A 3.35 T Actively Shielded Superconducting Magnet for Dynamic Nuclear Polarization Device

Dynamic nuclear polarization (DNP) is a method to obtain strongly polarized nuclear spins in solution, thereby enhancing sensitivity for nuclear magnetic resonance (NMR) experiments. In this paper, an actively shielded superconducting magnet for DNP has been designed. It has a warm bore of 150-mm diameter and consists of solenoid coils made of epoxy-impregnated NbTi/Cu superconductors. The center field of the magnet is 3.35 T, and the field homogeneity is 2 ppm over a 60-mm diameter and 40-mm length of cylindrical volume. The 5-G contour of the stray field is 1.5 and 2 m at radial and axial directions, respectively. In this paper, coil design, stress analysis and quench protection, cryostat design and thermal analysis, superconducting jointing, and switch of the magnet are presented.