DEVELOPMENT OF INTERNAL TIN NB3SN CONDUCTORS BY NOVEL MANUFACTURING TECHNIQUES

THE PRESENT INTERNAL TIN METHOD OF MANUFACTURING NB3SN CONDUCTORS HAS ADVANCED SIGNIFICANTLY OVER THE PAST SIX YEARS. WITH UNALLOYED NB3SN, CRITICAL CURRENT DENSITY (JC) OF OVER 1,400 A/MM(2) AT 10 T AND LONG WIRE LENGTHS HAVE BEEN REPRODUCIBLY DEMONSTRATED. WITH 1.2 WT% TI ADDED TO NB, THE HIGH FIELD JC HAS INCREASED TO AS HIGH AS 1,000 A/MM(2) AT 12 T. HOWEVER, THE INCREASED WORK-HARDENING OF THE ALLOYED NB HAS UPSET THE PROCESS TOLERANCE SUCH THAT LONG PIECE LENGTHS ARE NOT TO BE TAKEN FOR GRANTED. IN ADDITION, THE INTERNAL TIN METHOD (AS CURRENTLY ESTABLISHED)STILL INVOLVES LONG PRODUCTION TIME AND HIGH COSTS. THE LACK OF LONG LENGTHS OF ADVANCED CONDUCTORS WITH THE DESIRED TERNARY ADDITIONS HAS SERIOUSLY HAMPERED MANY OF THE RECENT MAGNET APPLICATIONS. THIS PROJECT INVOLVES A NOVEL VARIATION TO THE BASIC INTERNAL TIN APPROACH TO CIRCUMVENT SEVERAL OF THESE SHORTCOMINGS. THE MODIFIED TECHNIQUE HAS MANY POTENTIAL BENEFITS OVER THE CONVENTIONAL PROCESS: (1) GREATLY INCREASED DRAWABILITY AND LONGER PIECE LENGTHS DUE TO GEOMETRIC CHANGES IN THE NB-CU-SN COMPOSITE DESIGN PAVING THE WAY FOR HARDER TERNARY OR QUATERNARY COMPOUNDS THAT ARE SUITABLE FOR VERY HIGH FIELD APPLICATIONSAND INCREASED JC AS A RESULT OF BETTER UTILIZATION OF CONDUCTOR CORE AREA AND HIGHER NB CONTENT; (2) LOWER OVERALLCONDUCTOR COST BECAUSE OF FEWER AND SHORTER PROCESSING STEPS; AND (3) REDUCED AC LOSSES OWING TO NO FILAMENT DISTORTION AND LESS BRIDGING. A DEVELOPMENT PROGRAM WILL BE CONDUCTED TO FABRICATE NB3SN CONDUCTOR BY THIS NEW DESIGN AND TO INVESTIGATE KEY PROCESS VARIABLES. THE OBJECTIVE IS TO DEVELOP A COST-EFFECTIVE INTERNAL TIN CONDUCTOR IN LONG LENGTHS AND WITH IMPROVED ELECTRICAL AND MECHANICAL PROPERTIES.