Test results of two ITER TF conductor short samples using high current density Nb₃Sn strands

Two short length samples have been prepared and tested in SULTAN to benchmark the performance of high current density, advanced Nb₃Sn strands in the large cable-in-conduit conductors (CICC) for ITER. The cable pattern and jacket layout were identical to the Toroidal Field Model Coil Conductor (TFMC), tested in 1999. The four conductor sections used strands from OST, EAS, OKSC and OCSI respectively. The Cu:non-Cu ratio was 1 for three of the new strands, compared to 1.5 in the TFMC strand. The conductors with OST and OKSC strands had one Cu wire for two Nb₃Sn strands, as in TFMC. In the EAS and OCSI conductors, all the 1080 strands in the cable were Nb ₃Sn. A dc test under relevant load conditions and a thermal-hydraulic campaign was carried out in SULTAN. The CICC performance was strongly degraded compared to the strand for all the four conductors. The current sharing temperature at the ITER TF operating conditions (j_op = 286 A/mm ², B = 11.15 T) was lower than requested by ITER.