RECENT ADVANCES IN BISMUTH-BASED SUPERCONDUCTORS

Significant progress has been made in the development of high-critical -temperature (high-T-c) mono- and multifilament bismuth-based supercon ductors by the powder-in-tube (PIT) technique. High critical current d ensity (J(c)) has been achieved in both short- and long-length monofil ament conductors. J(c)s up to 1.2 x 10(4) A/cm(2) were achieved in an 850 m long multifilament conductor. Pancake-shaped coils and test magn ets, fabricated from long conductors, were characterized at various te mperatures and applied magnetic fields. One such magnet containing 480 m of high-T-c tape generated a record-high field of 2.6 T at 4.2 K. M ultifilament conductors appear to possess better mechanical properties and retain a higher percentage of their initial critical current unde r strain than monocore conductors, which is important for practical co nsiderations. PIT processing of superconducting tapes with AgAl2O3 as the sheath material is perhaps another route to improve mechanical pro perties.