Construction and properties of a 1-m long Nb3Ge-based AC superconducting power transmission cable

We have constructed a prototype 1-m long, coaxial ac superconducting power transmission cable utilizing Nb3Ge-clad tapes, Tapes up to 20-m long were produced by pulling 25-μm thick by 0.64-cm wide copper substrates through a continuous coating chemical vapor deposition reactor. Nb3Ge layer thicknesses in the range 3-5 μm were deposited on both surfaces and around the edges of the substrate. A total of 50 m of Nb3Ge-coated tapes was incorporated in this cable, with all tapes exhibiting critical current densities Jc@ 14 Kgeq 1.8 times 10^{6}A/cm². The cable was fabricated after the BNL double-helix design. Losses measured in the cable were found to be high, ∼ 1 mW/cm²at 500 rms A/cm, and comparable to losses in similar 1-m Nb3Sn-based cables. We believe that these high losses are not a result of material dependent properties.