Fabrication and tests of EF conductors for JT-60SA

The conductors for plasma equilibrium field (EF) coils of JT-60SA are NbTi cable-in-conduit (CIC) conductor with stainless steel 316L jacket. The production of superconductors for actual EF coils started from February 2010. Nine superconductors with 444 m in length were produced up to July 2010. More than 300 welding of jackets were performed. Six nonconformities were found by inspections as go gauge, visual inspection and X-ray test. In order to shorten the manufacturing time schedule, helium leak test was conducted at once after connecting the long length jacket not just after the welding. The maximum force to pull the cable into jacket was about 7.6 kN on average. The mass flow rates of 9 conductors showed almost same values indicating that there are no blockages in the conductors. The measured current sharing temperature agreed with the expectation values from strand performance indicating that no degradation was caused by production process. The coupling time constants of conductors ranged from 80 to 90 ms which are much smaller than the design value of 200 ms.