The ${rm J}_{rm c}({rm B},{rm T})$ Characterization of Commercial NbTi Strands for ITER PF 1&6 Coils

摘要

The commercial multifilamentary NbTi strands produced for ITER poloidal field coils PF1 and PF6 have been characterized on ${rm J}_{rm c}({rm B},{rm T})$ at various manufacturing stages: bare strand, Ni-plated strand and the strand after impregnation heat treatment. We present the results of critical current measurements at magnetic fields in the range of 4.5–10 T, and temperature within 4.2–7 K. Current sharing temperature $T_{rm cs}$ of these strands has been determined with a precision of few tens of mK, using fit formula that provides the critical current density as a function of temperature and field. The results show that $T_{rm cs}$ of commercial strands exceeds the required value of 5.9 K at 6.4 T and the operating current of 33 A. These measurements allowed us to get a database, essential for the future analysis of the experimental data, and to find the strand characteristic parameters for the ${rm J}_{rm c}({rm B},{rm T})$ fit.