Development and First Test of the 15 T Nb₃Sn Dipole Demonstrator MDPCT1

Fermilab in the framework of the U.S. Magnet Development Program (MDP) has developed a Nb ₃ Sn dipole demonstrator for a post-LHC hadron collider. The magnet uses 60-mm aperture 4-layer shell-type graded coils. The cable in the two innermost layers has 28 strands 1.0 mm in diameter and the cable in the two outermost layers has 40 strands 0.7 mm in diameter. An innovative mechanical structure based on aluminum I-clamps and a thick stainless steel skin is used to preload Nb ₃ Sn coils and support large Lorentz forces. The maximum field for this magnet is limited by 15 T due to mechanical considerations. The first magnet assembly was done with lower coil pre-load to achieve 14 T and minimize the risk of coil damage during assembly. This paper describes the magnet design and the details of its assembly procedure, and reports the results of its cold tests.