Characteristics of Ag-Au alloy sheathed Bi-Pb-Sr-Ca-Cu-O superconducting tapes for current leads

Abstract

Oxide superconductor tape with Ag-Au sheath was studied for current leads. A 100-cm-long current lead of 1000 A with 0.2 W/kA heat leakage was designed using Ag-11 at. % Au alloy sheath with low thermal conductivity. The overall current density of the superconducting tape is required to be 350–770 A/cm2 at 77 K when the superconductor cross-section ratio in the tape is 0.35–0.7. Bi-Pb-Sr-Ca-Cu-O superconducting tape with Ag-11 at. % Au alloy sheath was fabricated and the critical current density Jc was measured. The overall-Jc was 1700 A/cm2 at 77 K under 0 T. The possibility of the current lead of 1000 A under 0.28 T with 0.2 W/kA was made clear.

Thermal conductivity of single and multi-stacked DI-BSCCO tapes

“…On the other hand, the small value of κ(T ) for type G tape is often observed in a solid solution. The behaviours of κ(T ) observed here resemble those of other Bi2223 tapes sheathed with silver-based alloys [4,5,6,7].…”

“…The absolute value and the temperature dependence of κ(T ) strongly depend on the sheath material, the sheath/Bi2223 ratio and the fabrication process [4,5,6,7]. As far as we know, the κ(T ) of DI-BSCCO has not been reported.…”

“…In this case, however, we must correctly estimate the amount of heat leakage through the tape [4]. The heat leakage Q leak through the tape between the low and high temperature sides, T low and T high , respectively, is generally given by…”

Conceptual design of a forced-flow-cooled 20-kA current lead using Ag-alloy-sheathed Bi-2223 high-temperature superconductors

“…Geometrically, these are no longer bulk material but tapes or wires consisting of a core made of Bi-2223 or Bi-2212 HTSC and a silver or silver-alloy sheath. An interesting development has been given in [8,9]. This group uses silver-gold alloys which have thermal conductivities comparable to that of phosphorous-deoxidized copper, i.e., several orders of magnitude lower than that of pure silver.…”

“…Each tape has a cross section of 8 mm x 0.3 mm, the superconductor fraction is 0.65, the stabilizer is made of silver with 3 at.% Au to reduce thermal conductivity, as proposed in [8,9]. A total of 27 tapes are stacked to form a so-called 'module" of 8 mm x 8.1 mm cross section.…”