REBa 2 Cu 3 O x (REBCO) coated conductors exhibit irreversible critical current ( I c ) degradation under tensile strain beyond the irreversible strain ( ɛ irr ). While this degradation is attributed to cracking, the specific crack evolution process and its quantitative relation to I c degradation remain unclear. Here, the multiplication of cracks in REBCO tapes under tensile is characterized. It was found that surface particles disrupt continuous crack propagation, causing fragmentation of the REBCO layer. A shear lag model describes how the stress distribution evolves with fragmentation spacing. A probabilistic fracture model then predicts the two-regime spacing reduction as a function of applied strain. The discontinuous crack network acts as the residual flow channel for current once strain exceeds ɛ irr . Crack spacing determines the remaining I c in this regime. An analytical model is thus proposed to capture the I c degradation behavior based on the quantified fragmentation process. Additionally, this study suggests approaches to obtain a wider safe operating strain range through tailoring of the fracture behavior, expanding the practical application limits. This work provides new insights into the progressive cracking mechanisms governing irreversible I c degradation in strained REBCO tapes.

Non-centrosymmetric superconducting materials represent an exciting class of novel superconductors featuring a variety of unconventional properties, including mixed-parity pairing and very high upper critical fields. Here, we present a comprehensive study of TaIr₂B₂ (with <em>T_c</em>=5.1K), using a set of complementary experimental methods, including bulk- and surface-sensitive techniques. We provide evidence that this system is a two-band, yet it behaves as a single-gap superconductor with a strong coupling. The upper critical field of TaIr₂B₂ significantly exceeds the Pauli limit and exhibits a nearly linear temperature dependence down to the lowest temperatures. This behavior, rarely seen in superconductors, is discussed in terms of anti-symmetric spin–orbit interaction, two-band-, and strong-coupling effects, as well as disorder.

A fine-filamentary CuZn sheathed MgB 2 wires produced by Hyper Tech Inc were used for 12 strand Rutherford cable of thickness 0.70–0.76 mm. Critical currents of short cable samples were measured at 4.2 K and external fields 4.0–8.0 T and also at temperatures 15–25 K and magnetic fields 1.0– 5.5 T. The threshold of engineering current density J e = 1 0 4 Acm −2 for the cable size of 0.72 mm × 2.55 mm was obtained at field of 4.5 T and temperature 4.2 K and at 2.3 T for 20 K, respectively. Magnetization measurements of the cable with transposed strands and twisted 20 μ m filaments have shown reduced AC losses, but, the coupling currents loss contribution was still visible. AC losses measured for the same size Rutherford cable made of single-core wires demonstrate the effect of well decoupled filaments. Consequently, the cabling of thin single-core MgB 2 wires shows a promising way for low loss conductors suitable for AC applications.