The superconducting magnet wound by high temperature superconducting (HTS) wires attracts extensive interest in high magnetic field and at low temperature. However, different from the conventional low temperature superconducting (LTS) magnet, the persistent operation of the HTS magnet with persistent current switch (PCS) is not commercial at present because of the immature jointing technique between HTS wires. This paper presents a conceptual design of a Bitter-like superconducting magnet by stacking (RE= rare earth) BCO annular plates magnetized by flux pump, which can operate in persistent mode. The induced field characteristics and temporal response of the superconducting magnet were firstly analyzed by theoretical simulation using the Finite Element Method (FEM). The design method of REBCO annular plates and construction details of the Bitter-like superconducting magnet were then detailed herein. A model Bitter-like superconducting magnet was fabricated by stacking REBCO annular plates without joint resistance and its feasibility with persistent mode was experimentally validated at 77 K. The technology has potential application in NMR magnet and high field magnets.

Superlattices and trilayers consisting of three isostructured 123-type oxide superconductors, $\mathrm{Gd}123∕\mathrm{Nd}123∕\mathrm{Eu}123$, were prepared on $\left(100\right)$ ${\mathrm{SrTiO}}_3$ using off-axis pulsed laser deposition. Superconducting transition temperatures $\left(T_c\right)$ in the superlattices reduce monotonically with decreasing constituent thickness $\left(d\right)$, while $T_c$ and transport critical current density $\left(J_c\right)$ of the trilayers show no such suppression, being as good as in pure 123 thin films. Individual flux pinning and collective thermal-activated flux motion characterized by $\log J_c$ vs $\log H$ reveal flux pinning crossovers with field, temperature and layer thickness. Epitaxial-strain-induced thickness effects and correlated defects are applicable to account for the suppressed $T_c$ and flux pinning crossover in the present superlattices.

In the present work, monodisperse BaZrO₃ (BZO) nanocrystals with controllable sizes are successfully introduced into trifluoroacetate metal–organic deposition derived (Y,Dy)Ba₂Cu₃O_7−δ ((Y,Dy)BCO)-coated superconducting tapes to act as effective pinning centers. The BZO nanocrystal addition strategy is extended to upscaling coated conductors as long as hundreds of meters, and as thick as 3.4 μm, of (Y,Dy)BCO layers. The corresponding superconducting performances of BZO-added (Y,Dy)BCO-coated conductors are systematically investigated under various applied magnetic fields and temperatures. It is revealed that the I _c (77 K, self-field) of BZO-added tapes decreases linearly with BZO concentration, while the corresponding in-field lift-factors increase for all studied BZO additions. In-field J _c values under various fields at low temperatures show that the (Y,Dy)BCO tape with 5%-BZO addition exhibits a better performance than that of other concentrations. Besides, this benefit of BZO addition appears identical for both thin and thick samples, as well as for tapes that are hundreds of meters long. The angular dependence of in-field I _c also shows that significant improvement occurs in all the studied angular ranges after nanocrystal BZO additions, demonstrating that the nanocrystal addition strategy is of great value for upscaling commercial (Y,Dy)BCO tape for in-field applications.

The added BaMO₃ (BMO, M = Zr, Hf) nanocrystals into REBa₂Cu₃O_7−δ (REBCO, RE = Y or other rare earth) superconducting films by the technology of preformed nanocrystal addition from colloidal precursor solutions have coarsened after sintering of the REBCO films, which limit the BMO size control and flux pinning enhancement. In the present work, the evolution of the size of BaHfO₃ (BHO) nanocrystals in the YBCO films is studied. The collection process of BHO nanocrystals is optimized to successfully separate BHO with an average size of 6 nm into two parts with average sizes of 4.5 nm and 7.7 nm, respectively. The evolution of three different BHO sizes in YBCO superconducting films with a thickness of 2.2 μm and 10 mol% addition reveals that the small-size preformed nanocrystals decomposed at high temperatures to release Hf ions, resulting in the coarsening of other preformed BHO nanocrystals. After modulating the BHO size by reducing the amount of small-size BHO, the coarsening factor is reduced from 1.6 to 1.1, leading to a better in-field performance, especially at low temperatures. At 30 K@1 T, the critical current density (J _c) of the 7.7 nm BHO-added YBCO increases by 23% and 50% than cases of 6 nm and 4.5 nm, respectively, being of great guiding value in the technology of performed nanocrystal addition.