THERMAL-STABILITY IN HIGH-T-C COIL AND MAGNET DESIGN BY PROCESS-CONTROL OF BI(PB)-2223 AG MULTIFILAMENTARY TAPES/

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 a mount of matrix and superconducting materials during processing. The i ntermediate deformation step between sintering stages has been found t o be crucial in optimizing the performance of the processed composite tapes as well as governing the thermal stability of the subsequently m ade 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 va lues of the fill factor. However, increasing the number of co-wound ta pes would require either a reduction in the fill factor or an increase in cooling rate for thermal stability to be sustained as would otherw ise be achieved with the metallurgically same single tape.