JC(B,T) characterization of NbTi strands used in ITER PF-relevant insert and full-scale sample

In the framework of the R&D for the ITER Poloidal Field Coils (PFC), a testing campaign was achieved on NbTi strands used in PFC-relevant modules. Three candidate NbTi strands have been used for manufacture of two Full-Size Joint Samples (PFIS and PF-FSJS) and the PF Conductor Insert (PFCI): - one strand manufactured by Europa Metalli (Italy), Ni plated and 0.81 mm diameter; - one strand manufactured by Alstom (France), with a CuNi barrier and 0.81 mm diameter; - one strand manufactured by Bochvar VNIINM (Russia), Ni plated and 0.73 mm diameter. An extensive test campaign has been performed at GHMFL (CNRS, Grenoble) in 2003 using the CEA VTC facility at temperatures ranging from 4.2 K to 7.5 K and at magnetic fields ranging from 2.5 to 10.5 T. The results showed that all three strands have quite close performances in the ITER PFC operating range despite their structural differences and that due to the critical current density curvature with temperature, they fail to meet the 1.5 K PFC temperature margin criterion by 0.2 to 0.3 K. Additionally, applications of corresponding fits to PF-FSJS tests showed consistent results and finally a brief discussion on fitting formula is presented.