European development of high performance Nb/sub 3/Sn strand for the ITER model coils

The ITER model coils will use two types of strands, one with high Jc, HP I, one with low hysteretic losses, HP II. Main specifications for the two strands are: HP I: Jc (nonCu)>700 A/mm/sup 2/ at 12 T @ 4.2 K, hysteresis losses<600 mJ/cc (+-3 T); HP II: Jc (non Cu)>550 A/mm/sup 2/ at 12 T @ 4.2 K, hysteresis losses<200 mJ/cc (+-3 T). HP I strand performance is likely to be achieved by internal tin Nb/sub 3/Sn, HP II by a bronze route strand. About 25% of the 26 tonnes required by the model coils will be contributed by the European Community. The companies EM-LMI, Italy (for internal tin) and Vacuumschmelze, Germany (for bronze route) have been selected by ITER for the strand production. The achievement of HP II performance was already demonstrated by Vacuumschmelze on a 10 km strand manufactured for NET in the frame of a former contract. On the other hand, the HP I internal tin strand was to be developed. In view of this, a contract has been assigned to GEC Alsthom Intermagnetics, France, to have a back-up option for internal tin strand. EM-LMI (HP I strand) and Vacuumschmelze (HP II strand) have successfully manufactured Nb/sub 3/Sn multifilamentary wires complying with ITER specifications. Work is in progress at GEC Alsthom Intermagnetics to achieve HP I strand performances.<
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