Compact high field superconducting coil

In the frame of the program to fabricate compact laboratory superconducting high-field magnets (of order of 18 T @ 4.2 K and 20 T @ 1.8 K) a 17.7 T @ 4.2 K coil with 39 mm clear bore was developed and preliminary tested. The design field was reached without any training quenching. The innermost subcoil was wound of a doped Nb₃Sn wire with numerous internal tin sources. The two intermediate subcoils were wound of multifilamentary Nb₃Sn bronze route wires. The outer subcoil was wound of both Nb₃Sn and NbTi based wires. The current density averaged across the conductor cross-section is 120 A·mm^-2 at 17.8 T and 196 A·mm^-2 at 15.9 T. The total stored energy is 1.05 MJ.