The shielding-current-induced field is a serious concern for the applications of coated conductors to magnets. The striation of the coated conductor is one of the countermeasures, but it is effective only after the decay of the coupling current, which is characterised with the coupling time constant. In a non-twisted striated coated conductor, the coupling time constant is determined primarily by its length and the transverse resistance between superconductor filaments, because the coupling current could flow along its entire length. We measured and numerically calculated the frequency dependences of magnetisation losses in striated and copper-plated coated conductors with various lengths and their stacks at 77 K and determined their coupling time constants. Stacked conductors simulate the turns of a conductor wound into a pancake coil. Coupling time constants are proportional to the square of the conductor length. Stacking striated coated conductors increases the coupling time constants because the coupling currents in stacked conductors are coupled to one another magnetically to increase the mutual inductances for the coupling current paths. We carried out the numerical electromagnetic field analysis of conductors wound into pancake coils and determined their coupling time constants. They can be explained by the length dependence and mutual coupling effect observed in stacked straight conductors. Even in pancake coils with practical numbers of turns, i.e. conductor lengths, the striation is effective to reduce the shielding-current-induced fields for some dc applications.

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We discuss the Josephson current between two noncentrosymmetric superconductors. The coexistence of superconducting order parameters between spin-singlet ∆S and helical p-wave spin-triplet ∆T enriches a variety of low-temperature behavior of Josephson current depending on their relative amplitudes. We will show that characteristic behaviors of the Josephson current for ∆S > ∆T are clearly different from those for ∆S < ∆T. The topologically protected zero-energy surface bound states are responsible for the clear difference. We conclude that the Josephson current well reflects character of the topological surface states and the pairing symmetry of noncentrosymmetric superconductors.

A single pancake coil wound with a copper-plated multifilament coated conductor, with four filaments, was put in a cusp magnetic field, and the magnetic field was measured near the coil at 30 K. A similar experiment was performed by using another reference single pancake coil wound with a monofilament coated conductor. Numerical electromagnetic field analyses of these coils were carried out, and the calculated shielding current-induced fields (SCIFs) were compared with the measured ones in both coils. The temporal behaviour of the calculated SCIF in the coil wound with the four-filament coated conductor was also compared with a series of exponential components, in which a coupling time constant extrapolated from short sample experiments was used as the time constant of the primary component. Current distributions in the coated conductors wound into the pancake coils were visualised. In particular, the temporal behaviours of the current distributions in the four-filament coated conductor and their influence on the SCIF were discussed.

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