ITER poloidal field-full size joint sample: DC test results

The ITER Poloidal Field-Full Size Joint Sample is a prototype sample dedicated to the tests of both conductor and joint relevant to the ITER Poloidal Field Coils. This sample, made of two straight conductor legs, connected at one end to each other, has been manufactured in industry and extensively tested in the SULTAN facility at Villigen, Switzerland. This paper is dedicated to a detailed analysis of the DC performances of the two legs, based on the same conductor layout, but with two different NbTi strands: a Nickel coated pure copper matrix strand from Europa Metalli (EM), and a bare strand from ALSTOM (AL), with internal cupronickel barrier. Critical currents, and/or quench currents, and current sharing temperatures have been measured in the range of interest for the ITER magnets, namely with a background field from 4 to 7 T, temperatures in the 4.5-7.5 K range, sample currents up to 80 kA. An 'instability' of this conductors, more pronounced in the EM leg despite the higher Cu:non-Cu ratio of the strand, has been evidenced, in agreement with other NbTi large conductors behavior. The effect of cycling on both critical and quench currents showed no significant evolution, as the test have been performed on virgin samples, and repeated after more than 500 electromagnetic cycles.The results allowed to evidence the features common to the two legs, peculiar to NbTi large CIC conductors, and the differences in the two legs performances, which could be attributed to a different current distribution among the main sub-cables (petals). (authors)