Residual Resistances Ratio in NbTi Strands Extracted From the ITER PF1/6 Conductor Sample After SULTAN Tests

Abstract

The residual resistance ratio (RRR) is an important parameter affecting the stability of superconductors and the quench protection properties of magnets. During the manufacture and testing of cable-in-conduit-conductors, RRR may change noticeably. Recently the RRR changes of Nb 3 Sn strands for conductors of the ITER toroidal coils have been studied during the manufacturing process, heat treatment and SULTAN testing. Here we present the similar study of RRR of Nb-Ti strands used for conductors of the ITER poloidal coils. RRRs of the strands were measured in as-received condition and at different stages of the PF conductor manufacturing. RRR of strands extracted from ITER PF conductor sample after electromagnetic and thermal cycling in the SULTAN test facility was also measured. For this purpose the strand samples were extracted from different locations in the cross-section of the PF conductor and from different positions along the axis after testing in the SULTAN. The results about the RRR change during the manufacturing process and after the SULTAN tests and also the details of experiments are presented and discussed.

Challenges and status of ITER conductor production

“…As a result of these investigations, the heat treatment of three of the TF strand suppliers (two bronze and one internal tin), which called for a 200 h high temperature plateau, had to be modified. For two suppliers, the plateau duration was reduced to 100 h [111], whereas for the third supplier, the plateau temperature was lowered.…”