In this paper we study the feasibility of Fe(Se, Te) coated conductors on a simple rolling-assisted biaxially textured substrate (RABiTS) template. Starting from commercially available Ni–5 at% W tapes which show an out-of-plane orientation of about 7° and an in-plane orientation around 5°, we realized a RABiTS template for Fe(Se, Te) coated conductor fabrication by depositing CeO ₂ thin films on the metallic tape. The oxide buffer layers, deposited via pulsed laser ablation, exhibit an out-of-plane and an in-plane orientation suitable for Fe(Se, Te) deposition and act as a chemical barrier against Ni diffusion. Fe(Se, Te) thin films deposited on such a simple template show a superconducting transition at 16 K and very high upper critical field values with a Δ T _c,0 of only 3 K in 18 T. The transport critical current reaches values of 1.7 × 10 ⁵ A cm ⁻² at 4.2 K in self-field and is reduced by less than one order of magnitude up to 18 T, remaining isotropic with respect to the magnetic field direction.

The introduction of artificial pinning sites in ${\text{YBa}}_2{\text{Cu}}_3{\text{O}}_{7-\delta }$ (YBCO) epitaxial thin films has been obtained by pulsed laser deposition (PLD) technique from YBCO-${\text{BaZrO}}_3$ (BZO) composite targets with BZO concentration ranging from 2.5 to $7\text{mol}\mathrm{\%}$ . The typical critical temperature, $T_c$ , drop observed in YBCO-secondary phase films grown by PLD has been successfully recovered by increasing the deposition temperature. Transport properties analyses revealed improved pinning force values for YBCO-BZO films for BZO concentration above $5\text{mol}\mathrm{\%}$ . These films exhibited an anomalous dual peak structure which has been ascribed to the presence of two pinning contributions. The crossover field, $B_m$ , separating these two pinning regimes has been observed to be temperature independent suggesting the occurrence of the matching field effect. The measured value of $B_m$ agreed with the matching field value, $B_{\Phi }=K{n}_d{\Phi }_0$ , as evaluated from transmission electron microscopy investigations. The mark of this phenomenon is retained down to 10 K, making YBCO-BZO more performing than pristine YBCO films at applied magnetic fields below $B_m$ in all the temperature range inspected. On the contrary, in the high magnetic field range (above $B_m$ ), the effectiveness of correlated pinning is progressively reduced on lowering the temperature suggesting that at low temperatures the dominant pinning contribution arises from isotropic pinning centers.

Pulsed laser deposited thin Y Ba₂Cu₃O_7−x (YBCO) films with pinning additions of 5 at. % Ba₂Y TaO₆ (BYTO) were compared to films with 2.5 at. % Ba₂Y TaO₆ + 2.5 at. % Ba₂Y NbO₆ (BYNTO) additions. Excellent magnetic flux-pinning at 77 K was obtained with remarkably high irreversibility fields greater than 10 T (YBCO-BYTO) and 11 T (YBCO-BYNTO), representing the highest ever achieved values in YBCO films.

Electrical and mechanical characterizations of YBCO coated conductors diffusion joints obtained in a 2 mm wide, Cu stabilizer free commercial tape provided by Superpower Inc. were reported. Two conductor pieces were overlapped for a length of 20 mm and kept in contact under a pressure as high as 80 MPa. A face-to-face approach was used, with or without an additional Ag tape insert. The joint was realized by Ag diffusion at a temperature of 200 and 400°C in N₂ and O₂ atmosphere, respectively. The resistivity of the joint was measured at 77 K in N₂ bath. The mechanical properties of the joint were characterized by means of single-lap tensile test operated at room temperature at a rate of 0.5 mm/min. The best results were obtained by high temperature joining in O₂ atmosphere. The resistivity of the joints was as low as 3.1 × 10^-12 ¿ m². This value is almost halved if an Ag insert is used. The mechanical properties of the joints are strongly dependent on the use of an Ag insert, since maximum load as high as 60 N can be applied if no additional insert is used. This value enhances to about 100 N when an Ag insert is employed. However, the joint obtained at low temperature in N₂ atmosphere is also interesting since the joint resistivity was slightly increased to 4.7 × 10^-12 ¿ m² and a maximum load as high as 50 N was obtained indicating that diffusion joints can be safely handled. These results are promising in perspective of oxygen free diffusion joints in Cu stabilized coated conductors.

Technologies based on High Temperature Superconductors (HTS) are evolving rapidly toward maturity. Within the magnetic confinement fusion environment, several projects are demonstrating the possibility to integrate HTS in the coil systems. With respect to Low Temperature Superconducting (LTS) technologies, HTS could allow extending the operating space of fusion coils, either at higher temperatures, or at higher magnetic field levels, and in any case with larger operating margins. Different perspectives and development strategies are proposed, depending on whether HTS is considered a technology to completely substitute LTS, or to integrate and extend its performance range. A fundamental common requirement is the assessment of the layout, the feasibility, and performance demonstration of high-current conductors. Starting from the results achieved with the Al-slotted core cable-in-conduit conductor, and with a view on existing concepts for standard copper and aluminum cables, we have designed a new HTS sector-cable concept, to allow a flexible conductor design and a robust industrial processing. Several trials have been carried out, to verify the manufacturing approach, using either Al- or Cu-based stabilizers. Prototype sub-cables have been characterized at 77 K and self-field, as a necessary step toward the final target of a CICC operating stably with 60 kA at 4.2 K and 18 T, that is presently of interest for the EU-DEMO Central Solenoid Coil.

In the present contribution, we report on the experimental study of the bending behavior, at 77 K, of a Cable-In- Conduit Conductor comprised of a stack of REBa $_2$ Cu $_3$ O $_{7-x}$ (REBCO) tapes inserted into a helical duct formed in the extruded Aluminum cylindrical core. The investigation has been carried out by powering each single tape individually. By the analysis of the single tape Ic dependence as a function of the bending radius, Rb, the effect of bending strain as a function of tape position inside the stack was investigated for each tape. The results evidence the good bending strain tolerance of all the tapes, showing the onset of degradation at Rb $\approx$ 0.25 m, ascribed to the slippage occurring among tapes within the stack. Interestingly, the decrease in the intertape contact resistance between neighboring tapes with respect to the straight cable condition reveals that the bending stress results in a beneficial additional transverse load on the stacks, which leads to a more uniform compaction of tape stack. The experimental Ic behavior with Rb has been explained considering that the current transfer mechanism among tapes might mitigate the degradation of the tape Ic due to the bending strain. The identification of the mechanisms acting on individual tapes under cable bending conditions is a relevant achievement in perspective of the interpretation of the electromechanical behavior of the conductor with all tapes powered in parallel.