Mechanical Responses of a Semi-Open Split Nb–Ti Superconducting Magnet Reinforced With Cantilever Structure

A novel design for providing a high field based on a semi-open split Nb-Ti superconducting magnet has been developed. It is to incorporate in the versatile multi-field test facility established for professional tests of field-dependent and mechanical behaviors of low-temperature and high-temperature superconducting wires and tapes. The semi-open split superconducting magnet (the peak magnetic field in the coil up to 7.8 T) is a good candidate to generate a transverse field in a large work region of Ø100 mm × H800 mm. On the other hand, its semi-open shaped configuration for samples makes it feasible for a non-contact optical technology of digital image correlation (DIC) for being utilized in full-field deformation measurements under extreme conditions. Since the irregular-shaped configuration and large deformation due to attraction; mechanical behavior of support structures of the magnet will be crucial for its stability and operation function. In this study, an internal reinforced cantilever structure for splitting the superconducting magnet poles was proposed to bear the large attraction from Lorentz forces and keep a stable configuration under operation conditions. Analysis based on a finite element method was performed to obtain deformation and stress profiles of the superconducting coil windings and reinforced cantilever structure with contact nonlinearity. The effect of geometrical parameters of the cantilever on axial displacements in the split magnet system was addressed. Experiments on excitation and quench of the assembled split superconducting magnet were performed at 4.2 K to capture strain responses. The numerical predictions showed reasonable agreements with the observations on structural stress/strain states. It indicated that an optimization analysis of the cantilever structure is necessary for a high-field irregular-shaped magnet system for its assembly and excitation.