Evaluation of Bending Strain in Nb3Sn Strands of CIC Conductor Using Neutron Diffraction

The superconducting property of Nb
₃
Sn strands is very sensitive to strain. The transverse electromagnetic loading has been considered as a major origin of the degradation of Nb
₃
Sn cable-in-conduit conductors (CICCs) due to the local bending. Since the bending pitch is around 5 mm due to contacting of strands compacted by the electromagnetic transverse loading, there is a possibility of a large bending strain with small deflection of strands. The bending strain of the strands cannot be evaluated from only the small deflection obtained visually. Measuring bending strain of Nb
₃
Sn strand in CICCs is important for evaluating the conductor performance. Neutrons, which have a large penetration depth, are a powerful tool to evaluate the internal strain of Nb
₃
Sn in the CICC. This paper shows that the bending strain in Nb
₃
Sn strands of CICCs can be determined by the neutron diffraction profile nondestructively and quantitatively.