Martin Munz

Fabrication of Bi-2223 tapes

For the use of silver or silver-alloyed Bi-2223 tapes in different applications of power engineering, very good electrical and mechanical properties are required. Besides high critical current densities of up to 100 kA/cm/sup 2/ the tapes have to cope with high mechanical stresses and strains and need low AC losses with respect to the variety of applications. At Vacuumschmelze we produce and develop different multifilamentary tapes with high strengthened matrix, low AC losses and high electrical performance. Overall critical current densities >7 kA/cm/sup 2/ and critical currents up to 80 A in lengths of up to 800 m have been measured in the production line. In short-samples current densities over 10 kA/cm/sup 2/ have been achieved, An overview of the fabrication process, the optimization of different process parameters, the microstructure of the filaments as well as the electrical performance of the multifilamentary tapes in different magnetic fields and at different temperatures are given. Also AC loss and mechanical measurements of different tapes will be shown.

Progress in the preparation of technical HTS-tapes of type Bi-2223/Ag-alloy of industrial lengths

We report about the improvements on overall critical current density j/sub e/, long-length processing, mechanical properties, and insulation. These topics are discussed for Bi-2223/Ag-alloy tapes for typical DC-applications, for AC-applications which require twisted filaments to achieve low-loss properties and for current-lead-applications (EAS is producing Bi-2223/AgMgAu-HTS-tapes for the CERN-LHC-Project). The state-of-the art production of Bi-2223/Ag-alloy tapes at EAS allows for overall current densities of >100 A/mm/sup 2/. There is progress out of the development line to a value of more than 120 A/mm/sup 2/, which will be transferred to the production line in the near future. Regarding AC-tapes with twisted filaments, it is possible to prepare tapes without a reduction in overall current density if the preparation parameters are kept within a well defined window. Both types of tapes are available in piece-lengths of up to 1500 m. The requirements on the piece-lengths of Bi-2223/AgMgAu-HTS-tapes for current leads are less stringent. This type of tape is available in piece-lengths up to 300 m with overall current densities up to 90 A/mm/sup 2/.

Bi-2223 tapes - specific performance for different applications

In the past (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ Ag/Ag-alloy-sheathed High-Temperature Superconductor (HTS) tapes (Bi-2223 tapes) have been proven being suitable for building quite different system components for a variety of applications. Nevertheless it revealed that applications like Power Transmission Lines, Transformers, Motors/ Generators, SMES, very high field magnets and MRI put very special requirements on the tapes which differ from application to application. The most important point is that the tapes will provide cost-efficient performance for the special application. This means that its not sufficient to analyze the price in

High temperature superconductor current lead for connecting a superconducting load system to a current feed point

/kAm, but additionally its necessary to consider e.g., AC-losses, geometry, mechanical strength and insulation properties and how they contribute to cost. We discuss a subset of the different requirements from the view of a tape supplier. We depict the current status of the tape production unit lengths >1000 m, overall current densities /spl ges/100 A/mm/sup 2/, steep E-I-characteristics n-value /spl ges/30 at standard conditions and even at low temperatures and/or high magnetic fields), low AC-losses combined with remarkable critical currents of 50 A/mm/sup 2/, reliable properties of mechanics and insulation.