Field Measurement Results of the 15 T Nb₃Sn Dipole Demonstrator MDPCT1b

A 15 T Nb ₃ Sn dipole, MDPCT1, with cos-theta-type coils was developed to demonstrate a possible magnet design for a post-LHC proton-proton Collider. The magnet has 4-layer coils with 60-mm aperture, and has graded current density between the inner and outer layers to maximize performance. The coils are constrained by vertically-split, thick iron laminations, connected by aluminum I-clamps, and a thick stainless-steel skin. The magnet was previously tested at Fermilab with reduced pre-load, and achieved record 14.1 T fields at 4.5 K. Now the magnet was reassembled with full pre-load and cryogenically retested. This paper reports the magnetic measurements results of these tests, including field strength, geometrical harmonics, coil magnetization, and iron saturation characteristics of the demonstrator.