Recent Status on High Temperature Superconducting Bi_2Sr_2CaCu_2O_(8+x) Wire Development at NYSIS: 1-90 Meter Length J_cs and 3 Meter Diameter Ring Furnace Design

摘要

The status of long length, Bi_2Sr_2CaCu_2O_(8+x) (Bi-2212) wire development at the New York State Institute on Superconductivity (NYSIS) is reviewed and updated. Transport J_cs (4.2K, 0 T) of Bi-2212/Ag oxide powder-in-tube single-filamentary tapes have reached 70,000-80,000, 50,000-60,000, and 30,000-40,000 A/cm~2 for 1, 4-15, and 40-90 meter length tapes, respectively. The decrease in J_c as the tape length was increased from 15 to 90 meters was attributed to the (measured) sensitivity of J_c to temperature nonuniformities (±3℃) in the box-type furnace used for annealing. To reduce this problem, a ring-type high-temperature furnace (～3 meter diameter) was designed and constructed which provides a large-volume (～13~w x 10~h x 1000~1 cm) processing zone with expected excellent temperature uniformity (±0.5℃). The advantages of the ring-type furnace for processing of kilometer-length conductors are described.