The influences of stresses/strains on critical current, Ic in REBCO high temperature superconducting (HTS) tapes wound onto a round cable were investigated. Firstly, the HTS tapes were helically wound on copper tubes with various diameters in range of 2.95-8 mm, where considerably better results were achieved in case the superconductor layer of tape was positioned during winding at the inner side of the helix. The cables with tape wound on the tube with diameter of 6.35 mm were subjected to bending tests with various bending radii in range from 21 to 60.5 mm. The Ic degradation as a function of both, the tube diameter and bending radius has been studied by measuring current-voltage curve, from which the critical current was determined. The Ic degradation in all samples was confirmed by microstructural investigation of HTS layers using scanning electron microscopy.

Alternating current (AC) losses in superconducting tapes (SCTs) are one of the main concerns for their use in applications where costs of heat dissipation need to be reduced, such as pulse magnets. Modification of the tapes by striation has been shown to significantly reduce AC losses, and several filamentization methods have been developed. Up to two orders of magnitude decrease in AC losses was reported in previous works with laser ablation, mechanical grooving, or chemical etching. However, a different approach may have to be used to achieve similar results for those SCTs (or their applications after striation), which are more prone to degradation by the side effects of the mentioned methods. We proposed a procedure based on chemo-mechanical etching, which avoids problems arising from thermal degradation and mechanical pressure. Our method intended for the REBCO (RE = rare earth metal, B = Ba, C = Cu, O = oxygen) based high-temperature SCTs yielded low and reproducible AC losses, low cost, retention of the relative critical current up to 93%, and preservation of the mechanical properties of the tape substrate.

This study aimed to enhance the performance of Ag-stabilized high-temperature superconducting (HTS) tapes with a focus on reducing magnetization losses. Two approaches were employed: dividing the tapes into narrower widths and introducing striation at the level of the superconducting layer. The process of laser ablation proved to be an effective method for implementing these modifications. The quality of the cut edges and grooves was assessed using scanning electron microscopy. To evaluate the electrical properties, measurements were conducted on the critical current and magnetization loss in samples at different stages: in their initial state, after cutting, and after the striation process. Of the two modifications, the striation process more effectively reduced the AC losses in the HTS tapes, approximately by one order of magnitude. The retention of critical current remained high after cutting, but varied with the number of created filaments after the striation process. Subsequently, a short cable was wound from the cut and striated HTS tape. This cable demonstrated a remarkable sixfold reduction in AC losses compared to the initial HTS tape.

We enhanced the performance of superconducting tapes during quenching by coating the tapes with various composites, with regards to the application of such coated systems in superconducting fault current limiters. In composition of the coating, we varied the type of epoxy matrix, the content of ceramic filler particles and the use of reinforcement in order to optimize the thermal and the mechanical stability of the coated tapes. By this way modified superconducting tapes were able to reduce the maximum temperature 170 °C of not modified superconducting tape to 55 °C during the quench with electric field up to 130 V m⁻¹.

We prepared overlap soldered joints of high-temperature superconducting tapes, using various materials and preparation conditions. In order to select the joints with optimal performance, we correlated their electrical properties (derived from current–voltage curves) with the microstructure of the respective joint cross-section by scanning electron microscopy. With the first group of joints, we focused on the effect of used materials on joint resistivity and critical current, and we found that the dominant role was played by the quality of the internal interfaces of the superconducting tape. Initial joint resistivities ranged in the first group from 41 to 341 nΩ·cm². The second group of joints underwent a series of thermal cyclings, upon which the initial resistivity range of 35–49 nΩ·cm² broadened to 25–128 nΩ·cm². After the total of 135 thermal cycles, three out of four joints showed no signs of significant degradation. Within the limit of 100 thermal cycles, reliable soldered joints can be thus prepared, with normalized resistivity not exceeding 1.4 and with normalized critical current above the value of 0.85.

Alternating current (AC) losses in REBCO (RE – rare earth metal, B – barium, C – copper, O – oxygen) high-temperature superconductors, can be reduced by several orders of magnitudes by the tape striation. Various methods were investigated so far for the decrease of the superconductor's width-to-thickness ratio, and new methods (or novel combination of previously reported methods) are still developed. A reason for the latter efforts is to reduce the superconductor's degradation, which cannot be completely avoided, and it is inherent to each method. Unfortunately, the degradation also seems to depend on the architecture (i.e., on the thicknesses of layers, deposition techniques used, chemical composition, etc.) We thus compared the ac losses of REBCO tapes striated by a chemo-mechanical method, by photolithography, and by laser ablation approach. The ac loss measurements and transport properties of Ag-stabilized superconducting tapes from SuperPower are complemented by the analysis of their structure. All methods resulted in a substantial decrease in normalized ac loss (more than 9 times at 36 Hz for tape with 15 striations in compare with non-striated tape. The photolithography method exhibited the highest decrease of ac loss, but also led to a notable decline in the critical current.