A multifilamentary 15.5 T small magnet

A multifilamentary Nb₃Sn coil is wound with a 1.8 mmm diameter Nb-tube processed Nb₃Sn conductor and subsequently reacted. This magnet coil was fabricated and tested with an NbTi back-up. The insert has a 38-mm bore, 138 mm outer diameter and 223 mm length, whereas the NbTi back-up is 150 mm in length. Both magnets were connected in series and charged simultaneously at 4.2 K: 15.5 T was attained after many premature quenches, due to debonding between the bore tube and the coil winding. The current density at 15.5 T is 131 A/mm² for Nb₃Sn, and 142 A/mm² for NbTi.