MULTIFILAMENTARY NIOBIUM-TIN SUPERCONDUCTING WIRE CONTAININGCOMPOSITE FILAMENTS WITH ARTIFICIAL PINNING CENTERS FOR IMPROVED HIGH FIELD PERFORMANCE

A CONTINUING NEED EXISTS FOR ADVANCED SUPERCONDUCTING WIRES THAT CAN OPERATE IN INCREASINGLY HIGH MAGNETIC FIELDS. THE NEXT GENERATION OF MAGNETS ARE ANTICIPATED TO GENERATE FIELDS OF 12 TO 18 T, AND A CONDUCTOR IS NEEDED TO OPERATE EFFECTIVELY IN THESE HIGH FIELDS. NIOBIUM-TIN (NB3SN) SUPERCONDUCTING WIRE CAN OPERATE IN HIGH MAGNETIC FIELDS, AND DOPING AGENTS CAN BE ADDED TO INCREASE THE UPPER CRITICAL FIELD OF THE MATERIAL SIGNIFICANTLY HIGHER THAN THAT FOR BINARY NBSN. AN UPPER CRITICAL FIELD AS HIGH AS 31 T, WHICH HAS BEEN REPORTED FOR GALLIUM-DOPED NB3SN, CAN EFFECTIVELY EXTEND THE OPERATING RANGE OF NB3SN CONDUCTORS. FINE GRAIN SIZES ARE DESIRABLE FOR OPTIMAL CURRENTS. HOWEVER, REACTION HEAT TREATMENTS AFFECT THE NB3SN GRAIN SIZE AND THE CURRENT DENSITY OF THE NB3SN LAYER. THE WORK IN PHASE I IS TO IDENTIFY THE OPTIMAL GRAIN SIZE IN AN NB3SNCONDUCTOR AND TO ALLOW THE GRAIN SIZE TO BE ENGINEERED INTO A COMPOSITE FILAMENT AND TO BE PREDETERMINED, REGARDLESS OF THE REACTION TEMPERATURE USED. BRONZE ROUTE PROCESSING AND INTERNAL TIN TECHNIQUES ARE BEING EVALUATED FOR THE TECHNICAL AND ECONOMIC IMPACT ON THE MANUFACTURING PROCESS. PHASE II IS TO INCLUDE WORK TO INCREASE CRITICAL FIELD VALUES.