Low Temperature and Magnetic Field Performance of Spliced Commercial YBCO CC

Abstract

The design of next-generation magnets based on 2G high-temperature superconductors requires a careful investigation of the possibilities and performance of joints between different superconducting wire pieces. In this paper, we present a study of the electrical performance of splices made with commercial Superpower ReBCO tapes at both 77 K and 4.2 K. For this study we developed a special splicing device based on the hot-bar soldering technique that allowed estimating the degree of reproducibility of the splicing method in view of future standard series production. During our study we investigated the influence of the splicing parameters (temperature, pressure, duration, flux fluid, solder composition, cooling etc.) on the final joint performance in terms of specific resistance, critical current degradation and n-value degradation. The best performing splice was characterized at 4.2 K in perpendicular magnetic field up to 11 T. The results show an excellent degree of reproducibility with no appreciable degradation of the original tape performances. The ultimate splice resistance seems determined by the intrinsic architecture of the tape rather than by the splicing method itself.

Soldered joints—an essential component of demountable high temperature superconducting fusion magnets

“…The range of R J values reported in the literature is large. The R J of similar soldered joints with the same CCs can vary from ∼4 to over 1000 nΩ cm 2 at 77 K [7,[34][35][36]. Inconsistent results are also found in the magnetic field dependence of R J .…”

“…Inconsistent results are also found in the magnetic field dependence of R J . Some studies claimed that there was no observable field dependence of R J [7,36]. Other studies demonstrated that R J of the samples fabricated using the same kind of CCs changed significantly with an applied magnetic field [37].…”

Pursuing low joint resistivity in Cu-stabilized REBa2Cu3Oδcoated conductor tapes by the ultrasonic weld–solder hybrid method

“…On the other hand, joints with sufficiently low resistance can be formed by simple soldering techniques for some applications such as power cables [9][10][11][12][13][14][15]. Joint resistance can be reduced below 10 −7 Ω when the superconducting layers in overlapped CC tapes are in closer proximity by removing other layers such as the Cu stabilizer, Ag cap layer, or solder material [5][6][7][8][15][16][17][18][19].…”

Microstructures of superconducting joint between GdBa2Cu3O y -coated conductors via additionally deposited precursor films

“…8,9) While the length of NbTi wires could reach 10-15 km and 40-50 km for 0.5 T and 2.0 T magnets, respectively, the longest REBCO CCs with homogeneous I c reported so far are approximately 1 km, even in optimum fabrication conditions. 3,10,11) Several joint methods have been developed to lengthen REBCO CCs, such as use of a solder joint, 12,13) a diffusion joint using a metal stabilizer, [14][15][16] and a superconducting joint. [17][18][19][20] In the case of solder joints and diffusion joints, the presence of resistance is inevitable due to solders and stabilizers at the boundaries, which cause current loss and heat generation resulting in an inhomogeneous magnetic field.…”