many years now by companies such as American Superconductor Corporation (AMSC) in the USA and Sumitomo in Japan, though AMSC has now abandoned BSCCO wire in favour of 2G wire based on YBCO. Typically, precursor powders are packed into a silver tube, which is then extruded down in diameter. These are then repacked as multiple tubes in a silver tube and again extruded down in diameter, then drawn down further in size and rolled into a flat tape. The last step ensures grain alignment. The tapes are then reacted at high temperature to form dense, crystallographically aligned Bi-2223 multifilamentary conducting tape suitable for winding cables or coils for transformers, magnets, motors and generators. Typical tapes of 4 mm width and 0.2 mm thickness support a current of 200 A at 77 K, giving a critical current density in the Bi-2223 filaments of 5 kA/mm2. This rises markedly with decreasing temperature so that many applications are implemented at 30–35 K, even though Tc is 108 K. Applications Electrical power transmission : 1G conductors made from Bi-2223 multifilamentary tapes. e.g. : Holbrook Superconductor Project Electromagnets and their current leads : Testing BSCCO tapes at CERN Discovery BSCCO as a new class of superconductor was discovered around 1988 by Hiroshi Maeda and colleagues at the National Research Institute for Metals in Japan, though at the time they were unable to determine its precise composition and structure. Almost immediately several groups, and most notably Subramanian et al. at Dupont and Cava et al. at AT&T Bell Labs, identified Bi-2212. The n = 3 member proved quite elusive and was not identified until a month or so later by Tallon et al. in a government research lab in New Zealand. There have been only minor improvements to these materials since. A key early development was to replace about 15% of the Bi by Pb, which greatly accelerated the formation and quality of Bi-2223. Properties BSCCO needs to be hole-doped by an excess of oxygen atoms (x in the formula) in order to superconduct. As in all high-temperature superconductors (HTS) Tc is sensitive to the exact doping level: the maximal Tc for Bi-2212 (as for most HTS) is achieved with an excess of about 0.16 holes per Cu atom. This is referred to as optimal doping. Samples with lower doping (and hence lower Tc) are generally referred to as underdoped, while those with excess doping (also