B,T,\theta)$.
Additionally, lengthwise $I_c$ variations are prominent in tapes cut from the sides of 12 mm-wide production tapes, especially when the magnetic field aligns with the ab-plane. In contrast, tapes cut from the center exhibit stable $I_c$. Flux jumps are observed in samples with thick REBCO layers and thin Cu stabilizers, suggesting potential thermal instabilities. These findings provide crucial insights into the performance of CC tapes in high-field magnet and nuclear fusion applications. A. Francis, G. Bradford, A. Xu, R. Ries, D. Larbalestier contributed. NHMFL is funded by NSF DMR2128556 and the State of Florida.
| Session | Conductor Material Research |
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