Test of the ENEA Joint With a NbTi Large CiC Conductor

This paper describes the results of the measurements performed in June 2011 on a NbTi cable-in-conduit conductor curved joint in the ENEA Superconductivity Laboratories (C.R. Frascati). The effectiveness of the joint design, patented by ENEA, had been already verified for the Nb₃ Sn EDIPO conductor; in this case, it has been applied to a NbTi cable-in-conduit conductor. The joint was manufactured and instrumented by ENEA, using part of a JT-60SA toroidal field conductor sample (namely the TFCRS) produced by Luvata Italy and successfully tested in SULTAN. For testing purposes, the NbTi “shaking hands”-type joint was hosted in a variable temperature cryostat with a background superconducting magnet. The sample was used as the secondary coil of a transformer having the background magnet as primary coil. Measurements were preceded by preliminary code simulation studies computed in the Matlab workspace, and by 3-D finite element method analyses, to estimate the test requirements and its feasibility. The joint resistance value, found to be less than 2 nΩ has been derived both by the sample current decay time constant evaluation and by calorimetric calculations. After a short description of the joint design and fabrication, as well as of the test instrumentation and geometry, the joint resistance evaluation will be presented, together with the data analysis procedures and results.