Electromagnetic Design and Mechanical Analysis of a 28.2-T/1.2-GHz High-Field NMR Magnet

A 28.2-T Bi2212 nuclear magnetic resonance magnet was designed using linear programming (LP) and nonlinear programming (NLP) approaches. This magnet, with a 34-mm cold bore diameter, comprises a 17.48-T Bi2212 superconducting insert and a 10.72-T low-temperature superconducting outsert. LP was first utilized to determine the initial distribution of the Bi2212 coil clusters. The current density for each coil was then fine-tuned to align with the safe design criterion, which focuses on the hoop stress from electromagnetic forces of the superconducting coils. The NLP optimization was employed to refine the geometric dimensions of the coil clusters, determining factors such as inner and outer radii and height of the coil blocks by considering the strand dimensions and the critical current density scaling laws associated with the superconductors. The magnetic field uniformity of 4 ppm over a 10-mm diameter of spherical volume was achieved. The detailed electromagnetic design and mechanical analysis results were presented.