EUROPEAN DEVELOPMENT OF HIGH-PERFORMANCE NB3SN 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 t he two strands are: HP I: Jc(non Cu)>700A/mm(2) at 12T@4.2K, Hyst. los ses<600mJ/cc (+-3T); HP II: Jc(non Cu)>550A/mm(2) at 12T@4.2K, Hyst. l osses<200mJ/cc (+-3T). HP I strand performance is likely to be achieve d by internal tin Nb3Sn, HP II by a bronze route strand. About 25% of the 26 tonnes required by the Model Coils will be contributed by the E uropean 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 al ready demonstrated by Vacuumschmelze on a 10 km strand manufactured fo r NET in the frame of a former contract. On the other hand, the HP I i nternal tin strand was to be developed. In view of this, a contract ha s been assigned to GEC Alsthom Intermagnetics, France, to have a back- up option for internal tin strand. EM-LMI (HP I strand) and Vacuumschm elze (HP II strand) have successfully manufactured Nb3Sn multifilament ary wires complying with ITER specifications. Work is in progress at G EC Alsthom Intermagnetics to achieve HP I strand performances.