Thermal stability in high-Tc coil and magnet design by process control of Bi(Pb)-2223/Ag multifilamentary tapes

Abstract

It has been found that the degree of thermal stability of Bi(Pb)-2223/Ag pancake-shaped coils at 77 K can be determined by controlling the amount of matrix and superconducting materials during processing. The intermediate deformation step between sintering stages has been found to be crucial in optimizing the performance of the processed composite tapes as well as governing the thermal stability of the subsequently made pancake-shaped coils. Results obtained from numerical analysis of the finite element method has shown that monolayer coils produced from Bi(Pb)-2223/Ag composite tapes are thermally very stable with high values of the fill factor. However, increasing the number of co-wound tapes would require either a reduction in the fill factor or an increase in cooling rate for thermal stability to be sustained as would otherwise be achieved with the metallurgically same single tape. © 1996 Plenum Publishing Corporation.