Analysis of the CICC Performance Through the Measurement of the Thermal Strain Distribution of the Nb-3 Sn Filaments in the Cable Cross Section

The knowledge of the thermal strain distribution of the Nb3Sn filaments in a cable in conduit conductor (CICC) cross section is a key parameter in understanding the cable performance evolution when it undergoes electromagnetic (EM) cyclic loading. A CICC is a complex system and as such it behaves in a way that is not directly predictable by studying the single components. Reversible and irreversible phenomena occur together; therefore, the explanation of the observed CICC properties is not straightforward. The magnetic susceptibility measurements, via an appropriate data reduction, allow to quantify the thermal strain. Several ITER toroidal field (TF) and central solenoid (CS) samples have been measured with this technique in the SULTAN test facility. Each cable behaves differently from the others; however, it is possible to identify common features. For some samples, the evolution of the performance with the EM cycles is dominated by the change of the strain distribution during the EM load; for others, also the irreversible phenomena play an important role. The magnetic measurements have been used in this paper to analyze the performance of several CICCs.